EFACE "'"' S
":"i.las of Human Neuroscience combines
f'C'I)e~~ and beauty of Dr. Frank N etter's illu5tra
;:)a)icting both regio nal and syste mic neuro 'r '.\ ilh updated info rm ation and beautiful new
n:o-ts to reflect our growing understanding of --e-g.ions and systems of the brain, the spinal ~.'j(j the periphery. This Atlas also includes new ~ns through the spinal cord and the brain ~ \'. e ll as coronal and horizontal sections cor "::O.,., ....-ith ,'vIRls. We have chosen to let the iIIustra :J'1J'\ ide the focal point for learning.. rather than
org. detailed written explanations th at cou ld - ..,:e <: Tull textbook in itself. VVe have provided ..¥C :lgure legends to point out some of the
and provide regio nal and functi o nal co ntexts for the information, as appropri ate, to encourage true understanding rather than ro te memorization. In a diSCiplin e as complex as the neurosciences, th e acquisition of a true understanding of the major regio ns and hierarchies of the nervou s system is esse ntial for developing a working competence in basic and clinical neuroscience. This Atlas illustrates basi c human neuroscience, no t clinical conditions and disorders, such as multi pl e sclerosis. Alzheim er's disease, strokes, spinal cord and brai n injuries, the agnosias, aphasias, and apraxias, or o ther majo r conditio ns. These topics are m ore appropriate for a future volume .
func tional aspects of each illustration, particu as 'rese aspects relate to problems that a cJin i -.0\ encounter in assessi ng a patient with """'0_,<,'"cal symptoms. The figure legends, com .. 'th th e excell en t illu strati ons, provi de a =~ =-'" ~n ders tanding of the basic components, :..JnZ.cloon, and functional aspects o f the region or Je.- vider consideration . (J(de - [Q provide an optimal learning experi ::-"01'" jtu dents of neuroscience, we have orga -5 4t1as in three parts: I. Overview oi the ..>.....: 5\ stem, II. Regional Neuroscience, an d III. ~JC 'euroscience. This organization affords ~ - th e benefit of looking at some of these -"""neu ral stru ctures and systems in two or __ cr:erenl contexts, or from two or three -~i. poi nts of view, so m eti mes as part of an ~ ... so me times with a regional emphasis, 5lJr"""€ti mes wi th a view toward understanding _"'1C"io ning of a speci fic system spanning the 5. Thoughtful repetition from novel perspec 5 a usefu l too l in acq uiring a comfortable ... g 'nowledge of the nervous system that will di'1ician s w ell in evaluating and treating ..3\\ith neurolo gical problems and th at will oe neuroscience researchers and educators -- a broader and more comprehensive under ,,",n:lh ~. oi the ner vous system. .... ,;,ome information, su ch as th at on upper '. er m otor neu ron s and th eir control, d<:.o..ec :actual informatio n must be acquired and """-'i"::ood as a preliminary step tow ard under COt"DrS cli nical aspects of m o tor disorders; w ith 4,- un derstanding. the clini cal aspects fall Onto place. We introdu ce co re information
Part I. Overview of the Nervous System We begin with an introductory overview of neurons and their properties, gross features of th e nervous syste m, and an understanding of the sup porting tissues and systems such as the vasculature, the menin ges, an d the cerebrospinal fluid b ecause we believe that it is necessary to understand this body o f information before delving into the details of re gional and systemic neuroscience. Thus, Part I. Overview o f the Nervous System first presents the unique ch aracteristi cs and properti es of the cellular foundations of the nervous system. including neu rons and their stru ctural, neurotransmitter, and electrical properties, and the supporting cells, the glia. Specific exa mples of primar y sensory neurons, low er m oto r neuron s, and auton omic pregan· glionic and postganglio nic neurons provide preparatory examples of th e inputs and outputs of the nervous system, esse ntial for understandi ng both regional and system ic neuroscience. The next po rtion of the Overvi ew introduces the m ajo r structural features of the nervous system, including the principal su bdivisi ons and th eir func tional roles, in a manner that is consistent w ith introduc to ry labo ratory exam ination o f the human nervous system. Thus, students are in troduced to lateral, midsagittal, basal, and some cross-sectio nal views of the forebrain, with the intention o f obtain ing a "big picture view. This is followed by a similar in troduction to the brain stem and cereb ellum and the spinal cord. It is during this introductory overview that students sho uld become familiar with the telencephalon, th e di encephalon, th e brain stem, the spinal cord, and the peripheral M
VII
~er\ DUS s y ~t em
and acqu ire an understanding of he major associations and relationships among r ~e com pon ents . Subsequent sections of the O verview introduce ~ e men inges, the ventricles and cerebrospinal 'u id, and the vasculatu re, all components of the "tensiv€ supportive and protective infrastructure .i the nen eu s system. Because the vasculature of ne bra in an d spinal cord is a very important pa rt of ieurological ass ess ment and understandin& \'\'e horou ghly in troduce it in the Overview and follow his \",ith additional reference and explanation of lOre specific de tails in Part /1. Regio nal ~ euro sc i e n c e and Part III. Systemic N euroscience. inaih. the Overview presents developmenta l neu osdence, showing how the mature nervous sys ~r-l devel ops an d how so me of the important ~mction al relatio nships reflect associatio ns that .egan during neural development.
'art II. Regional Neuroscience
Ian II. Regiona l Neuroscience begins in the periph 'fal nen o us system (PNS ) and moves rostraUy. This pproach pelm its students to gain a thorough Inderstan ding of the inputs and outp uts of th e cerr 'al ner\'o us system (eNS), th e brain and spin al Drd. before attempting to understand more ros tral E'gions that are involved in processing of inputs to, nd regulation of outputs of, the eNS. The in troduction to the PN S establishes a lorough understan din g of primary sensory inputs nd motor and au to nomic o utputs of th e CNS. 'onceptua lly, some of the most important ustrations in the Arras are th ose tha t outlin e secondary senso ry channels-the reflex, cerebel t, and lemniscal channels thai further process imar. sensory input to the CNS, (2) mo tor hierar ~ es, focu sed first on th e lower motor neurons M "" s that supply sk eletal mu scl e fi bers, regula >fl 0 1 these LMNs by bra in stem and cortica l )per motor neuro ns (UMNs), and th e co ordin a 110 and modulation of UMN regulati on by the ~ebellu m and the basa l gangli a, and (3) pregan onie autonomic connections to peripheral tar ts through autonom ic ganglia, and the central O.IllS irom th e brain stem, the hypothalamus, and ;> limbic str uc tures that regulate and coordinate mautonomi c and neuroendocrine o utflow. A
Kough un derstand ing of these hi erarchies-as
~nted in the in troduction to the PNS-is the
InOation ior the rest of the Atlas.
The section on the PN S next offers a systematic collection of illustrations of roots, plexuses, and peripheral somatic nerves, w hich prov ides a smooth transition between th e central and the periphe ral aspects of neuroscience. The illustra tions of the major peripheral nerves are con ducive to acquiring a better un derstanding of neuropathies, w hich are so frequently enco untered in medical practice. 'vVe have tried to bring together the basics of periphera l nerve anatomy, fu nction, and cl inical deficits in as simple and suc cinct a fash ion as possi ble in the figure legen ds for the periph eral nerves. The section on the PNS next outlin es the o rgani Zation and the major d istribution networks of the auto nomic nefVOU5 system . These illustrations are important for many reasons, including understand ing auto nomic disorde rs and the effects o f a ho st of pharmacological agen ts that infiu ence th e auto nomic nervou s system and its associated adrener gic and cholinergi C receptors. In addition, w e are becoming increaSingly aware that maj or life stres sors and life style factOfs play an importan t role in the onset,. progressio n, and o utcome of atheroscle rosis and cardiovascular disease (including cere brovascular disease), cancer, diabetes, chronic pulm onary disease, and even neurodegenerative diseases and that these factors exert their phys io logical effect in large part th rough neural o utflow via the autonomic nervous system and v ia hypo thalamo-pituitary-neuroendocrine outflow and that they have an impact on cytokines, hormones, infl amm atory mediators, and a va riety of immune responses. The updates to our und erstanding of peripheral autonomic mechan isms include th e depiction of autonomic interactio ns with cells of the immune system and w ith metabo lic cells such as hepa tocytes and fat cells. ..,jj The brain stem is usua lly the " terra incogn ita" o f neuroscience cou rses and can be an exercise in memorization and m inutiae if not pro perly o rga nized. This Atlas provides the o rgani zatio n for rather st raightforward understanding of the brain stem, despite its com plexities and intricacies. The brain stem has six major components: (1) sensory nudei and their pathways- includin g secondary senso ry nuclei and pathw ays for incoming sensory information to th e brain stem (tri geminal, auditory, vestibul ar, taste, visual), as w ell as somato sen sory nuclei and chann els, (2) LMNs for the cranial nudei, and descending UMN chan nels that control
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brain stem and the spinal cord,
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preganglionic neurons, and
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paras\ mpalhelic components of the
~ OU 5 sy stem, (4 ) cranial nerve nuclei ..i..()Cl~ ~ \ hieh clirectl y ove rlap with, and ~Jo'''_'d U1. the i irs! three components, (5) th e =::..:J~.meI its afferent and efferent conn ee
forebra in struc tures and their connec tions, and the olfac to ry system are provided Part III, Systemic Neuroscience. We also have updated the forebrain section w ith an over view of the chemicaUy specific systems of the brain, specifica lly the n oradrenergic, serotonergic, dopaminergic, and c holinergic sys tem s, which provide extensive inn ervation to \vide sp read eNS regions and w hic h are so frequently targeted with neurol ogical and psych iatric drugs.
the reticular formatio n. Th e crani al
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.awJ "netf nuclei are vital compon ents fo r :':::::=oowi,.,:;: both the brain stem and th e localiza ~ ....,."" ~ in the context of th e neuro logica l his ~na lionJ and they are the appropriate ""·'--uneerstanding the first three compo
brain stem, noted above. The Netter
- .a-e lucid, thorough, and readily under uundations fo r this process. to the Netter illustrations, we have _~ ::-:.ect io ns thro ugh the spinal cord and !'-er:l. These cross-sections will allow -va: or" Human Neuroscience to be used .=..or. and bas ic sc iences guide for stu 3ting th e need for a separate, d eta il ed -_c:;:.:,....",ic at las. In add ition, an excellent set of _ _. ..........-izon t.::d and coronal sections, carre ... ·~I im ages, is provided. These cross ct'lfonals, and horizontals emphasize the Impo rtant struc tures and avoid the use --":",", , '-ibels and minutiae that get in the way --.oets ta nding and obscure the " big pic aDded to this section o n the brain stem ~~rati on s o f Ihe retic ul ar formation, a ·~·o n 0; the eNS that cuts across all ;:d b invo lved in w idely varied neural 'Oft
a. cord, brain stem, and fo rebrain
COI11
=e:lI;' 0.: the Regio nal Neuroscience section Ocali zi ng and regional information impor ~ersta nd in g the co nseq uences of lesions c ( tes. In th e forebrain section, we emp ha ......~'11 U S and the hypotha lamus in the ...." e diencephalon; we include the sub _""-'" \ JJ th e basal ga nglia and the epithala ..... -'"Ie h\ pothalamus and the limbic system . _ - -.... £> telencephalon has fou r major func ov-ponenls-cerebral cortex, basal ganglia, i"Of"din sys tem, and o lfactory system- we -=c,..~",r . emp hasi ze th e ce reb ral co rtex anatomy .....-eGio ns in th e Regio nal N eurosc ience sec - -
Part III. Systemic Neuroscien ce Part III. Systemic Neuroscience provides a more d etailed understanding of the p eripheral and cen tral mechanisms of the sensory system s, the motor system s, the au to nomic-hypo thalam ic-limbic sys tem s, and some higher func tio ns. The founda tions for understanding the secondary senso ry and higher--order processing of sensory p athways begin w ith Ihe illustrations in the intro du ction to th e PNS in Part 11. The systemic sensory components includ e the somatosensory, trigeminal se nsory, taste, audito ry, vestibular, and visual sys tem s. To rellect current understandin g, seve ral modifi cation s to Dr. Netter's artwork have been m ade, as well as new art crea ted by John Craig, MD and Ji m Perkins, MS, MFA, particu larly in the secti ons on the so m atosensory system and the visual sys tem . A llhough we focus extensively o n the lem n isca l pa thways for sensory processing and conscious interpretation of inco ming sensory informa tion, appropriate diagrams and connectio ns for reflex and cereb ellar pathw ays are included w hen appro~ priate ((or example, w ith the vestibular sys tem ). Th e systemic motor components include LMNs, UMN s, the ce rebellum, and th e basal ga ngli a-of co urse, with the acknowledgment that th e ce rebe l lum and th e basal ganglia are involved in coo rdi natin g and m od ulating ce ntral circuits more wides pread than just motor system s. For th e UMN pathways, each sys tem is illustrated, with emphasis on the functio nal role. The cerebellar connectio ns included in this section emphaSize the relationshi ps be tween specific zones of the cere· bellum (vermis, paravermis, la teral hemispheres) w ith appropriate d eep nuclei (fastigial, globose and em boliform, d entate) and the UMN systems with w hich they connect (reticulospinal and vestibul osp inal, rubrospin al, co rticospinal ). Similarly, th e basa l ga nglia co nnectio ns show inter connections w ith the cortex through the thalamu s, including modu lation of the cells of origin of th e IX
corticospinal system and other cortical ou tflow. However, other basal ganglia loops are also included: even thou gh basal ganglia disorders have become known for their motor involveme nt, and are often ca lled "movement disorders," w e now know th at many other loops exist, linking other regions of the thalamu s and the co rtex with the basal ganglia, for cognitive as w eI! as emotiona l behavioral influences. The autonomic-hypothalamic-limbic sectio n inclu des deta iled updates and understanding of this important set of interconnected circuitry through the hypothalamus an d limbic system that ultimately regulates many behaviors, neuroendocrine outflow, and viscera! activities of the autonomic nervous system. We begin with the understanding that many of the connections of th e hypothal amus an d limbic sys tem focus on auto nomic and neu roen docrine outflow. In the last decade, the ro le of the hypothalamu s as a focal point for converging influ en ces from forebrain sources, brain stem so urces,
x
and circulating mediators has become better eluci da ted. This is renected in several new illustrations. The secti on s on limbic forebrain structures (hip pocampal fo rmatio n, amygdaloid nuclei, septum, cingulate cortex) have been redone and exp and ed, reflectin g both the newly discovered complexities of the circui try and the focus o n converging influ en ces, particularly through the hypothalamus and au to nomic o utflow of th e e N S. It is our hope that the three parts of this Arlas Overview of the Nervous Sys tem, Regional Neuroscien ce, and Systemic Neuroscience-will provide students wi th a comfortab le w orking kn owledge of the basic com ponents, o rganization, and functional aspects o f the nervous system and that this fou ndation w ill serve them well for inter pretin g neurological exam inations, understanding most neurologicaJdiseases and di so rders, and evalu atin g and treating patien ts with neurolo gical problems.
CONTENTS P ~ RT
I: OVERVIEW OF THE NERVO US SYSTEM
........... . . ... .. ... ...... .... ... . .. . ...
Section A
Neurons and Their Properties
Section B
Brain . ..... ... .
Section C
Brain Stem and Cerebellum ............... .. . . ....... , . , . . . . . . . . . . . .. • • • . . .. 35
Section 0
Spinal Cord ........ . ........ ... .......... .... . ... .............. . . .• •• .... 37
Section E
M eninges ... ............ ... , . . . . . . .. . . .. • ••....
< ... . .. ....
4
21
. .... . . •.. ..... 42
... .. ...... ... . .. .... .... 43
and the Cerebrospi nal Fluid . ..... .•. . 46
Sectio n G Vascul ature ............. ... ........... .. . ........... ...... . ... .. . . ... .. Section F
Ventricles
Section H
Develo pmenta l Neuro science (DVA) . . . . . . . . . . . . . . . .. . . . . .. . . . . . . . . . . . . . . . . .. 67
P~ RT
II : REGIONAL NEUROSCIE NCE
Section A
Peripheral Nervous System (PNS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . .. 86
Section B
Spinal Cord ..
Section C
Brain Stem and Cerebellum ...... ........ .. ... . ........ ... ...... . ........... 150
Section 0
Diencephalon
Section E
Telencephalon
P~ R T
.. .... . . . . . ......
. ..... ".. . . . . ... " , 141
" , . , ' , . . . . . , •••• . . . . . . . . • • , . . • • • • . . . . . . , ' , ••
,""", . ""
I~
... , .. ..... ..... ....... ...... 179
III : SYSTEMI C NEUROSCIENCE
Section A
Sensory Syste ms ... , , . , , , , , ..... . ' . . , , ' , , , , . .. ' , , , •• . ... . . , , , . .. , , , • . ..... 214
Sectio n 8
Motor SysLems .. .... . .. ....... . . . ....... . ....... . ..... .... . .. ............. 240
Section C
Autono mic1 H ypothalamic, and Limbic Systems ... . , ........... . ,. , " " ' " " , .264
Index
... , , , , , , ... , , , . , , , , , , ...... •• . .. ' , , , , ' , , , , , .. , . , 299
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1£\\ OF THE NERVOUS SYSTEM
EL 0 ," 5 A D THEIR PROPERTIES
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= ........ Ua:. ""'_ L :-:
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E 'euronal Structure -\ pes of Synap ses
' eurona l Cell Types
Glial Cell Types
\\\ elination of e NS and PNS Axo ns Development of Myelination and Axon Enshea thment H igh Magnification Vi e"v of a Ce ntral Myeli n Shea th
OOTRA N5M I5S ION '-3: Svn ap ti c Morphology L9:
Chemical Che mic al Chem ical Chemical Chemical
NeuTOtransmissio n: Amino Ac id Synap ses
Neurotransmissio n: Ca techolamine Synap ses
Neurotransmissio n: Seroto nin Synap ses
Neurotransmissio n: Peptidergic Synapses
Neurotransmissio n: Cho linergic Synapses
~ ICAl
"='_
PROPERTIES
1.10: ~e uronal Restin g Potential
E:.".., U 1: G raded Potentials in Ne urons
F;o"..,_ 112:
_ _ 1-13: c.~_ 1.1 ~:
'-."_ 1.15: fu..,,_ 1.1 6:
-\ct;on Potentials
Propaga tion of the Action Potential Con ductio n Velocity Presynaptic and Postsynaptic Inhibition Spa lial and Te mporal Summation
B R~IN
.---- 1.17: s".." 1.18 : ~= 1.19: &:= 1.20: 1.21 : i' 1.22:
Interi or View of the Base of th e Adu lt Skull Foramina in the Base of th e Adult Skull Surface Anatomy of the Forebrain: Latera l View l atera l View of the Forebrain: Fun ctional Regions l ate ral View of the Forebrain: Brodmann A reas A natomy of the Medial (Midsagi ttal) Surface o f the
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Brain Medial Surface of the Brain: Lobes and Functional
Areas
Medial Surface of the Brain: Brodmann Are(ls
Anatomy of the Basal Surface of the Brain: Wi th th e Brain Stem and
Cerebellum Removed Basa l Surface of the Brain: Fun c ti ona l Areas and Brodm ann A reas Hor izo ntal Brain Sections Showing th e Basal Ganglia Major Limbi c Forebrain Structures Corpu s Ca llosum: Horizontal View Corpus Callosum: Schematic Vi ew of the Lateral Extent o f Major Components Hippocampal Formation and Forn ix Thalamic Anato my Thalamic Nuclei
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re 1.24: 1.25:
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SECTION C. BRAIN STEM AND CEREBELLUM Figure 1.34: Brain Stem Surface Anatomy: Posterol ateral and Anterior Views Figure 1.35: Cerebellar Anatomy: Ex ternal and Internal Features
SECTION D. SPINAL CORD Figure 1.36: Figure 1.37: Figure 1.3 8: Figure 1. 39: Figure 1.40:
Spinal Column: Bony Anatomy
Spinal Cord: Gross Anatomy In Situ
Th e Spinal Cord, Its Men inges, and Spin al Roots
Spinal Cord : Cross-sectional Ana tomy In Situ
Spinal Cord W hite and Gray Matter
SECTION E. MENINGES Fi gure 1.41 : Schematic of the Meninges and Their Relationship to the Brain
SECTION F. VENTRICLES AND THE CEREBROSPINAL SPINAL FLUID Figure 1.42: Ven tricular Anatomy
Fi gure 1.43: Anatomy of the Fourt h Ve ntricle
Figure 1.44: Circulation of (h e Cerebrospin al Fluid
SECTION G. VASCULATURE Fi gure 1.45: Figure 1.46: Figure 1.47: Figure 1.48: Figure 1.49: Figure 1.50: Fi gure 1.51: Figure 1.52: Figure 1.53: Figure 1.54: Figure 1,55: Figure 1.56: Figure 1.57: Figure 1.58: Figure 1.59: Figure 1.60: Figure 1.61: Figure 1.62: Figure 1.63: Figure 1.64: Figure 1.65: Figure 1.66:
M enin geal Arteri es: Relationship to Skull and Dura
Arterial Supply to the Brain and the Meninges
Arte rial Distribution to the Brain: Basal View Arteri al D istri bu ti on to th e Brain: Frontal View and Coronal Section Schema tic of Arteries to the Brain Schematic of the Circle of \'Villis Arterial Distributi on to th e Brain: La te ral and Medial Views Color Illustration of Te rritories of the Cerebral Arteri es Angiographic Anatomy of the Internal Carotid Circulation Angiographic Anatomy of the Vertebrobasilar System Vertebrobasilar Arterial System Vascular Supply to Ihe Hypothalamus and the Pitui ta ry Gland Meninges and Superficial Cerebral Veins Veins: Superficial Cerebral, M eningeal, Diploic, and Emissary Venou s Sinuses Deep Venous Drainage of the Brain Deep Venous Drainage of the Brain: Relationship to Ven tricles Venous Drainage of the Brain Stem and the Cerebellum Arterial Blood Supply to the Spinal Cord: Longitudinal V iew Anterior and Posterior Spinal Arteries and Th eir Distribution Arterial Supply to the Spinal Cord: Cross·Sectional View Venous Drainage of the Spinal Cord
SECTION H. DEVELOPMENTAL NEUROSCIENCE Figure 1.67: Figure 1.68: Figure 1.69: Figure 1. 70:
2
Formation of the Neural Plate, Neu ral Tube, and Neural Crest Neurulation Neural Tube Development and Neural Crest Fo rmati on Neura l Proliferation and Differentiation: Walls of the Neural Tube
.-...we 1.71 :
I~ e ura l Tube and Neural Crest Deri vatives - __:re 1.72: Earl y Brain Development: The 28-Day-Old Embryo 1'e I. 73: Early Brain Development: The 36-Day-Old Embryo 1. 74 : Ea rly Brain Development: The 49-Day-Old and the 3-Mo nth-Old Embryo s e 1. 73: Forebrain Develo pment: 7 Weeks Throu gh 3 M o nths '" 1. 76: The 6-Mo nth and the 9-Month Central Nervous System 1. 77: Development of the Ventricles r: 1. 78: Com parison of SIll-Week and Ad ult Central Nervous System Regio ns ~e 1.79 : Develo pment of M o tor and Prega nglio nic Autonom ic Nuclei in the Brain Stem and the Spinal Co rd """",, 1. 80: Alar and Basal Plate Derivatives in th e Brain Stem "" 01' 1. 81: Developm ent of the Fourth Ventricl e I. 8 2: Develop ment of Peripheral Axons
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figure 1. 71: Figure 1. 72: Figu re 1. 73: Figure 1. 74: Figure 1. 75: Figure 1. 76: Figure 1. 77: Fi gu re 1. 78: fi gure 1. 79:
Neural Tube and Neural Crest Derivatives Early Brain Development: The 28·Day·Old Embryo Early Brain Development: The 36-Day-Old Embryo Ea rly Brain Development: The 49-Day-O ld and the 3-M onthD ld Embryos Forebrain Development: 7 Weeks Throu gh 3 M onths The 6·Monlh and the 9-Month Central Nervous System Development of the Ventricles Comparison of 51f:z-Week and Ad ul t Cen tral Ner vous System Regions Development of Motor and Preganglionic Autonom ic Nuclei in th e Brain Stem and th e Spin al Cord Figure 1. 80: Alar and Basal Plate Derivatives in the Brain Stem Figure 1. 81: Development of the Fo urth Ventricle Fi gure 1. 82: Development of Peripheral Axons
3
OVERVIEW OF THE NERVOUS SYSTEM
Neurons and Their Properties- Structure
Neuronal Structure
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FIGURE 1.1: NEURONAL STRUCTURE _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Neuronal structure reflects the func tional character istics of each neuron. Incoming information arrives at a neuron mainly through axonal terminations
on the eel! body and dendrites. These synapses are iso lated and protected by astrocytic processes. The dendrites usually provide the grea test surface area of the neuron. Some protrusions from dendritic branches (dendritic spines) are sites of speCific axodendritic synapses. Each neuronal type has a characteristic dendritic bran ching pattern (dendritic tree, or arborization s). The neuronal cel! body varies from a few micrometers to more than 100 )..lm in diameter. The neuro nal cy toplasm con tains extensive rough endoplasmic reticulum (rough ER), which reflec ts the massive amount of protein synthesis necessary to m aintain the neuron and its processes. The Golgi apparatus is involved in packaging potential signal molecules for trans port and release. Large numbers o f mitochondria are needed to meet the huge energy demands of neurons, particula rly to maintain ion pumps and membrane potentials. Each neuron has a si ngle (or occasionally no) axon . Th e cel! body tapers to the
4
axo n at the axon hillock, and the ini tial segm ent of the axon containing the Na channels is the first site where axon potentials are initiated. The axon ex tends for a variable (up to 1 m or more) distance from the cel! body. Axons larger than 1 to 2 ).1m in diameter are insulated by myelin sheaths provided by oli godendroglia in th e eNS or by Schwann cells in th e PNS. A n axon may branch into more th an 500,000 axon terminals and may terminate in a highly locali zed and circumscribed zone (e. g., somatosensory projections for fine discriminative touch), o r it m ay distribute to many disparate brain regions (e.g., noradrenergic axonal projection s of the locus coeruleus). Axons o f macroneurons (Golgi type! neurons) term inate at a disfa nce from the cel! body and dendritic tree. Axons o f micro neurons (Go lgi type !l neuro ns, local ci rcuit neurons, or ;nterneurons) terminate loca lly, close to the cell body and dendritic tree. Because each neuron type has its own speci alization, there is no "typical" neuro n, although pyramidal cells or lower motor neurons often are used to portray the "typica l" neuron. L
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OVERVIEW OF THE NERVOUS SYSTEM
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~ plus
-"'~"..,.
axode ndritic synapse
t
~~ :'>--... ,~ ~. "
c'
"
, go' ; '
.
/
::>':.~
t •
,
0,
" .
I, ,
I. Serial syna pse
• - t itie synapse
... L
u
~J~
Dendro de ndri tic;
'Y"'P" K. Inner plexiform la ye r of retin a i~ '
~
,,~.
r.')l. ~ .
~'a~gli'o n , '"
}~i~~cell ' t'in%%j')r) \
j
,.g9'
"
,._., " ,'/o'"::<:'P ; '
::~,uceU ----,71~· ",;/~
!
rj '
\
I
.
I
. .,f f'-~ . -+......,,..<.....,~
M uller cell - {supprn-tingl
j
!
(
M o SSy cell axon
+_-+____VC""
Amauioe cell processes \.
2: TYP ES O F SYNAPSES _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ --e
site wh ere an arrivin g action pote n ::h e\citC'l li o n-secreti o n co upli ng invo lving "5 J.
rlis ge rs th e release of one o r more "'li tters into th e synaptic cl eft (typi cally "'"l-:; neu ro transmitter acts o n receptors on
neuro nal mem brane, altering th e mem rial irom it s restin g state. These post _ "en tia ls are ca ll ed "graded" potenti als. ~€ S ca rrying informatio n to w ard a
target neuron termin ate as axodendriti c or axosomati c synapses. Specialized syn apses, such as reciprocal synap ses, or complex arrays of synaptic interac ti ons provide specifi c regulatory control over th e excitabili ty of th eir target neurons. Dendrod endriti c syn ap ses aid in th e coo rdin ated firing of gro ups of related neuro ns (sLlch as phreni c nucl eus neuron s causin g co ntracti on of th e diaphragm),
5
OVERVIEW OF THE NERVOUS SYSTEM
Neurons a nd Their Properties- Structure
~
MulIJpol.,. (pyr~ mjclal) ceU 01 ce.",h,,,l
.
_
Bipolar ctll ofO.Jnial n. VIII
~Unipola. 'ello( ~SOt'( c;r ~",.1
Associatio n..!' commissural and
g.lIlglia of
n n, v, VII, I X Of X
thollamlC el'ldlrlg~
,I inllied fibers
(J~f' ee ne....e endings {unmytlina.<."tl fihe.'1
SpeQiI~ ltrll!l'ldin&
u,,'poLa. sen!oOry cel of
of u anl,ll nn
dossel spinill tOol ~ndiun
HI, IV, V, Vl VII,
IX, X. XI
Of
XII ----.l
Multipolar 1:('11 of lowe. b ra in
,''')ioafed .,rferent
moIor cenTers
1\)I..tu~ipotdrYiKe •.JJ
-
/
moro.- (autnn<)m!(;)
cd! of ,pinal cord
,/
"!.'tV",
Rl!d : Motnr neuron
Blu e: Sensory neumn Purpl e: Inlerneuron Cr;ay: Glia l and
robe<
n... urilen,"l~t ce ll s ;lnd my~lin
NOle : Ce!cbcll it' cell s no t Ii"
",evl
shoWrl here
";:"""' $.a tp.Ii.p. nl~ RP.n~aw inlempuron
,lin,""
leedbadl ·Ii,
tie mur....
)(SchwafV1 ce lls
~ Myell n shealh
M}'('r.n $l>eath~ MOtor
a.d'K mlJSCle Srri aK'
<w-oodJlcelk
,~Free ne!'>'e e"di oss
~ En(~psu l atE'd end ln ~ .......... Musck,: spindle
~~f!% · ','l.!.N
FIGURE 1.3: NEURONA L CEll TYPES _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ l ocal interneurons and projection neuro ns demon strate characteristic size, dendritic arbo rizatio ns, and axonal projections. In the eNS, glial cells (astrocytes, microglia, oligodendroglia) provide suppo rt, protection, and maintenance of neurons. Schwa nn cell s and satellite cells provide these func tions in the PNS. TIle primary sensory neurOns (blue) provide sensory transduction of in co ming
6
energy or stimuli into electrical signals that are conveyed into the eNS. The neuronal o utflow from the e NS is motor (red) to skeletal muscle fibers via neuromuscular junctions, o r autonomic preganglionic (red) to autonomic ganglia, w hose neurons inn ervate cardi ac mu scle, smooth mu scle, secretory gland s, metaboli c cells, or cell s of the immu ne system.
The ir Properties Structure
OVERVIEW OF THE NERVOUS SYSTEM
.-
J. Perki'ns M S. MFA
C: DN "....'"
~.
G LIAL CE LL TYPES _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
- - ,...- ~id e structural isolatio n of neurons _ -'-.a:pses. and they provide ioni c (K' ) ~=:a>a' trophic support. and suppo rt for __-','-'" ~ ;;naling functions to neurons. c.~ :ro-~ provide myelination o faxons in «roglia are scavenger cells that partici ~ X\ tosis. infla mmatory responses, - ~ JD: ¥J0 \\ th fac to r secretio n, and some
.....
immune reactivity in the e NS. Pe rivascular cells participate in similar activiti es at sites near the blo od vessels. Schwann ce ll s provide mye lination, ensheathment, tro ph ic suppo rt, and actions for grow th and repair for peripheral neurons. Activated T lymphocytes can enter and traverse the eNS for immune surveillance for a period of approximately 24 hours.
7
OVERVIEW OF THE NERVO US S) STEM
'\e urons and Their Pro pert:irs:-St ru ct ure
CENTRAL NERVOUS SYSTEM
PERIPH ERA L .' ERVO U S SYSTEM
Sensory neuro n
cell body
Pia m,lter
Oligo dendro cyte
~
SchWimn cells associate d w ith myelin sheaths 01 myelinated axons
f--- - - - ·t-I
Bouto ns of associati o n neuro ns synapsi ng
with preganglionic aulonomie neuron o f CwainSlem o r spinal cord
Schwa nn cells assoct
.'i;"' " "
,,;
Postgan glionic ne uro n of sympathetic or parasympathetic s.::a n~li o n
"
/•.
<~~~;.'....~~-.....S~~i"·.",._I ; ._~~
aSS()~i~~:Onn~;~rons "<': " ~b7 -,;:,c ';';'4iiP S~'napsin !\ with somatic moto r neuron s of brai n
or spinal cord
M5.MfA
~ ,.~
Axon s terminatin g o n mo tor {,Ilel p lal es o f striated (voluntary) m uscle
FIGURE 1.5: MYELI NATION OF eNS AND PNS AXO NS _ _ _ _ _ _ _ _ _ _ _ _ __
Cent ral myelinatio n of axons is provided by o li go dendroglia. Each oligodendroglia I cell myelinates a Sin gle segment of several se parate central axons. In th e PNS, se nsory, motor, and preganglionic- auto no mic axons are myelinated by Schwa nn cells. A Schwa nn cell myelinates only a single segment of one axon. Unmyelinated sensory and auto nomi c postganglioni c axon s are ensh eathed by a
8
Schwann cell, which provides a singl e enwrapping arm of cytoplasm around each of several such axons. The space betw een adjacent myelin segments (a node of Ranvier), the site w here the axon membrane contains sodium chann els, and allow s the reinitiati o n of action potential s in th e co urse of propagation, a process called saltatory conductio n.
-
Neurons and Their Properties-Stru cture
OVERVIEW OF THE NERVOUS SYSTEM
A. Unmyelinaled 'axons>' of peripher"t neufon,s
::i
or viscp.rai motor,)
""~
(sensory, somatic motor t beins surroutidec:/ by
:"
cytoplasm 01a neurilemmal (Schwarm) . cell ~'.
B. Myelinated 011(00.01 peripheral neuron
(sensory, somatic.motor of Ihetic
0 1 vi5c.ernl motor)
being surrounded by a wrapplng'oi cell memb~eoia
neiJ(ileml)'lal (~wann)
",Jl
c. Mye linated .uon
"1
of eNS neu rons being SUfm~lIldcO by il wrapping of cell
membrane of an oliKodendlOcyte.
;
1 -1 1:
:~
r
Unmyelinated axans
)
of e NS neurons ale leit unprotected.
,
'il
Axon O ligodendrocyte
FIGURE 1.6: DEVELOPME NT OF MYEliNATION AND AXON ENSHEATHMENT _ _ _ __ _ ng
\r\yelination is a cooperative interaction between the neuro n and its myelinating support cell. Unmyelinated peri pheral axons are invested with a 5ingle la yer of Schwann cell cytoplasm. When a peripheral axon of at least 1 ~m in diameter trig gers myelination, a Schwan n ce ll wraps many
layers o f ti ghtl y packed cell membrane around a single segment of that axon. The oligodendroglia I cell ex tends several arms of cytoplasm, whi ch then wrap multiple layers of tightly packed membrane around a single segment of each of several axons.
9
OVERVIEW OF THE NERVOUS SYSTEM
Neurons and Their Properties-Structure
Cell body oi an
"
(neurilemmal <:ells plJ)' similar role
10 periphera l nervous system )
Cell m embrane of myelina ted axon '\
Mitochondrion in cytoplasm of
neuronal .. xot~
..;/#d.*';....y"";,.1':'?#.~.
layers o f cell membrane of o ligodendro cyte
Minute ma ~se s of cytoplas m trapped between fu;ed laye rs of cell membrane of oligodendrocyte _ __
w ra pped JfOUnd ,)XOfl of a myelina ted neuron of central nervous system (the lipid of lipoprotein
coostituting fused ceU membrane is mye lin, w hich gives mye linated axon a w hi te. glistening appearance)
~~~ ° 119N :
........ : :
FIGURE 1.7: HIGH MAGNIFICATION VIEW OF A CENTRAL MYELIN SHEATH _ __ _ _ _ _ Fused layers of oli godendroglial cell membrane w rap aro und a segment of a central axon, prevent ing ioni c flow across the cell membrane for the entire myelinated segment. The node between 2 adjacent segments is bare axo n membrane,
10
which contain s Na'" chann els. These nodes are sites where acti on potentials are reinitiated in th e con duction of propagated action potentials. Illustration after Bunge, Bunge, and Riis.
-
IctUrl:
-
Their Properties-Neurotransmission
OVERVIEW OF THE NERVOUS SYSTEM
Sc hematic vf ~yn il p l ic rndi ngt
Dend rite'S Num ero us bo ul o ns (Srnaplic km)b sl 01 presynaptic ne ur () n ~ l~rm in ,'lin g nn 01 mOtOf nellion arid i'~ riendri te'S
fnlil rgl!d ~rdion vf bo ulo n
Axok!mma
---+--i
G lial p'~"", 1
,
'
sYlklpticckh P,eiynaptic nlembrane ( den~ly
""ii,,,,," j __
Post$y n ~p ( ic
....
;.
membrane
( clC
.
..
---..:--.... .. -
~~"
. . f/f"-::,, . .C"·:'; ' F"';;:;'-';:> .
;~'
....
"'.
,
- ' --~ -. -
. '
.. . .
,.,
.
~~
=ICU RE 1.8: SYNAPTIC MORPHOLOGY _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ __
es
.. - ,apses are sites where neuro ns co mmuni ca te -h each o ther and w ith effector or target cells. - "e upper figure show s a typical neuron that ""E'C eives many synaptic contacts on its cell body Mld associated dendrites. Incoming axons lose -reir myelin sheaths, exhibit extensive branching. .a:1d terminate as synapti c bouto ns (terminals) o n i"le targe t (in this example, motor) neuron. The lower fi gure show s an enl arged axosomati c :errn in al. Chemi cal neuro transmitters are packaged . '1 synap tic vesicles. W hen an actio n po tential 'nvades the term inal regio n, depolarizatio n triggers
Ca 2• infi ux, and many synap tic ves icle s fuse with th e presynap tic membrane, releasin g packets of neurotransmitte r into the synaptic deft. Th e neuro transmitter binds to recepto rs o n the postsynaptic membrane, w hich result s in graded excit(ltory or inhibitory postsynaptic po tentials, or in neuro modulalory effects on intracellular signalin g systems, in th e targe t cell. Some nerve te rmi nals possess presynapti c receptors for their released neurotransmitter. Acti va ti on of these recepto rs regul ates neurotransmitter release.
11
OVERVIEW OF THE NERVOUS SYSTEM Amino acid
Neurons and Their Properties-Neurotransmission
Catecholamine synapse
s\'napsl'
gg
:1 }JTryplophan ', .
receptor
l
f
;t
//
02. .~
II i -\\
JrrH \",\ )j:..
/1
Pfesyna,Ytic
Gl ut,1 ma !e °0 00
o·
\~
Serotonin synapse
,,>".- ,
'I
f 5-0H tryptophan\\;)-(
i
ALAAD 5-OH.trypt amlne ,,_ (ser?tonin)
(~
~ __ Metabolism
' .
~'
'lS"!..-
~
r -.,\
' I' L~ "·~l) !
Peptide synthesized in cell body
\<\
_,:I)
~
\\ \~
M
JPf'
f.;) l
d,)., l' '. . . ~ r . ~r
Peptide synapse
~~,
..
I . ,i
" 'if~_'-- "_j~" A'
'-', H';~ffi~~ _
..I uptake carrier
~
Acetylcholine
synapse
j .-
_ 0_ ~.)
FI GU RE 1.9: CHEMICAL NEUROTRANSM ISSION: AMINO ACID SYNAPSES _ _ _ _ _ __
Amino acids are compartmentalized in synaptic \ esi cles (or release as neurotransmitters. The amino acid glu tamate (depicted in the diagram) is th e most abu ndan t excitato ry neurotransmitter in the ( 01 S. Following rel ease from the synaptic vesicle,
12
some glutamate binds to postsynaptic receptors. Released glutamate is inac tivated by uptake into both th e pre- and th e postsynaptic neurons, where the amino acid is inco rpora ted into the Krebs cycle or reutilized for a variety of fun c tions.
"T""-er
Properties-Neurotransmission
, f 5) _~""'-;
'A PSES _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
C\s are synthesized from th e
..c'" rosine, taken up competitively -'C." ,
a carrier system. Tyrosine is syn b\ h rosine hydroxylase (TH ), a
r'\3.
.--etic enzyme. Additional conver 0 '\1occurs in th e cytoplasm via acid decarboxylase (Al AAD). ~ n.aptic vesicles for subsequent ~,"".....",rgic nerve termin als, dop a se (DB H) furth er hydroxylates .--;....~.;·""e in the synapti c vesicles. In "€ -erminals, norepinephrine is :-IE'
~
'~
OVERVIEW OF THE NERVOUS SYSTEM
PSES
methylated to epinephri ne by phenylethanolamine N-methyl transferase (PNMT). Fo llow ing release, the CA neurotransmitter binds to appropriate receptors (OA, alpha and beta adren ergic recep tors) on the postsynapti C membrane, al te rin g postsynapti c excitability and/or second messe n gers. CAs also can activa te presynaptic receptors, mod ulating the excitabili ty of the presynaptic terminal. CAs are inactiva ted m ainly by presynaptic reuptake (hi gh affinity uptake carrier) and by metaboli sm (MAO deamin atio n and CO M T methylation) and diffusio n.
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
?Sized from the dietary amino ~"en up competitively into the -.:"I'" ~ stem. Tryptophan is synthesized !nJ(> an by tryptophan hydroxylase -g svntheti c enzym e. Conversion ;.:;:o...,.-ophan to 5-hydroxytryptamine 0'. the decarboxylase A LAA D "'Dplasm. Sero lonin is stored in =olJow in g release, it can bind to
receptors on the postsynapti c membran e, alterin g postsynaptic excitability and/ or second messenger activation. Seroto nin can act o n presynaptic receptors (5-HT receptors), modulating exc it· ability of th e presynaptic termin al. Serotonin is inactivated mainly by presynapti c reuptake (hi gh affini ty uptake ca rrier) and also by meta bolism and diffusion.
..=""-..
~
'APSES
_______________________________________________
- ae :ivnthesized from prohormones, : S' n :,esi zed in the cell body fro m an -~_
rne larger precursor peptide is
~ ti ona ll y to active neuropeptides,
§ed in synaptic vesicles and trans ::radeh by the process of axoplasm;c \ esicles are stored in the nerve re eased by app ropriate excitati o n "'"' '5 induced by an action potential. =,""",Ie bi nds to receptors on the
-C
S)
~APSES
postsynaptic membrane. In the CN S, there is o ften an anato mical m ismatch betwee n th e localizalio n of peptidergi c nerve terminals and the locali za tion of cells possessing membrane receptors respo nsive to that neuro peptide, suggesting tha t the amount of release and the extent of diffusion are impo rtant factors in neuropeptide neurotrans mi ssion. Released neuropeptid es (I re inactivated by peptidases.
_______________________________________________
"-Ch I is synth es ized from dietary (oA, deri ved from the me tabo .a the enzyme choline acetyl ';T. '\Ch is stored in synaptic g ~ele ase{ it binds to cholinergic
recep tors (nicotini c or muscarini c) o n the post synaptic membrane. influencing the excitability of Ihe postsynaptic cell. Enzymatic hydrolysis (cleavage) by acetylcholine esterase (AChE) rapidly inactivates ACh.
13
OVERVIEW OF THE NERVOUS SYSTEM
F.x(racellular Ilui d +
Neurons and Their Properties-Electrical Properties
11111 11 11-1
Axoplasm
N.l-+
if"'''
'-:/
m+
-- ~
~~
;",,'C
a
(1
(Na t "" . - !
Res';!Jr>Cc '" t50 mY
,I I
~~~ " ICoN
'~ '.-.-.: ::
I Equivalem
I_
;- EO'';~ ~ vvv l L·~-~'~'~m~vjl--I
\.
.AAA;.
'I
""",I
di.oll''''''
RM'
-?On .\.'
FIGURE 1.10: NEURONAL RESTING POTENTlAl _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Cations (+) alld anions (- ) are distributed unevenly
ac ross th e neurona l cell me mbrane because the membrane is differentially permeable to these io ns. The membrane's permeab ili ty to ions chan ges with depolari za tion (toward 0) or hyperpo larizati on (away from 0 ). Ion distri bution depends o n the forces of charge separation and diffusion. TI)e lypical neuro nal res ting pote ntial is approxim ately - 90 mV w ith respect to the extracellular fluid. The extracellular concentrat io ns of Na+ and CI- of 145 and 105 mEq/L are hi gh compared to th e
14
intracellular conce ntration s of 15 and 8 m Eq/L. The extrace llular concentration of K+ of 3.5 mEq/ L is low compared to the intracellular concentration of 130 mEq/L. The resting potential of neurons is dose to th e equilibrium potential for K+(as if the membrane were permeable o nly Lo K+)_Na+is actively pumped out of the cell, in exchange for inward pump ing of K+, by th e Na+-K+·ATPase mem brane pump. Equivalem circuit diagrams for K+and for CI-, ca lculated usin g th e Nernst equation, are illu strated above.
~rties
OVERVIEW OF THE NERVOUS SYSTEM
. u rons and Their Properties- Electrical Properties
--
Chemical Synaptic Transmission
_ ..." - - ---1
~~----
@
Q
._.
"
©
'"....... - - - " ®
inS)""";':
'""~ ,,.,,...,. ........
@
®
®
~~----
~
wr.... """"~ .~..a"" =""I~'Y ".""PI"
"'1 in/libiloo S)'~_. ~"""";"rf wbsl3nce
boUlon . .. ( i uS
'<"Ieas<'(! br i n Itn~ Inc'~._ ptome
,....,. ~ nd I('>
~«l.
~ ...... N.~
~"C(..II"" " "
obhW 01 ".,...<).....11'''' m ..ml...ne to '"
IOdcr bu, ~ 10.'1.-. "· ~Dutof
",,,,... in l0pos~
""".... ou•• d~1O
....~,#,~~C~
p........l
R.....c~.
R~~'" .,," ionic OJn...,' iIow ... in .. d l'Kllon ..~ Iit.h ~~ 10 dtopoIari>r po". lyn3Q\io.· ~I II depc>1aru • ...., .~
""''' (utrl'lll. .0..... in dire<1ioon
mom
nfll(f> to ~ cb'i.I~ pm"_pl i~ cell. Th.. n',,/'"'' dfIxIbnUlion bo, . .. ~ noOo. oJ;i&o.ull..........~ dtvubnz;olion
fi"", .t"e
ynapOC cdL
_'''''''v
""O'ic,h .... ~1II>o1d
.,
,,!
> <
-"
"
•
-•
"
"
FIGU RE 1.11 : GRADED POTENT IALS IN NEURONS _ __ _ _ _ _ _ _ _ _ _ _ __ )f
Excitato ry and inhibitory neurotransmission are processes by w hich released neuro transmitter, act in g on postsynaptic membrane receptors, elicits a loca l or regional perturbatio n in the membrane potentia l: (1) toward 0 (d epo lari za tio n, excitatory pos tsy nap lic potential [EPSP J) via an inward flow of Na+ caused by increased permeabi lity of the mem brane to positive ions or (2) away from 0 (hyper polarization. inhibitory postsynaptic potential
(l PSPI) via an inward flow of CI- and a compen sato ry outward flow of K+ caused by increased membrane permea bility to CI-. The resu lt ant EPSPs and IPSPs exert loca l influences that diss ipate over time and d istance but contribute to th e ove rall exci tability and ion distribution in the neuron. If sufficient excitatory innuences bring about depolar iza tion o f the initial segment of the axon above threshold, an action potential is fired .
15
OVERVIEW OF THE NERVOUS SYSTEM
Neurons and Their Properties-Electrical Properties
+ 20
. ;;
Action po tential
0
1&
\
Na + co nductan ce
\
~
" '"
I ms::....J ~
E o
- 70
K- co nduc tance
I" . . . . . . .~ =:s=
( .L ..........
0~5
-l
_ _ _ _A ,..
"
,.
1.0 ,
A,_ _ _
Membrane
..... ,.
=1:
"1:
Na+'
I
Stimu lus current prod uces depolari zation
Na+ · ~ . K' ~I_
K'
+
a - ==::::;: a
-1+ +
~
"
~~:\""" ~f~i'"" ·'m
NiI+~
K+
"-
A
(1
+ 20
At firin g level Na+ conduc· tance g reatly iocrea56, givin g rise to sllong iowa rd Na + current,. leads 10 exp losive positive feedba ck w ith depolarizatio n increasing Na-+ conductance
CI~
+1- - 15 '
.J
+
~
~
K+ conductance increases, causing lepolari zatio n; Na" cond uctance le turn~ to no rm al
""--,, + +
~!p
°lION
-
;
•..: •.•.: .
+..J , Equivalent circuit diilglarru.
FI GURE 1.12: ACTION POTENTIALS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Action potentials (A Ps) are all·or-none, nondecre mental, electrical potential s that all ow an el ectrical signal to travel lon g distan ces (a meter or more) and trigger neurotransmitter release through electroch emical coupling (excitation-secreti on co upling). APs are usually initiated at the initi al segment o f axons w hen temporal and spatial sum matio n o f EPSPs cause suffi cient excitation (depo larization) to open N a-+ channels, all owing the
16
membrane to reach threshold. Thresho ld is the pOint at which N a+ infiux through these Na+ chan nels cann ot be countered by efflux of K-+. W hen threshold is reached, an AP is fired . As the axon rapidly depo/arizes during the risin g phase of the AP, the axo nal mem bran e increases its K+ cond uc tance, w hich then allows inAux of K+- to counter the rapid depolarizatio n and bring the membran e potential back towa rd its res ting leve l.
erties
-
Ne urons a nd The ir Prope rti es- Electri ca l Properties
OVERVIEW O F THE N ERVOU S SYSTEM
Ex llacelluill' poten tial .. 1 mY
Inh .Kellul.n polen]ial -(>0 mY
Axop lns m
Ex tracellular
Intracellular potentia l +20 mY
po tentiil l - ~
mY
2
InlrM:ellul31 potffili.:!I -7S mV
Intrac e llular
pOlenlial (mY )
Resti ng polen!ial
-70 f---~;-t-'===--~--==
.,I
t
J, ~ tf. c I~ po ten!ial (mVI_5 1 _ _ _ _=~===~------ : ~. -.;::
Exlrace llular
0
----,\1') I
' - 1,OrnsoPc - '
,e
FIGU RE 1.13: PROPAGATION OF THE ACTION POTENTIAL _ _ _ _ _ _ _ _ _ _ _ __ W hen an AP is initi ated at a specific site o n the axona l membra ne (usually th e initial segm ent), the inward flow o f Na-l- alt ers the extracellular ion environment, causing a local flow of charge from adjacent regio ns of the axon. This induces a depo larized state in th e adjace nt node of Ra nvier or patch of axo nal membrane, bringing th at regio n to
thresho ld and resu lting in the reinitiation of th e AP. The presence of myelination alo ng axo nal seg ments resu lts in the reinitiatio n of the AP at the nex t node, thus hastening the velocity of conduc tio n of the AP. The resultant appearance of the AP skipping from node to node dow n the axo n is call ed sa ltatory cond ucti on.
17
OVERVIEW OF THE NERVOUS SYSTEM
A. Myelinated fibers
+ ;./:.J.}
L
, ..
Neurons and Their Properties-Electri ca l Properties
.. -
Site where ac tion potential is reinitiated
/
+
Node
B. Unmyelinated fibers
/l
C. Classification of nerve fibers by si;re and conduction velocity
12°i 1 10
1
100
~
M yejin.lledfibers/4 '
~ Alpha motor neurons to extlaiusal stria ted (somatic ) m usc le fibe rs (malOf end plates)
90
80
Gamma mOtor neurons to intrafusal l"ibers o f spindles
\
in striated muscle
~~ ° IIliN 1\'::.'::
Group I (Ao: fib ers) Ja fro m primary muscle
spindle endings: p roprioceptio n; Ib fro m Goigi tendon o rgans: p roprioception
70
Co nduction velocity 60 (meterslsec) 50
G roup 11 (AP libers) flOm secondary endings of muscle spindles: proprioception; from specialized
U,'U'PIOIS in skin and dee p ti ssues: touch, pressure
40
30
20 10
Group III (AS iibeTs) irom iree a nd from some sp ecialiled endings in mus<:le and joints: pain; irom ski n: sharp pain, hea l, cold, a nd some touch and press ure; a lso man y viscera l afferents
IP'" /" Unm yelinated jibers
? - G roup IV (C fibers) 'rom skin
FIGURE 1.14: CONDUCTION VE LOCITY _ _ _ _ __ _ __ __ _ _ _ _ _ _ __ The AP travels down the axo n by dep olarizing adjacent patches of membrane (panel B), leading to the AP's reinitiati on. The speed of pro pa gation increases with larger axonal diameter an d in the
18
presence of a myelin sheath (pa nel C). In myeli· nated axons, the AP is propagated from node to node, a process called saltatory conduction (panel A).
erties
-
' eurons and Their Properties-Electrical Properties
OVERVIEW OF THE NERVOUS SYSTEM
Presynaptic Inhi bi~~~~:;;::"i~::= tion ;Po ~~st~synaP ~ ~: lic Inhibition =="-~
•
(lnhibilo'1' libef\
,
(ueil,llory iibei' )
MOlor neuron
Axon
""~ mV oW
A. Only E fi rH
-,,,
in E t~r m;n,,1
~}ft!%
" "lION .....: : :
,,
9O mV ~ike
mV
~90mV
- 70 EPSP in mOlar nl"Oron
(lrohobirOf y iih~r)
,,, ,,
A', O nly E fi res
r------- ~~j ~
-{.o j
EPSPin mOlo. neuron
-6()
-70
~
-7U B. O nl y I frre~ l l'lng.l,lS ting parlial d~pol':l.fi l;.ltion
in E rerminal
NO response in moror neuron
C. t firC1 before E P.arlial rkpolariwion of E rermin.J1 reduO!~ spike to ao mV, thus relea$ing less tl an5mitter $u!)!ilO1nce Smaller ( PSP in motor mwroo
8'. O nl y I fires MOIor np.ur()fl hvper poLlri~ed
- 70 J
.20
-70
~
- 80 .,
,, ,
, ,,~80mV ,
,
C. l ll rHbefo(~E
OepoLlIil.llion -<0
-70
of molor
-(,()
neuron reM>
-70
lI~ni" only f fir M
-B
-70 J ~
-v----
FIGURE 1.1 5: PRESYNAPTI C AND POSTSYNAPTIC INHIBITION
Inhibitory syna pses modulate neuronal excitability. Presynaptic inhibitio n (left) and postsynaptic inhibition (right) are shown in rela tion to a moto r neuro n. Postsynaptic inhibitio n causes local hyper po lari za tion at the pos tsynap tic site. Presynaptic
inhib itio n invo lves th e depolari zati on o f an exci tato ry axon terminal, w hich decreases the amount of Ca++ influx thaI occu rs w ith depo lari za tio n of that excitato ry terminal, thus reducing the
resuhant EPSP. 19
OVERVIEW OF THE NERVOUS SYSTEM
:::~~: ~L)t ~'---.J
-;.,J
(;0
,, ~~,
Excitatory fi bers
'-::::::::======
==~ l: hibiiOry fibers -
Neurons and Their Properties-Electrical Properties
A,oo
-
Inhib itory hi
A. Rest ing state: mOlor n erve cell sh own w ith syna ptic b o ut nns of
B. Partial depolariza tion: im pulse from one excita tory fib er has
exci tato ry an d in hibito ry nerve fibl? rs ending cl ose to il
caused partial (below firing thr esho ld) de polar izatio n o r motor ne uro n
Exci tatory fib ers
'"
'-...........~ \ '-
Exci ta tory (ib er5
'"
,,"<:':0,
tnh ibito ry 11
Inhi bitory fi
C. Temporal exd t..tory summa ti o n: a series o f impulses in o ne
D. Spatial e~ci tatory summation: impuls5 in two excita rory fiber!>
excita tory fiber to gether produce a supra thresho ld depolariZdlion
cause
that triggers an action potential
threshold tri ggerin g an actio n po ten tial
Excitatory fibers
l
:so: -:""'(\
tlVO
synap tic depolari zatiol1s th at together re ach firing
Excita to ry iibe rs
-
Inh ibitory fi
Inhibi tory fibe rs
E. Spatial excitatory summation with inhi bition: impulses fro m
E. (con tinu ed): motor neuron now receives addition;!1 excitato ry impulses a nd reaches firi ng threshold d espite a simultaneous inhibito r)' impulse; add itio nal inh ib itory impu lse", might still prevent firing
two exCitatory fibers reach molor neuron but impulses from inhibitory fiber prevent depolarization from reaching threshold • Axon{s) activaled in each sce nari o
,p ,f$
tT· I~~oN
:,.".,.::~
FIGURE 1.16: SPATIAL AND TEMPORAL SUMMATION _ _ _ _ _ _ _ _ _ _ _ _ __ Neuron s rece ive-multiple excitato ry and inhibitory inputs. Temporal summation occurs w hen a series o f sub thresho ld EPSPs in one exc itatory fiber pro duces an AP in the postsynaptic cell (pan el C) . This occurs because th e EPSPs are superimposed on each oth er te mpora lly before the local regio n of membrane has completely returned to its resting stale. Spatial summatio n o ccurs w hen subthreshold
20
EPSPs fro m 2 or more synapses trigger an AP because of synergistic interactio ns (panel D). Both temporal and spatial sum matio n can be mod ulated by simultaneo us inhibitory inpu t (panel E). Inh ibitory and excitato ry neuron s use a wide variety of neuro transm itters, w hose actio ns depend o n the ion channels o pened by the ligand-recepto r inte raction.
·perties
OVERVIEW OF THE NERVOUS SYSTEM
Brain
,
Sphenoid bone r has
>-
,
Anterior cranial fossa
:
Middle
Ilor
)
-/
Sella
~ craniill
turcICa
I
fossil
Groove for int. G1rotid
• Jlbers
)
-
I Posterior !>cranial
,
Suklls for , I
Occipital bOne BaSilar
.
Suki for post
v
iN ,..;:
Internal Internal
i
Sulcus of sup.
FIGURE 1.17: INTERIOR VIEW OF THE BASE OF THE ADULT SKULL _ _ _ _ _ _ _ _ __
)d· I. ~n d
The anterior, middle, and posterior cranial fossae house the anterior frontal lobe, the tempo ral lobe, and the cerebellum and brain stem, respectively. The fossae are separated from each o ther by bony structu res and dural membranes. Swelling or mass lesions can selectively exe rt pressure within the
individual fossae. The perforated cribriform plate allows the o lfactory nerves to penetrate into the o lfacto ry bulb, a site w here head tra uma can result in the tea ring of the penetra ting o lfactory nerve fibers.
:or 21
OVERVIEW OF THE NERVOUS SYSTEM
Brain
f Olamen ceo:um - - - - - - - - - - Ve in 10 sup. '-
a.., If. and n.
/ " Forami nil of - - - - - - - - - - - - 0liac(ory f'lefYIi' bun dles c ribriform plate I. e lhmoidal forame n - - - - - Po,!. e thm oirl ol a
Optio:. ca n.al- - - - - - - - - - { ./
, v. and n.
Optlclill n. Ophlha lmk a. Oculomolo l (11 11 n. ThlOchl(!'a r CIVI n .
......... SU..,. orbilai i'sswe- _ _ _ _ _ _
Ophthalmic n. {
Abducen s (VII n. Sup. ophth a lmi c \"
__ fo/;)rnen 'Olundum - - - - - - - - Maxillary n.
Mandib ul,ll n. . .uessory meningeal a .
•• ............ f Otamen ova.., - - - - - - - - -
lesser pelroSdI n .
{ , .
{
!0,..----Foramen $pinosom· - - - - - -
of mandibul ar n.
';~;=~~~~'1··f" ~'··~.t~. FOtam e n 01 Vesalius -
."'&;: , (inconsla nli '',_"(.,>,~
.. :~..~".;~'' fOX')meI'l lace
Middle menin!!eal a. at'ld v.
Meningeal branch
-n*-\
of
(occasiooal1yl
. -:i -
- - - - - - Sm all e m is.,.. ,y v.
__ __ __ _{
1m. Cdrolid .1.
1m. carotid n. plexu s
~Hiatus of canal oi - - - - - - - - - les,er petrosal n. ~ . .,.?'t~~~~ _~,
Hia tus of ca nal of - - - - - - - - - G re~ler petrusa l n.
it::"'"~ ....
{ . acous tic mealUS - - - - - -
Facial (V IJ ) n. Vesl ibulocochlear (VIII) n.
labyrinthine a. - - Vestibula, aqueduct - - - - - - - - Endolymphatic duc t M as toid for,lmen ____ __ _ { (incon stant)
EmiS>J ry~. " Bra nch of OCCIpi tal a. Ini. pelroS
" Jugular fo ramen _ _ _ _ _ _ _ _
(X) n.
AcCe5SQfY (XI) n.
{
SIgmoid sinus
I'OSl. meningeal .l. "
CondylJ( Col nJ I· - - - - - - - -
{
linconstant) '\ Hypoglor.5al <:
Emi ss ary v. Menin geal branch o f asc end ing p/1ar yngeal i1.
Hypoglo~1 (XII) n. Medulla oblo ngala:
" Foram en ma!!nvnl - - - - -
{
Meo in ges Vertebra l aa. Sflina l roots of a(Te>$ory nn .
~~p " 11liN .. : ::,': \
FIGURE 1.18: FORAMINA IN THE BASE OF THE ADULT SKULL _ _ _ _ _ _ _ _ _ __ This illustration of the foramina in the ba se of the skull lists the major nerves and blood vesse ls that course through each opening. Press ure,
22
traction, or masses can damage structures travers
ing in these tightly co nfined spaces.
I
-
ers-
OVERVIEW OF THE NERVOUS SYSTEM
---------------------------------------------
Brain Brain
i I margin of cerebrum
Frontal (Fl . irontop;llletal (FPJ and temporJI (T) opercula
'e<,.p." "·",,.'lsu lcus In ferior
Supe rior irOOlal gyr u~
p~rietJI
lobu le
, I Middle frontal S~ U \
- _ _ _~;.~~
Inferior frontal sulcu~
_ __
Inferior
fro ntal gyru ~
Lateral
(syivi,m ) lisw re
{
Anle< IO<
. . , ~III ,IS "'m,,, I Posle, ;o< ramus mar gin 0 1
Temporal
temporal
cerebru m
gy r u~
Superirn lcmpo ral su lc us
OC(lpit~1 ~uk:u ~
Preoccipital notch
Middle temfXIrJI gvrus lnie-rior lemporal ,ukus
Tempo ral
I,..
Short los ula
{
.
limen Lun!: gyru s
FIGURE 1.19: SURFACE ANATOMY OF THE FOREBRAIN: LATERAL VIEW
The convo luti ons of the cerebral cortex allow a ':i ge expanse o( cortex to be compactly fo lded , to a small volume, an adaptation particularly p'ominent in primates. Major dependable land ~ar k s (lateral fissure, central sulcus, pariero occi pi tal fissure) separate the forebra in into lobes. n e lateral (sylvian) fissure separates the temporal " be below from the parietal and fro ntal lobes
above, and the central sul cus separates th e parietal and the frontal lobes. Several of the named gyri are associated w ith specific functional activities, such as the precentral gyrus (mo tor cortex) and the postcentral gyrus (primary sensory cortex). The insula, the fifth lobe of the cereb ra! cortex, is deep to the o uter co rtex and can be see n by o penin g the lateral fissure.
23
OVERVIEW OF THE NERVOUS SYSTEM
Drain
,t<,
,ttlP
"~
FIGURE 1.20: LATE RAL VIEW OF THE FOREBRAIN: FU N CTIONAL REG IONS _ _ _ _ _ __ Some circumscribed regio ns of the cerebral hemi sphere are associ ated with specific fun ctional activiti es, includin g the motor cortex and the su p- plemental and pre motor cortices, the frontal eye fields, and the primary and associatio n sensory cortices. Part of th e auditory co rtex is visib le at th e inferi o r edge of th e lateral fi ss ure (th e transverse tempo ral gyrus of Heschl). The visual cortex is seen
at the occipital po le. Language areas of the left hemisp here includ e Broca's area (expressive lan guage) and Wernicke's area (receptive language). D amage to these cortical regions results in loss of specific functio nal capabilities. There is some over lap but not absolute concordance betwee n func tional areas and th e named gyri (e.g., mo to r cortex and precentral gyrus).
,tb< 0'-lN FIGURE 1.21 : LATERAL VIEW OF THE FOREBRAI N : BROD MAN N AR EAS _ __ Brodmann areas of the cerebral cortex reflect unique architectural characteri stics of the thickness and layerin g of the cerebral cortex from histolog ica l observations origin ally mad e by Korbinian Brodmann in 1909. This numbering o f cortical areas is still used as a shorthand for describing func
24
_ _ _ __
tional areas o r regio ns of the cortex, particularly those rela ted to sensory functi ons. Some overlap exists between functi onal areas. For example, the motor co rtex is area 4/ th e primary sensory cortex includes areas 3, 1, and 2, and the primary visual co rtex is area 17.
l
Brain
-
OVERVIEW OF TH E NERVOUS SYSTEM
Brain Cingu lale gyrus C mgul.l le
Pr E'Ceflt ral sulcus Par.lcentra l lobul~ ~co'pc;·
ca ll osum Precun e us
Su lcus of corpus ca llosum
Superior sagittal , inu s Sep{IJm pell uc id um
:K-'''. _~
Illlerventrlcular foram en
s of )Ver· nc Irtex
Cho rOid p lexus of 3rd ventricle Parie toccipila l SUlW5 Stria med ullari5 of thalIDllJS
lnterthalamic adhe5ion
ClJnelJs Calcm ine curtex IlJpper bank)
Thalamus _"-'''"
Anlerior commissu re
Habenul.ll commissure Calcarine slJlcus
Subcallosal
(pa rolfactoryl are a
f'araterm inal g,,",
Lingu;:d gyrus C.J. I(.lrine cortex (lower bankl
--C'"
Pineal gland
Lamin a Ie/minalis
Strai ght sinus (in tentori um cerebellil ""'"'' o,~I",11 vein (of Galelll Posterior tepithalamicl commissure Super io r and inierlor colliculi Cere bellum Su periol med ulla ry velum 4th ve ntricle and cho roid plex us
Op tic chiasm
'f
'n gel.
~ulcu~
Cemral (ro l.l ndic)
I
Mammillary
Pituita ry gland (anterior and po",,'o,, /
Mldbtain
obIong':lId Cin gula le Mammillothalamic
..
Cerebral aqued uct lof Sylvius)
In fe rior medu llary velu m
t::5:i::;;~:::~;R_O~~n~ }
I
':'>
Sody
of corpus callosum
Splenit.m Cuneus
I
O pt ic (111) ne rve ~<.. ,'--.
Lingual gyrus
Olfaclory trac t Collate ral "I<,' ''-.;~ Rhina l ,,"' "'_..: Medi a l occipitolemporai
gy'"' -__-=::=
Ocdpitotemporal >ulru s
laler occipitolem(lOfai g\'ft.!s
_co~,C"m'""~}
offomix
hippocampus Denta te gyros Parah'ppocam paJ gyrus
FfGURE 1.22: ANATOMY OF TH E MED IAL (MIDSAG ITIAl) SURFACE OF THE BRAIN _ _ __ Th e entire neuraxis from the spinomeduUary junc ti on throu gh the brain stem, diencep halon, and telen cepha lon is visib le. The corpu s ca ll osum, a major co mmi ss ural fiber bundle interco nn ecting the 2 hem ispheres, is a landmark separating the cerebral cortex above from the thalamus, fornix, and subcortical forebrai n below. The ventricular 5vstem-including the interventricular foramen, the third ventricle (diencephalon), the cerebral aque duct (midbrain), and the fourth ventricle (po ns and medulla}-provides intern al and external (sub arachno id [SA] space) fluid protection to the brain.
The thalamus serves as a gateway to the cortex. The proximity of the hypo thalamus to the median eminence (tube r cinereum) and the pitui ta ry gland reflects th e important role of th e hypothalamus in regulatin g neuroe ndocrine function. The C·shaped course of the fornix, from th e hippocampa l forma· tion in the temporal lobe to th e septu m and the hypo thalamus, is shown below. The midsagittal cut thro ugh the brain stem reveals the midbrain colliculi, sometimes called the visual (superior) and auditory (inferio r) tecta.
25
OVERVIEW OF THE NERVOUS SYSTEM
Brain
Primary moun .limbic,; cingulate Ul<'1ex ,
Supplem ental moto r co rte\
_ _ ParKentral lobu lt!
;;~
lali
Corpus callosu m
:::-- Vi~ a l assoc i.ltion (OfttK
P, ima'yvlsuaJ cortex
Calcarine fissure
Pil:\.lit
Cefebellum
~~~ °IIllN :\
....... ;:
Meduh obIo~.a ·
FIGURE 1.23: MEDIAL SURFACE OF THE BRAIN: LOBES AND FUNCTION AL AREAS _ _ _ __ The cingulate cortex is labeled the limbic lobe, reflecting its association with o ther limbic forebrain
stru ctures and hypothalami c co ntrol of the auto nomic nervous system. Fun ctional areas of the cortex, particularly those invo lved w ith vision, are
best seen on a midsagittal view. The sensory and
,
motor cortices associated w ith the low er ex tremi ties are located medially and are supplied by the anterio r cerebral artery. This region is sel ectively vulnerabl e to vascular or mass lesio ns, resu lting in contralateral motor and sensory deficits of the lower extremi ty.
~~~
Oll!!l\l ;:·,'::: 1
f
R,
FIGURE 1.24: MEDIAL SURFACE OF THE BRAIN: BRODMANN AREAS _ _ _ _ _ __ _ _
a
CI
The Brodmann areas of the cereb ral cortex are labeled on this midsagittal view. The major regions are the primary ( 17) and associative (18. 19) visual
26
co rtices and the continuation of area 4 (motor) and areas 3, 1, and 2 (primary sensory) o nto the para central lobule in the midline,
tic
-'"",
l>
Brain
OVERVIEW OF THE NERVO US SYSTEM
Bra in
Fron tal pole
of (;u rpus Glllosurn
O rbil.:t!
,
Lamin.:t termin.:t!is
-- ---
O rbi lal gyri
l .:tler.:tl (sylvian)
/V,"', (1 11) nerve Pitui t.J.ry gland Temporal pole Optic h act
An terio r (rost.:ll) perforared su hst an(;~ Tuber dnereum M ammillary body Posterior perforated substance
-
:!mi
he
Cere b,..1
Rhinal sulcus
pedu ndt'~
,Iy
(crU)
g in
ct!rebri)
l ateral ~e nl culat e bodv S lIb ~ tan ti ~ n i s r~
Lat er al
occipi to temporal
gyru s
M edial ~ e ni c uliJt t'
bndy
Occipito temporal
sulcus
Reel n!.ldcus
Medi al
ocdllitotempolal
Pulvinar
,,'"' - --"'4[
Supe.ior Icr.lni ..1l t:nllkulu5
CoUateral sulcus - -
PariJhippocampalgyru~ --=~~~td+
Cer~hr ..1aqueduc t (of
SVMus)
Splenium oi oorpu~ callosum
Uncus
Cingula te gyr us
FIGURE U5: ANATOMY OF THE BASAL SURFACE OF THE BRAIN: W ITH THE BRAIN STEM AND CER EBELLUM REMOVED _ _ __ _ _ _ _ _ _ _ _ _ _ _ __
-
,nd
1-
Remova l of the brain stem and cerebeHum with a cut throu gh the midbrain exposes the underlying cereb ral cortex, th e base oi th e diencephalon, and th e basal forebrain. Ba sal hypo thalamic landmarks, from caudal to rostral, include the mammillary bo di es, th e tuber cin ereum, the pituitary gland, and
th e op tic chi asm. The proximity of th e pituitary gland to the op tic chi asm is importan t be cause bitempora l hem ianopia can result from optic chiasm fiber damage, a possible early indi cation of a pituitary tumor.
27
OVERVIEW OF THE NERVOUS SYSTEM
Brain
O li,lctor y hulb Ex ec utiv" an ticipiltory
Optic nef\'e (Il ) (tun
,.--- O pliC ,ril el
JI,\ ommlii ary body
.Vluhi.lcnsorv a~s()(]ation artlol 'i
~!~
" lJiliN ',';::: I
Prim
FIGURE 1.26: BASAL SURFACE OF THE BRAIN: FUNCTIONAL AREAS AND BRODMANN AREAS _ This view provides inform ation about the medial
lem porallo be on the left side of the brain, espe cia lly the cortical regio ns associated w ith the
hipp ocampal formatio n, the amygdaloid nudei, and the olfactory system. O n the ri ght side of the brain, the Bro dmann areas are noted.
He
"'" .~
L>l' C~
!)
.,.,
'dJ.....
cor 28
Brain
OVERVIEW OF THE NERVOUS SYSTEM
Brain
Genu 01 corpus c.Jllosum
/;ep',"", pelludrlum Head o f caudale nucll'US
Anterior li mb _ Genu Posterior limb II
} 'nlernCl , capsu le
co rtex
I ( p
Claustrum
~:::::::;:i=- Habenula
Tail of Ciluoolte nudeu!>
Pineal gland 1.1Ieral vemride CIUS 0 ; iornix
Hippocamp us
and fimbrr a
Spleniu m o f corpus callosum
\P,,,,,,.,ioc loccipital)
horn of faleral
ventricle
Cauda te { nucleus
Head _
_ -, 't .~- - -. ----- - --
lev~ ls of {A - - ~ect10nS
------ ---- B --- ------ ---- -
-\+ - -- -------
lentiform nudeus to p u tamen ) {globus p.-tllidus med"1
Schematic
,::;""'~~~~~~~~iM~:.~di:"~;'::~~:: body
..
iAIU'm"YI",'di'o'I,~"idh",b"'.i'")g·-i-"~"i'.'l ' 'io",hiP
::.
ol,h.,I, ",""
',"" 'O~:'eu,
body
~ ~,
nud eus. cauOOle nucleus olnd amygdaloid body lviewed from sidl't
.S _ Ie
FIGURE 1.27: HORIZONTAL BRAIN SECTIONS SHOWING THE BASAL GANGLIA _ _ _ _ __ Two levels of horizontal sections through the fo re bra in reveal the major anatomical features and relationships of th e basa l gangli a, the intern al ca psule, and the th alamus (bottom illustration). The (.-s haped ca udate nucl eus sweeps from th e frontal lobe into the temporal lobe. In the internal capsule, the anterior and posterio r limbs and the genu con tain major connections into and out of the cerebral cortex. The relatio nships of the basal ganglia, the
internal capsule, and the thalamus are important for un derstanding imaging studies and the involve ment of specifi c fllnction al systems in vascu lar lesio ns o r strokes. Th e extern al capsule, th e clau s trum, th e extreme capsule, and the insul ar co rtex, labeled from medial to lateral, are landmarks used in ima ging stud ies. The fornix is sectioned in the crus and the column.
29
OVERVIEW OF THE NERVOUS SYSTEM
Brain
BrdJ
IntenhJ lamK adhesion
.;>'nte, ;o, n ucleus oi thal amus
i~'
Intcrv!3 nlrlculal foramen
Slri,l lermina lis A.nte:IOr commi~",u l e
Stria medu lJ.lris
Cingulate Rvrus
Imgli~eum,- ~ Corpu~ c
--
¥
..p.~
"""""
.'
............. -"
S.. ptum pe Jiuci cilH'll
'~
f'fccomnll$sural iorOl" __
r1 ,
Si2'lllil l rlll
S ubcallo~i'llarl'a
~
. '
, ~
RG
-e ~
wmlO..l
Jr =-~
tcm1ITlcli iS
.:;; ?"
b""'
Q liaclory
l r ~c l
{
medial I.Herdl '
Anterior p~ rfor,lted substan ce -----~/ Optic chiasm
/
PO~l commiSSll(al
fornix
Mam ll1illMY b ody an d
i11anlmiliothaia mlC IraC I
Medial fort-blain bundle /
Amygdaloid h odv
(nucl ei)
Parahipp ol:ampal gyru s
Interp edunculM nudeu> Dest:ending (onne<:tions to reticular
and legmental nud ei of brainslem
Fasciculul> relr(){lexus
I
(dOfsal longi tud inal fasciculus)
~~~
c :\":.":;: ll9N
FIGURE 1.28: MAJOR LIMBIC FOR EBRAIN STRUCTURES _ _ _ _ _ _ _ _ _ _ _ __ Many of the structures and their pa thways in th e limbic system form a ring (limbus) aro und th e diencephalon. They are involved in emotional behavior and interpreta tio n of external and internal st imuli, Th e hippocampal formati on and its pat h ways, th e fornix, curve int o the anteri or pol e of the diencephalon. The amygdaloid nuclei give rise to the stria terminaiis, a C-shaped projection (0 the
30
hypothalami c and basal fo reb rain stru c tures. Th e olfacto ry tract co mmuni cCl tes directly with th e
cortex a nd othe r forebrain structures, bypassing the thalamus. Connectio ns from the septal nuclei to the habenula (stria termin ali s) interconnect the limbic forebrain w ith the bra in stem. The amyg dalo id nuclei and the hippoca mpal formatio n (shaded) are deep to the cortex.
-'G
..·3.1
cal;
c"'...
,--,.,
Brain a rain
OVERVIEW OF THE NERVOUS SYSTEM
--------------------------------------------Anatomy of the Corpus Callosum
:- (:e,,·",,1 longitudinal fissure oi corpus callosum
:- lod,,,'om griseum (on upper surface o j corpus callosum )
latefal longiludinal striae _ Bo¢, of
Splenium of corpus callo sum
f iGU RE 1.29: CORPUS CALLOSUM : HORIZ ONTAL VIEW _ _ _ __ __ _ _ _ _ __ The co rpu s ca llosum, th e major fiber commissure oetween the hemispheres, is a co nspicuous land mark in imaging studi es. It is viewed from above after dissection of the tissue just dorsal to its upp er
'Jrine us (tissure)
t lris
su rface. Horizontal cuts taken deeper (more ventral) will section the genu anteriorly and the splenium posteriorly (see Figure 1. 27),
, fib ers
Medial 1
stria
Lateral
•• .j.1)'t:
stria
I[l;N
" ·,"c.': :
The
e ng th e to
e g
Occipilal iorceps (forceps major )
fiGU RE 1.30: CORPUS CALLOSUM: SCHEMATIC VIEW Of THE LATERAL EXTENT Of MAJOR COMPONENTS _ _ _ _ _ _ _ __ __ _ _ _ _ _ __ __ Many of the commi ssura! fibers of the co rpus ca llosum, particularly the " forceps" of fibers inler connec ting the fronta l and the occipital areas, curve rostrally and caudally after crossing the
midline. These interconn ecti o ns allow communi· ca tion to take place between the hemispheres, wh ich is essential for coordinating the activity of these 2 "separate" hemispheres.
31
OVERVIEW OF THE NERVOUS SYSTEM Di ~sect jon
Brain
B"
of the Hipp oc.amp a l Formation and Fo rnix ~. ,....--- {,,; enu of co rpus C
Ilud, H ead of caudale nl1c1e ... ~ Col"mns of fornix
Stria terminalJs
trody of iomix 1"1:'5 hippocampus
Uncu s
~~:~::,~~fornJX ~ Fimbriol 01 hippoca mpus ~.Hrppocampu~ '
.......,;:;.
Commi s>ure of fornix iplen iufll 01 corpu, callosum lal er
-"" Pos!elior (occipital) horn o f 1~leral ve ntricle Tajl of c~ u d ate nucle us 3·D Re cunstructi o n of th e fo rnix Columns
Th e Hippo ca mpal Formation in Co ronal S~ction
Fimb ri.:l 01 hippocampus
,
Choroid plexus
Com mis 5tJ<"e
of CnJlJ of
Hippoc.:.mpJl wlcus
"
• -<
,~
." ",
Subioculum ventr icl e
De ntate
ill "' ["ws of hippocampus I
boditl~
Amysd aloid
iii
Efltorhinal cort e~
FIGURE 1.31: HIPPOCAMPA L FORMATION AN D FORNIX _ _ _ _ _ _ _ _ _ _ _ __ The cor tex, w hite matter, and corpus callosum
have been removed, th e lateral ve ntri cles have
bee n opened, and the head of the caudate and the thalamus have been dissected away close to the midline, allowing a downward view of the full extent of the hippocampal formation, including the dentate gyru s, and the associated fornix. This view reveals the relationship between the hippocampus pro pe r and th e dentate gyrus. Th e 2 limbs of the forni x sweep upw ard medially, eventually runnin g si de by side at their most dorsal positi on ben eath the co rpus callosum. The full extent of this archin g,
32
C-shaped bundle is seen in the lower left d iagram. The hippocampal formation occupies a large por tio n of the temporal pole o f the lateral ventricle. The den tate gyrus is adjacent to subco mponents of the comu Ammo nis (CA) regions o f the hip pocampus prop er (the CA 1 and CA3 regions), th e subiculum and the entorhinal cortex. CA l pyrami· dal neurons in the CA 1 region are sensitive to ischemic damage, and their counterparts in th e CA3 regi o n are se nsitive to damage from high levels of corti costeroids (cortisol).
FIG The righ
has
nu el
and
rem fro n in t~ pro( eire;
OVERVIEW O F THE NERVOUS SYSTEM
";.l,
Sel>tum p elludrlum
e>1l11c1e
o-.;.aple,us
/,Cnl'cm,,, of forn ix
/ ,,,to', , ,, tubercle
_"" , _etJ(al v. ,/
/
" " 0 terminalis
II" to"h" I"" " ad hesion medu ll,u is
lal~ral
geniculate body
Medial geniculate body
Brachium of inferior coliiculu s
-",-~ ,
Superior co llicu lus
Inferior colliculus
r, "Heral
.:..It:a.-ine sulcus - _/ ~;.....el
_
~~L
~MICANATOMY
________________________________________
.....:::-::>- 6 \. 'ew ed from above. The entire - brain, just late ral to the thalamus, Ed. the head of the ca uda te IIf"er,
secti oned, the corpus callosum
oorsaJ to the th alamus have been :he th ird ventricl e has been opened
sl.u ia ce. The pin eal gland is present ~.;~•. tlS"t
caudal to th e third ven tricl e; it "",...:""i..-1. a horm o ne that he lps regulate ~ . sleep, and immune responses.
The superior and in ferio r colliculi are shown, depicting the do rsal surface of the midbrain. O n the left, the tempo ral horn of the lateral ventricle, with the hippocampal formation, has been exposed to show the relationship of these struc tures to th e thalam us. The terminal vein and the choroid plexus acco mpany the stria term inali s alon g th e lateral margin of the thalamu s. The stria med ull aris runs alo ng the medial surfa ce of the dorsal tha lam Ll s.
33
OVERVIEW OF THE NERVOUS SYSTEM
Brain
3.d Internal medull':Hy
la mina
,
J ld ventricle
'-- Reticular nucleus o f rhalJmus
M idline (medi
Ivi
Thalamic nuclei
I,ml i!)')
eM LD lP M MD
Cenllome(!ian l ateral d(){Si)1
" '\.
Wller,ll posterior Medial woop
(extern al medullar y Lamina and ret icular nuclei removed)
Ventral anfE'.rior
Schematic section through thalamus
VI
(at level of broken
VP VPl
Vem fal intermedial Venlrallal!!''}/ Venlral posteriOf h 'eolroOOrs.al) Ventral postefOlarerJI
line sho wn in figure
alr ighll
VPM Venltal poSleromedial
Mediill genic ula.!! body
Shem;ttic represe ntation of thalamus
Medial dorsal
VA
\It
lille!']1 geniculdte body
_ _ Lateral cell mass
_
Medial cell mass
_
Anterior cell mass
~~p CIIiiN :'.-,.:: : :
FIGU RE 1.33: THA LAMIC NUCLE I _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ These figures illu strate the subdivision of th e thala mus into nuclear groups (medial, lateral, and ante rior), separated by medullary (white matter) laminae. Many of these nuclei are "specific" thala mic nuclei that are reciproca lly connected w ith dis crete regions of the cerebral cortex. Some of the
34
nucl ei, such as those embedd ed in th e int ernal medullary lamin a (intra laminar nucl ei such as cen tro median and para fascicular nuclei), and the ou ter, laleral shell nucleus (reticular nucleus of the thala mus) have very diffuse, Nnonspecific" associations with the cerebral cortex.
-
Br~ain
OVERVIEW OF THE NERVOUS SYSTEM
Stem and Cerebellum
Posterol ate ral view /"Vp '" tract A "",II genicu late body
(l V) n .
II Vl n. r'
>m'--;
cerebellar l)edun cle
Superior me,,",,II,,yv',,.I"
Medi al e mo'o" ,r e -,
:-;
,,
Rhomhoid fossa of 4 th veonlricle - - - - ..,
f"",:~::;:::::;J~
ti
Cuneate
Gracile
Dorsal roots of I 5t spina l n. ((1 1
~
peduncle [II n.
I II
peduncle
°
~=~I~GIosS()Phary n 8eal (IX) and vagus (X l nn. HWoglossaltrigo ne I trigone AccesslXY (Xl) n.
tract
Anterior view
Optic
ill
1
Temp oral lone
Tuber
oop:,~,c:::~==::=t~~
Cerebral pi
Posterior pE'floralcd
substance
I
n.
~~1::J4=;::'~"'" UV ) n. --=~~~::,~~' {Vt) :~: o.n.
In
:....
I (VII) n.
Lateral genlculale Basilar
I
I.
,m,,,,_
Middle cerebellar
(Villi
___
ped uncle - - - - Ii, VenTral roots oi lst spina l n . (C1 I
-
"cen-
Outer,
lala
Ons
- - - -'k
FIGU RE 1. 3 ~ : BRAIN STEM SURFACE ANATOMY: PO STE RO LATERAL AND ANTERIOR VIEWS_ Top) Th e entire tel encephalo n, most of th e dien cep halo n, and th e cerebe llum are rem oved to show the dorsa l su rface of the b rain stem. Th e 3 cerebel lar peduncles (superior, middle, inferio r) are sec tioned, and the cerebellum is removed. The do rsal roo ts and the cranial nerves provide input to the sp in al cord and provid e input and output to the brain stem, respectively. The fourth nerve (troch lear) is the on ly cranial nerve to exit dorsa lly from the brain stem . The tubercles and trigones on the floor
of the fo urth ventricle are named for nu clei just benea th them. (Bottom) The left temporal lobe is di ssected to show the anterior (ventral ) surface of the brain stem. Th e cerebral ped uncles, caudal extensions o f the posterior limb o f the internal cap sule, ca rry corticospinal and corticobulbar fibers from the internal capsu le to the spinal cord and the brain stem, respectively. The decussation of the pyramids marks the bo undary between the ca udal medulla an d the cervica l sp inal cord.
35
OVERVIEW OF THE NERVOUS SYSTEM
Brain Stem and Cerebellum
Superior surface
~ Q u<,drangula. lobule
Pri ma ry tis sure
J,1
Ce ntral lob ule
Hori:w nt.J.lllssu re Simple x lohule SUi'>""iOf vermis
~
Oeclive
f'~tlunJte
iissure
Sup<::.iors!'ml
Follum
lun ar lo bule
~
t-I o riz()nl al f'~.\ure
- - Inierio. sem ilunar lobull'
Inferior surface Superior (Cemral lobu1r,o --.
~
verm iS
,be ll
,II,
'···1, Inferior medu lluy ve lum _ _ _
1I'I1".io. vermis
NOO"'. --
{
Uvula- - - - Py ram,d . -
~ ~
Tuber- - -
--
" (post-
P051~rior cerebellar no tch
, ii,>u re
/
tal n, SLln:' labul<:
fissure
Section in plane of superior cerebellar peduncle - ''''-..~ -. ~~
Decuss.ation of superior cerebell ar peduncles
~ " ft..~-'{, w -., . , r'
.,
~CerebralpedullCle
J~~ , -- --Med'al longiru diIlJl l asCirulus
'iel ~SupoeriOt cert:~ IIM
1/,
a
rei De nlate nu cl e u s~
Emboli fornl nucleus....
pedunde
:;J~CerebeollJ. r co rtex
~!p
CIIl!N
".......:'
FIGURE 1.35: CEREBELLAR ANATOMY: EXTERNAL AND INTERNAL FEATURES _ _ _ _ _ __ (To p) The top 2 diagrams show the superior (dor sa l) an d inferior (ventral) surfaces of th e cerebel lum. The ven tral surface of the cerebellum is the roof of the fourth ventricle. The anterior, middle, and flocculon odular lobes of the cerebellum are trad itional anato mical subdivis ions with w ell descr ibed syndromes from lesions. The vermis, par avermis, and lateral hemispheres are cerebellar cortical zones w ith specific projection relationships w ith deep cerebell ar nucl ei (vermis with fa stigial nucleus and latera l vestibular nucleus, paraverm is with globose and emboliform nuclei, lateral hemi spheres w ith dentate nucleus), connecting w ith specific upper motor neuronal systems regulating
36
specific typ es of motor activities. (Bottom) The major intern al subd ivisions of the cerebellum are show n. The cerebellar cor tex (3-layeredl, the outer 2.one, is infolded to form numerous folia. The wh ite matter, carryin g affe rents and efferents assoc iated with the cerebellar cortex, is deep to th e foli a. The deep cerebella r nuclei are deep to the w hite mat ter. These cell groups receive most of the output from the cerebell ar cortex via Purkinje cell axon projections and receive coJiaterals from mossy fiber and cl imbing fiber inputs to the cerebellu m. The cerebellar peduncles are interior lo the deep nuclei; these massive fiber bundles interconnect the cere bellum w ith the brain stem and the thalamus .
OVERVIEW OF THE NERVOUS SYSTEM
;'pinal Cord
An terior view
Axis [( , :2J
l eft latera l view
Posterior view
.-="
TI2 ---'~
13
-
J:;
Saoum (51-5)
e ter li te
,d he
,t· t
iber :Iei; re-
FIGURE 1.36: SPINAL COLUMN: BONY ANATOMY _ _ _ _ _ _ _ _ _ _ _ _ _ __ Anterio r, latera" and posterio r views o f the bony spinal column show the relationships of the inter vertebral di scs w ith the vertebral body. The di scs' prox imi ty to th e interve rtebral foramina provides an an ato mical subs trate for understandin g th e pos sible impingement of a hern iated nucl eus pulposus on spina l roots. Such impin gement ca n cause
excruciating, radiating pain if dorsal roots are involved and loss of mo tor contro l of affected muscles if ventral roots are invo lved. In the adult, th e spin (l l co rd ex tends caudally onl y as far as the L1 vertebral body, leaving the lumbar cistern (subarachno id [SA] space) accessibl e fo r w ith drawal of CSF.
37
OVERVIEW OF THE NERVOUS SYSTEM
Spinal Cord
CI 1st cervica l n. Cervical enlargement
C7 8th cervical n. TI hllhoracic n. Spinal d ura mater Fila ments of nerve fool
Conus l1ledullans Ca uda equina
[5 '-.. Srn lum b~r n.
51 1st sacral n.
~~~ ° 11!!N ..... ~
,.,' :
Filum terminate :;th Scleral n. CoccVg€
:
FIG URE 1.37: SPINAL CORD: GROSS ANATOMY IN SITU _ _ _ _ _ _ _ _ _ _ _ __
FIGU
The posterior portio n or the vertebrae is removed to show the postefior (dorsal) surface of the spinal
Th e u
co rd. Ce rvical and lum bosacral enlargem e nts re llect innervation of the limbs. The spina! cord extends rostrally through the foramen magnum, continu ous
\\ it h the medulla. The conus medullaris is located under the L1 verte bral body. The longitudinal gro\vth of the spinal column exceeds that of the spinal cord, causing the spinal cord to end consider-
38
ably more rostral in an adult than it does in a new born. The associated nerve roots traverse a consid erable distance through th e SA space of the lumbar cistern to reach the appropriate intervertebral foramina of exit. In the lumbar ci stern, this collec tion o f nerve rools is the cauda equina (horse's tail). Th e lumbar cistern is a large reservoir from whi ch ( SF can be withdrawn. The filum terminale anchors the spi nal cord caudally to the coccyx.
reflec! tour c extenl overl) memt nerve struct l
_ Spinal C~I Cord
lew
Insid
mbJ r ~c-
tail). ch
hors
OVERVIEW OF THE NERVOUS SYSTEM
Posterior view Rami communicante5-_ _ _ _i~::;;;
Docsa! rool - --
- - -,
DorSdllOo t (spinal) ganglion
Afachnoid - - - - -
Mesothelial septom in
posterior mediilo ,~',:~~~~:::=-~l
Pia ma Ier love rlying ~na l Filaments of dors al root - - - - - - --;--:;
Denticulate li gament _ _ _ __
+""""'"
__
Anterior view
Lateral fun iculus
Filaments of dors al rOOl
.3l~"",--- While malter
Dorsal roo t Dorsal rool (spin
I nerve Ven ltal (001 Filaments of
""--C,---_
vent rill root
An terior median iissI,lIe Anterior funiculus
FIGURE 1.38: THE SPINAL CORD, ITS MENINGES, AND SPINAL ROOTS _ _ _ _ _ _ __ The upper illu stration shows both intact and reflecteq menin ges. The pia ad heres to every CO Il tour of the spinal co rd surfa ce. The arachnoid
extends over th ese contours and ad heres to the overlyin g dura, a very to ugh, fi brous, protective membrane. These meninges extend outvvard to the nerve roots. The denticulate li gaments are fibrous structures that help anchor th e spinal cord in place.
The posterior spina l arteries supply the dorsa l spinal cord with bl ood and run ju st medial to th e dorsal root entry zon e. The lower illu stration shows the spinal cord with the menin ges stripped away. Both the dorsal and th e ve ntral roots co nsist of a convergence of rootlets that provide a continuous dorsal and ventral array of roo tl ets thro ughout the spinal cord.
39
OVERVIEW OF THE NERVOUS SYSTEM
Spinal Cord
Sl'ction throogh thoracic vertebra
Dura mater SrmP
Ve ntral space
Pia mater (adherent to spinal cord)
Dor~JI rOOI
fsp lnal) sanghon
Spinal nervt.' ' -
Ventral ramus
(intercos tal
nervel_
¢
Section throu gh
lumbar vertebra
Sympathe ti c ga nglion
Ramus r.ommunicans -" Vf>nlr...1rool ~\ -'" Spinal nerve
--:- r-......
~,~ ""::.--
Ventral r
~ Cauda equiniJ
Filum lelminale
~ ~p " 11liN :\":.".'::
FIGURE 1.39: SPINAL CORD: CROSS-SECTIONAL ANATOMY IN SITU _ _ _ _ _ _ _ __
AGt
(Top) The spinal co rd in th e sp inal canal is sur round ed by meninges. Dorsa l and ventral roots course through the intervertebral foramina. The
-
epidural space, with its associated fat. is sometimes used for infusion of anesthetics. Arteri es and veins are associated w ith the spinal nerves and nerve roots. Some segmental arteries provide anasto motic chan nels for blood flow from the aorta to augm ent flow from the anterior and posterior spinal arterial systems, w hich ca nnot sustain the
40
entire spin al cord. Th e sympath etic chai n ganglia (paravertebral), important for fi ght-or-fli ght responses, lie adjacent to the vertebral body (ven trally). The dorsal and ven tral rami of the sp inal nerves distribute to specific regions. The sp inous process extends dorsally, w here it can be palpated by physical exa m. (Bottom) The SA space of a lum bar vertebra, co ntaining the filum termin ale and the roots of th e cauda equin a, is shown.
-opl ;
i"""dy '\'
caud
desc, i-St5
~'"
-
OVERVIEW OF THE NERVOUS SYSTEM
Spina' C...I Cord
Sections through spinal cord at various levels
,
',. ,
C5
T2
-, ,
id
"c'Y"" .-( , I.,
";.;,/.
/
ent 10
~
:0,(/)
J
"
\, )
'~
,
.
'" '. I . .
~
~
"
.,:J
.g "'-'1 .j 4~'K "1<7' ~>'<' '~"Z""'~';W: "
flllOid
!1er
I,
~'-~
j~
,
- ' - - -/ "
.._-'" /'
/
11
Principal fiber tracts of spinal cord (composite) E$ Ascending pathwa ys
_ m.~
Desce nding pathways Fibers passing in both directions
Fasckulu$ ,;" , ililll , _ _ Fasciculus '"'''''' ' - _ _
r
Anterior white commi ssure
Lateral (crossed) co rti cospina l (pyramidal) trac t
Dorsolateral fasciculus (of LI",w~I-, Pos terior
La teriJ l (medu ll ary)
II
reticu lospinat tr ac t
Spinothalam ic Ira ct and Spillorelicul ar Iract
Anterior o r medial (pontine)
leliculospinal tract
Anterio r (vemral)
Tectospinal trac t
Spinoolivary tract Fasciculus p,op'I''' ~~
-
19lia
(ven
,I
JUS
'i !ted
lum_ d tile
_ _ ""'", I ,,, {uncrO$>ed} COllicospinal lracl
FIGU RE lAO: SPINAL CORD WHITE AND GRAY MAITER _ _ _ _ _ _ _ _ _ _ _ __ Top) Seven spinal cord levels are shown, depicting the relative size and th e vari ability in th e amount of gray matter at each level. Levels associated with the limbs have greater amo unts of gray matter. W hite matter increases in absolute amo unt from caudal to rostral, reflectin g th e level-by-level addi tion of ascendin g tra cts and the term inati on of descending tracts. (Bo ttom ) The gray matter con sists of dorsal and ventral horns and, in the Tl and L2 segments, an intermediola teral cell column
(lateral horn) wh ere pregangli onic sympathetic neurons reside. Th e white matter is subdivided into dorsal, lateral, and ventral funiculi, each containing multiple tracts (fasciculi, bundl es ). The tracts con veying pain and temperature information travel rostrally in the antero lateral funi culus, the spino thalami c/sp in o reticular system. Fin e discriminative sensation is conveyed throu gh the do rsal funiculus. Dorsal roo t entry zones and ventral root exit zon es are present at each cross-sectional level.
41
OVERVIEW OF THE NERVOUS SYSTEM S<.pt.'rioJ
Me ninges
~ilt'll~1
(pldu",! Sj).)ce ( l'OlCn h~1l
Ar,l rhnn,cI ~(''''u l.llion
inQ('fIling (f(Jvw1a)
s~ull
V~ I l() U ' l a~u l1J
Suba r~ chn o id
'race
Ink'rioI
Middle meninge••1 "'lef)' ~n d
>inu5
~~
ve in
"
,.
,, "
'> .,,: " .
"" "u
1"
L1cuna
";: ; ••-/;~- :.. ....,"' •. • ,..
. . . . . . ~. :::::::.==____~____ __ r.
".-~. <"", 'f" r
>,, ,"· r · ,'" . Y.""; , , ' .... ~ r
_.. ~~w
. ; . ...... . , .... .~ ,... ",.," " " ' - - C~I\'a,ia ~," "~;~ V: .y{>:;_•• ~ _ Duramater (ou rer .1nd ," "'" Iav....s) ,,' , ~~~'_~ ",. ..y:"..--S
!1~
"'
,.:
,",,-'
",~ -·r 1'Vf<.. ' " . "1~~~ 'i7. I""i f{
1, '
,,\~Yl\..
, -• - -
uf>durJl lp~Ce IPot~nliJI)
Arachnoid
Subarac hno id space
Pi;,. maIer
- -- -
Celeb,')1hemiS(lhoe,e
~!? ,II~
FIGURE 1.41: SCHEMATIC OF THE MENINGES AND THEIR RELATION SHIP TO THE BRAIN _ _ The meninges provide pro tection and support for neural tissue in the eNS. The innermost mem
brane, the pia mater adheres to eve ry co ntour of neural tissue, into sulci, fo lia, and o th er infoldin gs. It adheres tightly to glial endfoot processes of astro cytes. The arachno id mater, a fine, lacy membrane ex terna l to the pia, extends across the neural su lci and foldings. Th e subarachnoid (SA ) space (between the arachnoid and the pia), into w hich the CSF flows, provides buoya ncy and protectio n to the brain. Arteries and veins run thro ugh the SA space to and from the eNS. The rupture o f an arter ial aneurysm of cerebral arteri es resu lts in an SA hemorrhage. The dura mater, usually adherent to th e inn er arachnoid, is a to ugh protective outer membrane. It splits into 2 laye rs in so me locations
42
to provide channels for venous blood, the venous (dural) sinuses. Th e arachn o id granu lations, o ne way valves, extend fro m the SA space into the venous sinu ses, especially th e superior sagittal sinus, all owin g (SF to drain into the veno us blood back to the hea rt. Blo ckage (e.g., acute purulent meningiti s) can res ult in increased intracrania l p r~ sure. Bridging veins drain into the dural sinuses. These veins are subject to tearing as they enter sinus as a result of trauma, especially if there is some atrophy in the brain, permi tting venous bloo to accumulate in the subdural space as it dissect:; the inn er dura from the arachnoid. This subdural hematoma can be life-threaten ing from increaseD intracranial pressure, edema, and the accum ul at: of blood from the hematom a itself.
tre
-
OVERVIEW OF THE NERVOUS SYSTEM
Meningentricles and the Cerebrospinal Spinal Fluid
Anterior (frontal) hom
}
l. lateral Inferior (tempor ~ l ) hom
v entricle
POSleflor locclpllc) l) hm n
Cp.rehral.1queduct (o i Sylvlu s)
4th ventri cle
[
l.la lelill apeflure Ifora me n o f l usc hka J l. lateml rp.r.p. s~
_ -
fo rJmen lof Monro)
.1 d
M edian aperLurE: Ilor.lmen of M af\l'ndie)
" Co' j)US ullOSl lm
R_I,lINal ve"tride Body of caudate nudeu~
Choroid plc)(u~ of loll e ra I ven tricl E'
Suprapineal recess
I
Stri
i
R. Ih~ l amostr iate Bod\' uf furnix
,; ;,
.;
-' . , -
-,.
"-'
VC II)
Tela cnOr'OIde'l ()[ :lrd ,elltricie
~::::::::::::: Ch o roid plexu s (J I 3rd ventrl circ ::
Thal amu s
GP", f~'len_'I~d------ ------ -- fl . O' , U5 P<' I u S
[in terndllil and ('xlem.~i [el segments)
LelltifortYI
I nue cu~
_ _- - Internal capsule
C-----
_ - - - 3rd vcnTricle
HYPolhal 3m us
~r-!2:;;:::~~~==:::::::::::::::: Tall 0 1 c.ludiltP. nucleu~ O ptic trac l
:::
_ - --
Cho roid ple xus of iJleral ventricl e
"'t-- ===== w--'--::
Inlellor (lemporal) hom of latc", 1ven rricl e Fimbria 0 1hij>p0campU5
---
HillPOc.:J mpus
lenous
one he
fal blood, lent II pres
es.
'er the
is blood
ecfs
Ira l
sed
lation
-'-~ Piilmilt e r
- - : --
-
De ... tate g)'(U5 Suhirulum P.J ra hippo campal (.Ortex
'(,,;'=:,----:,.,;- - - fl1 10rhlll JI CO"ex
FfGURE 1.42 : VENTRICULAR ANATOMY _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ __ The lateral ventricl es are (-shaped, reflectin g their dssociation w ith the develop in g telencep halon as it sweeps upward, back, and then dow n and forward dS the temporal lo be. The positio n of the lateral ventricles in relatio n to the head and body of the caudate nucleus is an important radio logical land mark in a va ri ety of co nditions (hydrocephalus, cau date atroph y in Huntington's disease, and shifting of the midlin e w ith a tumor). (SF fl ow s through the foram en of M o nro into the narrow third ventricle,
then in to th e ce reb ral aquedu ct and th e fourth ventricl e. Blockage of tlow in the aqu edu ct can pre cipitate int ernal hydrocephalu s, w il'h swelling of the ventricles above. The escape sites for (SF to flow into the subarachnoid (SA) space cisterns are the medial foramen o f M agendie and the la teral foramina o f Luschka, w here blocka ge of (S F tlow can occur. Th e choroid pl exu s, extending into the ventricl es, prod uces the CS F.
43
OVERVIEW OF THE NERVOUS SYSTEM ~Hi
PO;;\f . io . "iew
Ventricles and the Cerebrospinal Spinal Fluid
venlnclC'
Habenula. trigon!'
PUI\-jO,l'
l aterJI }
Geniculate bodies
....Iedial
Pine ,l l gl.lnd '
-
Supe rior colliculus Media n sulru s Tro ch lear (IV) nervl!---.. Superior medullary velum
Cere~lJar , ,o'd I~oondcs {"p
~-<
Locus (oeruleus area ') r
_.
SJJ!.,..\, C:y'l ~
MIddle
Sui(us limitans
. or
Fold,,1c~hcu lus
Inll'rio!
VesTibulilr alea
La l!"....1
"
~ medull.n e --- ~
HyposiosS.l1nerve trigone
----w- ~
Inferior (ovea
Tubf'rcu luon cinE'reum
f-
(spinal trac t oi tri8emin.,' nerve) '
f----
Cunea te tuberd e / V'l g>ll tfll!one l
"-<J..:i<~
Posterio r mt!di.m
~ulcus
F.1Kiculus Cuneatu~ F.1sck u\us 8 .acill~
~~p ClliiN
Me dian s.lgiuaJ sectio n Ha benular co mmiSiu(e
Body of fornix
\\':.':: :
ChorOid pll'xUS ()f 1m ventrlc.ie
Interventri cul ar fUfill11en
.
c."'
Sple nium oi co rpu ~ ca llosum
1.
(OIMOl'lro) ~
~reat
'r hil~ilmu~ ~ '\Il1. t:omm lssure "'1'> .'lj
lemin
Post. co mmis~ure M~mmi ll arl'
uody
OpTiC chiasm
.Ct'rehral .lQuedu([ \oi Sy [viu~l
I
..
~ . '"
~
_.
r
'-" lgula
Central lubulf'
. h-t
.
O culomotor lUi ) nerve - - - r Supt'rior r.n lliculus
cereUr.ll ve in (ofCillel1)
Vermis
-
Su p. medullar y velum IIlI. medullary ve lum
Medial Iongi[udi n,)l iil!rOculus./
Choroid plexus of 4th velltrid e
4 [h vent ricle
"
Tonsil \ ~ ,1Ae
_ " -- --
""m;d } Uvula Nudule
Vermis
FIGURE 1.43: ANATOMY OF TH E FOURTH VENTRI CLE _ _ _ _ _ _ _ _ _ _ _ _ __
FIGUI The rho mbu s-shaped fourth ve ntricl e extends thro ugh the pons and the medulla. The foram in a of \ \a gendie and luschka must remain pa tent for proper flow of CSF into the cisterns. Bilatera lly sym· metrical pro trusions, depreSSions, and sulci on th e floo r of the ve ntricle defi ne th e und erlyin g anatomy 01 bra in stem regions. Vital brai n stem centers for cardiovascular, respirato ry, and metabolic fu nc tions just below the floor of the ventricle ca n be
44
damaged from tumo rs in the region. The lateral margins of the ventricl e are embraced by th e hu ge cerebellar peduncles interconnecting the cerebel lum with the brain stem and the diencephalon. These relationships are important fo r interpreting imaging studies in the co mpact brain stem region s, w here diagnosis of tumors and vascular lesio ns is challenging.
Cereb late-ra a s s~
cou ld In erea: fo urth
p rOVIC
under: cisterr w irhd . lion o·
'Iuid
Ventricles and the Cerebrospinal Spinal Fluid
OVERVIEW OF THE NERVOUS SYSTEM
- 5"",,'M""".11
SInus
Dura I ;
Choroid "Ic,",
,' fl'" "," ",'01.,1
Interpeduncu lM cist ern
N ", :
Cereb ral J(jueduct (01 Sylviu;)
La!!:'r,1 ] "pefl llfe (f(> ramcn nf
l"",h"'i /'
ChorOId plt>l
Dura m",, -
Cistern of g r~ ,lt c:erebralll('in Cerelwlloml:'dullJrv
d, l", rn (cister na m,lgna) 5uhar acnnoid ,pact' (foramen 01 Molgendit>l
, GURE 1.44: CIRCULATION OF THE CEREBROSPINAL flUID _ _ _ _ _ _ _ _ _ _ __
11
huge
bel-
I.
ing ~i on s,
IS IS
erebrospinal fl uid now ing thro ugh the ventricles .uteral to third to ce reb ral aq ueduct to fourth ) ~5 es through several point s w here obstructi on ~{J ·d preci pitate internal hyd rocephalus a nd ea sed in tracrani al pressure. (SF flow from the 'ih ven tricle into the ci sterns of th e SA space "ides externa l cushioning to prevent injury to '""'Iderlying eNS ti ssue from minor trauma. Some -e'r ns (e.g., th e lumbar cistern) prov ide sites for rxh~ wa l o f CSF (lumbar puncture). The absorp 0 : (S F from the SA space into th e venous
r'
draina ge through the arachnoid granu lations is dri ven by flow through th ese o ne-way va lves. Prod ucti on, flow, and absorption of (S F mu st· be in precise balance; disru p tion of this process results in e xternal hydrocephalus. Flow of the (S F in the ve ntricl es also can act as a fluid-deli ve ry system (or dow nstream intluences o f speci fic media tors (e.g., prostaglandins, interleu kins) and is an internal paracrin e comm unica tion channel for som e struc tures close to the ventricles.
45
OVERVIEW OF THE NERVOUS SYSTEM
Vasculature
. - ____'-,.--~ .
~ t/· ~
r~H i eta ll~,r.J ,In c! fron tal (an t,) br anches of minnie meningeal a.
Middle
menin&e~J
Alilchnoidg, anuJation$
~
Openingoi superior cerebral v. V('nou~
men inge~I.l.
Ant erior
_.'
....""~#'s-..r..;.«~
r..cu na
SupPlior
a.
sag;",,1sinus
(i/om anterior ethmoidal
D ut ~
mater
MaslOid branch
(Ii occipital a .
A nterior and posterior ml'ningeal brilllche!> o f vertebral ...
Milstoid branch il
t,$.-
Mcnin i\fol l branches of asc tmd ing pnaryngeOiI ,1.
Temorral branch (cu t) ,lod
dor ~1
meningeal branch or
rru:,ningohyp op h)'St'-allrunk
Midcile alld .Jcccssory meningeal3<]. --l,! Meningenl b ran ch Of ~osteflor ethmoidal
il .
AI)le rior n)e nlnge;;tl a.llm m anll'rim Clhmoidal aJ --li! \I;,
Intem..,1 (,lIOUd a. and Its nlenin ~oh)'pophystc'al trun k (in phanto m) Mi dd l ~ m~nln 8ea l
a.
Accessory memnge,ll a.~ Sup l2'rfici;:tI tem "orai a.
Po steri o r aUricular .1.
hternal carotid a. --!:
~~ft%
c lIQN : .......,' :1
FIGURE 1.45: MENINGEAL ARTERIES: RElATIONSHIP TO SKULL AND DURA _ _ _ _ _ __ Meningeal arteries are found in the outer pOrlion of the d UI'a an d supply it with blood. They also help supply adja cent skull and have some anastomoses vvith cerebra l arteries. The skull has grooves o r sulci for the men in gedi vessels. This relatio nship reflects an important fu nctional consequence o f skull frac tures. Fractures can rip a m en ingeal artery (usually
46
the middle m eningeal artery) and allow arterial blood to accumulate above the dura. Su ch an epidural hemato ma is a space-occupying mass, and it can produce increa sed intracrani al pressure and risk of herniation of the brain, particularly across the tentorium cerebelli . Even very fine fra ctures can have this dangero us co nsequence.
,
ture
OVERVIEW OF THE NERVOUS SYSTEM
Vasculature
R. and I. mi dd le cerebral ail.
L mi ddle meningeal a.
:una
"
~i n u s
mdter
R. and I. posl I.:erebral aa.
R. MId I. anl cerebral iIiI.
_-<..."
AnL COmmumGlling iI.
R. and I. sup.
R. ophthalmic i1.
cerebell cl r aa.
Ba.ilar a. -
-"4
cC) ll1munica tin g a.
Cavernous sinus
Masloid branch of
L. Int. auditory (labyrinthi ne) , - -"
Post. meningeal branch of I. ascendi ng pharyngCill
eoch
,
R. superficial t emporalJ.
igeal
c--_ _ _ _ _ Carotid body
hra nch lai d.
R. sup. larynlZe" la. R. asce nding phary ngea l ~ . carotid sinu s
Tlwroid <.iIrli lagc
R. cornmon c;;lrotid a. R. int'. thy roid a.
Transverse process of C6
K deep cervical a.
It inL Ihoraeie a.
Brachioceptl
R. thyrocervical trunk R. costocervi c
~
/
' ImN ...-:;: ' ~'
FIGURE 1.46: ARTERIAL SUPPLY TO THE BRAIN ANO THE MENINGES _ _ _ _ __ __ _
II
s, and and
)55 ~S
can
The internal carotid and vertebral arteries ascend thro ugh the neck and enter the skull to supply the brain w ith blood. The tortuous bends and sites of branching of th ese arteries (such as the bifurca tion of th e common carotid artery into the interna l and the external carotids) produce turbulent blood Ilow, and atherosclerosis can occur at these loca tions. The bifurcation of the common caro tid is
pa rti cu larly vu lnerable to plaqu e form ation and occlUSion, threatening the major anterior part of the brain w ith ischemia, w hich w o uld result in a "stroke." Studi es of blood flow through these arteri es are important diagn osti c tools. M agn etic reso nance arteri ography (MRA) and Doppl er flow studies have replaced the older dye studies for cerebral angiography, for most purposes.
47
OVERVIEW OF THE NERVOUS SYSTEM
Vasculature
Vas.1
Anterior (ommuoic
'.,
Circle of Willis
Anterior cerebral artery, Recurrent a. (of Heubnerh,.
Medial an d lateral le nticulostriat e aa. Middl e cereb ral
,
lateral olbitofron tal .... ~
"'I
Ascendin g Irontal (unde labra} branch--....J
"1
." •
Posterior cerebral artery - -
-~
"
Superior cerebellar
..,",
Basilar a . and ponline b ra nches Internal auditory (labyrinth ine)
""
~
Vertebral iI . -
~~ A':'.s.;,~
Posterior inferior c er~ bellar 01 .-- ~. ~
PoslenOr5P1nala. ~:~, Y\ ; \ ____ An terio r co mmunicatin g artery
l,.--- Anteriol cerebral ilt1ery
~ Middle cerebral artery '1.. , POS teri.orcomm.u niC
~ ~
-
Ante nOf chorOId al a.
.
,.:~,1
,-
r--
Optic
p-~
Ifact
peduncle
moo-ot choroidal a. Poste rior lateral choro id al a . Choroid plexu s o f late ral ventricle
- - MediClI genicula te b ody
~ Lateral ventricle
;f~f' ~,.,...,.
c ,iC~ ........"
FI GU RE 1.47: ARTERIAL D I STRIBUTION TO THE BRAIN: BASAL VIEW _ _ _ _ _ _ _ __ Top) The anterior circulation (mid dle and anterior cereb ral arteri es [MeA, ACAJ) and the posterior circula tion (the vertebrobasilar system and its end oranch, the posterior ce rebral artery [PCA]) are ;.hown. The right tempo ral pole is removed to s.ho\\ the course of the MeA through the lateral rIss...; re. The circle of Willis (the paired A CAs, M CAs, and PC-\s and the anterio r and th e 2 posterior commun icati ng ar teries) appears to allow free flow Of blood around the anterior and posterio r ci rcul a~8
tion of both sides, but it is usu ally not sufficiently patent to allow byp ass of an occluded zo ne. (Bottom) The circle of Willis and the course of the ch oro idal arteries are shown. Th e arteries supplying
the brain are end arte ries and do not have suffi cient anastomotic channels w ith other arteries to su stain blood flow. The occlusion of an artery sup plying a specific territory of the brain results in func tional damage that affec ts the perlormance of the structures deprived of adequate blood now.
Gtcl ~e
co
-'00 .
'
.,., COl
·t?'air. - -ne - i:"L1.
:.e e:t -Kri
n
:culature
OVERVIEW OF THE NERVOUS SYSTEM
\ as culature
Frontal view with hemispheres se parated, tilted for a view of the ventral brain stem Co rpus call05um
Paracenlral
•cleof Willis
a.
Frontal br.lilc ht!~ lateral orbilorrOnl.!1d_ Ascending fro nlal (candelabral hrandl Front()poiJ. r ~ .
'~,d':;:~h''',
Ant parietal P r ecent r~1
Anterior cerebral arteries
(prcrolandic)
~nd cent r~1
Medial orhitoironl
R«u rr en l a. (oi Heuhnerl
Tempural branches In t. Middle cerebral artery and hranche s, deep in laterOlI _ _ -.--j~7J)~ ce re hral (sylvia n) fissur e
cmotlO~ .
Ant. cho ro id<:l l <:I.
Posterior cerebral arte ry
AnI. commu nicating - - '"' audilury tlabyrin rhine) .,.
An I. Inf. cerebellar
' -- - Po,t. mi. cerebellar a.
il.
PO, I. spinal a. - -- _-""
- - --
An I. s.p in al ~.
Coronal section through the head of the caudate nucleus Fro ntal horn of 1",,,,,,, ",.,""", Co rp.., s striatum Callosomargina l aa. (head o1 lhe ca..,dale aM P""~'")' Medial and latera l
dlld
'''' ;'"''''''0',.",
~. "",,>fcorpus callosum
Prece nuallprerola ndic l, cerllral (rola nd ie)
and parielal b,"""h,, -~ lateral cerehrallsylvi an)
Inte rnal
11,,," ,,/1
c~ p,ul£
(anlerior li mb)
' -.;,.- 5epl\ lm pellucidum :>:-~"...- ROSTl um of corp us callosum
Temperal b ,."d' .,,-~
'"'. <.;o,~ ,..-\ ~==:=:;;,
Recurrent
Op li C chias m
-
FIGU RE 1.48: ARTERIAL DI STR IBUTION TO THE BRAIN: FRONTAL VIEW A N D COR ONAL SECTION _ _ _ _ _ _ _ _ _ _ __ _ __
_
_ __
Ily
he jying to
up [une
he
The course of the ACA along the midline reflects its blood supply to the zone of the sensory and m otor
cortices, which are associated with the contra lateral'lower extremity; an ACA stroke thus affects the contralateral lowe r limb. Th e M eA co urses laterally and gives branches to th e entire convexity of the hemisphere. End bran ch infarc ts of the MeA affect th e con tralateral upper extrem ity and, if on the left, language functio n. More proximal infarcts affecting the MeA d istribution to the internal
capsule cause full contralateral hemiplegia w ith drooping of the contralateral lower face; this results from damage to cortico spinal and o ther cortico moto r fibers in the posterior limb and to co rti co bulbar fibers in th e genu. Th e lenticulostriate arteri es ("arteries of stroke" ) are thin branch es of th e M eA that pen etrate into the basal gan glia and the internal capsule regions in the forebrain. A stro ke in this area produces the classic contra lateral hemiplegia.
49
OVERVIEW OF THE NERVOUS SYSTEM
An'erim r.ereb¥J,1arl ery
Middle cerebr al artery
Vasculature
~~(
j'c, te ri or c0l11muniC3!ing
Antenor comnluniGlling
..
Pu <;teri or cereb ral artery
'."
O pht ha lmic arte ry
~ :..-:e; n n
Caroticotympanic bra nch of
intern,; j caro tid arter~
a
Suprao rbi ta l artery
, :;-.<..
Supr atrochlear art er y l acrimal artery
:11
Dor!>al nasal arl ery Middle meningeill drle'
1f-:1
Middle men in geal "fIery An gular artery
M 3:.:illar ya rter y
f1. Ii:.. \. " Superficial te mporal arter~' \ Pm terio r auricular afl ery
Anteri or inierior cerebellar " ' G... ./"\\.
FaCial artery Posu= ,ior infe rior cerebella r artery / ' Occipital arte ry lingual artery Asce nding pharyngeill artery
Superior thyro id 5
Co m mon c.lrOlid ar tery ~i
..#1
...
Anterro r ~pj nar artery
Spina l segmen ta l med ull ary branch es Vert ebra l arter y AKe ndin g cervical arl <, ry ,- Com mon calO ti d artery
Inferi!)r ,11yro icl art ery ,
Df!ep cer vical arte ry
ThylOcervicaJ trun k
Transve rse ce rvical artery
,,"""
.ti::,:...d
Suprasca pul ar artery
.:c~ Supr<, m(' in tercos tal arte ry
~ Co" o" ..,«>1~"k Subda~'ia n
Sutx iavian artelY Brac hioce phalic tr unk
U
artery
Internal thoraci c artery
'it
Anastomoses
,,,h Aorta
{
Descending, ~_==:=: Ascending -
1 Rlghl-lelt
~~p
. ,.~
2 Caroti d- Vertebr
3 I/\Iemal c;arc)[id- EJ,: temal carotid 4 Subcl avi an-Ca rotid i Subdavjan-Vertebr
FIG L RE 1.49: SCHEMATIC OF ARTERIES TO THE BRAIN _ _ _ _ _ _ _ __ __ _ __ Thi s schematic diagram shows the entire layo ut of separation of the anterior (M e A, ACA) and poste
me an erial blood supply to the brain, including rior (vertebro-basilar, PCA) circulation are evident
anasto moses. The ci rcle of Willis is present in the in this diagram.
uoper central po rti o n of this schematic. Th e relative
"2 01
en 011
30
u
•
OVERVIEW OF THE NERVOUS SYSTEM
'asculafure \ asculature
Vessels dissecloo Qut: infe rior view AMerior cerebral artery (Az segmenO
_--1 1
u".....,-- Medial striate ilTlery (recurrent ':lr1ery
01 He ubne r)
M teromedial centrilil perioraling) arteries
"" m,,"') - --;;;;;ft.p.( Ophthalmic artery ----I~f:~'
Hypo th alamic artery
Anterior ce rebral art ery (AI
Internal carotid ", n..y
Ii_-<~''''''O''''''''
" ",,,1 ilenticulost ri ale) a,rerit's
--::J;;:;;;;~~f<
Middle cerebral arl ery Posterior y
WM'""I''''"g"',,,y ---!J-....l~.-:.
Superior hypop hyse~1 artery Inferior hypophyseal art ery
rosterio r cere brill il rlt':y I
AnleriO( choroid,,1 artery
segment)
, "h,)"m,,,u),oc,,I(,,,oc,,,,.. mllllll,,y: allery
' P'"" ,"O,..."i, I ceollal (per'orating) artery
SUllerio r cerebellilr ilrt ery
",,~ //'-;"'-~ Pontine "',~I,, __..o::;;;~ Basilar
anches
Vesse ls
Posteromedial centl al (pa,,}medi.m) arteries ~--
Anterior inferior cerebellar illteo"V Verlebrill il rtery
Thabmoperlorallng artery
labyrilld'line (I ntemal acoustIC) a!tery
~~-.A
in situ : infer ior view Ante ri or ce rebral artery
---",:-11..11--,--:- Anterior co mmuni ca,in g ..rter y Cavelno\ls sinus
Su perior hyl~"hy,,,') ""
Iniundibu lum (pituitary stalk) alld lon~ hypophyseal portal veills
Middle celebral . , ..""" .
,
(nierior hypophyseal artery
:.--
Adef)ohypophy-;is (anterior lobe of pituitary gland)
Neurohypop hY'lois Ipmterior lobe of pnuilary gland )
Poitt'llor communicatin8 art~ Efferen t hypophyseal \'eills "lal carotid
Posterior cerehral artery
0;;;;0;,-.- _ Postelomedial central {perioriltingl arteries Superior ce rebell
-~- Basilar artery
FIGURE 1.50: SCHEMATIC OF THE CIRCLE OF W ILLIS _ _ _ _ _ _ _ _ _ _ _ _ __ )oste ident
Th e ci rcl e of W illi s surround s th e optic tracts, the pituitary stalk, and th e basal hypothalamus and is the most frequent site of cerebral aneurysms. It includes the 3 sets of paired cerebral arteries plus the anterior communica ting artery interconnecting the ACAs and th e posterior co mmunicatin g arteries int erco nn ectin g th e MCAs and the peAs. The free flow of arteria l bl ood th rough the communicating
arteri es is usually in sufficient to perfu se the brain
adeq uately in the fa ce of an occlu sio n to a major cerebral artery. An aneurysm is a ballooning of an artery resulting from an inherent weakness in the arterial wall. A rupture can lead to a subarachnoid (SA) bleed, with loss of perfusio n to vital CNS territories.
51
OVERVIEW OF THE NERVOUS SYSTEM
Vasculature
\ ""
Laler.ll view AnI. p
Ce nlrill (ro Jandic l branch
,." 1
Precenlral (prerolandic) branch
Ascending frontJI {cand ela b ra ) brJ nCh
.'
-
j;. ,1 ?"
Termin(ll cortical branc/1...,
~"'~-.' I
_~
oi I. po<;lenor ce rebral ;;l.
Tr rrn ir'lil i co rti cal branch es
01 anI. cerebral ilil.
lateral orbitofronlal a. Post ttom pora l L. middle
bra n che~
L anterior
An i. tem por~ 1 branches
cerebral artf'ry~
cerebral arlery ~ A nt. communicating iI .
R. anferior cerebral arterY / ' l. internal carotid
il. /
Medial view
Paracent ral iI. PericalLosal i1. Precuneal ...
[nl.lrantal { posterior bril nches
Mldrll Ante,i
R. posterior ~rebril l art ery
Post pericOIliosal a. ( J)1owmilrginilJa.
PJrietoocdplta l br~ n ch Post. tem po ral bra nc h
R. anterior cerebral artery ~ ~ Medial O'h to iro nta l J .
'ted
All t. temporal h ranch ...... . ~ _
Ca lC J r101' b ran c h
~- . (ommuniQ ling a. ~ ReC\J rre n t ~.
(of lil'u b ner ) R. in tern al cJro tid a. /
Post. c ommunic atin g a.
~~~ O '.~N
fl GIoRE 1.51: ARTERIAL DISTRIBUTION TO THE BRAIN: LATERAL AND MEDIAL VIEWS _ _ __ lOP The ,'v\ CA sends th e named branches alon g the 5wJdace or the hemispheric convexity into the ~ron:a: and parietal lobes and into th e anteri or and middle regio ns of rhe temporal lobes. Occlusion disrupts 5ensor v and motor functions on the con trala:efal bodv, especially the upper extremity, or on the entire contralateral body if the internal capsule is aiiected . (Bo ttom) Th e ACA distributes
,-,
to the midline region o f the frontal and parietal Jo bes. Occl usion disrupts sensory and motor functions on the contralateral lower extremi ty. The PCA distrib utes to the occipital lobe and the inferior surface of the temporal lobe. Occlusion disrupts mainly visual functions from the contra lateral visual field.
FlGL, -t:"
SJ
~"'"
-,
culature
Vasculature
OVERVIEW OF THE NERVOUS SYSTEM
branches ebral .1.
II II II
Anterior celebr..1,ule ry
Mid dle ce re bral
Posterior cerebral ilftery
>ranch
II§N •.•.".,'::
\ '.';.': ::
;
-
FIGURE 1.52: COLOR ILLUSTRATION OF TERRITORIES OF THE CEREBRAL ARTERIES _ _ __ Th e specifi c mid lin e and lateral territo ri es of di stri bution of th e ACA, M CA, and PCA illustrate the exclu sive zo nes supplied by th ese major arteries
and make particularl y d ear the wa tershed zones at the junctions of th e majo r cerebral arteries.
.
53
OVERVIEW OF THE NERVOUS SYSTEM
Vasculature
Femoro cel"('b ral Angiography L>'.... I ... oj« "
o~
Vase!
-
f.......t ~~
~".:..IJlo...l. C.ilr> "", ,, , ~..,. I '
,;",1 A~:",c<
o', . ~~ . I
.' It
•.
k'fII;a,ro"".....,
, .....,,:,01
Op "" ''''''''
"',~
(in terhe1j
f iGU RE 1.5 3: ANGIOGRAPHIC ANATOMY Of THE INTERNAL CAROTID CIRCULATION _ __ The left plate is an angiogram lateral view of the in ternal ca ro tid arterial circulation after injection of a rad io-opaque contrast agent into th e internal ca rotid artery. The major branches of th e internal carotid artery, particularly th e anterior cerebral and
middle cere bral arteries, are delineated. The right j'):ale is an angiogram frontal view o f the internal carotid arteri al circulation afte r injecti on of a radio
opaque contrast agent into the common carotid artery. The majo r branches of this arterial system are delineated. MR an giogra phy is used commonly to investigate the status of the cerebral arteries, but does not provide the same level of detail fo r anatomical purposes that standard angiography provides.
Heads d. Thala1 )a telal I~
,
Arteri es of Posterior en nia) Fossa V~nehral AnV<>&r.I<M:,,~ ria! Ph~
,
fiGURE
The vertl l ·;:""'~O bfMlC~----.J ......, Ini. CCfeWI
<>1" 1 PQ>I.inr = ct-..:l MI .
,CICoN 1 ~ '.'.-' : :
FIGu RE 1.54: ANGIOGRAPHIC ANATOMY OF THE VERTEBROBASILAR SYSTEM _ _ _ _ __ The upper figures show angiogram s of both lateral and ironlal views of the vertebra-basilar (posterio r) circulatio n after injectio n of a radi o-o paque ca n· lra~t agen t (dye) into the vertebral artery. Th e major 2Ilerial branches o j thi s arterial system are delin e2 red. The lower figure is an M R angiogram show ing both the in ternal carotid and vertebro-basil ar
54
circulatio n. The maj or branches of these arteries are labeled. Angiograms with contrast agents pro vide more detailed anatomical info rmation, but are mo re invasive than MR angiography. MR angiography is used w ith greater frequency, although use of contrast agents still occurs for specific diagnostic purposes.
the basil.
extend if ing w ed ~ can prod tralateral age abm ipsilatera to m s. Thl the largel such as tI
(PI CA ), tf
ulature
OVERVIEW OF THE NERVOUS SYSTE M
3Sculature
in,m::.r
•••
Arteries of Posterior Cranial Fossa Crur~
-
•
of fornix
Septum pellucirlum
dnood,
Lateral and medial geniculate bodies of left ,h,l,c-,",_/"
Corpus callosu m
~.<> oi
_
ltid em nonly 'S, but
hy
'ro
An!. cerebral aa. Longitudinal '_,,(hemispheric) 11
,
Post. horn of r. lateral ventricle
•
o~
\
"
. _
-(;o dds of
.
"'alamogeniculate aa. Medial and OL'erallentlculostriate aa. Ant. choroidal 0
Right} (horoid plexuses of Left lateral ventricles
Right and le ft pulvinars Splenium of corpus (~llosum R, post. pericallosal a. Parietooccipi ta l and Calcarine branches of r, post. cerebral
L. sup_ colliculus
_ __
Sup_ vernlian .1_ Post, medial choroidal a. (to choroid plexus of 3rd ventricle)
Ant. cerebral" ___ Optic:.: (IIJ n. and ophthalmic a. Middle cerebral a.
Pos!. latera l choroidal a_
Thalamoperforating aa.
L. post. cerebral J. with ant. and pos t. temporal branches
Post. communicating a.
Lateral marglllal branch of sup. cerebella r a.
Lint carotid a. Sup. cerebellar a.
Inf. vermian a. (in phantom)
Basilar a.
Choroid al point and (huroidal a. to 4th ventricle
Int. auditory (labyrinthine) il_
TonsHiohemispheric branches Outline of 4th ventricle (broken lineJ Post. meningeal hranch of vertebral a,
l. post. spinal a, L vertebral a_
Ant. spinal J.
FIGU RE 1.55: VERTEBROBASILAR ARTERIAL SYSTEM _ _ _ _ _ _ _ _ _ _ __
The vertebral arteries unite at the midline to form the basilar artery. Medial penetrating branches extend into medial zones of the brain stem, supply ing wedge-like territories. Infarcts in these branches can produce "alternating hemiplegias," with con tralateral motor deficits (corticospinal system dam age above the decussation of the pyramids) and ipsilateral brain stem/cranial nerve signs and symp toms. The vertebral and basilar arteries give rise to the larger short and long circumferential branches, such as the posterior inferior cerebellar artery (PICA), the anterior inferior cerebellar artery
_ __
(AICA), and the superior cerebellar artery (SeA). Strokes in these arterial territories produce a con stellation of ipsilateral brain stem sensory, motor, and autonomic symptoms and contralateral somatosensory symptoms. For example, a PICA infarct results in loss of pain and temperature sensa tion on the contralateral body and the ipsilateral face. The end branch of the basilar artery is the peA, distributing to the visual cortex and the inferior temporal lobe. Occlusion results in contra lateral hemianopia. .55
OVERVIEW OF THE NERVO US SYSTEM
Vasculature
Vas.c-li
/.
,.
~
-,,? J
Hypolhill"mic vessels
PefJQ
(
s...
'"! ;
,
W ~
Supe rior hypophyseal a rlefy
l ong hypophyseal portal veins
\
Pos teri()( branch
}
(from internal caro tid A. or pest. com municating A.)
Shorl hyp0l-'hysea l portal v e lr'l S
.......
Art ery of trilbecula
Trabc
Effercot "eirt 10
Anterior lobe Second ary plexus of
hypophysE'ill porlal syste m
L.l!e r.ll brimch /
,nd
Efferent vein to c;wernOU$ iilluS
Q; Imenor hypoph yseal ;Jrteryl Irom the Internal Cilroti d A.I
Ca\'ernous sinus
.) ~fJ!:
Inte rn al carotid allery Posterior commu nica1ing artery
ft l'{fI
Superior hypoph \~e3 1 artery
InieriQr nypoph\'seal arter,' /
~~p
ClmN
1\·.·.·:::
FIGL RE 1. 56: VASCULAR SUPPLY TO THE HYPOTHALA MUS AND THE PITUITARY GLAND _ _ TI-e supe rior hypophyseal arteries (from th e le A or tt:e posterior communicating artery) supply th e h\'pothalamus and th e infundibular stalk and anas to"'10se w ith branches of the inferior hypo physea l arte'"\ [irom rhe leA). A unique aspect of this arter ial distribu tio n is the hypophyseal portal system, \\ ho~e pri mary plexus derives from small arterio les arrd capillaries that then send branches into th e ~~erio r pitui ta ry gland. Thi s plexus allows neu ro ns that produce hypothalamic releasing and inhibito ry
56
facto rs to secrete th ese facto rs into the hypo ph yseal po rtal system, w hich delivers a very hi gh concentratio n directly into the secondary plexus in the an terior pi tuitary. Thus, anterior pituitary cells are bathed in releasin g and inhibitory factors in very high co ncentrati on. Thi s private vascular co m muni cation channel allows th e hypothalamus to exert fi ne control, both directly and throu gh feed ba ck, over the secreti on of an terior pituitary hormones.
su~
""ece;\e --cludir -omtfl; food il .:;.load (I and ou.
:ulature
OVERVIEW OF THE NERVOUS SYSTEM
ta.sculature
Calva ria
Arachnoid granula tion
s"p,""m sagittal sinus
Emissary v.
Skin
- lobe Falx ce rebri
Diploic v. Pia m aIer
Epidural space (potential)
Superior Cf'febral v.
Subdural space
Cerebral Arachnoid Subarachnoid space
igh .us in
ells n :om to
FIGURE 1.5 7: MENINGES AND SUPERFICIAL CEREBRAL VEINS _ _ _ _ _ _ _ _ _ __ The superi o r sagittal sinus and other dural sinuses receive venous blood from a variety of veins, including superficial cerebral veins draining blood irom the cor tical surface, meningeal veins draining blood from the meninges, diploi c veins draining blood from channel s loca ted between the inner and o uter tables of the ca lvaria, and emissary vein s,
which link the venous sinuses and diploic veins with veins on the surface of the sku ll. These chan nels do not have valves and permit free communi cation between these venous systems and the venous sinuses. This is a Significant facto r in the possib le spread of infectio ns from foci outside the cranium to the venous sin uses.
ed
"
OVERVIEW OF THE NERVOUS SYSTEM
Vasculalure Cerebra l v. penetrating subdura l space 10 / (bridglng "eim)
Scalp, skull, meningeal ;md cerebral blood vessels
~ ntet
Vas(
sinus
gr
Fronw l and 1),lfIelal tribUIJ:rit!s
of superrldal temporal v, -........
r rontal ilnd parietal branches
of supertlci,ll temporal a. ArachnOid gra"ula(;on inden tin g skuliliove~i
Middle meningeal
a. and \"
Ve nom lacuna
Deep middle and ~ upe l fi cjal
lemporal
Thalamos\rlilte
o1a. and vv.
imd internill cerebral vv_
,"d Ct'rt!bral vv.
""
Tenl!
Diploic and emiSYry veins of skull
Parietal emissary v. Fron tal d iploic v_ ~
Po~l erior
temporal diplok: ....
Occipital emiSSilry v, Anterior temporal
O ccipita l diploic v.
~
diplojc ,, ~ ~1
til M~IOid
emiSMry v.
~~p ° 11!!N
l\': :.'::
FIGURE 1.58: VEINS: SUPERFICIAL CEREBRAL, MENINGEAL, DIPLOIC, AND EMISSARY _ __
FIG UI
Venous blood drains from the skull, th e meninges, and the cerebral cortex into the superio r sagittal si nus an d other dural sinuses. This area is vulner·
The ia
able to infectio ns and co ntamin ation from drainage from superficial venous networks into the central venous sinus channels.
slons ( (onfin of the nor sa thedu deep r
jugula the sIr into th
58
iasculatu n:
OVERVIEW OF THE NERVOUS SYSTEM
ulalure
; In"''''''''',I"' (circular) sinus and pi tuit.l ry gla nd
Super ior ophthalmic v.
Basilar plexus
Internal caro tid
3.
d space
:e meningeal 11.
and,_
) middle dnd superficial temporal aa. and 11\
I Deep ,md superfiCial middle «('rebral V\.
n.
::::'ft::--
Superior
and inferior
~trosal sinuses
Jugular foramen Sigmoid sinu~ Accessor y (XI) n .
e.:..:~7-'-_ HypoglosS
O pening of an inierio r cerebrdl v.
Confl uence of ; '''''.; - - - ' Superio r sagina l si nus
---"::::'''::::::':::':''':_--<
Infe ri or sagittal ; """',
--:t
Greal ce rebral v. ("f Galenl Intercallet'nous sinus
- - ..j
SuperIo r pelrosa l ~nus Sllilight sinus Inierior petros.al
"~"~"""
- -::'1f!
Sigmoid sinus --"""~
Ocdpital sinus
FIGU RE 1.59: VENOUS SINUSES _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ __ Image tra l
The falx cerebri and th e tentori um ce rebelli, protru sions of fused inner and ou ter dural membranes, co nfine the ante ri or, mi ddle, and posteri o r fossae of th e skull. O uter (s uperio r sagittal) and inner (infe rior sagittal) ve nous chann els found in split layers of the dura drain blood (rom the superficial and the deep regions o f th e e NS, respectively, into the ju gular vein s. The grea t cere bral vein of Galen and th e straight sinu s merge w ith th e tran sverse sinus into th e co nfluence of sinuses to drain the dee p,
poste rior regio ns of the eNS. Infection can be introduced into the cereb ral circulation through these sin uses. Ve nous sinLIS thro mbosis can ca use stasis (a backu p of the ve no us pressure), w hich ca uses in adeq uate perfusion of the regions w here drain age should occ ur. Th e pro trusions of d ura are to ugh, rigid mem branes through w hi ch porti ons of the brain can herniate w hen intracranial pres~u re in creases.
59
OVERVIEW OF THE NERVOUS SYSTEM
.,.,. ~ ',. ,
E:"
Vascu lature
1
'~:Jl- longilUdi n
~,
'J\
AntE"=OJ (erern-al vv. Rf)5irUm oi ( 01PUS callosum 5~plUm
pelluddum
leriOl septal v. He.ld of c nucleus t erminal (caudate) v,
Inlen'entricular foramen (or ,'-'\onro) Colum ns 0 1 iorn ix Thalamoo;:tri.1te v. Superior choroidal \'. and choroid plexus oi lalera l venllicie
,I Tela (horoidea oi Jrd venl ricle Direct I.ltera!,' Posterior lemlinal (caudate) v. ternill ceteoral " " . Sasal 'to (of Rosen l h ",!)
G reat cerebral o:. loi Ga len) Inf~i nr ~a:; itt,'1 s irlU';
i£hl 5i l entnrium ce rebelli ,~ "'''r Tran sverse :;inus Cunllu enc:e of ~inu s('s Superior sagittal sinus
~ ~!¥ ~;@N , ':;, ...
Dissection from above
Uncal ...,
Ant criOI cerebral v. Superficial m iddl~ ce.tc'bral v. (draining to sphenopariet.ll sinus), Infer ior cerebra ~
Ba!>dl v. {of ROSt>fllhal,
Med ial genicu lJle bony
Splenium of
corpus cJlio!oum
Great cerebral 1/. (of Galt'fl l
Interior anastomOlic v.
(of Labb e)
Dissection from below
FI GURE 1.60: DEEP VENOUS DRAINAGE OF THE BRAIN _ _ __ _ _ __ _ _ _ __
FI'
(Top) This superior view of the thalamu s and the basal ganglia reveals the venous draina ge of deeper forebrain regions into the posterior venous sinuses. (Bottom) Thi s basal view of the brain w ith
Su bIc
60
the brain stem removed illustra tes the drainage of forebrain and mesencephalic veno us blood into the great cerebral vein of Galen, heading toward the straight si nu s.
g"
dr.
:ulature
Ige of into " ard
OVERVIEW OF THE NERVOUS SYSTEM
Vasculature Subependym a l Veins
~ V('i n, u n
I"'N, I w all 0 '
"""' n r.l~
V",n; on me,li,-rI .... ,, 11 J"d flo o ' <.i f v "')l ric l ~ =---;z All 'llhlOf , -ei", --' ~;r"
roM
lcrm,nal fClurl~I"')' (po.t
p~"
of IhJf.l1llosvial.· ~_ ,
In L cc r~ Or" 1 ,,_
,,,f
G 1 corpus C3110Sllm
~
/>'
'\
~fe"
(",-cb r. ,I"
foIGa "",' :'
I
/
D""'I> middle cereb, ~I ,. In/. lhaL'''·'OS1r h)lf' ""_
B;o,.a IY.lui ,,'_""," In!. hom o f l" lcd
(,-,r~he
4th """" ,,<. 1..
Carotid Angiogra ms; Venous Phase (Su bependyma l an d sup erfi cial vein. opac ifi ed) \~" .
Sup_ s.~li:jl!~1 sonu,;
',e..,",,' IWUd.-.lf') , _
-
L;Uer~ 1
projectio n
Fro nta l p roj e
v '""~~,""
FIGURE 1.61 : DEEP VENOUS DRAINAGE OF THE BRAIN: RELATIONSHIP TO VENTRiClES Subependymal regions of the e NS drain veno us bloo d into th e inferior sagittal sinu s (left) o r the great cerebral ve jn of Galen (right). bo th of wh ich drain into the straight sinus. O cclusio n o f a vein in
this regio n causes a blockage of drainage and a backup of pe rfu sio n, w ith resultant ischemi a oi the tissue in th e re gion s of drainage.
61
OVERVIEW OF THE NERVOUS SYSTEM
Vasculature
Veins of Posterior Cranial Fossa l. Slip ilnd inL callicuti
~eft
P"rt, of c"r~bdillm L lingula TU tub.>r CL centTdllobult, P ~yrilmld
putvinar
C
o
Right thalamus
culm""
U
uvula
d".cJlv~
N T
ron,il
folilJm
nodule
Int. cerebral n, Splenium of (orp<JS callosum
Medial geniculdte
Great cerebral v. (of Galen)
Lateral mesencephalic v.
}{
\i,
V~.', ~-
Ii Inf. th~l,lnlostria'e VV.
. '
Inf. sagittal sinus
~
_ .,:, -:> ,
..
-;7 ~ ~- .;";';;'1'<" ~- ~;: ;' i!i"-,:, ::/ ~;- Linconst'lnt) /' .
/ >
<-}, / "\:.,
,:.,v;,.'$B .;; .' .' ,."
--"'
Sup.
vermi~n
Ant. cerebral v.
Optic (tl)
v.
Straight sinus
11.
Falx cerebri Deep middle cerebrcll v.
Sup. sJgittal ,inus Tentorium cerehelli (cut)
Anl. ponto mesenceph;
Preculminate v. of sinuses rOetros~1
v. (dlJilling to sup. pelrosal sinus)
L transverse sinus
i. vermian v. \ ~,llx cerebclli (cut) and occipital sirius
nti Vestibulocochlear (Villi
~~
r-acial (VII) v. Ant. medullary
.,
,
L.laterJI nrJchial v.
Vein of laterJI recess of 4th ventricle Sup., middle and
mt. cerebellar peduncle~ 4th ventricle Ant. spinal
" Int. cerebellar hemlsphcricvv. Precentral v.
v.'
. spinal v.
~~~ ©IIiiN :W'-.': :
FIGURE 1.62: VENOUS DRAINAGE OF THE BRAIN STEM AND THE CEREBElLUM _ _ _ __ The venous drainage of the cerebellum and the brain stem is anatomically diverse. The veins of the posterior fossa drain the cerebellum and the brain stem. The superior group drains the superior cere- bellum and the upper brain stem posteriorly into the great cerebral vein of Galen and the straight sinus or laterally into the transverse and superior petrosal sinuses. The anterior, or petrosal, group
62
drains the anterior brain stem, the superior and inferior surfaces of the cerebellar hemispheres, and the lateral regions associated with the fourth ventri cle into the superior petrosal sinus. The posterior, or tentorial, group drains the inferior portion of the cerebellar vermis and the medial portion of the superior and inferior cerebellar hemispheres into the transverse sinus or the straight sinus.
•
lature
-
OVERVIEW OF THE NERVOUS SYSTEM
Vasculature
Anterior vi ew Pus/eri or cerebral a.
Posterior view
~A
Postelio. inferio r cerebellar a.
Superior cerebellar a.
Pos terior spin al aa.
Basilar
.
..
~
filmid
ifu le
'
An/c riOI inferior cerebellar a. Pos terior inferior ce re bellar Posterior rad icular
Anterior s~ n a l a . Cerv ical
Vertehral a.
verte Or.:te
Deep cerviC;1J.1.
Anter ior radicular aa.
A~ce ndin Fl
Ascending cervical a. ~Iar v.
Deep cervical
SI.)nl)
Subclavian a.
~:v,
•
-'>-..,
c.erviLal a.
Subdavian .1 .
Anterior ra dicular a. Pos terior intercostal a. "<~7r{~ t
~rebri
19i1lal Thoracic ,'erte-brae
n
("'~\~) iiI,r;
.:O>iJ---t-- Posterior in te rcostal a.1 .
cut) ~le
v.
Artery of Ada mkiewicz (major ameriOlladiculill a.)
--"im
Anteri or ra dicular a.
"'--r--
Posteri or rad icular aa.
lumbar aa.
Anastomotic loops to posterior spinal
lumbar vertebrae
*.-"-- An astomotic loo p ~ to anterio r spinal a.
iN '.'J,:
, l,' Ie,·,,1Sdcral (or median saer" l) a, lateral SGlClal (or med ian saoal) a.
-
ri
e
- -H ,j
FI GU RE 1.63: ARTERIAL BLOOD SUPPLY TO THE SPINAL CORD: LONG ITU DINAL VIEW _ __ The major arterial blood supply to th e spinal co rd derives from th e anteri or spinal artery (ASA) and the paired poster io r spinal arteries (PSAs), bo th bran ches of th e vertebral artery. The actual blood tlow through these arteries, derived from th e poste rior circulatio n, is inadequate to mai ntain th e spinal cord beyond the cervica l segments. Radicular
arteries, deriving from the aorta, provide major anastom oses with th e ASA and the PSAs and supplement the blood flow to the spinal cord. Impaired flow thro ugh these critical radicular arter ies, especially durin g surgical procedures with abrupt di sru ption of b lo od flow through the aorta, ca n result in spinal cord infarct 63
OVERVIEW OF THE NERVOUS SYSTEM
Vasculature
\,
Arteries of cerviCilI
cord exposed from the rear
Basilar artery Posterior inferior cerebell ar artery
Verte bral a rtery Anterior spinal artery Spin al ramus
Pm/erior spinal ar tery Posterior radicular artery
Pre-laminar branch
~~p
. ,~~
~t , ~
An terior spinal artery
Post-central branch
Ii-
-t-'
1( ~~
!l ij
t
' -:"J,'
Anterior centra l arter y - -_ _ _--, Spinal ramus
•
roo' .Jl4jj.~
N eural bran ch
..~:.:;;:;,"
Anterio r radicular artery
(-; «-}
Posterior ra di cular artery - Internal .pinal Mteries Po slerior central artery
Pre-bmina r branch Pos terior spinal artery
~;!". ,!";;!" q:A;7i -'~ t.: :..e "" -'.
.•.:.;;..:.,~' .~. -
.- ,
'" ' ._ . ~~+."
. , _: :",~~:~,:,
.,~~
Arteries of spinal cord diagrammatically shown in horizontal section
FIGURE 1.64: ANTERIOR AND POSTERIOR SPINAL ARTERIES AND THEIR DISTRIBUTION _ __ Th e ASA and PSAs travel in the SA space and send branches into the spinal cord. The ASA sends alter· natin g bran ches into the anterior median fissure to supply the anterior two-thirds of the spinal cord. Occlu sion results in ipsilateral flaccid paralysis in mus cles supplied by the affected segments, ipsi lateral spastic paralYSis below the affected level (upper motor neuron axonal damage), and co n tralateral loss of pain and temperature sensation
64
below the affected level (damage to the antero lateral spino thalamic/spinoreticular system). Th e
.. ~ I
PSA branches sup ply the dorsal third of the spinal
r.;c
cord. Occlusion affects the ipsilateral perception o f fin e discriminative touch, vibratory se nsati on, and joint positi on sense below the level of the lesio n (from damage to fasciculi gracilis and cuneatus, the dorsal columns).
(asculatu lll
-
~ ulature
OVERVIEW OF THE NERVOUS SYSTEM
7.:;:..,,;=;;::;;;:;;;::-::--- Posterior spinal aa. _ _" """iio, radicular a. _ _' Po ;(e"io, radicular aa.
r ___ Boa n, h to vertebral body and du ra mat~r ' - - - S oii ,,11 branch ' - --IDo,,, ramus o f posterior intercostal a.
L _ -'>,,,.,,,,',,et,oall anastomosis _A"v,~ .eb..'
anastomosis
Section through thoracic spine
~_ ~~;~:.:~~::~~,:::: ~Q
I branchesa, from pial plexus
Central branches to right side of ,p;n" w,d -----A~r:5:
_,Cen'"
branches to left side of cord poste rior spinal a.
Anterior radicular ,,-- - - -
Pial arterial
_-Zo" supplied by pen etrating branches from pial plexus
p' e"'----
-
Zo,oo supplied by central branches
r - _ Zone supplied by both central
Posterior radicular a,-- -- - -,/i
branches and bra nches (rom pial plexus
Anterior 'p;' ""a,----~c...-3.\;:;',4.~:::~5 Schema of arterial dist ribu tion
-
11-
P"';'e,;,", radicula r a.
.
;
""--Pia' " ""ii,11 plexus
-
FIG UR E 1. 65: ARTER IAL SUPPLY TO THE SPI N AL CORD: CROSS-SECTIONAL VIEW _ _ _ __
"I I
of
The major contribution to the arterial blood supply of the spinal cord derives fro m the aorta via the radicular arteries (top). This intercosta l blood sup ply also distributes to adj ace nt bony and muscular
strud ures. The penetrating vessels supplying the spinal cord derive from central branches of the ASA and from a pial plexus of vessels that sur rou nds the exterior of the spinal cord.
d
:he
65
OVERVIEW OF THE NERVOUS SYSTEM
Vasculature
Veins of Spinal Cord and Vertebrae ~ Anlefior ex!ernal venous plexus
,
..._____Posterior external venous plexu s
inlernal venous plexus ...erlebral v. 'srverlebral \'
An teriOI and posterior radicular w
Anterio r external
plexus Anterior internal
,I, POSlerior internal
plexus
Anterior spinal v. Anterior central v.
Basivertebral v. Ant erior intern al
venous plexus
"j- v
PoSleno r ra dicula r v.
-
- -Internal spinal vv.
" '17.~ ~;c.-~~~,-
~ f$~'
.,. ., ....~>.•,"1>.~'
.........:: ~~.~~'b..":~",",N~ ;<~..
;$- ~Posler~;centraJ v. ,
.
Po stenOf spInal v.
Posterior inh~rn,) 1 venous p lexus
~~p " ..•.
° llliN
".: : ~
FIGURE 1.66: VENOUS DRAINAGE OF THE SPINAL CORD _ __ _ _ _ _ __ _ _ __ An ex ternal and an internal plexus of veins extends along the length of the vertebral column, fo rming a series of venous "rings" w ith ex tensive anasto moses around each ver tebra. Blood from the spinal cord, the vertebrae, and th e li gamen ts drains into these pl exu ses. Changes in intratho rac ic pressure
66
and (SF pressure ca n be conveyed through these venous plexuses, affecting the venous vo lume. U ltimately, these venous plexuses drain thro ugh the intervertebral vei ns into vertebral, posterior intercostal, subcostal, and lumbar and lateral sacral veins.
f
a
"
Ll
- ose
h
OVERVIEW OF THE NERVOUS SYSTEM
"¢~"".......",,
Oropharyngeal
membrane
- --,rf"''--. .,
Lens plDcode
Hypophysis
Pa raxial column Intermediate
col umn ~--la'eral plate
"'ppearance of the "'lj!ural pl ate
OP lic area
Neural crest
'\:eulal plate
forming neural tube
Interm ediale~_
Spin'}l
_
mesoderm
'-, traemb ryonic
Dellelopmental (ates of
local regio n§ of ectoderm of embryonic disc al 18 days
AGU RE 1.67: FORM ATION OF THE NE URAL PLATE, NEURA LTUBE, AN D NEURAL CREST _ __ - " e neural plate, neural tub e, and neural crest form ',h e 18-day sta ge of embryonic development.
- "'e underlying no tochord induces the neural plate, r d a midline neural groove forms. The eleva ted ..a.:eral margins become the neural folds, tiss ue
destined to become the neural crest with a future co ntribution to many components of the PNS. At this very early stage of embryonic develo pment, these neural precursors are vulnerable to toxic or other forms of insult
67
OVERVIEW OF THE NERVOUS SYSTEM
Neuril l plate of forebra in
Developmental Ne uroscience
lr;
'0 0-"
Neural groove ~
<
Neural fold s E E
q "!
n it,,"
Fu lure neu ral cre~t,
"Neural fold
;,
Primitive streak-- '
Embryo at 20 days (dorsal vi ew)
Neural ,..-'-' f' of fo rebrain----;;-i
Neural groove - - -
Neural folds""- c
E ~ ~
Fu ~d neural folds-
1SI cervical wmile
Caudal neuropore
~~;r.:
CIIilI\I
- Embryo a t 21 dayS
,',":,":::
(d OlSal view )
FIGURE 1,68: NEURULATION _
_ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ __
fl(
In the 21· to 22-day-old e mbryo, the ne ural plate, w ith its midline ne ural groove, thi ckens and begins
no
to fold and elevate alo ng eith er side, allowi ng the 2 la teral edges to fuse at the dorsal midlin e to form
the comple ted ne ura l tu be. The centra l ca nal, the site of the future develo pmen t of the ventricular
system, is in the center o f the neural tube. This process of neurulation continues both caudally and rostrally. Disruption can occur because of failure of fu ll neural tu be fo rmati o n cauda lly (spin a bifid a) or rostrally (anencephaly).
"'"
~o
pia
;Je'
len
me pia
68
~I Neuroscie~ elopmental Neuroscience
OVERVIEW OF THE NERVOUS SYSTEM
,
,
The neufallube wi. form the blain and spinal cord, the two co mponen t.. of th e central nerVOU5 system (eNS)_The n e ur~l cre!11 wi ll give ri..e to all of the neu rons whose cell hnd ics are lo ca ted outside the eNS in tile pt>riphetal nl'rYOU!i system {PNS) o f n erves, gan glia. an d plexu~e s.
ral fold Deri vatives of the neural tube ioclude:
Neti rollS oi the eNS Support in g ce ll s of the eNS Somatomotor neurons of the PNS Presyn aptic autO nom iCneurons of PN S
Derivaliv,"s of the neural crest indude; Sensory ne-utom in the PNS Po>tSynaplic au tonomic neuron s Schw ann (neurolemma) cells Adrenal medull.. cells Head mesenchyme Me1anocytes in the ~kin
i'lrachooid and pia mater of meninges (dura m.:lIer from mesoder m)
Embryo al24 days (dorsal view)
.. ~_ L ------r:......,
Ectoderm
__
--:eural crest
\
-.
'-.:'.7.
'1eural tube -spinal c",n>-~
~
Sensory ne\Jron o f
dorsal spinal ganglion
Dorsal spinal ga nglion Spin al cord Sympa thetic tronk gan glion
~.>.< ___-;r ':'.,: : ~"
Visceral mOtOr neuron 01 sympa thetic ga nglion
,,~.;'·r.~~; Cortical p rimordium 01 suprarenal gland
4th week
Dorsal mesen tery Germinal epithelium
Chromaffin ce ll, suprarena l
or future gonad
medulla ce ll
Sero sal li nin g (peritoneum) 01 abdominal celom (peritoneal cavity)
Get
61hweek
-
and
,
Ja)
FIGURE 1.69: NEU RALTUBE DEVELOPMENT AND NEURAL CREST FORMATION _ _ _ _ __ Th e dorsal and ventral halves of the neural tube are separated by the sulcus limitans, an externa l protru sion from the ce ntral canal that demarcates the alar plate from the basal plate. This important landmark persists at some sites in the adult ventricu lar sys tem , The alar plate is the source of generation of many neurons w ith sensory function . The basal plate is the source o f generation of many neu ro ns
with motor or auto nomic function in the spinal cord and the brain stem. The neural crest cells at the edge of the neural fo lds unite to becom e a dorsal crest, th e neural crest above the neural tube. The neural tube and the neural crest separate from the originating ectoderm. The neural crest gives rise to many cell types in the periphery.
69
OVERVIEW OF THE NERVOUS SYSTEM
Developmental Neuroscience
mater
~
Ce ntral ca nal
zone
Ma rginal lonp (w hi le maile r)
(gray m (l ll e rj
B. Spinal cord a t J months Exlern al limiting
Pial
membrane
cell
\
Migra ti ng neu roblasts
_ _
.::v
J
® :::-;.,..., Pia mater ./'l>-.......
@
4th ventricle
•
,
H
zone
,
zone
m,l\ler
Ependym al
Ma ntle
Marginal
layer
layer
layer
...
"l!
~ =gju
= , .~
C. Cerebellar hemisphere at 3 months
1:l ;
.Di: !ib
A. Neural tu be a t 5 weeks
;3
" ~
._ 'li
.3,
J!
-" ~
~ ~
Migrating neuroblasb
Latefal ventr ide
~~fi
zone
zone
j.~
oii
O. Cere bral hemisphere at 3 months
white maile r
cor tex
laye r
T Marginal zone
FIGURE 1.70: NEURAL PROLIFERATION AND DIFFERENTIATION: WALLSOFTHENEURALTUBE ___________________________________
CO( ~ ::
Early in development (5 weeks), neurob las ts in the ependyma l layer lining the central ca nal move back and fo rth from th e epen dymal surface to the pial su rface, replicating as they go. Neural migratio n fo l lows distinctive panerns in different regions of the neural tu be. In the spinal cord, neurons migrate in to the inner mantle zo ne, leaving th e ou ter mar gin al zo ne as a site for axonal pathways. In th e ce rebe llar cortex, some neurons migrate to a locatio n on the outer pial surface as an external
70
granul ar layer, from w hich granule cell s then mi grate inward to synapse w ith other neuro ns pres ent in deeper layers of the ce rebellar cortex. In the cerebral cortex, neuro ns migrate to the outer lone, where the gray matter remains o n the surface, external to the white mat1er. These developmental patterns reflect the anatom ical organization of the mature stru ctures, their blood supply, and th eir vuln erab ility to a variety of insults.
u"'"
'"
-~
Jft·
--:e
rce
OVERVIEW OF THE NERVOUS SYSTEM
Avelopme ntal Neuroscience
8lPOi.ll cell of ~g/liof CI.n~
n. VII'
., "
O>rom~iiinc d
oi .>d,e ... 1mo:tlull~
~ ria mote, cell
late r
eculM
Iver
FIGURE 1.71: NEURAL TUBE AND NEURAL CREST DERIVATIVES _ _ _ _ __ __ _ __ Neural tube ependymal cells give ri se to neura
blasts from which the ne urons of the eNS are
; pres.
derived. They also give rise to the glioblasts from
n the zone,
which the mature ependymal cells, astrocytes,
le ntal
,f the
and oligodendrogl ia are derived. Microglia, the "scavenger" cell s o f the eNS, are derived mainly fro m mesodermal precu rsors. Cells of glia l origin are the predominant ce lls that give rise to e NS tumors. Th e neural crest cells give rise to many
sensory neurons, postgan gli onic auto nomic neurons (sympathetic and parasympathetic), adrenal medullary chromaffin cells, pial and arach noid cells, Schwann cells (the supporting cells of the PNS), and other specialized cell types. Neural crest cells can be damaged selective ly in some disorders (e.g., familial dysautonomia) and also can give rise to specific tumo r ce ll types, such as pheochromocytomas.
peripheral neural structures, including primary 71
OVERVIEW OF THE NERVOUS SYSTEM
Developmental Neuroscience
•
Central nervous system at 28 days
Midbrain (mesencephalon)
Forebrain
Hindbrain (rhombencephalon)
{~___"
Optic vesi cle
Cervical flexure
E
E
I·
Spinal cord
'" M
/FO"b"" Forebrain (prosencephalon) ~
~--
Alar (rooO plate
..... Midbrain (mesencephalon)
Optic vesicle
~"" .....__Sulcus limitans
Hindbrain (rhombencephalon)
Opening of right Oplic vesicle
_
,
Basal plate / ' Spinal cord
~ 8asal plate
• I--- - Hindbrain
~ Sulcus limitans
<::;;
In these sections:
c=:=I A lar plate
Alar (roof) plate
,- - - - Midbrai n
Basal plate ~--- Spinal
Sagittal section
Frontal section (venlral to sulcus limitans)
cord
.p ~p
tf ~:H.'rI A.CRAIC...«e c~
r
FIGURE 1.72: EARLY BRAIN DEVElOPMENT: THE 28·DAY·OLD EMBRYO _ _ _ _ _ _ __ Some components of the neural tu be expand differentially, resulting in bends or flexures that separate the neural tube into ca udal to rostral co m ponen ts. The ce rvical flexure, caudally, and the cephalic flexure, rostrally, result from the differential expansion. Three regions of rapid cellular prolifera tion develop-the forebrain (prosen cephalo n) ros trally, th e mesencephal on (midbra in) in th e middle,
and the hindbrain (rhombencephalon) caudally. Th e ventricular system bends and expands to accommodate in creasing neural growth. An out growth of the caudal part of the prosencephalon extends from the future diencephalon to become the optic vesicle, giving rise to the future retina and its ce ntral connections.
-
..
"".i( ~,
.. .
'
a>
:n:
.•
C"1
.... .:::-
72
-l
;cience
-
OVERVIEW OF THE NERVOUS SYSTEM
evelopmental Neuroscience
Cranial n. VII (Facia l) (sensory and
Saginill section Metencephalon ~ 'h, Ice re bellum, pons)
Hindbrain . VIII
Cranial n. VI (abducens) 'm'''o,, \
Thin root of myelencephalon ('!',"'«dUI, oblong,na)
(se nsory)
(raniill n. 'V~J',~~:~,:~" (sensory 0'11
Sulcus 'ti"
n. IX
Cran ia l n. IV (trochle;)r) 'm,,,oO'-
mOLOO
"it,""
MesencePhalOn \ Cerebral aqueduct
Cranial n. X
,Midb rain .i.
"w,"',
•
(se nory a nd motor )
Cranial n.11! (oculomotor) (moto r) - - - -
3rd ventricle Opening of right telen cephalic vesicle
(myelencephalon)
Coccygeal n. (sensory and motor)
Opening of right optic stalk
" (,m',,, termina li s frontal section (venl ralto sulcus lirnitans) Lamina ventricle terminalis / ' Telencephalic vesicle
//_ (,,,,,,t' verllricle
1st cervica l n. (sensory " " mo;tm)-1
15l sacral 11 . (sensory and
mo,",)' -'." ,
1st lumbar n. (senSO ry
1st thoracic n. (Sensory
"d ~o'M"
"d moton-'
I aqueduct _ _ _ _ B,__,I plale
Central Nervous System: Crania l and Spina l Nerves at 36 Days
.--.J
1
(cerebellum, pons) - - "h ventricle
Sensory neurons and gan glia from neura l crest
- - - Myelencephalon (medull a oblongatiJ) In sagittal and fron\JI sections: ~ Alar (roof) plate
t¥%:.& Basal plale
ventricle ' _ _ _ Spinal cord - - - - Central canal
FIGU RE 1.73: EARLY BRAIN DEVElOPMENT: THE 36-DAY-OLD EMBRYO _ _ _ _ _ _ __
- day 36, the prosencepha lo n begins to expand ":JOKIly as the future diencephalon (thalam us and ",alamus) and telencephalon (basal ganglia, ebrain. olfactory system" and cerebral _:~
e for the dien-
iJ"erJJ I 'en/rides /.rom _ :o;r/"~~....,;<;:?"""""""....6--~
telencephalon. Th e rhombencephalon further develops into 2 distinct regions, the meten cephalon (future pons and cerebellum) and the myelencephalon (future medulla). Distinct spinal ~ford7"a?&7/~dw-§d?&P/d'ff87X:;;V
and motor neurons differentiate and begin to con· nec/ with the;/" taifetsin the/JC'/"jolJe-0"
OVERVIEW OF THE NERVOUS SYSTEM Central nervous syslem .1t 49
Developmental Neuroscience
da~'S
Cephulic flexure _ _ __ pons)
___ Roof of 4th ven tricle
113 obI E
E o ~
Te Iencepha Ion
Pontine
(cerebral hemi -
0 1{actory lobe (paleocortex)
1
newre
<;ni"~1 cord
O ptic I (pilui
Central nervous system at 3 months Cerebral hemisphere (neocone)! ) ~
Me~n(epharon
Ou tline of diencephalOfl
(ove rgrcw"" by cerebTa l hemisphere5) ·---~
O lfactolY lobe
Cerebellu m (metencephalon)
(pal eocortexl~ MedulliJ oblo nga ta
Optic nerve (crani al nn.1I
(myelencephalo n)
Hypo physis (pituitary glandl ./ E
E
Pons (metencephalOn)/'
~
,11
Cervical enlilrgern en t
of spinal cord
1
lumboS
,.",.':"
FI G URE 1.74: EARLY BRAIN DEVElOPMENT: THE 49-DAY-OLD AN D THE 3-MONTH-OLD EMBRYOS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ By 49 days of age, the diencephalon and the telen cephalo n differentiate into distinct components: the dorsal thalamus and the ventral hypothalamus, and the olfactory lobe and the future cerebral hem ispheres, respectively. The metencephalon (pon s) and th e myelencephalon (medulla) develop further and fold, sepa rated by the pontine tlexure dorsa lly. Between 49 days and 3 months, massive development of the telence phalon overrides and 74
covers the diencephalon. The cerebellum forms from the rhombic lips of the metencephalon, as neurOnS travel do rsally to overlie the future pons and eventu ally most of th e brain stem. The mesen cep hal on ex pand s dorsally, forming the superior and inferio r co lliculi (quadrigeminal bodies). The continuing growth of the sp inal cord as it connects with periph eral tissues in the developing limbs forms the cervical and lumbosacral enlargements.
J
cr FIG '\}eu (OSli
cep! po le in a I
( -sh, leavi
opsi
terml the s<
)science
OVERVIEW OF THE NERVOUS SYSTEM
velopmental Neuroscien ce
Telencephalon at 7th Weeks (tran w e rsesectiom
Forebrain at 7 Weeks (tranwersesectiun ) oi median teloCl'1e (3rd venlride-t
''''Ci>phalic vesicle
.
~o rJ I
Choroidal ",I" ," ,.
"
(lateral ven tricle)
- , 11---
!lemisphere; II
neopa llium) _ _
O Pffling lal era!
Interven tricular iorame n
betw{"{"n
: pend)'mall'," , ,, --" M ~n tl e
Roof of Jrd \'cntl ic1~ l lipp0l:ampus (iI,chi palliuon)
11,......... / Lateral telocelc
hemi sp here;
""">,
and medi ,m
laye r
lekJcel0S
Marglnn l la yer -
-
(b ~s~ 1
gangli o n)
lrd ventricle
fo ra men I
(3 .d Y(~nl ricle)
at 2 (coro n ~ 1 ~ecti o n;
(nglll "n,,, , ior view)
anteri or view)
Right cerebra l hem isphere
(n €(lp~ lIi lJ m.
ClJt edg e)
EpiphYSiS (pineal gla nd ) -:;"ii'''''''~
IO.,'='-
- ~dJral hem isphe re
=l o roid
Roof 0 1 lrd
ventricle
.',)dlliu m. Cl.H ~Ige)
~
>llp.,"<,",,", (archipa llium) Choro id p)e,;u s plOl rudinK III to right lJ, tera l v€ntfl df'
,1,,,,, --
a lo ng c h(') roi d lissum
Cho roid ,,'" " " --
Corpus ~triatu m Iba!>al garlglio n)
Thalamus _ -4"-; ventricle
(orpU$ striatu m ( b~s~ 1 ga ngli on)
ImClventr!l:lJlar foramen Open ing of (,wily of right n lla<.:tory lobe
fo rame n
l rd ve ntricle
" J If,K"'" lobes (paleo p alliu m)
lilmin;) lermillah
Right Cerebral Hemisphere at 3 Month s
Cerebral Hemispheres at 3 M o nths
(medial as pec\)
feo .onal ~ t ion )
Medi a l $uriace o { right ce rebl al
L (~OO I ; ~"~mi)::~:?~;i~
~~""'";'~;:~~~O~P:';i
Commissu re o j forllix (hippocampal
Lateral \ientri de
,
, I
(ovl!fin~of
(ho, old plexu$
rig ht lal eriJl A nte rior ~' na termin aII S--';~_ ".
OJf,lCloo y lobE> I
A -, /Jf% I
-
IS S
ns
s.e n
lr
'e eels
lts.
Cl ,I@N ........ ::
ve n tricl e ;!long choroid r. ssure Hippocampus
(archipallium)
Stria termin.-dis Th alamu s Icut surface)
i of div isi on betwee n diencephalon and telencephalon
Neopallia l/ , cortex"""" . Hippocampal COOI)U$ ( :,"d"~ i t nucle us [basal ganglia)
\l ;:;::~~";:J
Cho rQida l ve in a nd artery
Inte rn ,,1capsuleAn terior commi$~lJre
Interventricu l'cntride
G U RE 1.75: FOREBRAIN DEVElOPMENT: 7 WEEKS THROUGH 3 MONTHS _ _ _ _ _ __ ~,Jr o n s
of the developing telence phalon move :-:-ally, dorsall y, and then around the di en 'Y'Phalon in a C shaped course toward the anterior - e of the temporal lo be. The hippocampus forms a dorsal and anterio r positi o n and migrates in a _-5naped course into the anteri or temporal lobe, e.a . ing the fornix in its w ake. Th e amygdal a devel .; in a similar manner, giving rise to the stria B'minalis in a C-s hape. Th e lateral ventricles fo llow '-e same C-sh aped developm ental process
anato mically. Th e caudate nu cl eus also exte nds around the telencephalon in a ( -shaped pattern, vvith the head of the caudate remaining anterior and the m uch smaller body and tail follow ing as a thi nner C-sh aped structure thal ends ventrally in th e temporal ho rn o f the lateral ve ntricl e. Th e cor pus ca llosum and the anteri o r co mmissure co nnect the 2 hemispheres. The internal capsule funnels centrally in the core of the forebrain o n either side and co ntinu es caudally as th e ce rebra f peduncle. 75
OVERVIEW OF THE NERVOUS SYSTEM
Developmental Neuroscience
Brain at 6 montns ~
ItOmm
'II
Frontal lobe of left
-...~
ce rebral hemisphere ............
CentrallrolandlcJ sulcus
~
~
A~ Pa rielal lobe
InsulO1 [island of Reil) in la le ra llsylvian l sulcus
O lfilctory bulb -
-
-
Occipital lobe
....-';
Temporal lobe ~
Medulla oblol1 gata
Pons
.
L-----
_ _ Spinal cord
Brai n at 9 months (birth) ~.---------- 10.5
Precelllra] (motor) gyrus ____
"Ie"~
P''''en,,_,1
Left o:,rebra l hemisphere ~
Lateral (sylvian) sulcus
In sula (Island of Reil)
i~ \:},;:l
fo
'r
.
~
;{ .£'
$
_
'ht&
Pari etooccipital sulcus Pari ecal lobe
;.
~,:;.,
Occipital lobe
~
Cerebellum
Pon, (l lliiN
"'....'"
I
Po;<"n" , 1(..nso",1 gyms Postcentral su lcus
"'-'-- ~: y
.JCtf< ...CRAlC....
Centr,,1(rolandicJ sulcus
._~ ...~
\"
Olfact ory bulb Tempol'al lobe
E,
•
Y{
-<>I ""
mm
Pyra m id
Oli,,€'
r
:::1 -".-
Medulla oblongata Spinal cord
FIGUR E 1.76: THE 6· MONTH AND THE 9 ·MO NTH CENTRAL NERVOUS SYSTEM _ _ _ __ _ At 6 months, the brain ste m has differentiated into the medulla, th e pon s, and th e midbrain, with the cerebellum overlyin g them dorsally. Even though the diencephalon is rap idly developi ng, the overly ing telencephalo n shows mass ive grow th rostrally, then caudally, dow nward and forward into the ten) poral lobe. From 6 to 9 months, the cerebral cortex forms its characteristic convolutions w ith gyri and sulci, and the cerebellar cortex forms its distinctive folds, the folia. W ithin the forebra in, th e major
76
co mpo nents of the basal ganglia, th e limbi c struc tures (e.g., amygdala and hippocampal form ati on th e o lfactory system, and the cerebral cortex develop rap idly. M ost neurons are present at bin." except for some populations of granular cells in cerebellum, the hippocampal dentate gyrus, and the cerebral cortex, w hich form postnatally in response to environmental stimuli. The in utero cr postna tal environments provide major jnf1u e n c~ o n neuronal development and function.
troscienu
OVERVIEW OF THE NERVOUS SYSTEM
!!'iopm e ntal Neuroscience ;··oolal sectioll (ve nttal 10 sulcus limi ta os) at 3 6 days
Ependymal lining of cavities of brain at 3 monlhs
len lale.,ll venlrid e 3rd ventri cle
, ~r pi" . --
- L". ,·" I v{'ntrid!:!
- ,,"
Inlervent ricular foramen (of Monrol- - ---'iiC
0.1--- Optic 5til lk
_'d ventride
O ptic cu p
Infundibular recess :erebr al aq ued uct
Me.>encephdlon Basa l pJilte
\'Nenceph,don cN e bo:!IIllm. DO ''')-,
:~;::':~~':~;';;:'i~~~) -~ Cerebr;ll.:aqueduct (01 SylviusJ Lateral a perture of 4th ven tricle (of L",d>'''~/ in lat eral re('eS5
\l etacoele ..! th ventricle I
0141h
. Mage ndie)
'.--_ - Spinal cord
i I. .1l h vent ricl e
.u lcus
JryJ gyrus
CeOlral ca nal of spinal cord - -
-
' - -- - Central canal
dymailining of cavities of brain at 9 months
Right lateral ". ""i"
_------- ~;~~;::i~:
J)" - ---c
hOln of left laler.,1 ve ntri cle in fra ntallo be
!:.
RegIon of invagina tion oi
choroid p,, 'e,~,"~:,;,'::' ;::,~;'~~~--1
iis5ur e of la ........~~
~----- 'C..,,,,, P'''' oi lefllate ral ventricle
: -- - - -
canal
rec ess of 3td ventricle
0-- - - I'io" , 'l rece~s
~ lcus
Foramen in 3rd ven tricle
fa r inle rth ala mic ad h~ion
,,"p~pi ",,'1
~~~" f,"ii O' hom of Id t la ter al
ventricle in lemporal lob('
_IPo,,,,lo. I,om of left lateral ventriclE' in Occipi tal lobe
Thalam ic impression
Optic recess of 3rd "e<"" '~"
Infundibu lar recess
Region ofirwagination of choroid ple)(us alOllg cho.-oid fis~re of lateral vt!nrricle
Cerebral aqueduct (oi S" "i" "
'---
-
-
-L" I ,." " ,'1 ap erture (of Luschkal of 4th ve nlricle
------ ~~~~'~:.;.;;:~',~' (of Magendi C' ) ~-----.
(,,,,,,1 c.l nal o f spinal cord
fi GU RE 1.77: DEVElOPMENT O F THE VENTRICLES _ _ _ _ _ _ _ _ _ _ _ _ _ __
)ic stru c rmation ),
lex t at birth,
:ells in the
us, and
:YIn utero and uences
n e rapid growth of the brain stem and the fore """'" ain alters the uniform appearance of the ven tri d es. The C-shaped lateral ventricles follow the ;rowth of the telenceph alon, with limited access lJ"lto the third ventricle through the in terventricular ~ ra m e n of Monro. The narrow cerebral aqued uct ·emain s very sm all in th e upper mesen cephalon and opens into the rhombus-shaped and expand ng fourth ventricle. The foramin a of Magendie
(medial) an d Luschka (lateral) open the ve ntricu lar system into the developing cisterns of the sub arachnoid (SA) spa ce at th e med ial ancl lateral margins of th e fourth ve ntricle, respectivel\,. (SF reenters the venous system th rough the arac hnoid granulati o ns, o ne-w ay va lves allowin g drainage from the SA space into the dural (veno us I sinu ses. especially the superio r sagittal sinu s.
77
OVERVIEW OF THE NERVOUS SYSTEM
Developmental Neuroscience
Spinal Cord
5 1/2 we4'kS (tr~n""...·,,, """,on,
Mature tl<_~.,....._tIOnJ
Central can al
~.
OOl,al alar pia IE.'
C€'rI tr al canOl
'<' ~ Ep endyrna l1 ilye r
{se ns.o ry and coordi nJ.till ~ J
Sensory
_
--- Mantle la V@I 'M3rgif'lallil\'er
Ve ntral bdSill plale
5uk us Iim; l afl~
(mOlor)
4th ve ntricle
( ~ el1sory and l ooruinating)
Ependymal la)er
(motor)
Javer
... "
'.
$
l ocalion ,,;melo<
J4fo
<""vol
i '"
Mesencephalon
>~.
4thventrid e Dorsal ', mo ICfi
nudeu~ of the vagus
~ / Hyp oglossal nucleus
~ Tracts lwhite~a"el)
. .':>. -......."1
Mature \"""5\'('(lf !tKtiuo Oi ." .... ___ Superio r colliculu s
TectlumTegmentum
"~ . ', O
' ,"1anlle Ia... er Margif1.11 Iarel Sulcus limilam
-
Dience phalon
Nucleus of
Edlnger·westphal B~ _
Dorsal part
_1
Nucleus amb.suus I ~""" In ferior olivary n uc eus ----- - - Pyramid
'"""
!5'¥! ""' tf<:ft
I~rer
VeNial ba$.ll plate {mol o r)
·'~N
flU e ('I
Cerebral .1qlleciucl
[Jors,ll aiM plale (sen~or\-' and coo rdm
~~p
I .
, ~g ~.
nuc{,,;
'g"" mo"<'I'1
Sulcus iimi'ano; .i 1/ 2 weeks f(f,'"~'"..,e ,eCl,<>"'
Tracts (while matter)
::::;l"'-';.y Nucleus tractu s solit~riu s ~~Xt~ ,-- {rode" , oi ,he soli t ~" ,r3cti
,"...,n"""
Ma rwnal
- -
Vestibular
'OOId;n.~ng
.""lanl)e Iily~r
Ventral ba~a l platt'
,.
Mature (~~n~'@I'ie ",c~on,
lOC"'Km
Roof pl~l e
Dorsal alar plate
Lateral gray column Ihom)
:t{
~ Veotral sray <:olurnn (hom)
Motor
Medulla Oblongata
S 1/ 2 weeks I"an ;,..,.,~ ",,,,,,,n.
Dorsill gray co lumn (horn)
~ Tracts (whi te matter)
"
Red nucleus Peduncle
Diencephalon and Telencephalon
51/2 weeks " ra ,m'''' ..... "'',,n,'
Septum peNucidum,
Mature
11r' 0"''''5<)50:;(loo )
Choroid plexus (pro;e<: I",S ."I u 1.".,,1,·,n";clo .IonH ( hCfoid r,"," r~ '
Ruof p l ~te
,\I
\
3rd "enlricle
<'/ • - {
:..- Claustrum ,~t P"IP-In) Insula
EpendymallaYeJ Mantle layer
/ /~.L~ Lateral sul<:u~ I lobe o(
,) } rMarginal
plate (lhalam us)
o ( ,11M
layer
Th.Jlamus Hyp o
Ventral PM! of .llar pl~te
thal
(h),I)Olh a l a rnu ~ 1
,
Hypnth,lIJmi( sulc us M,unm,Jlarr rec e!..S
I cortex ISra, """ Ier) Iwh'l~ ",.11. "
Id body
FIGURE 1.78: COMPARISON OF 5'!:!,WEEK AND ADULT CENTRAL NE RVOUS SYSTEM REG IONS _
At 5 Y1 weeks, th e ventricular system becomes com paratively small er as neuronal growth occurs. In adults, th e ce ntral canal of the sp in al co rd is virtu ally obliterated. Th e fourth ventricle ope ns up later ally; the sulcus limitans demarcates motor nuclei (medially) and sensory nuclei (laterally). The cere bra l aqueduc t remains very small. The third ventri cle narrows to a sli t. The lateral ventricles expand massively in to a C-shaped form. The basal plate 78
form s motor and autonomic structures who se axons leave the eNS. The alar plate forms sensory derivatives in the spinal co rd and the brain stem, and stru ctures that migrate ve ntrally (inferior o live, po ntin e nuclei, and red nucleus). The rhombic lips, an alar deriva tive of the metencephalon, give rise to the cerebellum. The diencephalo n and the telen cephalo n are also alar plate deri vatives.
fI (
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OVERVIEW OF THE NERVOUS SYSTEM
Neuroscience
~~_
~~
hom)
CN III
"
CNIV ( NV!
~ ! ~orn)
CNV CNVU
CNVll CN IX
horn)
( NIX CN X
CNX CN XII
CNXI
" tIl€ vaBu ~ eN IV (GSE)
CN v (SVE)
CNVII (SVEJ
;:>naryngeal ,arches
CN VII (e VE) C N VI (eSE)
eN IX (CVE)
"
,
CN lX (SVE)
colum n
3racnlomOlor SV E) column
-
, .CSE) colum n
"' ,Ve,'"'' horn Lateral horn
lere
IV Note: GSE = General somatic efferent GVE = Ge neral visceral efferent SVE = Spe-ciaJ visceral effere nt
-!-
['nc',,' horn
.
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Spinal cord
fill
;qJll'.-u mw"
'5 _
fiGURE 1.79: DEVELOPMENT OF MOTOR AND PREGANGLIONIC AUTONOMIC NUClEI IN THE BRAIN STEM AND THE SPINAL CORD _ _ _ _ _ _ _ __ __ _
)ry
Gray matt er column s develop in the spin al cord for somatic lower motor neurons (ventral horn) and preganglio nic autonomic neurons (lateral horn). These columns extend rostrally into the brain stem, maintaini ng th e same general positi onal relati on ship to each other but organized into a series of sepa rate but aligned nuclei. A third grou p of nuclei
I,
ve, ps,
e 'en
develop in th e rh ombence ph alon as branchio mo to r neurons supplying pharyngeal arch musdes. Both the som atic motor and the branchiomoto r neurons are classified as lower motor neu rons and have axons eXitin g the e NS to syn apse on skele tal muscle fibers.
,9
OVERVIEW OF THE NERVOUS SYSTEM
Developmental Neurosci ence
Superior collicul1.l5 ------" J gray matter
Te gmen tumy., Retl(ulitr format,on ~ Sllbslanrl a nigla ~ < "<
'I.IZ
Temporoponlln e fibers ~h'
Cms cerebn
CortlcosPlnal 3?d
{
COrTlconud ear l lbers
~
;& . .
~
Z - . - - Medial ge niculate bod y
. ..' ~ ', -Oculomotornud eus
i"
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Med ial longil udi nal fasciculus
. "
M edial, spin al and tri geminal lemni sci
Nucleus of Edinger-Westphal
,
4
nucleus
~O culomol o r (III) n.
Frontopontme li bel) ~" .J ~ Section through midbrain allevel oisuperior collkuli __________________ Sup.
medull.ar\'Vel~#~
Sup. cerebellar
peodunr~~' ~ '.
Ant. spinoce re be ll ar tract
Mediallonglludinal faSCiculus
Reticular fo rm atio n
Mi dd le cerebe ll a r peduncle - -
_
4 th ventricle
Mesencephalic
. ,,~ ~1·-r
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~
..",.
Cortic ospi nal and cortico nuclear fi be r,
:---.~
~'"
.
gang lio n Median ra phe
_ _ _ _ _ _ _ _ _ _ _ _ _ _ Section through pons at level of trigeminal nerves In!. me dull ary ve lum Cho ro id plexus of 4 th ventricle
>m ....,. .t."'(
lei-
'. '
La teral cuneate tn r. cer~bell ar Post. spinoce rebellar trac t Ant spi nocerebellar Irac t ~ . . ;: •.'. Spi nal lemniscus (~i no thalamic tracts) Me di al lon gi tu dina l fascic ulus ~ Medial lem ni scus 4!ro. Section through medulla obI, Cen[ral canal ..........~ Hy poglossal nucleu s~ Post ~pi noc erebetla r lril C! ~~~
Dorsal vagal nud e us Solitary tract nucl e us Spinal tra ct a nd spinal nu cleus of tri ge minal n. Hypogiossoil t n ucleus In f. o livary nucl ei Hypoglossal (XII ,. .at level of inferior o livary nuclei - - - - - - - - - - - - - - Fascic ulu s gracili s Gracile nucleu s Fascic ulus (unealus
Spinotha lam ictraclS ~ :~
An t spinoce rebellar trac t Medi al le mn iscus -
in allract ilnd Spi nal nucl e us of trigemin al n. Int arcuate fibers
- - - - - - - - - - Swion through medulla oblongata Spinal trac t a nd .,pinal nucle us of tri ge minal Po ~t. spinoce rebe ll a r tract
Spinothala mi c trac ts-= Pyramid and ant. cortkos pinal tlbers
Gracile nucleus Fascic ul\p.> cunealus Dors.:l l ho rn Lateroill corticospi na l tract
Pyr
~~p
e llOl\ ••...•= :~
Section through medulla oblongata at level of pyramidal decussati o n
FIGURE 1.80: ALAR AND BASAL PLATE DERIVATIVES IN THE BRAIN STEM _ _ _ _ _ __ _ "The general patt ern of alar and basa l plate derivatives seen in the spinal cord continues into the brain stem. The alar plate derivatives are the se nsory nuclei, the rhombic lip from whi ch the cerebellum is derived, and nudei w hich migrate
80
ventrally to fo rm structures such as the inferior olivary nudei, the pontine nuclei, the red nucle u ~ and o thers. The basal plate derivatives are the motor an d pregan glio nic autonomic nuclei."
Iscience
) evelopmenlal Neuroscience
OVERVIEW Of THE NERVOUS SYSTEM
SII2 weeks Dorsal alar pl.lle (st;nsor,' and coordinating)
~--
Mantle layer
SulCU5 limitan~
Venlr.11basal plale (mOlorl
-
' - - - - - Ma rg in
3 1/ 1 months
Choroidal artery ,1" 0 ve in Choroid Sulcus II
r-- E,,,",, ,,,,, "00' o. 41h ventrid(' Epp.ndym,lilloor a/4th ven lricle
....._ .....~-- ~~:~~: recE.>SS oC ~ 4th ventriclE.>
f-_"
"'·Ian tle layer
'--- - - Margina l layer
Mature
ChOloidal ve~~els -"""'---~
lUclei i(XII ) n.
Epe ndymal flo or - - , o j 4t h ve ntricle
Vcstibul,jr nuclei ~_
_ ".',<'''·111 receS5 of 41h venlride • CI"Qc,, ;i c plexu s prutrud lr1 !!
through lilleral apertufe 4th verlLridc Descending (spinal ) - --j nucleus OlV
or
l\' udf'uS tractus '>Ol i lani u~ Oor\,,1mOlar nucleus or" X H)'po~kJSS
Jf%
' ""he " d.'
•
'.~
r
nucleus
J ,r~ crrG ... ~,."'
() .Imt'\l .. : . ~
FIGURE 1.81 : DEVELOPMENT O F THE FOURTH VENTRICLE _ _ _ _ _ _ _ _ _ _ __
or leus,
The expansion of the fourth ventricle from the ori ginal ce ntral canal of the rhombencephal on into its matu re form is a compl ex process. The sulcus limitans is conspicuous early in development (SY2 wee ks), and th e ori ginal lateral walls expan d out· ward and lay down hori zo ntally (31;2 months) as the roof plate expands to either side; as a result, the sulcus limitans becomes a landmark at the dorsal boundary of the medulla o n the floor of the fou rth
ventricle, separating the motor structures medially from the sensory stru ctures laterally. Th e latera l aperture o i the fourth ventricle open s into the SA space. In their mature form (lower illustration), these pa irecllateral apertures, the foram ina of Luschka, are major chann els bet\iveen the in ternal and the external circulation of the (SF and must remain open to prevent in terna l hydrocephalus. 81
OVERVIEW OF THE NERVOUS SYSTEM
Developmental Neuroscience
II.
Differentiation and Gro\ol.'th of Neurons at 16 Days
SI)lnalcord {EPeOdYmal la.~::::~ ~" ' ·-~ ·~::-
ItholJd c part)
Mantle I,we ,
...\,lI gin.l l laye r
P A:
~.
"
Neura l crest - - - - - - - -,
i
Spinal (Oro {thoraci<.. pam
Sensory cells I.on, neu ral crest Commisiural nell. on
ASSOciation neuron VentlJ! iu olc ulu$
Growing 10 dOfs.J.1surfare oi body
N
~!~
'...... ob~l~
......
imn , ,*",.>1
, """
CI19N , ',\",".' ::
Growing 10 IMeld l and ve ntral surfaces of body
'"'""~ ~
•
<7<"f, ! ~.
pn!i""'oc.
.)'mp."N:t'c,
• ' ..
g II
.........
Growin g to vi)Cera of body
\ """"" I Differentiation and Growth of Neurons at 5 to 7 Weeks (righl side of di
mo tor neurons
',I iunic ulu 5 ~ Ii,
Dorsal ramus of ~pm.ll nerve '\
from neur al crestl growirl g to end on smooth (involuntary) mus.c le and sweat glJn.9,.s
Ventr al ramus of sp in al
'vVr. lte ramus commurlkans
k, m OIOI thoracic viscera
Gray ramus Sympatr.el ic trunk
m otor Colia ter...1~ymPJ I r.elic tfUnk g
'I i,
I,
Igarlgliorlic, svmpathetic ~nd mOtor n e urons (derived from nllural crest) growin g to end on gland s .:md smooth (involu ntar y) muscle
FIGU RE 1.82: DEVELOPMENT OF PERIPHER AL AXONS _ __ _ __ _ _ _ _ _ _ __ Peripheral axon deve lopment is a co mplex process of neurite extension, trophi c and chemotactic factors. axonal guidance, and maintenance by innerva ted target tissues. Dorsa l root ganglion cells are bipo lar; a peripheral axonal process associates w ith simple or complex sensory receptor ceils, and a centra l axonal process extends into th e eNS. The lower motor neurons send axons to th e developing ske letal muscles through th e ventral roo ts or the moto r cranial nerves, formin g neuromuscular j un ctio ns. Ce ntral preganglionic axons exit in the 82
ventral roots and terminate o n sympa thetic gan glion cells in the sympa thetic chain or collateral ganglia or parasympa thetic intramural ganglia. Postganglionic axons form co nnections w ith target tissues, including smooth muscle, cardiac muscle, secretory glands, some metabolic ce ll s (hepato cytes), and immune cells in lymph oid organs. Sensory, motor, and autonomi c symptoms ca n occu r in periphe ral neuropathi es based on disrup tion of th ese co nnections.
A
-
euroscienr
REGIONAL NEUROSCIENCE PERIPHERAL NERVOUS SYSTEM (PNS )
-
neurons
loe tic
"ed ng lo
td ryJ
'<-I. INTRODUCTION AND BASIC ORGANIZATION
Figure 11.1: Schemati c of the Spin al Cord wi th Sensory, M oto r, and Autonomic Components of Peri pheral Nerves Figure 11.2: Relation ship of Spinal Nerve Roots to Vertebrae Figure 11.3: Sensory Channels: Reflex Figure 11.4: Sensory Channels: Cerebellar Figure 11.5: Sensory Channels: Lemniscal Figure 11.6: M otor Channels: Basic O rganiza ti on of Lower and Upper Motor Neurons
Figure 11.7: Autonomic Channels
Figure 11.8: Cutan eo us Receptors
Figure 11.9: Pacini an Corpuscl es
Figure 11.10: Interoceptors
Figure 11.11: Skin and Its Nerves
Figure 11.12: Neuro mu scular Neurotransmi ssion
Figure 11.13: Neuroe ffector Juncti ons
~.2,
SOMATIC NERVOUS SYSTEM
Figure 11.14: Figure 11.15: Figure 11.16: Figure 11.17: Figure IU8: Figure 11.19: Figure 11.20:
Dermatomal Distribution Cervica l Plexu s Phreni c Nerve Th oracic Nerves Brachial Plexus Cutaneous Innerva tion of th e Upper limb Scapular, Axillary, and Radi al Nerves Above
th e Elbow j
"
,
,~
get
e,
figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure A~3~
11.21: 11.22: 11.23: 11.24: 11.25: 11.26: 11.27: 11.28: 11.29: 11.30: 11.31:
Radial Nerve in the Forearm
M usculocutaneous Nerve
M ed ian Nerve Ulnar Nerve
Lumbar Pl exus
Sacral and Coccygeal Plexuses
Femora! and La teral Fem oral Cutaneous N erves
O bturator Nerve
Sciatic and Posterior Femoral Cutan eous Nerves
Ti bial Nerve
Common Peroneal Nerve
AUTONOMIC NERVOUS SYSTEM (ANS)
Figure JI.32: General Schema of the Autonomic Nervo us System Figure 11.33: Innervation of O rgans of the Immune System and Metabolic O rgans
Figure 11.34: Reflex Pathways Figure 11.35: Cholinergic an d Adren ergic Synapses Figure 11.36: Schematic of Cholinergic and Adrenergic Distributi on to M o tor and Autonomic Structures Figure 11.37: Autonomic D istribution to the Head and the Neck: Medial View Figure 11.38: Autonomic Distributi on to the Head and Neck: Lateral View Figure 11.39: Schematic of Autonomi c Distributi on to the Head and the Neck
83
Figu re Figure Figure figure figure figure Fi gure Fi gure Fi gu re Figure Fi gure Figure Fi gure Fi gure Figure Figure Figure
11 .40: 11.41 : 11.42: 11.43: 11.44: 11.45: 11.46: 11.47: 11.48: 11.49: 11.50: 11.51: 11.52: 11.53: 11.54: 11.55: 11.56:
A uto no mic Dis tributio n to fhe Eye Innel va tio n of the Limbs Tho racic Sympathetic Chain and Splanchnic Nerves Innervation of the Tracheobronchial Tree Innervatio n of the Hear t Abdom inal Nerves and Ganglia Innervatio n of fhe Stomach and the Proximal Duodenum Innervation of the Small and Large Intestines Enteric Nervous System: Longitudinal View Enteri c Nervous System: Cross-sectiona l View Innervation of the Liver and th e Bi liary Trac t Innerva tion or the Adrenal G land Autono mic Pel vic Nerves and Ganglia Innerva tion of t he Kidney and the Upp er Ureter Innerva tion of the Urinary Bladder anel th e Lower Ureter Innervation of th e Male Reprod uctive O rgans Innervation of the Femal e Reprodu ctive O rgans
B. SPINAL CORD Figure Figure Figure Figure Figure Figure
11.57: 11.53: 11.59: 11.60: 11.61: 11.62:
Cytoa rchitecture of the Spin al Co rd Gray M atte r Spinal Cord Levels: Ce rvica l, Thoracic, Lumb ar, and Sacral Spinal Cord Lower Motor N euron Co ntro l Spinal Somatic Refl ex Pathways Muscl e and Joint Receptors and Mu scle Spin dles The Muscl e Stretch Retl ex and Its Ce ntral Co ntrol via Gamm a M otor N eurons
C. BRAIN STEM AND CEREBE LLUM
Figure Figure Figure Figure
11.63: 11.64: 11.65:
11 .66:
Figure 11.67:
Fi gure 11.68: Fig ure 11.69: Fi gure 11. 70: Figure 11. 71: Figure H.72: Fi gure 11.73: Figure 11.74: Figure 11. 75: Figure 11 .76: Figure 11 .77: Figure 11.78: Figu re 11.79: Figure 11.80: Figure 11.81: Figure 11.82: Figure 11.83:
84
Brain Stem Cro ss-section al Anatomy (14 Leve ls) Cran ial N erves: Schematic of Distributi o n of Se nso ry, Moto r, and Autono mi c Fib ers Cran ial Nerves and Th eir Nucl ei: View From Above N erves of th e O rbit and the Ciliary Ganglio n: Dorsa l View and Cross-section Through the Cave rn o us Sinu s Extraocul ar Nerves (III, IV, and VI) and the Ci li ary Gangli o n: View in Relation to the Eye Trigeminal Nerve (V) Facial Nerve (VII I Vestibu locochl ear l\J erve (VIII ) G lossoph aryngea l Nerve (IXI Vagus Nerve (X) Accesso r ~1 Nerve (X I) H ypoglossa l Nerve (XII) Afferent Innervat io n of the Mouth and the Pharynx Reticular Fo rrnatio n: General Pattern of Nuclei in the Bra in Stem Reticular Fo rmatio n: Nuclei and Areas in the Brain Stem and Diencephalon Major A fferent Connectio ns to the Reticular Forma tion Major Efferent Connectio ns o f the Reticul ar Formation Sleep- \Nakefu iness Confro l Cerebellar O rganization: Lobes and Regio ns Cerebellar Anatomy: Lo bules Cerebellar Anato my: Deep Nuclei and Cerebellar Peduncles
E'IC EPHALON =i gure 11 .84: =ig ure 11.85: =igure 11.86:
Thalamic Anatomy and Interconnections \lVith the Cerebra l Cortex
The Hypothalamus and the Pituitary G land Schemati c of Hypothalamic Nuclei
E'IC EPHALON H orizo ntal Sectio ns Through the Forebra in (10 Levels) Cor0 I1 (1 1Sectio ns Throu gh the Forebrain (10 Levels) 11.89: Layers o f the Cerebral Cortex 11.90: Cortical N euronal Cell Types 11.91: Vertical Columns: Func tional U nits of the Cerebra l Cortex 11.92: Efferent Connec tions o f the Cerebral Cortex 11.93: Neuro nal O ri gins of Efferent Connec tio ns of the Cerebral Cor tex 11.94: Co rtical Association Pathways 11.95: Major Co rtica l Association Bundl es 11.96: Noradrenergic Pathways 11 .97: Serotonergic Pathways 11 .98: Dopaminergic Path\.vays 11.99: Centra l Cho linergic Pathways 11.100: Olfacto ry Nerve and Nerves of the Nose
Figure 11.87: Figure 11 .88:
Figure Fig u re Fig ure Figure Fi gure Figure Figure Figure Figure Figure Figu re Figur.
IS
85
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)-Introduction
!
Sensory MOlor • PregangliO" ~C •
sympa thetic
Dorsal
,
Postganglio nic ' • sym p.:Uhe tiC
Oor..al column
, , ,
I
Dorsal root
!
I
Vascular smooth
"
muscle, sweat glands, and arrector pili
Gray ramus communicilns
Sympathe tic chain
Rang~on
Spl,,,,hok o",v.
CoICte,,1
J. Pericins MS, MfA
" '\~r:-!
Sensory neuron oi
abdomina/I'isc€'ra
7
If
)t1( "" O 'If. ./
'V;:~::~;C
Skeletal m!Jscle
- - ./ ;
, ·~) 5-""/ '., j
~,... . ,
/ communicans
/"<",
'L
Sympathetic chain
Preganglionic sympathetic neuror passing to synapse in anomer sympaiheli(' chain ganglion N euroeffector junctions on smooth
~; muscle, cardiac muscle, secretory gldnds, metabolic cells, Immun e ce lls
" TO'; '
FIGURE 11.1: SCHEMATIC OF THE SPINAL CORD WITH SENSORY, MOTOR, AND AUTONOMI C COMPONENTS OF PERIPHERAL NERVES _ _ _ _ _ _ _ _ _ _ _ __ _ Periph eral nerves consist ofaxons from primary sensory neu ro ns, low!;r motor neurons (LMNs), and prega nglio nic and postganglionic autonomic neurons. The primary sensory axons have sensory receptors (transducing elements) at their peripheral ends contiguo us with their initial segments. The proximal po rtion o f the axon enters the eNS and terminates in secondary sensory nuclei associated with reflex, cerebellar, and lemniscal channels. LM Ns in the anteri or ho rn of the spinal cord send
86
axons, via the ventral (anterior) roots, to travel ir peripheral nerves to skeletal muscles, with w hirr, they form neuro muscular j unctions. A utonomic preganglionic neuro ns send axons via the ventra roots to terminate in autonom ic ganglia. Postganglio nic neurons send axons into splanch..... o r peripheral nerves and form neuroeffector junc tions with smooth mu scle, cardiac muscle, secrE tory glands, metabo li c cell s, and cells of the immune system.
~
REGIONAL NEUROSCIENCE
ral Nervous System (PNS )-Introduction
,-,<, ':' {C1abovespiJ),)lC1 nerveexits vertebra
51
lumbar disc p ro trusion doe, not usuall y affe ct ner ve e )( iling ab ove disc. liI \(> r
C()(lUSmedullaris ft ermin3\ion o f
spinal cord )
.-. terminaJ -
"'" part) - ---..:-'.
S'-+~,;:S2
"""'" P""":nal ilium Pill pan}
- -'Ill
+ --:-r'.,-i
S4-+~
55- =" ~
He m
ich
Inc
, !'
_ _
Cervical nerves ThOlao c nerves lumbar nerves
_
Sacraland coccygeal nerves
Me d ial p rotrusio n al disc leve l l 4-5 rare ly affects L4 sp inal nerve b ut may a ilect l S spina l ne rve and sometimes 5 1-4 spinal ne rv es
RE [1.2 : RElAT[ONSH[P OF SP[NAL NERVE ROOTS TO VERTEBRAE _ _ _ _ _ _ __ Dorsal (posterior) and ventral (ant erior) roots of <=-5pi nal cord segments extend from the spinal as groups of perip heral axo ns invested initially - meninges. As the axon s enter the PNS, th ey iate w ith Schw ann cells for myelination and .;poort. Th e roots exit through the in tervertebral -.mi na, compact openings between the verle. w here herniated disks (nucleus pulposus) can
impin ge o n th e nerve roo ts, producin g se nsory and/ o r motor symptoms. Sensory and mo tor axons enter th e dorsa l and ventral rami of peri pheral nerves. Auton om ic axons course from th e ventral roots into the w hite (preganglio nic) rami commun i cantes/ and po stga ngli onic axon s co urse throu gh the gray rami co mmuni ca ntes.
87
REGIONAL NEUROSCIENCE ~n
Periphera l Nervous System (PNS)-lntrodudi Ol
.....)' e h.n ""I.· _rfi e. OXT~AI
r>.1
PfRII' HtJV,1 "' [~VOUS SHTh,
~v()\..s SY STE,~ \
,
"'""
""~""pli< (IIe.Ofl'~
M......,.,.... p.k
!"-~ ",
muid~
<'Trim""",
""~~'''Iled
~I
1jlI""'e
I ,,, ,,· ~,
mol,,,. ""uron
""'"
). rClkin'
""''''A ~!ff'l!
Sk.lollal ruu od.
FIGURE 11.3: SENSORY CHANNElS: REFLEX _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Prima ry sensory axons communica te w ith sec ond ary sensory neurons in renex, cerebellar, and lemniscal channels carrying transd uced inform ati o n from the periph ery into th e e NS. The reflex chan nels interconnect primary sensory axons with anterior horn cell s (LMNs), thro ugh one or m ore synapses, to achieve an unconscious reflex m o tor response to sensory input. These respo nses ca n be elicited in an isolated spinal cord devoid of con nections from the brai n. The m onosynaptic retl ex c hannels connect primary senso ry axons from Sf<>t<,,~
muscle spindles directly w ith LMNs involved in muscle stre tch retlex contraction; this is the only monosynapti c reflex see n in th e human CNS. Po lysynapti c reflex channels are directed partic u· larly toward fl exo r (withdrawal) respo nses throu g.~ o ne or more interneurons to produce coordinatE": patterns of muscle ac tivity able to remove a por tion of the body iro m a potentially damaging or offending stimulus. This polysynapti c channel car sp read ipsilaterally and contralaterally through many segments.
Ch,nnel,· C..,.,b.ILa,
C[ NTRAL -:f.RVOvS SYSIr.~1
III
I'tRIf'H[R....LNERVOUS S'l'STEM
(",""~ I,,m
P,imowy ocn»ry nO""""
',uppOn' mu."''' 'I'
SKOf>d~'l' ...-or'j. " ..........
Prim".,-""",,,"')' ........"" cNlIx>
CI.rk.. , nucleus!
'" Iy~jn ,!<'m (...g.. I.*,."I~"MOI"
ouc\.,ou, l
'1)I1n
or~1n,
~.u,.' r><)(>\)·"I"'1
dot.;.:>Itoo'~!!lj!)n
~
in ;>1 coni (0) J..
~" I ~
-
,. Pet!.in,
c,1!!I!'lI
Mu ,cI<
FIGURE 11.4: SENSORY CHANNElS: CEREBELLAR _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Primary somatosensory axons carrying uncon sciously processed information from m uscles, jo in ts, tendons, li gamen ts, and cutaneous sources enter the CNS via dorsal roots and synapse vvith seco ndary sensory neurons in the spinal co rd or the ca udal brain stem. These neurons co nvey information from the periphery to th e ips il ateral cerebellum by se nding secondary sensory axonal
88
projectio ns through spinocerebellar pathways. The dorsal and ventral spinocerebellar trac ts cam information from the lower body (16 and belo\.\ ._ The rostral spinocerebellar tract and th e cuneo cere bell ar tract carry information from the upper body (above T6). Polysynaptic indirect spin o ce rebellar pathways (spino-olivo-ce rebellar and spino-reticulo-cerebellarl also are present.
roduct. 1"
REGIONAL NEUROSCIENCE
eral Nervous System (PNS)-Introduction
1 11 -~
,
., .'"
I. Porli ..
Or
-
r
E 1/,5: SENSORY CHANNELS: LEMNISCAL _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ sensory axons carryin g information des 'or conscious percepti o n arise from receptors .....:Qeriicial and deep ti ss ue. These axons enter ='-5 via the dorsal roots and terminate o n sec ...ar\ sensory nuclei in the spinal cord or the 5~e m. Secondary sensory axons from these ..e cross the midlin e (dec ussate), ascend as lem pa thways, and terminate in the contralateral us. These thalami c nuclei then project to ':c regions of the primary sensory cortex, -=rne-grained analysis of incoming co n perceived info rmation takes place. · ·o5oensory information is directed into either .opa thic or epicritic channels. Epicritic info rma - "line discriminative sensation, vibratory sensa oint position sense) is transduced by prim ary '""n neu ron s th at send myelinated axo ns to -50 in the medulla, nuclei gracilis (l ower body, below), and nuclei cuneatus (upper body, e -6). Nuclei graci lis and cuneatus give rise to ~i a l l emni sc u s, a crossed secondary sensory .!\ th at termin ates in the ventral postero \ Pl) nucl eus of the thalamus. This thalamic
nucleus has reciprocal connectio ns with cortical neuron s in the postcentral gyrus (Brod mann areas 3, 1, and 2). Protopathic information (pain, tem per ature sensa ti on, light movin g touch) is transduced by primary sensory ganglion cell s that project to neuro ns in the dorsal ho rn of the spinal cord via small myelinated and unmyelinated axons. These spinal co rd neurons give rise to th e spinothalami c tract (spin al lemniscus), a secondary sensory path way that terminates in separate neuronal sites in the VPl nucl eus of the thalamus. This portion of the VPL nucleus communicates w ith th e primary sensory cortex and a seco ndary area of the somatosensory cortex posterior to the lateral post central gyrus. Some unmyelinated nocicepti ve pro topath ic axons that termin ate in the dorsal horn of th e spin a! co rd interconn ect w ith a cascad e of spinal co rd interneuron s th at project mainly into the reticular formation of the brain stem (spinoretic ular pathw ay). This more diffuse pain system is processed through nonspecific thalamic nuclei, lead in g to pe rception of excruciating, to ng-lasting pain.
89
REGIONAL NEUROSCIENCE
Periphe ra l Nervous System (PNS)-Introducti oPERIPH ERAll\jERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM
Conical upper motor / "'.... neuron
-
Corticospinal tracl
Brain stem
upper motor neuron
(red nudeus, superior coliiculus,
vestibular nuclei, retic:uIM nuclei)
upper motor neuron tracts
J. Perkins MS.MfA,
0 1lON
'--':"."
m
"
FIGURE 11.6: MOTOR CHANNELS: BASIC ORGAN IZATION O F LO W ER AN D UPPE R MOTOR NEURONS ____________________________________________ Lower motor neurons are found in the anterior horn of th e sp in al co rd or in motor cranial nerve nuclei in th e brain stem. Their axons exit via the ventral roots or the cran ial nerves to supply skeletal muscles. LMN synapses with muscle fibers form neuromuscular juncti ons and release th e neuro
transmitter acetylcholine (AC h), which acts on nicotinic receptors o n the skeletal muscle fibers. A mo tor unit consists of an LMN, its axon, and the muscle fibers the axon innervates. LMNs are
90
regulated and coordinated by groups of upper motor neuro ns (UMNs) found in the brain. Brain stem UMNs regulate basic ton e and posture. Cortical UMNs (from co rti cospinal and cortiCD bulbar tracts) regulate consciously directed, or voli tional, movements. The cerebellum and the basal ganglia aid in pattern selection and coordI natio n of movement via connectio ns with these UMNs; they do not connect w ith LMNs directh.
~I
REGIONAL NEUROSCIENCE
:leral Nervous System {PNS)-Introduction
JG
PF.RIPI-IfRAL NERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM
Limbic forebrain slructures
(e.g~ amygdalo id nudeus,
some conica l 311'0'15)
Hypolhalamus
~ ~tem -:"I
/
and
'.-./ -1-".<'-;>'" •.--/
1
Hypoph ysea l portal sys tem Anterior
pituitiHY hormone~
Sensory ncuron in dors.. 1root ganglion neuron In lermediola(eral .:ell column in laleral horn of spinal cord
Refle)( connections
(T1 -l2) Ta rge'l t i ~~lI e
Sympathetic
gan glion cell
--
ins
~--------~=~~
~ ,
{
a ln
\.
Jt~;
.:;-"
I
~ :. -~':,: "
.~ "<"'. p:
RE 11.7: AUTONOMIC CHANNELS _ _ _ _ _ _ _ _ __ _ _ _ _ __ _ __
_=.=.,glionic neuro ns {o r the sympathe tic nervous rem (SNS) are found in the lateral horn (inter lateral cell column ) of the thoracolumbar (T1_ spina l cord. For the parasympathetic nervous 71 (PsNS), these neurons are found in nuclei o f
.......1nerves (CNs) III, VII, IX, and X and in 52-54
!-e
C·.
l""mediate gray matter of the spinal cord (a jOsacral system ). Preganglio nic axons exit the 5 \ ia cranial nerves or ventral roots and termi'n chain ganglia or collateral ganglia (SNS) or in amural ganglia in or near the organ innervated ...· 5]. Postganglio nic axons innervate smoo th
muscle, cardiac muscle, secreto ry glands, metabolic cells, and cells of the immune SYSlem . The SNS is a fighl-or-lligh t system that respo nds to emergency demands. The PsNS is a hom eostatic, reparative system active in the m ore quiescent digestive and eliminative functions. Prega nglionic responses are coordinated by autonomic " UMN" equivalents from the brain stem (autono mic centers), the hypo thalamus, and limbic forebrain struc tu res. These central regulatory system s coordinate auto no mic responses that affect bo th visceral func tions and neuroendocrine o uttlow from the pituitary gland .
91
Krause' <;
,
cY1ffk4
.;
,~"l{1 ,
\
""
Fre':! nerve
ending
free nerve ending
Sebaceous gland
I
Meissner's
I'.lerve plexus around hilir follicle
corpu~de
P,d,;"
cmpc,7
Free nerve ending
Ru fii ni term inals
\ Pacinian corpuscle
M erke l", d'ISC Ba~ e me nt
Lobula ted nucleus
membr.lne
·-(ifl ';
Axon terminill '~. M il0chorlddon
'~~ ~
;#
,
1 $1, ' <:~ O
')
~ ~t;.,. :.~
~jf 51S;~ ~l
-' S(.hwann cell
~---
Basil O:! pitheliaJcells
Cytoplasmic p r Olr u:)ion
M itochondria
Expanded axon terminal
Axon ~.,_
.·h_ ~cv.;/:~:.~~
C. Detail of Merkel's disc
SchwJnn cells
D . Detail of free nerve ending
~lp CIIl!N "..; .... .'
~
FIGURE 11,8: CUTANEOUS RECEPTORS _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ __ Glabrous skin and hairy skin contain a variety of sensory recep tors for detectin g mechani cal, therma l, or nociceptive (co nscio usly perce ived as painful) stimuli ap p!ied at the body surface. These receptors in clude bare nerve endin gs (n ociception, th ermal sensati on) and enca psulated endings. The latter includ e pacinian co rpuscles (fast-adapting mechanoreceptors fo r detectin g vibratio n or bri ef tou ch), M erk el's disks (slow ly adaptin g mechanore ceptors for detectin g maintain ed deformation o r
92
_
sustained touch at the skin); Mei ssner's corpu sclE"5 (fast-adapting mechanoreceptors for detecting moving touch); Ruffini endings (s lowly adaptin g mechanoreceptors for detectin g steady pressure applied to hairy skin), hair follicle receptors (ra pia adap ting), and end bulbs of Krause (possibly thermoreceptors). The initial segment of the pri mary sensory axon is immediately adjacent to the se nsory receptor.
)duction
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)-Introduction
, -------::==.::------, --.J
Pressure
lL-__
To amplilier
/-------~ Generator potential
"
-
:Ies
~------1f--l Sl node "---- - -t---My,, ";i" sheath
Action potential A. Sharp "on and oif' c hanges in p ressure at stan and end o f pulse applied to lamellated ca psule are transmilteo to central axon ano p rovoke generator pOlentials w hich in turn may tri gger action potc ntials; there is no response to a slow change in pre ssu re grad ient Pres,ure at central core and,
capsule Central core Unmyelinatl"d axon terminal
r - - -- ------:.,----- ---- --.J
Pressure
To amplifier
". . - - - - - - - - - - J-
1
"'._ _
Generato r po tenti,!! B. In ab sence of capsule. axon
responds to slow as well as 10 rapi d changes in pressure. C ener.'Hor potential dissipates slo wly. and th ere i~
no ·o ff' response Action potential
Pressure Na+ + +
Pressure applied to
+
+
-
•
+ -.'
,
_.,-,",":--
+
@:@'"
+
~~p ° 1I9N
,
"
1""... ::
If resu ll ant depolari zation al 1st (lode is great enough to reach threshold, an action potential appears which is propagated
'lCU RE 11.9: PACINIAN CORP USCLES _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ ?acinian corpuscles are mechanoreceptors that P21sfo nn mech anical fo rce or displacem ent in oiir"ge-diameter primary sensory axons into actio n . {entials. The mechanical stimulus is modified by --;e viscoelastic properties of the contributin g .-mellae of th e pacinian corpu scle and th e associ ~ accessory cells. An action potential results
wh en a generato r potential of sufficient magn itude to bring the initi al segment o f the axon to threshold is elicited. The o nset and cessation of mechan ical deformation enhance io nic permeability in the axo n, o ptimizin g the physio logiGll respon se of the pacin ian corpu scle to vibrato ry stimuli.
93
REGIONAL NEUROSCIENCE
A. Carotid body .1nd carotid sinus
Peripheral Nervous System (PNS)-Introductio r.
.1
Vagus (Xl nerve
ical sympathelic trunk gang lion
G I () ~ $(l philry n ge a l (IX) nerve ~ CarOlid
sinu~ ner...e ~
f-
~el rOfnand ibula r and
Ve ins from carotid bo dy - l i n~ual
External carol id '- -
Caroti d body
vein
[ntemil l jugular vein
'- - Jnle rna l l.:a rol id a rte ry
A rt ery 10 carot id body ............
Superior thyroid Jrtery -............
f-- -Caro tid sinus
Common cMolid 4111ery ___
C. Carotid sinus B. Carotid body Synap ti c endin g
Nerve
Basement rnembrilnC
Type [ iglomusJ cells I End othe liJ[ c e lls
~!p
° ::l~ .....: : ;
FIGU RE 11.10: INTEROCEPTORS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Interoceptors, including internal nociceptors, chemoreceptors, and stretch receptors, info rm the
eNS about the internal state of the body. The ca rotid body, a specialized chemorecepto r for detecting carbo n di oxide (in a hypoxic state) or, to a lesser extent, low blood pH resulting in increased respira tion, is associated w ith afferents of eN IX projec ting to caudal nucleu s so litarius in th e
94
medulla. The carotid sinus, a thin-walled region 0: the carotid artery, contains encapsulated and b c.-~ nerve endin gs th at act as stre tch recepto rs. Th ~ stretch receptors respond to increased art erial pressure as baroreceptors, eli ci ting a refl ex bract. cardia and a decrease in blood pressure via primary afferents of eN IX pro jecting to caudal nu cleus solitariLl s.
-------
Id u -
------------------- - - - -
REGIONAL NEUROSCIENCE
ral Nervous System (PNS)- Introduction
,~e; ,,",." corpuscle
of sweat gland
r
Cuticle - .:' "n al
' ''0''''' ,
De rma l pap illa lo r papilla ry layer)
Connective :r~s ue
layer
~ .·. ea t " " " " '-
Pac inia n corpuscl e
Ar(ery
Subcutaneous artery and vein
Elastic fjbers Skin liga me nts Ire lin
Cuta neous nerve
MOl o r (auto nomiC! nerve
11.11: SKIN AND ITS NERVES _ _ _ _ _ _ _ _ __ _ _ __ _ _ _ _ __
n b supplied w ith a variety of receptor types =-- : ..... re 11.8)
that transduce slowly and rapidly
~ mechanical sti muli and deform atio n into .a l impulses in prim ary afferent fibers. The ~r ve endings are associated mainly with =ptors, peripheral arbo rizatio ns of unmye Ed axons. Some nocicep tors and thermo ors are associated w ith small myelinated
axons. These axons contribute somatosensory info rmatio n collec tively to the spino tha/amicj spin oreticular lemniscal sys tem for protopathic sensa ti on. The more com plex encapsulated rece ptors co ntri bute somatose nso ry informati on to the dorsal co lumn/ mediallemni scal system fo r epicritic sen sa tion and are associa ted with larger myelinated axons.
95
Peripheral Nervous System (PNS) - Introductj o~
REGIONAL NEUROSCIENCE
SY""ti''''':~::::~~~',,~.,.,
_ r a~~~~~. " r
iI, Syn~plic
",
Synapli<: Folds
Active zone
Schwann cell process Acety lcholine I
,
I
- - - Mye lin sheath Neurilemma Axoplasm
Schwa nn cell Mitochondria Basement membrane
Presynaptic membrane Active zone
Synaptic trough
Sarcolemma Nucleus o f
musde celJ
Myofibrils
SynaPtic deft Postsynaptic
membrane Junctional fold Sarcoplasm Acety lcholine receptor sites
,f.l!'~
~(~;@\ ....•:
FIGURE 11.12: NEUROMUSCULAR NEUROTRANSMISSION _ _ _ _ _ _ _ _ _ _ __ A xons of lMNs that synapse on skeletal muscle fibers form expanded termina ls ca lled neur(} muscular junctio ns (mo tor endplates). The motor axon loses its myelin sheath and expands into an extended terminal that resides in a trough in th e muscle fiber and is covered with a laye r of Schwann cell cytoplasm. The postsynaptic mem brane is thrown into secondary folds. When an action po tential invades th e mo to r terminal,
96
hundreds of synaptic vesicles release their pack f ~ of ACh simultaneo usly into the synaptic cleft. The ACh binds to nicotinic receptors on the muscle sa rco lemma, initiating a moto r endplate poten ti"" (EPP), which is normally of sufficient magnitude L: result in the firing of a muscle ac tion potential, Ie, ing to co ntraction of the mu scle fiber. A single ~ cl e fiber has only one neuro mu scu lar junction, tL a motor ax.on may innervate multiple muscle fib€
-
REGIONAL NEUROSCIENCE
ra l Nervous System (PNS)-Introduction
A. Smooth muscle
B. Gland (submandibular)
Sy,,,p;,,h, ,;, te rmi nal ending
!d e ce lls (cut)
C. l ymphoid tissue (splee n)
Bloo d vesse l lumen
. II
Sec,,,,,," t ell cap enclo sing nerve axons
- ,," ,
.-:.~
..,-
Adv entiti,,1 zon!:'
n!-' uroe rrec lor
Varicosity
• cell ca p enclosing nerve axons
,I
Ii
lermin ,1ls
among T lymph oC)!tes in
peri,lrteri olar lymp ho id sheath
RE 11.13: NEUROEFFECTOR JUNCTIONS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ -"omic postganglion ic axo ns form neuroeffec
un ctions with cardiac muscle, smooth muscle secretory glan ds (6), metabolic cell s such as ":Ioa to cytes, and cells o f the immune sy stem (C). .rse nerve end in gs use mainly norepin ephrin e for ~ >iS and AC h fo r th e PsNS. Th ese endin gs do
:orm classic eNS
Of
motor endplate synapses
- ;:erminale as neuroeffector junctions, releasing otra nsm itter into in tersti tial spaces. This per
mils w idespread diffusio n of the neurotransmitter as a paracrine secretio n, initiating postsynaptic respo nses on cells with appro pr iate receptors (includin g many types of immun e ce lls). Som e close appos iti ons also are found, such as SNS end· in gs o n lymphocytes. Sm ooth mu scle cells th at are not innervated are cou pled by gap junction s and can contract together when the innervated smooth muscle cell contracts.
97
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)-Somatic
~~p
CJ(ij(\I
levels of Principal Dermatomes (5 Clavicles C5, 6, 7 Lateral pa rts of upper limbs C8; T1 Media l sides of upper limbs
(6 Thumb (6,7, 8 Hand (8 Ring and linle fingers T4 l evel of nipples
, ',';.',: .
Tt 0 T12 ll, 2, 3, 4 L4, 5; 51 L4 lSi 51, 2 S1 52, 3, 4
Level oi umbilic us Inguinal or groi n regions Anterior and inner surfaces of lower lim bs
Foot Medial side of great loe Outer and posterior sides 01 lowe r limbs
l atera l margin 01 fOOl ..nd little toe
Perineum
FIGURE 11.14: DERMATOMAL DISTR IBUTIO N _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ A dermatom e is th e cutaneous area supplied by a
single spinal nerve roo t; the eel! bodies are located in dorsal root gangli a. The spinal nerve roots are distributed to structures according to their associa tio n w ith spinal cord segments. The nerve roots supplying neighbo ring derma tomes overlap. Thus, secti on ing or dysfun ction of a single dorsal root produces hyp oesth es ia (diminished sensation), not
98
anesth esia (total loss of se nsation), in th e region predom in an tly supplied by that dermatom e. Dermatomal anesthesia req uires damage to at I 3 dorsal roots: the central dorsal root and the roo. above and below it. Knowledge of dermatomes impo rtant for identifyin g th e location of periphe-" nerve root lesions and distingu ishing them from peripheral nerve lesion s.
-------
- SO rnalll:
'"'eral Nervous System (PNS)-Somatic
REGIONAL NEUROSCIENCE
Greate r occipital n. (from dorsa l ramu s of C2)
"'" :ces50ry (XI) n.
l e!.ser ocopital n . Sternocleidomasto id m. (upper end)
Geniohyoid m.
Thyro hyoid m.
Nerves to anterior and lateral rectus capitis mm., and lo n8u 5 capitis and longus colli mm.
~ rool {descendens
~"';~ i) of ansa
cervicalis
Nerves 10 longus cap itis, lon8uS colli and levator scapulae mrn.
n:erior root (descendens ct-rvicalis) of ansa ce rvicalis
Trapezius m.
Nerves to longus colli, scalenus anterior and scalenus medius
Transve1secervical n . - - O m o hyoid m.
Sternothyroid m.
Communicatio n to brac hial plexus
- - - ---1,
Ansa cervicalis
fa nsa hypoglossil Phrenic n. ~Iej domas to i d
m.
.;.' end)
5",,,,:1,,,,,,:e",,, nn. (medial, intermed iate and lateral)
Motor fibers Sensory fibers Proprioceptive fibe rs
U RE 11.15: CERVICA L PLEXUS _ __ _ _ _ _ _ _ __
"
ra.
- 'e cervical plexus lies deep to the sternocle ido .c:o id muscle. Its branches convey moto r fibers ilclny cervical muscles and to the diaphragm. Its _ ry fibers convey exteroceptive inform atio n 'TTl parts of the scalp, neck, and chest, as w ell as :fIri oce ptive informati o n fro m muscl es, tendons,
_ _ _ _ __ __ __
an d joi nts. Sympatheti c sud o motor and vaso motor fibers travel w ith this plexus to blood vessels and glands, The superficial branches perforate the cervi cal fascia to supply cutaneous structu res; the deep bran ches su pply mainl y muscles and joints,
99
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)- $omatir
CJ} ven~ral
CJ
C4
Ventrc1 ! ram i {
(4
C5
ram!
C5
An terio r scalt'ne m, ~
R. common carotid a.
An t('rior scalene m.
/ :
Brachial plexus
Brach ial ple)(us
A ~
Righ i phrenic nerve ------
left phrenic nerve
R. subclavian a.
L subclavian a .
R. vaguS (Xl n. ~~
L. common carotid
IMernal thorJ cic a.---------;
vagus (Xl
"
Brach iocephalic
il.
11.
trunk -~-----:
Intern al thoracic ,l"
R. periC(1rdia
Thor(lcic cardia!.: nn.
cophrenic
L. pericardiaco phrenic a.
Superior vel),) cava
recurrent laryngeal n.
PeriCMdial bran ch of
Root 01
phrenic n.
left lung
Root oj
right lung
Phrenicoabdominal Oiilphragmatic pleur.l (cuO
iasl inal
pleura
:~~
Phrenic n n. (m otor and
branches ot phrenic nn. (to inferior surface of diaph ragm)
/"" ,
sensoryl
Lower intercosl;:li nn. 10
Innervation of diap hragm
~~p
c IlfiN " , 0, ""
FIGURE 11.16: PHRE NIC NERVE _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ __ The left and right phrenic nerves are the 1110 to( nerves that supply both sides of the diaphragm from the C3, C4, and C5 ventral roots. The phrenic nerve also contain s many se nsory nerve fibers, vvhich supply the fibrous pericardium, the media
100
slinal pleura, and central areas of the diaphrag matic pleu ra. Sympathetic postgan glionic nen E fibers also travel with thi s nerve. Dam age to t h ~ phrenic nerves ab oli shes inspiration, wh ich res..... in respiratory failure,
i)-So "",
REGIONAL NEUROSCIENCE
'iIIfr.1 1 Ne rvous Syste m (PNS)-Somatic
Spin;!1 nerve tr unk Co llateral branch o f intercostal n.
spmae m .
Sp in al ganglion
r- Me·dl,11
SubcostJI mm.
and
I r- I" te,,1b ra nches 01 ~
,,",,,,1 filrY! U5
. -;'i1lral latissim us clUfS; m.
Serratus
, r
-
Iransv~e
ligaments .J'het ic trun k Ra mi commu nicantes ~ray
and wh ite) _ _-'
(p,o>\,,,",, i nlerc.ostal
memb rane on externa l inte rcostal m.
Transversus abdominis
Co llateral bra nc h
rejoin ing main ''','leiio' cutaneous br,1nch
'''''",,' cutilneous branch Jnd il nterior
cutaneous branc h Communica tin g branch
of interco stal n. Internal intercostal m.
fxteroal
-=01 "'ill n.
~::: ',"ot;: ':;:'::I~ I m. membmne
External
oblique m.
E 1.17: THORACIC NERVES _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ __
_ ")airs of thoracic nerves are derived from .;"aJ and ventral roots of their correspond ing ~. These nerves do not form plexuses; they e cu taneous branches to the thoracic def IE'5 anel send other sensory fi bers to deeper ;;:Iruc tures, vessels, the periosteum,
parieta l pleura, the peritoneum, and breast tissue. Th e th o racic nerves also send motor fibers to mus cl es o f the thoracic and th e abdominal walls and carry preganglionic and postganglionic sympa thetic nerve fibers into and ou t of the sympathetic cha in.
101
Peripheral Nervous System (PNS)-Somati<
REGIONAL NEUROSCIENCE
5 Roots
!ventral rami)
3 Trunks
3 Ve ntral divisions 3 Dorsal divisions
3 Cords
To subdavius m.; (5,6
lenninal branches (2lrom each cor d ) Musculoculaneous n.:
( (4),5,6,7
l ong tllOracic n.; (5,6,7
Ax illary n.;
(5.6
'.
Radial n.; (5,
6, 7 8; T1
~
M edian n., ((5 ),
6, 7.8:Tl
.l;h..~'· '."-~~ - ,.-...7." . . .,"
).4-
~~ ~
. ,-'. '
Some contrib utions
inconstant
/ "?'"
.
M edial pectoral n.; C8; T1
~
Medial cutaneousn.offorearm;C8;Tl Medial c uta neo us n. of arm; T1
Ulnar n.; ((7), B; Tl
Thoracodorsal n.; (6, 7, 8
Infraclavicular Brancnes
From plexus rooLS
From lateral cord
Branch 10 phrenic
Long thora cic From superior flUnk Suprascapular To subclavius m.
C5, o. 7, 8
C,
C,
C5, 6, 7 ( 5,6 ( 5, (,
~~p - U!ill. ... , ~,., ;
Supraclavicular Branches To longus colli and SCdlene mm Dorsa l scapula r
1 st intercosta l :,,_
-.,.~ ~ ~ .
.
",e, ',--
C5, 6,7,8
latetal pectoral Musculocutaneous l a tefill root o f media n
CS,6,7 C(4). 5, 6,7 05), 6 , 7
From media l cord
Me dial pecto ral Medial c utaneous n. o f arm Medial c utaneous n. of fo rearm
C8; TI T1
C8; T 1
Ulnar Medial fOOl of median
07
C· •
From posterio r cord
Upper subscapular lower subscapular Axillary (d rcumtlex humeral) Thoracodorsal Radial
(5.
o
C;
(-::
-
(S .;, -
FIGUR E 11.18: BRACHIAL PLEXUS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ The brachial plexus is formed by the union of the
ventral roots of C5, C6, C7,
ca, and T1, with a
smaller contribution from C4. Sensory and symp a thetic fibers also distribute with the brachial plexus. The roots give rise to 3 trunks, 3 ventra l and 3 dor sal divisions, and 3 cords, as well as numero us ter minal branches, the peripheral nerves. This plexus is vulnerable to birth injury (superi or plex us para-
102
lysis), with paralysis of the deltoid, bi ceps, brach. and brachioradialis muscles, with sparin g of the hands, and sensory loss over the deltoid area af't,. the radial aspect of the forearm and the hand. Pressure of a cervical rib can ca use inferio r ple," injury (C8, T1 injury), whi ch results in paralysis (]I small hand muscles and flexo rs of th e hand, ", i'· ulnar sensory loss and possible H or ner's syndrc."-I'
i)-Soma
:Onlribuf, '"' om C4
0 0-'"
r am ~
/
REGIONAL NEUROSClE-. CE
-'",-",ra l Nervous System (PNS)-Somatic
Anterior (palmar) view
Posterior (dorsal) view
~
ooIIP'XJavicular nerves cervical
"',
__- -:':'~:~~~~:.:::~I;" ne rves cervical plexus - 0 , 4)
_, - CJ , ' 1- --£:'--_
nerve . ' ior latera l ::..G..""1eous nerve 1(5, 6) _ --ft ..i....
cuta neous nerve of arm (C5, 6)
- . nerve lateral -o"oous nerve .rn ICS, 6)
Rad ial nerve cutaneous nerve of arm ((5, 6. 7, 8) Inferior lateral cutaneous nerve of arm Posterior cutaneous nerve of fo rearm (C[5], 6, 7, 8)
·~-ior
----
,
Intercosto bfachial
nerve (T2 )
and medial
~ c u ta neou s
cutaneous nerve of arm
_ ~ oi iorea rm
(C8, TJ , 2)
" ;711
( oo \n!:>l.:.
.'lJJ part of
:' om T ~
Medial cutaneous nerve of forearm \C8, 11 )
'""\o:!.O.. !oculaneous ~g u s
( 'J
( aiE'f1e ........
.....e
- B lrco,~"
Lateral cuta neous ne rve of forearm (CS, 6, !7l) (terminal part of muscu/a cutaneous nerve)
" Ulnar nerve (C8, T1)
---,-A.'---.."
r....
branch
Dorsal branch and dorsa l digital branches
Radial nerve Superficial branch and dorsal digital branches (C6, 7, 8)
/f'.I hna, digital branches
c- . C' Median nerve
C5
~~'- Proper pa lmar
~
C
....-,," _ :.JJ branches ~
C: - 8)
digital branches Nale: Division variable between ulnar and radial innervalion on dorsum 0 1 ha nd and often aligns wi th middle of 3rd digit instead of 4th digit as shown
:E 11.19: CUTANEOUS INNERVATION OF TH E UPPER LIMB _ _ _ _ _ __ _ _ __ -" eous innervatio n of the limb derives musculocutaneous, axillary, radial, dn d uln ar nerves. These nerves are the - bra nches of th e brachial plexus. Unlike the re rv e roofS, the cutaneous senso ry distribu-
·-if
tio n of these periph eral nerves to th e upper limb does not overlap. Thus, a peripheral nerve inj ury or compression results in a zone of anesthesia corre
spondin g to its distribution.
REGIONAL NEUROSCIENCE Dorsa l scapular n('rve
Periphe ral Nervous System (PNS )-So ma tir: Dorsal Scapular Ner \l~ «(5 ), Suprascapular Nerve «(5, (6),
Suprascapular nerve
A)(iliary Nerve (C5, (6) and Radial Nerve «(5, (6, (7, (8; T1) Above Elbow (viewed from behind )
Supra5pil,,,tu s m.
/Deltoid m.
levator scapulae m.
(supplif'd al<'(J tJy
hranches irom (5 ilnd C61
. /Teres minor m.
..........-- Axillary nerve
UPller l;lIeral cutaneous n.
Rhomboideus ---- ~ !nlnor m.
o f arm
0.---- Rildial nerve Rhnmboideus
culant!Ous n.
miljorm.
alarm
In(rilspinatu~
m. c utaneous n. (If for e Olrm
Teres major m. Lower suh scapuldr n. Pos terior cutaneous n. of arm
late ral in termuscular
(brallc h of radial n. in axilla)
septum
Brachialis m . (Itltera l part)
Lo". he,d Tri cep~
bracnii m.
la le rcll hl'iUJ
{
Medial head
_ _ Brachiorad ialis nl .
~ -. ... 1
Triceps tendo n
M~ iill eptc.ondvle O le<:r..rnon
~:
,r".
Exten sor ca rpi radia lis b revis m.
~
Anconeus m .
~
Ex t"'n~o r digitOrum rn.
1;
u l n~ris m .
~
Extensor ca rp i
.tensor ctl fpi
radialis longus m .
~~p ° UgN
'\·....111
FIGURE 11.20: SCAPULAR, AXILLARY, AND RADIAL NERVES ABOVE THE ElBOW _ _ _ __ The dorsa l scapular nerve (C5) supplies the levator scapulae and rhomboid muscles; it aids in elevation and adduction o f the scapu la toward the spinal co lumn. A nerve lesion leads to lateral displace ment of the vertebral bord er of the scap ula and rhomboid atrophy. The suprasca pu lar nerve ((5, (6) su pplies the supraspinatus and the infraspina tus muscles; it aids in lifting and in o utwa rd ro tat ion o f the arm. A lesion results in weakness in the first 15° of abdu ctio n and in external rotation of the arm. The axillary nerve (CS, C6 ) su pplies the
104
delto id and teres minor muscles; it aids in abduc· tio n of the arm to th e horizontal and in outward rotatio n of the arm. A lesion results in delto id atrophy and weakness in abduction from 15° to 90°. The radial nerve (C S, C6, 0. C8) supplies the triceps, anconeus, brachioradialis, extensor carpi radialis, extensor digitorum, and su pinator muscles: and it aids in extension and nexion of the elbow. A lesion leads to paral ysis of extension and flexion of th e elbow and paralys is of supination of the forearm.
,
ZOf
l,
REGIONAL NEUROSCIENCE
·phe,al Nervous System (PNSj-Somatic -4c------R;,di;,'lne~e
Radial Nerve in Forearm «(5, (6, C7, (6; T1) (vj~~d from behind and 51ightly laterally)
r ---[)",p terminal bra nc h i-- Anconeu s m. Brachior,ldialis m. Extensor carpi radialis longu s m.
--
Supinator m.
--
Exte nsor carpi radi alis brevis m .
~----
Extensor supilliltor group of muscles
Extensor carpi ulnaris m. Extensor digitorum m. and extensor digiti minimi m.
Extensor indieis m. Extensor pollieis longus m. ' -_ - - Abductor poI rici~ lo ngus m.
Extensor pollicis brevis m".____-->
.l- - Posteri o r inte rosseous n. (deep bran ch of radial n.)
- - - - Superficial branch of radial n.
From {upper lateral
auxiliary nerv e
cutarleous n.
olarm Lower
lateral
cutaneous n.
of arm - - - - . /
From radial
Posterior cutar.eotlS n. of arm ____J P01;tenor
aJianeous n. o fforearm
s..".-riirioI Dorsal
digital nn.
branch 01
radial n. - - - - -_ _
-+
Cutaneous inne f'Villion fro m r
L RE 11.21 : RADIAL NERVE INTHE FOREARM _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ - e forearm, th e radi al nerve (C6, e7, C8 ) sup
s. motor fibers to th e ( 1) exte nsor carpi radialis, _ extensor digitorum, (3) extenso r digiti V, - ~\ie nsor carpi uln aris, (5) supinator, (6) abduc r!JOllicis lon gus, (7) exte nsor po lli cis brevis and rs:JS, and (8) extensor indi cis propriu s muscles. R;ppl ies th e po sterio r upper arm, an elongated ~ of th e posterior forearm, and the posterior
hand, thumb, and lateral 21h fingers. A lesio n results in paralysis of extensio n and flexion of the elbow, paralysis of sup ination of the forearm, paral ysis of extension of th e wrist and Angers, paralysis of abduction of the thumb, and loss of se nsation over the radial aspect of th e posterio r forearm and the dorsum of th e hand.
105
Peripheral Nervous System (PNS )-So matic
REG IONAL NEU ROSCIENCE
Musculocutaneous Nerve (C5, C6, (7) (only muscles innervat ed by
musculocutaneous nerve are depic ted)
Musculocuotaneous nerve
f8
J;
k
''tl/{I il/t ) . I. ..
V',~
J/
brachial
COf3coblachiaiis m .
' - Medial cutaneous nn. o f fOtearm and arm
Bi<:epsbl-achii m. (turned back)
Brach ialis m.
Art icula r b ra nch
LaterJ I cu taneous n. of forearm
Anteri or branch
Posterior branch
innervation
~~p•......
01lilN ; ';:
FIGURE 11.22: MUSCULOCUTANEOUS NERVE _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
F
supplies sensory innervatio n to the lateral forearm . A lesion results in w asting o f the muscles supplied,
weakness of flexion of the supinated arm, and loss
of sensation o n the lateral forearm.
T
The musculocutaneous nerve (C5, (6) supplies moto r fibers to the biceps brachii, coracobrachialis, and brachial's m uscles; it aids in flexion of the upper and lower arm, supinatio n of the lower arm, and elevation and adduction o f the arm. This nerve
"
t: a
t(
n
tr
In
106
- -- -
atic
~ ripheral
--- -
REGIONAL NEUROSCIENCE
Nervous System (PNS}-Somatic
M edian Nerve (C6, (7. C8i T1 ) (only mU$d es innerva ted by median nerve are de picted)
Muscu lo( ut
--- -f-_
Median nerve Posterior
Pron ator t ere~ rn. (humeri'll head)
Lateral cords of
brachial plexus Articular branch
Medial cutaneous n. of arm
Fl exor carpi radialis m.
' M"' -',II
cutaneou~ n.
of forearm
Palmaris longus m .
Axillary n.
Prona to r teres m. (ulnar head)
Flexor digitorum 5uperlidaiis m . (Iorned up) Flexor di)\itorum profun dus ffi.
([
Fle-xor poll io s lon gus m.
Pro nator quadratus m.
Palmar branch Abductor pollicis hrevi s Opponens pollieis
Flexor pollicis hrevis (superficia l he-adi deep head supplied by ul nar n.1
Flex/)( retinaculum
t st and 2nd lumbrical mm.
Anastomoric branch to \lln.u n.
Bra nches to dorsum of middle and distal phala nges
[)almilr
} digital nn.
9 GU RE 11.23: MEDIAN NERVE _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ - 1e medi an nerve (C 5-T1) supplies motor fibers the (1) flexo r ca rpi radialiS, (2) pronator teres, 3 pa lmari s lo ngus, (4) ft exor digitorum superfieialis .l nd profundu s, (5) fl exor po ilieis longus, (6) abdue 'or pollicis brevis, (7) fl exor poilieis brevis, (8) 0ppo -'"'2n5 poilici s breviS, and (9) lumhrical muscles of ·ne index and middl e fingers. It supplies sensory r nervation to the palm and the adjacent thumb, ·0
th e index and middl e fin gers, and the lateral half of the fourth finger. A les io n (from carpal tunnel syn drom e) res ult s in w eakness in flexion of the fingers, and abd uctio n and opposition of the thumb and loss of sensatio n, o r painfu l sensation in the radial distributi o n in the hand. A higher lesion also pro duces weakness in pronation of the forearm.
107
Peripheral Nervous System (PNS)-Somatic
REGIONAL NEUROSCIENCE
Ulnar N erve {C8; T1 J (only muscles innervated by ulnar nerve are depicted)
Ulnar nerve
l"1I1
-~ (1l0 blanche; above elbow)
J - Arti(uJ
Fle xor digitorum proiundus Ill. {medial portion on ly; l
portion ,lIpplied by an terior intero sseous branch o f median n.)
Flexor capri ulnaris m. (drawn ilside)
OO(S<'11 bran ch Pal mar bra nch / ' Superficiili branch Flexor pollj ci~ brevis m.
Deep branch
(deep heJd only; superficia l head and other thenar muscles ~ u ))f.l li e(1 by median n.)
= - - - - : : PalmariS brevis Ad ductor pollici s m.
:.-------Abdu ctor di giti mi nimi
Hypothenar
I
mu~ cle <;
,-
-
Flexor d igi ti min im; brevis
}
Oppone ns d igiti minim; Common p.almar digital n.
Palm.1r and dorsal inteross.e i mOl.
:I and 4th lumbrical mOl. (t urn ed down) ,er palm Jr digitJlnn. I nerves
~~p
C IIMI
l'tt.·:·t·
FIGURE 11.24: ULNAR NERVE _ _ _ _ _ _ _ __ _ _ _ _ __ _ _ _ _ _ __ Th e ulnar nerve ((8-T1) supplie s motor fi be rs to the (1) flexor carpi ul na ris, (2) flexor digito rum pro fundus. (3) addu elo r po lli eis, (4) abductor digiti V. (5) opponen s digiti V, (6) flexor digiti brevis V, (7 ) intero sseus dorsa l and palmar, and (8 ) lumbri cal muscles to the fo urth and li ttle fin gers. It supplies senso ry innervatio n.to the dorsal and palmar medial surfaces o f the hand for the little finger and
108
medial half of the fou rth finger. A lesio n results in wasting of hand m uscles, w eakness of wri st fi exion and ulnar deviatio n of the hand, weakn ess of abduction and adductio n of the fingers, "claw
hand" (hyperextensio n of the fingers al meta carpophalangeal joints and flexion at the in ter
phalangeal jo in ts), and loss of sensa tion in the
ulnar distributio n in the hand.
.
'
~
d
iIb<
1m.
REGIONAL NEUROSCIENCE
rp heral Nervous System (PNS)-Somatic
TIl
x hema 11
12 Ven tral rami o f spinal nerves
Ll
Gray f(l m i comm u nic a nl es ---,;';f'---"""---iJ'-flf£~_~
Muscula r bra nches 10 psoas
//
ilnd i liacus muscl('S ~ "
~
l4 ~
_ Femora l nerve Acces~ o ry ob1urat or
nerve (often absent)
An terior division Posterior division
l5
...,..,
Obturator nerve
""' - - - lumbosdcra llrunk While and gray ram i commun icantes
Diaphragm (cu t) Subcostal nerve (T12)
Sympathetic trunk Ilio hyp ogastric nerve
Ilioinguinal nerve
C..eni lotemoral nerve (cut)
Subcostal nerve (T1 2!
Iliohypogastric nerve ilioinguinal nerve Transversus abdomini s mu scl e
Quadratus lum bor um muscl e
Psoas major muscle Gray ram i communiC;Jn(es
Lateral cutaneous
nerve of thigh - - f emoral nerve - - -,
Obtu r,lIor n..ve .-- ~5 major mU$Cle (cur)
-
Lumbosacral tru nks
>
Genitofemoral nerve
Iliacus muscle late ra l Cul,l neoU$ nerve o f th igh Femoral nerve Genital branch (lnd Femorill branch of genitofemoral nerve Obturator nerve
CA: RE 11.25: LUMBAR PLEXUS _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ __ . u mba r plexu s is formed from th e anterior f'\ rami of th e L1, L2, L3, and L4 (oats within ";)Osterior substa nce of th e psoas muscle. The ..-xl som e of th e L2) root form s th e iliohypo -n:::: and ilio in guin al nerves and th e genito al nerves. These nerves co ntribute cHion to the transverse and the ob lique -:li nal muscles. Th e remai nin g roots form the
femoral, obturator, and lateral femoral cuta neous nerves. Lesion s of the lumbar plex us are unusual because of the protection of th e pl exus w ithin th e psoas muscle. Th ey result in w ea kness of flexion, I,oveakness of adductio n of the thi gh and extension of the leg, and decreased sensa ti o n on th e anterior thigh and leg.
109
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)- Somatic
'_~. ---;~- L4
Schema
. . An terior division ~ Posteri or divis ion
_----::~,
:.........: :?!.. -- /'
Superior glutea l
.~
_ l umbosac'" tmo k
" , ' l5
.
.
Gray ram i communicantes
Pelvic spla nc hnic nerves (parasympa thetic to
Inferior gluteal nerve
inferior h)'pogaslric fpelvic] plexus)
Nerve to piriformis ___
Tlbi
Scia tic nerve {
Coccygeal nerve
Anococcygeal nerve
Commo n fibular
(peroneal> nerve----J
!J ;1
!I • •
,/ Perineal bra nch of 4th sacral nerve Nerve to levator ani and (ischia-)
coccygeus muscles I
Nerve to qUJdr
nerve
nerve
N erve 10 o nturator inlt: mus-----.l (and superior gemeJlllsJ
culaneO\IS nerve of thigh
/ Sympathetic tr unk
lum bosac ra ll runk
Psoas miljar muscle
ra mi communicantes
Supe rior gluteal artery a nd ne rve
Pelvic. spla nc hnic nerves (cuI) (pa rasympa thetic 10 inierio r hypogastric [pe lvic1 plexus)
Obluri\l or nerve
Iliacus m uscle _ __ -' Inferior gluteal ilncry ~
Nerve to qu adralus femoris-----------...,
Internal p udenda l 03 r lery _ _ _-I
Nerve 10 obturator inlernus - --
Pudenda l nerve -
-
~~p
" ICoN .... .
-I
O btura tor In tt!fO US muscle ---~
Superior pubi<; ra mu s Pi riformi s mu scle
:
"."
::
.) '1
~
(Is<;hio-)c occygeus musc le Nerve to levalor ani muscle - - - -
~
leva lo r an i muscle ------.
.
Topography: med ial and slightly an terior view of hcmisec ted pelvis
splanchnic nerves (cur)
(symp.athelic to infe rior hypogastric [pelv ic! plexus)
FIGURE 11.26: SACRAL AND COCCYGEAL PLEXUSES _ _ _ _ _ _ _ _ _ _ _ _ _ __ The sacral and coccygeal plexuses are fo rmed from the roots of the L4-54 segm ents, located anterior to the piriform is muscle. Th e major bran ches include the superior (L4-51) and inferio r (L5-52) gluteal nerves, the posteri or femoral cu taneous nerve (51-53), the sciatic nerve (l4·53) and its tibial and common p ero neal divisions, and the pudendal
110
nerve (52-54). The pudendal nerve supplies the per in eal and sphin cter muscles, which aid in clos· in g th e sp hincters of th e bladder and th e rectum. Lesio ns of the sacra) plexus result in weakness of the posterior thigh and the muscles of the leg and fee l, with decreased sensation in the posterior thigh and a perianal/saddle locatio n.
FI(
Th,
ilio cle:
oft
leg jOir ane ane
-
~ r ipheral
REGIONAL NEUROSCIENCE
Nervous System (PNS )-Somatic
lateral fe moral
Lumbar
cutaneous nor" ,_
plexus
Femoral Nerve (l2, L3, l4) a nd l ilteral Femoral Cutaneous Nerve (L2, L3)
Femoral nerve Obtu ra tor n.
--- - 11
~A"mbO"~" "t ru n k
Iliacusm.- - - --'!'4!,; Psoas majo r m. ---f-'~ (lower part)
Artic ula r !Wig
- - --f
Sartorius I (divided)
~itiSl c utaneous femoral
Pectineus m. _---C
culaneous
" "§
~
"2
.~
,
~
0
0
Rectus
bt-anches of
femoris m .
(emaral n. - --
(d ivided) Sartor ius m {div idedl
Vastus Vastus
medialis m. Vastus lateral is m.
Artic ula ris gen us
.
Inirap.llellar brarxh of saphenous n.
Medial crural cutaneous branches of saphenous n.
Cutaneous
Note: o nly muscl es
innervation
Innervated by femoral nerve are shown
fi GURE 11.27: FEMORAL AND LATERAL FEMORAL CUTANEOUS NE RVES _ _ _ _ _ _ __ -;he femoral nerve (main ly L2-L4) innervates the to psoas, sartorius, and qua driceps fem o ris mus d es. It co ntributes to fl exio n and outward rotation of the hip, flexion and inward rotatio n of the lower eg. and extensio n of the lower leg around the knee ,oint. It supplies sensory fibers to the anterior thigh a..,d to the anterio r and medial surfaces of the leg .L.,d foot. A lesion results in weakness o f extension
of th e leg and flexion of the hip and leg, w ith qu ad ri ceps atrophy, and in loss of sensation in terri tori es of se nsory distribu tion. The lateral femoral cutaneous nerve suppli es sensation to th e skin and fascia of the anterior and lateral surfaces of the thigh to the level of the knee; lesions result in loss of sensation in this distribution.
111
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)-Somatic
Obturator Nerve (12, l3, L4)
"} II
L3
Iliohypoga. tric
lumbar pteX"us
L4
Itioinguinal n.
Lumbosacral trunk Genitofemoral n. l atera l femoral cu ta fleOU~
n.
Femoral " .
~.- '\1
Obturator nerve
1"
:. <
Posterior branch _ _ _.".,
brn nch -
:.~f'''--
If' 1J.
A ITicu lar
"
t·:
_ _ _ _ _ Adduct(ll'" brevis m .
An teriO~
'
./ Adductor longus m . ",... (divided)
branch
Posterior branch
~
ObluralOr ex lem us m .
Y' J.C1
1{ "
m.
ie II.)
Articular branch 10
knee joint H iatus of
ad ductor (anal
..,
t
Cutaneous innervation
Note: only muscles innl"fVatoo by obturator
nerve a re shown
~{ft% CII!!N "'-'"'-,':'
FIGURE 11 .28: OBTURATOR NERVE _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ __ __ Th e obturator nerve (L2-L4) sup plies th e pectineus,
add uctor (longus, brevi s, and magnu sj, gracilis, and exte rnal obturator mu scles. This nerve regul ates add uction and rotation o f th e thigh. A sm all cuta neous zone on the internal thigh is supplied by sen sory fibers. A lesion of the o bturator nerve results
in weakness of adductio n o f th e thi gh, w ith a ten d ency to abduct the thigh in wa lking. There also is weakness of external rotatio n o f th e thi gh. A smal l zone of anesthetic skin on the medial thigh is present.
FI
n
L4 n€
ne
L· tel
tril
ou up (L int trit ou
112
",' .
REGIONAL NEUROSCIENCE
'!r"p heral Nervous System (PNS)-Som ati c
Sd~ lic Nerve (14, LS; 51, 52, 51) and Poslerior Femoral Cutaneous Nerv~
1Jsll"I' ior femora l
rulaneoos nerve - '~ r ior
(51,52, 53)
..)._ _ -G,,,",, sciatic foramen
duneal
:t.,ri neal "'-.. nc;hes
- - - -- Sdalic
ne~
____ ("m'"," pe roneal segment
TibiOll segment oi sciatic nerve
of sciat ic nerve
_ong head
,:hidedlof ierno,i!> m.
O:;cep~
Cul;lnoouS innervation
lemOfj,> m .
- 4.
long hea d id ivi rlp.d) of biceps fem ori s m.
->.dduc;tor "I1
b\' ohtur.llnr n .) ~_
Semitendinosus
,emnmon peroneal nerve
~emlm cmbranos us
Tibi al nervI:'
_ - -----'0'1
Posteriu r
femoral cutil neous
7
'l "" ffill sur,,1 cut ilneOU~
11 .
\·Ied ial sural cutanoous n. communiC
G
Sura l n. - - So l e u ~
branch
-
m. - - - -C
Tibial n. - - - . .
Medial calcaneal bmnchcs --~
'Vledia l and lateral plantar nn .
From
Supcriiciill
'£t
peroneal n. SuriJl n.
/"",,, 1 calcanea l branche,
,,~_ l"'ffil dorsal
- --jC-
TibiJ I n. ivia med ial
calc Jn eil l bran chesl
cutolneous n .
FIG URE 11 .29: SCIATIC AND POSTERIOR FEMORAL CUTANEO US NERVES _ _ _ _ _ _ __ sciatic nerve is formed from th e roots of the ...":"53 segmen ts. The superior and inferior glutea l '-~rves branch proximally, just before the sciatic 1Efve's fo rmati on. The superi or gluteal nerve _-1-5 1) supplies th e gluteus medius and minim us, ~sor fascia lata, an d piriformis muscles. II con --:ibutes to abduc tio n and inward rotation and some ")Ut\ovard rotation of the thigh and to flexion of the _oper leg at the hip. The inferior glu teal nerve _+5 1) suppli es th e gluteus maximus, obturato r intern us, gemellus, and quadratus mu scles. It con -:lbutes to ex tensio n of the Ihigh at the hip and to ou tward rotati o n of the thigh. A lesion results in -I"'€
difficu lty cl imbing sta irs or risin g from a sittin g posi tio n. The sciatic nerve proper supplies the biceps femo riS, semitendinosus, and semimembranosus mu scles (hamstrin gs); and it regu lates flexion of th e low er leg. Because it branch es in to the tibial and common peron ea l nerves, maj or lesions of th e sciatic nerve result in w eakness of leg flexion, weak ness of all muscles below the knee, and loss of sen sation in the posterior th igh, poste rio r and lateral aspects of the leg, and sole of th e foot. The poste rior femoral cutaneous nerve (5 1-53) supp li es sen sory innervation to the posterior thigh, lateral part of the perineum, and low er portion of the buttock.
113
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)- Somatic
P,
Tibial Nerve (l4, 15; 51 , 52, S3) Medial
TIbial nerve
Common
(c ut)
nerve
($1,2)
.
F,~
tibial n.
ieular
Arti cular
branc hes
t
.
calcanea l
peroneal
Medial sural cutaneous n, --l..
branch
t; ;
Plantaris m.-----rft1
l ateral sural cutaneous n.
G~tro
(cut)
\....(51, 2J
k /*,\. .6. . . . ~>
I '\ Sural n. ($1, 2)
c nemius m .
Nerve to
Saphenous
popl iteus m.
IU , 4)
Crural inter osseous n.
Cutaneous innerva tion of sole
Soleus m .
Medial and lateral calcaneal branche$
Flexor re tinac ulum (cut)
TibiaJ nerve
Tibialis posterior m.
r Abduclor digiti minim; m.
\0:
(cut)
Medial calcanea l
rQuadratus pl(lntae m.,
""""
~i
Sural n. l ateral calcaneal branch
,
Medial
P'ant.IT_ _ _~' lot :
Flexor
hall uci. longus m.
I _
:: H~
~~p ° II·.·.· llill\l . ::
f lexor digitoriu m brevis m. Abductor hallucis
/
Oeep Sranch to: , 5t, 2 nd, 3rd plantar
, ,
inte rossei mm.; 3rd,4th lumbrical mm.; Adductor hallud s m.,
5
Articular branches
"
I,
e '-Superficia l Branch to:
"
(,
branch
U
Flexor (cu t)
e
d
d igital nn..
Cu taneous branches
(~
~
d(
FI GURE 11.30: TIBIAL NERVE _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ The tibia l nerve (L4-S2 ) supplies innervatio n to the (1) gastrocnemius and soleus (main plan tar flexors o( the (oot), 12) tibialis posterior (plantar flexor and invertor), (3 ) flexor digito rum lo ngus (plan tar flexor and toe flexor), and (4 ) flexor h aUucis lon gus (plantar flexor and great toe fl exo r) muscles, and (5) muscles of the foot, in cludi ng the abductor digiti minimi pedis, flexor digiti minimi, adductor
1 14 .
hallucis, interosseus, and third and fourth lumbrical musdes. Sensory branches supply the skin over the lateral calf. foot. heel. and small toe (sural nerve), and the m edial aspect of the heel and the sale of the foot. A lesion can resul t in weakness of plantar flexion and inversion of th e foot, weakness of toe flexion, and loss of sensation o n th e lateral calf and the plantar regio n of the foot.
FI G The the
aotE 50 r
extE
sian toru
p erc
lie
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)- Somatic
Common peroneal n. (in phanlom)
Common Peroneal Nerve (L4, LS, 51, 52 )
- --t- -lt:-:
Tendon o f biceps
femor is m.
-----i:-+
Art icular branches
Common peroneal Ant eri or tibial recurrent branch
~::-=":.1~~i Head 01 fibula
Extensor digilOrum longus m .
Peroneus
Deep peroneal nerve
nerve
longus m,
' _ . j' t
Tibialis anterior m.
Superficial
peroneal
Culilneous innervation
nerve
Branches of
lateral su ral
cu tan eous n.
digitOfum longus m.
Pero neus
longusm. Peroneus brevis m.
Extensor
- - -4-
hallucis longus m .
Medial dorsal
cu ta neous n .
Inlel mediate
lateral sural cutaneous n.
dorsal
cuta ne<Jus n.
Superior eKtensor ret inaculum
/ l.",,·,'1 branch of deep peroneal ".
- - --i
Infer ior
extensor retinaculum - - - (cut)
Laleral dorsal culaneous n. _ - -1'.\' (branch of sural n.)
10
/ Exleo" " halluds
Superficial peroneal n.
brevis m. and ExtenSO( digilorum
brevis m. . / """,di,'1 branch of deep peroneal n. ~-P",p.. dorsal
Proper dorso, ,'_
_--~tJ1t di~ital nn. -
00 .
FIGURE 11.31: COMMON PERON EAL NERVE _ _ _ __ _ _ __ _ _ _ _ _ _ __ The comm on peroneal nerve (L4-S1) branches into the deep peroneal nerve, supplying the (1) tibialis anterior (foot dorsiflexion and inversion), (2) exten so r hallucis lo ngus (foot dorsiflexion and great toe extensio n), (3) extensor digitorum longus (ex ten sion of toes and foot dorsiflexion), (4) extensor digi torum brevis (extension of toes), and the superficial peron eal nerve, which supplies the perone us
longus and brevis muscles (plan ta r flexion and foot evers io n). Sensory branches supply the lateral aspect of the leg below the knee and the skin on th e dorsal surface of the foot. A les ion of this nerve can result in weakness of dorsiflexion of the foot, weakness of toe extension, and loss of sensation of th e lateral aspect of the lower leg and the dorsum of the foot. 11 5
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)- Auto nomic
Oculomotor (1111n.
\
Facial (VII) n. ~ :' ~
Gl ossophar~'ngea' {IXl n. Medulla
obl on 8 ,~ r a
Vag us (X) n. ( 2
1).
..
~,<~,
_ _,:':;?'
_
( I
I::
;
I"
-~
~.:.: ;;,_:!
. ~ __ "'~"!._~___ :"'~_- ---~
~:-.: -=.,;~:CiliJry gall!;lion .. ,
(- I _ __ _ ..
.-
{M
---
__ __ __~ i/
...
:;'1
~:;:k
----~-=::'~
- - ----- - ---
, ~--- --___
"'
~ :1!"'-",• ~'I:, _ "' . '
-
...
-
Pe
Intracranial vessels
Ey, Lacrim al gland
p(eryg~~rat~~~ "
-- -...
ngI'?!J..-.:.--: . " <. -:.~
. ~.._......
~ ... "'.._
Paro tid slanrl
.....
~
Sublinguill ''lnd submandibular glands Peripheral cranial blood vessels Larynx
Trach ea Bronchi a nd lu ngs
Swe.1\
gla nd
H eart
Shown kir only
Peripheral
Stomac h
v ess ~ 1
seg men t
live r Gallbladder ii,
Pi.tnCfeas
H.,i r fo llicl e
Adrenal glands Brow n
f,1t
Ki dnl?Ys
Intestines l~'m ph oid
organs
Dista l co lo n
Bladder
Ii
Coccyx
Inf. I""
Sympa the tic fibers prega nglio nic ____ postga nglionic
Pa rasympilthetic fibe rs _ preganglionic
... _ ... _ o osiganglio nic
-
Antidrom ic condu ction
~~~ ·,1liN
:"'; -": 1
FIGURE 11.32: GENERAL SCHEMA OF THE AUTONOMIC NERVOUS SYSTEM _ __ _ _ __ Th e autono mic nervous system (AN S) is a 2-neuron chain. The pregan gli on ic neuron arises from the brain stem or the spinal cord (eN S) and synapses o n postganglio nic neuro ns in the sympathetic chain, collateral ganglia (sympathetic), o r an intra mural gan gli on (parasympathetic) near the o rga n inn ervated. The sympathetic division, derived from neuro ns in the Tl-L2 (thoraco lumbar) lateral horn, prepa res the body fo r fight o r flight-mobiliza tio n for emergency respo nses. The parasympathetic division is derived from neuro ns in the brain stem
116
j . Pi'! ~
o~ ....
FIG UI
(cranial nerves [CNs] III, VII, IX, and XI and the sacral spinal cord (S284 in termedi ate gray). This craniosacral system regulates reparative, homeo static/ and digestive func tions. These au to nomic system s achieve their actio ns th rou gh innervation of smooth muscl e, ca rdiac muscle, secretory (exocrin e) glands, metabo li c cells (h epatocy tes, brown faO, and ce ll s o f the immun e system. Normally, both divisions wo rk together to regulate visceral activities such as respiration, cardiovascular func ti on, digestio n, and some endocrine functions.
theA '
musclE immun d ivisiO! patheti tiation,
lymph
tivity ar Im mlJ nl cell-mel
!) nom ic
REGIONAL NEUROSCIENCE
·phera l Nervous System (PNS )-Autonomic •
Pl-egangliollic sympathet ic
. --- ---- Poslganslioni<: symPiJthelk • Preganglionic vaf
( 1
------ ---------" ----- --
............
Thymus
.................. --- - - --~
IA!------ --------------" ---- -----/" --- --- --0 0
, 1.,' -- ----- - -_ . . -.. -.. --- ---,
.
----~~-.....,-J
Cervi<:al Irmph nodes Upper limb hont' ma rrow
~
Sympathetic chain ganglia
Brown fat
_________ _- of Pulmonary MALT
-- ;.,i,f--~<~~- -------- ------------- - -- -- ::::fi--~;:".} - --- -- -------- - - ----- - -- ~~- ------- ---------- ---------
Liver anrl ht>paIOCYle~
Spleen Supenor afld inferior nle5el"llenc I/,J.ngfla
Mesen te rrc lymph nodc~ GALT (e. g., Peyer's patches l wil h
parasympa thetic intramural gangliJ.
J....---- - --------- --- - --///:>
.-
J. Perkins
'.
~- ' -'. -----<
-,-
InS,-Jl nal Iyml)h nodes Lower limb bone marrow
"'S, M1'"
,,,... ,,
-
r
FIGU RE 11 _33: ORGANS INNERVATION OF ORGANS OF THE IMMUNE SYSTEM AND METABOLIC _____________________________________________ The ANS innervates the vasculature, the smooth muscle ti ssue, and th e parenchyma of organs of the immune syste m mainly th rough the sympath etic division. In the bo ne marrow and the thymu s, sym pathetic fibers mod ulate cell proliferation, differen tiatio n, and mobiliza tio n. In the spleen and the lymph nodes, they modulate innate immune reac· tivity and th e ma gnitude and timing of acquired immune responses, parti cularly the choi ce of ce ll-m ed iated (Th1 cytokines) vers us humoral
(fh2 cytokines) immuni ty. Autono mic fibers regulate immune respo nses and inflammatory responses in th e mucosal-associated lymphoid tissue of the gut and the lung and in th e skin . Extensive neuropep lidergic innervation, derived fro m bo th the ANS and primary sensory neurons, is present in the parenchyma of lymphoid organs. Postganglionic sympathetic nerves also su pply hepatocytes and fat cells.
11 7
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)-Auton omic
Sympathetic tru nk
Spinal gangli.
commuicans
Sympathetic
tru nk ganglion Gray ramus communicans
~~~
0 1liiN 1\'.... : ; •
Sympathetic fibers _ _ preganglionic ____ postganglionic
Pia.l'ilSympathelic fibers _ preganglionic __ • • postganlionic
Afferent fibers to spinal cOf'd - - Afferent fibers 10 brain stem
FI GUR E 11.34: REFLEX PATHWAYS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Autono mic reflex pathways consist of a sensory (afferent) component, interneuro ns in the ( NS, and autonomic efferent components that innervate the peripheral tissue respondin g to the afferent stim ulus. The afferents can be autonomic (e.g.,
from th e vagus nerve), processed by brai n stem nuclei such as the nucleus soli tarius; o r they can be somatic (e.g., nociception), processed by spinal
118
cord neurons. The preganglionic sy mpathetic or parasympath etic neurons are activated through interneu ro ns to prod uce a reflex auto nomi c respo nse (e.g., co ntractio n of vascular smoot h mus cle to alter blood pressure, increase in heart rate and contractility). The efferent connectivity can be relayed via splanchnic o r somatic nerves because of the complexity of auto nomic efferent pathways.
•,
, , t
,
t
f
mit
REGIONAL NEUROSCIENCE
"cripheral Nervous System (PNS)-Autonomic
Salivary glands Trachea and brOnchi
Vagus (Xl n.
Heart
Striated muscle ~.
,'I Peripheral arterioles
Visceral arte rioles
Gastroi n te~t inal lrac l
Pelvic splanchnic nn. Bladde(
C Cholinergic synapse A Adrenergic synapse Sympathetic fib ers _ _ preganglionic ____ postganglion ic
Parasympathetic fibers
- - Somatic fibers
- - preganglionic ____ postganglionic
- - Anlidromic conduction
f iG URE 11.35: CHOLINERGIC AND ADRE NERGIC SYNAPSES _ _ _ _ _ __ _ __ __ The AN S is a 2-neuro n chai n. All sympathet ic and parasympathetic prega nglionic neurons use acetyl choline (ACh) as the prin Cipal neurotransmitter in sy na pses on ganglion ce ll s. These cho linergic (e) synapses activate mainly nicotinic (N) receptors o n ~h e ganglio n cells. Postga nglionic parasympathelic neuro ns use ACh at synapses (C) w ith target tissue m activate mainly muscarinic (M) recepto rs. Postganglionic sympathetic neurons mainly use
no repinephrine (adrenergic responses lAD to
activate both alpha and beta recepto rs on target
tissues. Alth o ugh ACh and norepinephrine are th e
prin cipa l neurotransmitters in autonomic neurons,
man y co-localized neuropeptides and other neuro
mediators, including neuropeplide Y, substance P,
somatostatin, enkephalins, histamine, and gluta
mate, are present.
119
REG IONAL NEUROSCIENCE
Peripheral Nervous System (PNS )-Autonomic PERIPHERALNERVO US SYSTEM
CENTRAL NERVOUS SYSTEM
-
Luwer
motor
neurons
,t;)
Skeletal muscle
Sympathclic
.o,~ . A '
chain ganglion
~
==
<... . " .
.
~aF '~{,
........"
~
;"'
- -",'/J
Collateral ganglion
Sympllthet ics T1-l2
C N --l....-tll'i;
,.,..
,
~
'-~
. /
~- '
T,,' gct tissue Adrenal '
1
R
.. , _.. ~ .'~
~"
Epil1ephrine
.,
It
NOlepjnephril)t~
-,
:"'t<~
ChrOm.l.ffin cell
(,,,,,;,, ;,j • ' , ' ,,,d . ",,1) ~' , 'S , _
~.;'" 1
p ara)'nlpathcl ic5
',-.
.
g,"~;o"
,c'if:)
'm"m",,1 ,""""" _"""'<'
'
C
\
"
..
~ : ~ ''' .-'l: i
t "/. ~,
",:
Targe t tIssue
Receptors
5yn/l PsK ~ Adrcnerl4lC
C Cholinergic
(. Of ()
.l..!vna or betJ il
N
Nicotimc
M
,"\ t lIS(.lf i r1 i("
.-
J. Perkins MS, MfA
..
, ..,."
FIGURE 11.36: SCHEMATIC OF CHOLINERGIC AND ADRENERG IC DISTRIBUTION TO MOTOR AND AUTONOMIC STRUCTURES _ _ _ _ _ __ __ _ _ __ _ __ All preganglionic neurons of bo th the sympath etic and parasympathetic nervous system use acetyl cholin e (AC h) as their neurotransm itter. All gan glion cells possess mainly nicoti nic receptors for the fast response to cholinergic release from pre ganglio nic axons. H owever, additional muscarinic receptors and dopamine receptors on ganglion ce ll s help to mediate lo nger term excitabili ty. The postganglionic sympathetic nerveS use mainly
120
norepin ep hrine (NE) as th eir neurotransmitter, and target structures in th e periphery possess different subsets of alpha and beta adrenergic receptors fo r respo nse to N E. Some postganglio nic nerve fibers to sweat glands use ACh as their neurotransmitter. Postganglio nic parasympathetic nerves use ACh as their neurotransmitter, and target stru ctures in the periphery possess mainly musca rinic recepto rs for response to ACh.
l
"
REGIONAL NEUROSCIENCE
"e-'pheral Nervous System (PNS)- Autonomic
Tti genmlnal M n.
5ensol)' (001 Motor
p etf05d I n .
Nasociliary n. Deep pelfOSdI n .
{
root}
ISY;:::~~:I~footn.
ciliary
of ganglion
:"""i "i'~ n.
Facial (VII) n.
\'Plh, "mi' n.
Veslibulo
coch lear (V ii I)
nn .
Intern al carotid n.
Otic
ganglion
Superior
lal)'ngeal n. Superior cervical
lingual n.
symp.1lnel ic
trunk ganglion Vagu~ (X)
n.
Internal carotid .1. Cervical sympa thetic trunk - - ' Superior cervical cardiac branch of
Submandibular ganglion
I meningeal 3. and plexus 3.
'(I,m,",," carotid a. and plexus Superior ceMc.a1sympathetic card iac n.
aod plexus
,p~p
4
e lM!
I·.·...·:::
FIGURE 11.37: AUTONOM(C DISTRIBUTION TO THE HEAD AND THE NECK: MEDIAL VIEW _ Autonom ic nerve distri buti on to th e head and the neck incl udes compo nents of both th e parasym patheti c and th e sympathetic nervous systems. Parasymp ath eti c co mponents are associated w ith CN s III (ciliary gan gli on), V II (pterygo palatine. sub mandibular ga nglia ). and IX (oti c gangli o n). Th e vagus nerve and its associated ganglia do not innerva te effector tissue in the head and the neck, altho ugh they are present in the neck. Sympathetic
components are associated w ith the superi or cer vical ganglion an d, to a lesser extent, th e mi ddle cervical gangli on. The geniculate gangli on (eN V II), the petrosal gangli o n (CN IX). and th e nodose gan glio n (e N X) process taste inform ation. They are so metim es th o ught of as autonomic afferents, but they are no t compo nents of th e auto nomic efferent nervo us syste m.
121
REGIONAL NEUROSCIENCE
Peripheral Nervous .System (PN S)-Autonomic
Int
carotid n. Closso
pharyng,e_-=-,'_-:
(IX) n.
v~gus
( x. )n . _ _ _~
(cu t)
Sup. cervical
sympathetic
tru nk
ganglion
Pharyngeal plexus Sup. pharyngeal branch of vagus n. Ext. carotid a. and plexus laryngeal n.
Gray ram i
Int. carotid a. a nd carotid sinus branch of glossopharyngeal n.
Carotid body
Carotid 5inus
Syp. cervical cardiac branch
0 1 vagus n.
Sup. cervical sympathetic cardiac n.
Phrenic n.
M idd le cervical sympathetic (fun k 8
Common carotid a. and plexus Middle cervical 5}'mpathetic cardiac n.
Vertebral ganglion Vertebral a. and plexus Recurrenl laryngea l n.
CerviCOlhoracic (stella te) ganglion Ansa wbclavi3
+-
Va2US (Xl n . (c ut)
Inf. <;ervical sympathetic cardiac n.
Subclavian a.
~~p clliiI\I .... :\
-:;:
=
FIGURE 11.38: AUTONOMIC DISTRIBUTION TO THE HEAD AND NECK: LATERAL VIEW _ __ The parasympathetic nerve fibers to the head and the heck regulate pupiUary constriction and accom moda tion for near vision (CN III, ciliary gangli on to pupillary constri ctor musde and ciliary muscle), tea r production (CN V II, pterygopalatine ganglion to lacrimal glands), and salivation (eN VII, sul:r mandibular ganglio n to subma ndibular and sul:r
122
lingual glands; eN IV, otic gangli o n to pa ro tid gland). Th e sympathetic nerve fibers to the head and th e neck derive mainly from th e superi o r cer· vical ganglio n, w ith synapses to the pupillary dilator muscle, the swea t glands, the vascular smooth m u~ de, and the thymus gland.
< , -~
-. 3.
'I
REGIONAL NEUROSCIENCE
->1era l Nervous System (PNS)-Autonomic
CENTRAL NERVOUS SYSTEM ~m pathe ti cs
1 -I
Ciliary ganglion ( ranial n. I!I
. . .""'."",.~ "",~;};.-,.,..,-="","",
....: ellS of _~- .\ eslpha l
\
, :~Derior
I'ERrPHERALNERVOUS SYSTE M
...;;::::;~~,..".....
~~ 1 ,
Pupi llary conSlriclor m.
Ciliary m.
""'.
'>';'-4'~ ~
" Plerygopalilline ganglion
I.acrimal glilnd~ Nasal m UC05.)1 gla nd~
Subma nd ibula r ganglion
Submandibular gland Sublingu.11 !!Iand
( rilni,JI n. V II
4--=-
... . atory - ~cleus
,-.
I'·
'~
",. (.-c:-:r~.::-,
I...~: .~ .. ,
Qli<; g,\nglion
P,lrolid gl,1nd
-,.- -. /'
'Ierior
,..w. ato ry
'-:"y
~ ucl eu s
1):., '
,
\ ..-,-
p,al hl!ti cs
/,,\ I '/
•
Superior ce rvical gans-lion
Tl-n -:ermedio
I,ateral
~d1 column
, J. Pe rkins .,,~
MW.
..,. 0,"",,, .",
~weat
glands and
vilscul,)f smooth muscle
in hc.1d and nl"ck
CU RE 11.39: SCHEMATIC OF AUTONOMIC DISTRIBUTION TO THE HEAD AND THE NECK _ ' onomie innervatio n to the head and the neck aerived from parasympathetic neurons in the n stem, including the Edinger-Westpha l nucleus " III), the superior saliva tory nucleus (CN VII), ,... the inferio r salivatory nucleus (CN IX), and
from sympathetic neurons in the Tl -T2 inl.ermedio laleral cell column in the spinal cord. The associ aled ganglia and targe t (effecto r) tissue are also illustr
123
Peripheral Nervous System (PNS)- Autonomic
REGIONAL NEUROSCIENCE
From Hypothalamus Shofl
Orulomolor n. rool o f c iliarY8il nglion (motor)
r
J
- - - Edingcr-Wt>Stph
Oculomotor
'e<:' Dilator of pupil
Sphincter
of pupil
Ciliary
muscle Descending Nude!." ofTrigemil)al N. (\ Nilsociliary n.
g
Nasociliary n. rOOI of ciliary ganglion Ophth
caro tid
[)iexus
Intern al ca rotid a. Superior ce rvi cal sympatheti c trunk S<'lngJion /
Thor acic part of spina l cord
Gray ramus communica ns----....tf 15t thoracic sympath eUc trunk ganglion
Sympathetic Fibers - - - - - Pre ganglionic
- - - - - - Postgan glionic
While ramu s communicans
Parasympathetic Fibers - - -- - Pregan glionic
- - - - - - Postganglionic Afferent Fibe- rs
Pupillary lig ht Reflex Pathway
~~? I··""';..
Ot'Scending Pathway
~-
< ION , ~"-.",,
FIGURE 11.40: AUTONOMIC DISTRIBUTION TO THE EYE _ _ _ _ _ _ _ _ _ _ __ _ Pa rasymp(l thetic preganglio nic nerve fibers fro m the Edinger.Westphal nucleus innervate the ciliary ganglio n, w hich supplies the ciliary muscle (aiding in (lccom moda tion to near vision). and the pupil lary constrictor muscle (constricting the pupil). Sympa thetic preganglio nic nerve fibers fro m the T1 ·T2 intermediolateral cell colum n innerva te the superior cervical ganglion, w hich supplies the
124
dilator m uscle of the pupil. The pupillary light retle'. is a major renex in neurological testing. The afferer" limb is acti vated by light shone in either eye via eN II, processed thro ugh the pretedum to the Edinger-Westphal nucleus on both sides (via the posterior commissure); the efferent limb consists of automatic outtl ow to the pupillary constrictor muscles of both sides.
~ h e r a l Nervous System (PNS)-Autonomic
REGIONAL NEUROSCIENCE
Intern al c.1 rotid n.
Cervical sympathetic trunk ganglia
,"
.._------------------ ..·,k"
~
cardiac nn.
l owe r lu mbar and sacral sympathetic
.:.::
trunk ganglia
~" l1Ipa lhet ic
fibers
preganglionic - -- postgangli onic
Sympatheti c railli to lumbar sacral plexuses and nerves 10 lower !imb :\
..•.•
,':
:
-G URE 11.41: INNERVATION OFTHE LIMBS _ _ _ _ __ __ __ __ _ _ _ __ -....Io nomic innervation of the limbs derives (ro m ~ sympatheti c nervous system. Prega ngli onic Tll pathetic nerve fibers from th e tho ra columbar -ermediolateral cell column supply sympathetic "ain ganglia. These ganglia send postgan glionic _~a dren e r g ic nerve fibers throu gh the gray rami
communi cantes into the peripheral nerves to supply vascular smooth muscle (vasomotor fibe rs), sweat glands (sud omotor fibers), and arrector p ili muscles associated w ith hair follicl es (pilo motor
fibers).
125
REG IONAL NEUROSCIENCE
CerviCOl ho rilcic
(~lell ale) ganglion
Ansa subc lavia
__
..,
L 1S f,
Peripheral Nervous System (PNS)- Autonomic
Cervicotho rOl eiC
{stellate) ganglion
- ;.'.. '
R. svmpalhet
Cervical ca rd iac nn. (sympathetic a nd vagal)
Cervical
c(Hdiac nn.
rS)'mp." hctic
L vagus n. (c ut)
.,nd va&
syml?athctic___~/ cardi.K nn. R,
vaglls n.
(Cllt l
Thoracic cardiac nn . (sympathetic an d vagal)
n ,oracic vd.gal
bral1ches to
pulmonary and
<:ardial" pfe.-.::uses
Branches to ant. and post.
5th intercostal n
(a nt. ra mu ~ of
Slh thorac ic sp inJ. 1n.) - - - - -/
Cardiac plexus
G rOll' and wh ite rami communicn
L sympathetic trunk
5t h thora cic symp~th (;ti {;
trunk
/
g;mg ll on ----~
R. greater Ihor3cic splanchni C: n. - - - --
Sympathetic branch esoph
to
plexus
pulmonary plexuses
~~-----
Thoracic duel
Thoracic aorta plexus
Esophageal pl exus
l. greater thorac ic spranc hn ic n.
Thorac ic aortic plexus
L lesser thoracic splanch nic n,
R. lesser thorac ic splanchnic o.
Ant.vaga! tru n k
R. lowesllhorac ic spla nc hnic n.
Azygo~
vein
(c ut j - - - --
Inf.
D ia ph ragm
(pune
,f ,f~ 4 ~{II""-I
n-,'.-;;:
FIGURE 11 .42: THORACIC SYMPATHETIC CHAI N AND SPLANCHNIC NERVES _ _ _ _ __ The sympathetic chain is a conection of sympa thetic ganglia that receive inpu t from the thora co lumbar preganglionic nerve fibers derived from the spinal cord_ The ganglia, interconnected by nerve trunks, are located in a paravertebral array from the neck to the coccygeal region. Postgan gli o ni c noradrenergic nerve fibers from the sympa-
126
Ihelic chain supply effecto r tissue in the periphery. Some preganglioni c nerve fibers do not synapse as they trave l through the sympathetic chain. These fibers co ntinue along th e splanchni c nerves to synapse in co llateral gangli a, wh ich supply noradrenergic innervation to effec tor ti ss ue in th e viscera.
REGIONAL NEUROSCIENCE
·pheral Nervous System (PNS)- Autonomic From hypoth alamic !
and higher centers !
,
\~~, ~~;t:~f~::;: to smooth mU$(le alld glan&;; alfer ent
i, , tracheobronchial muco~.a, and alv~oli) GI~ ,oph"y n"
Jescending tracts in spinal cord
--\ -
.. nerve (I X)
Affer ent nerves from 1t"C~~ n~e and sinuses (via ~ trigeminal (VI and glossopharyngeal [IX1 nerves) may also initiate renex~ in airway~
SuperiOl cervical sympathetic ganglion
'coo Symp"h.'lk nerves {adrenergic)
Caro tid
Larynx
body-\b-lfJJ
-~ ofacic
,a cord
,..--->.
art""
Sympathetic trunk -
--It
.athetic l'ibeN - -- - Preganglionic • • - - - - Postganglio nic ~""mpathetic
Cough receptors
Pulmonary p \ ,'"" "--
l'ibf:rs
- - - - Preganglionic - - - - - - Postganglionic ~ nt
fibers
·,energic lerminals (norepinephrine
I'd or epinephrine)
:-'"IOlinergic terminals (acetylcholine)
RE 11.43 : INNERVATION O F TH E TRACHEOBRONCHIAL TREE _ _ __ _ __ _ __ - 5\ mpa thetic
(noradrenergic) and parasympa M: cholinergic) innervation supply smooth -'e of th e tracheobron chial tree. Sympath etics e !rom th e sympatheti c chain, and parasympa - derive from vagal autonomic input to local lUral gangli a. Sympathetic influences result in -oc:hodilati on, and parasympathetic influences
result in bronchoco nstriction. Additional n euro~ peptidergic innerva tio n, some as co-localized o r in dependent autono mi c fibers an d some as pri· mary afferent fibers, a!so di stributes alo ng the epithelium and among the alveoli, where it ca n influence innate immune reactivity and the pro duct ion of infl amma tory media tors.
12 7
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)- Autonomic
Dorsal vagal
Su perior cervical sympathetic
Iract nucle us
t
tru nk ganglion
: ~J.
Superior cervical sympathe tic
'>'.
card iac nerve
Supe rior cervical vagal
cardiac branches Middle cervical sympalhe lic
tr unk ga nglion
Mid dle cervical sympathetic - - - -if(
cardiac nerve
Verte bralgangl ;;,o:O:.::=======~~~J Ansa subclavia-
Cervicothoracic (5Ie))ale) ganglion
Ventral ramus o f T 1 - - - - - (intercos ta l n.J
Inferior cervical sympalhelic--
~
cardiac nerve
,'
2nd th oracic sympathet ic tru nk ganglion Thoracic vagal cardiac branch -
;:;;.:;
White ram i communicantes<
4th th oraci
trunk ga nglion
Thoracic sympathetic cardiac nn.
Cardiac
Sympathetic fiber;; - - - - Preganglio nic
'.
plexus
Parasympathetic fibers ____ Preganglionic
- - - - - - Postganglionic
- - - - - - Postganglionic
Afferent fibers
Afferent fibers
~~~ l· rMOo.
o "~ ...., "
FIGURE 11.44: INNERVATIO N OF THE HEART _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ Sympathetic noradrenergic nerve fibers (derived from chain ganglia) and parasympathetic choliner gic nerve fibers (derived from cardiac intramural ganglia innervated by the vagus nerve) supply the atria, the ve ntri cles, th e sinoatrial node, and the atrioventricular node and bundl e. Sympatheti c noradren ergic nerve fibers also distribu te alo ng
128
the great vessels and the coronary arteries.
Sympathetic fibers increase the force and rate 01
cardiac contraction, increase cardiac output, ane
dilate the coronary arteries. Parasympathetic iibers:
decrease the force and the rate of cardiac contra:
tion and decrease cardiac output.
~ he ral
Nervous System (PNS )-Autonomic
REGIONAL NEUROSCIENCE
""pathetic tru nk _ _ __ -W'3.cic duel - - - - - - - '
:-e,lter and - - - - - - , ~""" thoracic - - - - --i! -"lchnic nn. ')"Irenic n. - - ---;; --['rior '"€1llC il. __- - - - pl exus ::'eater and - - - --::
~r thorac i c - - -,
An terior and posterior vagal trunks Cel iac plexus and gangl ia
l. grL'atL'r and lesser thora(;ic spanchni(; nn. Sup. rne:.enteric ganglion L. aonimrenal ganglion
':"'1chnic nn. 3drenal
o;:'(U 5 ~----~
L. IOWl'St thorilcic splanchnic n.
.aorti corena l ~~I ion - - -
l. sympathetic tru nk
- Iow esl
tabdominal
Intermesen teric
--::~ac ic
~
aort il) plexus
.e:nchnic n.
tnf. mesenteric ganglion
';enal iI . .....-.d pl xus C
.~
tnl. mesenteric and plexus
;:\ mpathetic
-_111..--
-
-
/
~ ',,~ and ~
J.
ie rami
.:ommu nica nt€s
l. colic J. Jnd plexus
L. common iliac ,,_ and plexus
C ,,:erna chyli - ---'
cd [u mb,n ~.:TI pil theti c
Sup. rectill iI and plexus
- ...nk ganglion
C-a\ ramus :~·m m u n i can5
~ ...m bar 5p:anchnic nn.
hypogJstric plexus (presJcrJI no:
- ureter a.."'Id plexus
H ypogJstric nn. to r. Jnd L inferior hypogastric
'- testicular a.
(pelvic)
.;.-d plexus - --'" .:-i!cral p.:!rl of '_ ;vmpathetic trunk
plexu~es
l. sacral plexu5
FIGU RE 11.45 : ABDOMINAL NERVES AND GANGLIA _ _ _ _ _ _ _ _ _ _ __ _ __
-ne abundance of sympa thetic nerves in the ..bdomen and the pelvis is associated w ith innervan of th e gastrointestinal (C I) and urogenital sys em s, associated vessels, the peritoneum, and the - rena l gland. Th e lumbar portion of the sympa '""'etr c chain and its branches and the splanchnic ""€ rv es and th eir collateral ganglia (celiac, superior
and inferior mesenteric, hepatic. aorticorenal. adrenal, superior hypogastric, others) innerva te smooth muscle, glands, lympho id ti ~~ u e, and meta bolic cells in the abdomen and the pelvis. Most of the collateral ganglia (plexuses) also contain parasympath etic contri bu tions from the vagus nerve and associated g(lnglia.
129
REGIONAL NEUROSCIENCE
Peripheral Nervous System (PNS)-Auton o lili...
R;.m,
left 71h thoracic sy m pathetic trunk
6tll rhoracic sympathetic trunk ga nglio n
--"t ",. ,
ganglio n
7th inter
Esoph ageill plexu s
cos l al n. ~
While
Aorti c plexu s
"d
left greater th oracic splanchnic n.
Spinal gan glio n and ve ntral roo t of 8 th thoracic spin,.r n.
Posterior vagal trunk and celiac bra nch
Right grea ter andlcsser thoracic splanchni c nn.
/
, .
l eft gastric a.
Celiac ganglia
and plexus
Anterior vagal lfunk - -...I ~-l ia c tir
Splenic a.
", 't""" .s..£";\i .., ..;~ :
Ce liac trunk~-----~~.,
Right lowesl lhoraci c
~
spla nchnic n. Common
hepatic a. Righ t
;~
gastric a. -
l
Superio r mesenteric g,mglion Aor ticorenal
ganglia l e lt gastro epiploica.
Renal a.
~ Gastrod uodenal
J.
~ Righ i gastro
epi ploic a.
~n !Inferior panc reaticoduodenal a. Sympathetic fibers _ _ Pregan glionic _ _ _ _ POSlgangliooic
Parasympathetic fib ers _ _ Pregan glionic
- - Afferent fib ers
~~p ° lmN
• - - - Posiganiion ic
FIGURE 11.46: INNERVATION OF THE STOMACH AN D TH E PROXIMAL DUODENUM The stomach and th e proxim al duod en um receive sympathetic inn ervation in abunda nce from the celiac and superio r mesenteric ganglia and to a lesser exten t from the thoracic sympathetic trunk ganglia. The celiac and superior mesenteric ganglia receive preganglioni c input from the greater and lesser thoracic splanchnic nerves. Parasympathetic
130
,,\':, : :
- ----1
iibers distribute to th e stom ach and the proxi' duodenum fro m the celiac branches of the \ a~ nerve. Sympath eti c fibers decrease pe ri stals i ~ ., . secretomotor activities . Parasympathetics inc- peri stalsi s and secreto motor activity (s uch as gastrin and H e !) and relax assoc iated sphinci
~ h e raJ
REGIONAL NEUROSCIENCE
Nervous System (PNS)-Autonomic
._- _- - •• "-"'<""-.....- -- -
..... 003_'
....- ...... ----
-
RE 11.47: INNERVAT ION OF THE SMALL AND LARGE INTESTINES _ _ _ _ _ _ _ __ ..aonomic inn ervation of the small and large -.:.ti nes is suppli ed by extrin sic sympatheti c and ..IJ2S\ mpath eti c fibers. Sympathetic innelVation .es irom the TS-L2 intermediolateral cell -n n of the spinal cord, and it distributes to co l e d! ganglia (superior and inferio r mesenteri c, ..eel. Parasympathetic innervation derives fro m e .a. gus nerve and from 52·54 interm ed iate gray -e spinal co rd, and it di stributes to intramural
ganglia and plexuses via eN x and pelvic splanch
ni c nerves. Sympatheti cs generally decrease peri.
stalsis and secretomotor function s (i.e., decreased
fluid secretion). Parasympathetics in crease peri
stalsis, relax involuntary sphincters, and increase
secretomotor activities. The extrinsic innervation of the intestines is integrated with the intrinsic (enteri c) innervation.
131
Periph e ral Nervous System (PNS)-Autonomi c
REGIONAL NEUROSCIENCE
Myenteric; p lexus lyi ng on longitud inal muscular layer. Fi ne secondary bu ndl~ crOSSing meshe$ (duodenum of gu inea pig. Champy-Cou jard, o sm ic stai n, )( 20)
Subserous plexus
l ongiludino l inlJ
plexus
M yenteric
(Auerbach's)
plexus Group of multipolar neurons, type II, in
Circu lar intmmuscular
ganglion of myenteric; plexus (ileum of cat. Bielschowsky. silver stain, x 200)
plexus
{Meissner's} plexus Periglandulnr plexus
Submucous r>1~xus (ascending colon 01 guinea pig. Stained by gold impregnation, x 20
Lumen
\
f--- Mucosa and mucosill gla nds - - Muscul"ris mUCOSiJe :---Clands ............. Submucosa ,........... Circular muscle layer I muscle
I peritoneum
~lp " 11iiN :~ .; :.
;
.
FIGURE 11.48: ENTERIC NERVOUS SYSTEM: LONGITUDIN AL VIEW _ _ _ _ _ _ _ __ _ Th e ent eri c nervou s syste m prov ides intrin sic inn er vation to th e small and large intestin es. The myen teric (A uerbach's) and submu cosal (Meissner's) plexu ses are its main el ements. The myenteri c plexu s mainly controls motil ity; th e submu cosa l plexu s mainly con trols fluid secretio n and absorp ti o n. Neurons of th is system intercon ned with o ne another and w ith neuronal processes of the ANS, although man y neuronal co mpo nents of this network are free of auto nomic influ ence. More
132
than 20 distinct neurotransmitters have bee n
ide ntified in enteric ne urons (e.g., AC h, substance
P, serotonin, vasoactive intes tinal peptide [VIP],
so matosta tin, nitri c ox ide INO]). ACh and sub
stance P are excitatory to smooth muscle, whereas.
VIP and NO are inhibitory, Optim(l l functioni ng 0;
the GI tract requires coordinated interactions
between end ocrin e, paracri ne, and neurocrine
mediators.
REGIO NAL NEUROSCIENCE
_ ·pheraJ Nervous System (PNS)- Autonomic Vagus ne rves
• .. - - -- • .. - - - - - - ••- - -
) t
Symllathetic chain
\
\
Preganglionic sympathetic Poslga nglionic sympath e tic Preganglionic parasympil thellc Postg.m gl ionic p.:l rilsympathetic Inlrinsic e meric ne urons
••- - - "'"(!fenIS
!,
J
!Y.t "-_ Spl.:mchnic nc r\'e)
Celiac or mt!'Se nteric g,1nglia
Mesen teric nerves
[oI!owing ~'--l+--i l blood
vessels
Mesentery
Petvic nerves
plexus Cir cu lar - - ----: muscle
plexus mucoSde
Muc05a - - - -
-
GURE 11 .49: ENTERIC NERVOUS SYSTEM: CRO SS-SECTIONA L VIEW _ _ _ __ _ __ _ - .he myenteric and submucosa l plexu ses, some rons are innervated by sympathetic nerve fibers m the sympath eti c chain and collateral ganglia '"'W:I by vaga l or pe lvic splanchnic parasympa th etic ~ 'e fibers; o ther neuro ns are independent of ionomic regulation. Auto nomic postganglionic
and intrinsic neufopeptidergic nerve fi bers supply macrophages, T lymp hocytes, plasma cells, and other ce ll s of th e immune system with innervation. Thi s provides a regulatory network that mod ulates GI tract host defenses and immune reacti vity of gut-associated lymphoid tissue (G ALT).
133
Periph eral Nervo us Syste m (PNS)- Auto nomk
REGIONAL NEUROSCIENCE
~r"".~ " '' ..
Sympathetic fibert - - - - - Preganglionic - - - - - Postga nglionic
f
I' I
Pa rasympathetic fibers
Hj,J
Dorsal roOi ganglion
.=%\ '11'
- - - - - Preganglio nic
- - - - - Postganglionic
Affe re nt fibers left grealer Ihorolci<
Righi gre
n. ~
Poste rior v.agal lrunk -\----\ RighI phrenic
spklnchnic:; n.
nV
''\( l x.
t-- A nterior vagal lru""
,r'
.)
,
~,J
\ I
Common areas of rererred pain in
biliary di5eases
tt\ t
,
t L
<';ji. ,w,~-;",,;
r - Anterior vagal tfonk Celiac ganglia
H~ ....llc tri;>d
j
' - '- ~ .
Splenk artery Aorta
artery aocl plexus
~~~ ,.......
.
c~
FIGURE 11,50: INNERVATION OF THE LIVER AND THE BILIARY TRACT _ _ _ _ _ _ _ __ Sympathetic nerve fibers to the liver derive from
T7-10 spinal cord and distribute main ly via th e ce liac ganglion and its associated plex us. Parasym pathetic nerve fibers to the liver derive from the abdom inal vagu s nerve. Postgangli onic n o r adre n er~ gic sympathetic nerve fibers end directly adjacent to hepatocytes and initiate glycogenolysis, increase blood glucose for fight-or-flight respo nses, and induce gluconeogenesis. Autonomic innervation
134
helps to regulate vascu lar, secretory, and phago cytic processes in the liver. The gallbladder, espe cially the sphincter ampull ae and the sphin cter ex the choledochal duct is also supplied by au!o nomic nerve fibers. The sympatheti cs ca use contractio n of the sphincters and dilation of the gallbladder; the parasympathetics cause open i~ the sph incters and contractio n of the ga ll blad ~
REG IONAL NEUROSCIENCE
-oheral Nervous System (PNS)-Autonomic
cortex OH
,.,,,.
!
CH.CHr t-.;H
A
CH J
OHJ...y' OH
;
Conversion sti mulated by cortisol
,
-;
pressure elevation OU/pUi
Glycogenolysis; hyperglycemia FfA
•
Urinary
(free fatty
excretion
acid s)
of metabolites
-
?}~ lipolysis
• -:C U RE 11.51 : INNERVATION OF THE ADRENA L GLAND _ _ _ _ _ _ _ _ _ _ _ __ -" path etic preganglionic nerve fibers from neu in th e rl O-L1 intermediolateral ce ll column
III1S
~s
throu gh the sympathetic chain and travel in
~ nc hni c
nerves to directly innervate adrenal
-edullary chromaffin cells, which fun ct ion as sym ~.h e ti c ganglion cells. An adrenal portal system D)I1 \ eys blood fro m the adrenal cortex direc tly to ~ adrenal medulla. Highly concentrated co rtisol -;:.e~ved from action of the hypothalamo-pituitary ildrenal (HPA) axis bathes the chro m affi n ce lis,
inducing the enzyme phenylethanolamin e N-methyl tran sferase (PNMT), which is responsible for the synthesis of epinephrine. Approxim ate ly 70% to 80% of th e adrena l medull ary o utput of catecho lamines is epinephrine; the remainin g output is norepinephrine. Both epinephrine and norepinephrine can be taken up into sympathetic postganglion ic noradrenergic nerve termi nals by the high-affinity uptake carrier and subseq uently released.
135
REGIONAL NEUROSCIENCE
Peri phe ral Nervous Syste m (PNS)- Aut on or-" ~ 2nd lumbar sympatheTic tfunk gan&lion
Gray and wh ile ram i
communlc,:mles ~ Right
__
svrnp all1elic (w l1k
•
[nterrnesentenc (abdominal aortic) p lexus
~ Infenor mesen teric gan glion Lumbar splar1chn ic nn.
a'nd il~ . IJ ird lu mb'!l gilnghon ~ ':r lnferio. mesen teric.i'l. and plexus
G ray ra mi
/ Superior hypogastric plex us Ip resac rill n.) Right and lei! hypgaslric 1) 1'1 .
/Superior rectal a. i.Jnd plexu!> Nerves 'rom inferior
1st sacral s\'mpathetic
trunk
hypogastric
plel(u~!t
to sigmoid ilnd
f.!
descenc1ing colon
Gray fil m!
ureteral plexus Sacril l part o f sv mpil thetic
/Seminal vesicle Ductus deferens
Solcral
~ ~p c lIl!N ,,","'/;
Pelvlt,; spl.mchn ic n n. (S.1C1i1 1 p a rasympa TheTic OUlnOW) ~
Pudendal Right iniC'rior hypo g.ls tri t (pelvic)
:
............Vesical ple)(u~
~ ~ _ f - InferiOr rectal plexus
...
~Prostat ic pleKus Cavernuu) plexus
r - DorSJI n. of ptnis
FIGURE 11.52: AUTONOMI C PELVIC NERVES AND GANG LI A _ _ _ _ __ _ _ _ __ _ Th e sympath eti c nerve fibers supply the pelvis th ro ugh the sympCl thetic tru nk gangli a and the superior hypogas tri c pl exus. The fibers travel along visceral and vascular nerves to the colo n, the ureters, and the great vessels such as rhe inferior mesen teric and common iliac vessels.
136
Parasympatheti c nerve fibers ari se fro m the 52·5"; int ermediate gray of the spinp.1co rd and trave l via th e pe lvic splanchnic nerves to distri bute witf"-. the branches of the inferior hypogastric plexuses. The intramural parasympa thetic ganglia are in, or adjacent to, the wall of the o rgan innervated .
REGIONAL NEUROSCIENCE
eral Nervous System (PNS)-Autonomi("
Solitary tract "'""""' ---::i~;'=:=--+' Dorsal vagal nucleu~
p;lthelic fibers _ __
Preganglionic
.JIIII. ..F - -
. ... ...... Postganglion ic
MeduJla oblongata
»vasympalhetic fi b e~ - - - Prega nglion ic - ......... .. Postganglionic
) -- -Gray ramus
"'"(' r(' nt fibe rs
-
, - --
- - - 1/'8" ' (X) n . - --
Spi na l ganglion
1-- - - - - D,,,,,""", m>ers -
Ventra l ram us o f T J 1 (intercos tal".) - pollhelic; Irunk .." . ';"
- -- - --c."'-
- - S'P;",'I cord (TI O to l 1)
~~~
i-- - l",",'ho,,,;, splanchnic n.
- --<
~t5~'---- CO",,'I thoracic splanchnic n. • H lumbar spJ.m cnnic". ---,t"-;
~:---
A,,"oo,,,,,
ganglion
1<>- -- R,", ganglion U:~~j:--- Intermese nteric plex u~
,-f-"«~~su perior hypogastric pleKus (pre SaCr.l1 n.)
--::-~-- Hypogastric n. Sacral plexus ---<:t~ Pe lvic splanchnic nn.
- - - + -<E
~
- - - Infe rio r hypogastric (pelvic) ple)(U5
C URE 11 .53: INN ERVATION OF THE KIDNEY AND THE UPPER URETER _ __ _ _ _ __ "T"'l pathetic innervation of the kidney and the 4!JPer ureters arises from the T1 0·ll intermedio fal ("ell column preganglio nic neuro ns in the nal co rd and travels th ro ugh the lower th oracic axf upper lumba r splanchnic nerves to synapse in ~ celiac or aorti corenal gan glia, Postgangli onic IDers travel in fascicles that accompany the upper ..r.:>teric, renal, pelvic, ca lyceal, and segmental .ra nches o f the renal vessels. Parasympathetics are . ~ rri b uted to renal ganglia by th e vagus nerve and
pelvic splanchni c nerves via a lo nger co urse through o ther plexuses. The sympathetic nerve fibers stimulate renin secretio n (and the renin angiotensin-ald ostero ne system), decrease the glomerul ar filtrati on rate (GFR), stimulate proximal tubu le and co ll ecti ng du ct N aCI reabsorption, and stimulate co ntractio n o f the ureters. Parasym pathetic nerve fibers cause relaxatio n of smoo th m uscle in th e pelvis, the calyces, and the upper ureters.
137
REGIONAL NEUROSCIENCE
ndi
Peri pheral Nervous System (PNS)-Autono mir
Descending fihers
Sympathetic fibers
fibE?rs
_ _ _ _ Pregan glioilic
- - ............ Postga ngli onl(
Spinal :Ii.
C rayramus
Parasympathetic fibers - - - - Preganglion ic
Renal gangJi()('l
... ..... _ - - Postga nglior
ganglion
Somatic motor fibers
Renal artery and plexus
Affe rent fibers
lumbar parI of spinal cord
spin., 1n. splandlnic nn.
~ J l '~
I Jl
Imermesenleric plexus
' ~I
/ ' Superior hypogastric plexu s (pre 5acr~
Ascending fibers
'I 9f-Des<:ending fibers
...,..H ypogastric nil.
Sacral splanchnic nn. ,. -"
l'rO';.:.. p.e'
no.
~1p ....•.
I'ude ndal n.
.
1. .... kI.. ,~
" ,~~, ;;
mus ~
Sphincter urethrae in
deep perineal space between layers of urogenital diaphragm
FIGURE 11.54: INNERVATION OF THE URINARY BLADDER AND THE LOWER URETER _ _ __ Sympathetic innervati on of the bladder and the lower ureters derives m ainly from the L1-L2 pre ganglioniC neurons in th e spi nal co rd and travels through sacral splanchni c nerves to the hypogastri c plexus. Parasympathetic innervation derives (rom the 52·54 intermediate gray o f the spinal cord and distributes to intramural ganglia in the wall of the
138
bladder via pelvi c splanchnic nerves. 5ympa th~
nerves relax th e detrusor muscl e and contract·
trigone and th e internal sphincter. Parasympa... ....
nerves contract the detrusor muscle and re la\. ~ trigone and the internal sphincter, thu s stimu la
emptyi ng of the bladder.
"~-:"'''€r al
Nervous System (PNS)-Autonomic
~:1! etic fibers - - - - Preganglionic -- - - - Postganglionic
=- - - CeliilC !\i1nglion
splanchnic n. (from T5· T9)
"1r.li5".m pathetic fibers Preganglionic -- - - - Postganglionic
Lesser thoracic - -splanchnic n.
~I iibers
Lowest thoracic splanchnic n.
REGIONAL NEUROSCIENCE
-
Superior mesenteric ganglion
7
-----:000:
:':C_---Aorlicorenal ganglion ~-- Renal ganglion
~"---Interrnesenteric
plexus
;;;;tii~'---Inferior mesenteric ganglion
Right testicular a. and p,,'"'---_j~
,---Ir- - - - Superior hypogastric plexus (presacral n.l
splanchnic 1111.
Sacral plexus
Sacral Pudendal 0.------\
~r- Pcd'od," o. - --
Inferior hypogastric (pelvic I I Vesical
Penile cavernous
- oors,ll n. oj penis
i-- - - Epididymis - - - Ductus deferens '-----Testis
GU RE 11.55: INNERVATION OF THE MALE REPRODUCTIVE ORGANS _ _ _ _ _ _ _ __
- oathetic innervation of the male reproductive from T1 O-L2 intermediolateral cell ~m n neurons and reaches the superior hypogas .. - ole xus via thoracic and upper lumbar splanch ne rves. Parasympathetic innervation derives -;:r-1 the S2-4 intermediate gray of the spinal cord travels to the inferior hypogastric plexus via - .ic splanchnic nerves. Sympathetic nerves ~e contraction of the vas deferens and the pro 'aJc capsule, and contract the sphincter to the ,"":2J1 S derives
bladder, which prevents retrograde ejaculation. Sympathetics also contribute to vascular responses in the penile corpora cavernosa related to erection; beta-receptor blockade can result in erectile dys function. Parasympathetic nerves regulate the vas cular dilation that initiates and maintains penile erection. Sympathetics and parasympathetics must work together to optimize sexual and repro ductive function. 139
REGIONAL NEUROSCIENCE
Sympathetic fibers Pre ganglionic
- - - - - - Postganglionic
5th thoracic
,ympathetlc trun k gan~l ion
Peripheral Nervous System (PN S)-Autonomic
--""-"",-,,
T 4 -~~ ;.W'
I ;) ~
- ...:.::...=---:
. ,~_ _ Ll:fr svmpa\hc trunk '
'::5"_
Parasympathetic fibers - - - - - Preg
Gray ramus - - - -
- - - - - - Postganglionic
communiC
Afferent fibers
\-Vhi te ramus----"""" communicans
... ::::::::.
Celiac
gan~ ;i""
• " , -_ _ Aor licorenal
Greater 1horacic splanchnic 11.
I.e~se( th~l aciC splanchnIC n, loweSI lhof3CC
splan<.:hnic 11 .
./....
ganglio n
;;;:<""'-
mesenteric
.;:;q-~ T12 -:---_~
ganglion
---...--:?. -.= -:o.", .:i
L -...
Ren;,1g'lngl,
Inferio r
if:7
mesenteri C
ganglio ll
-',.- - n l "" lJ ~ (presacr,l .
.,.
Ov arian il. and plexus
Ovary
~{t' 1.1'
Hypug..1 wk
~ Pelvic 5planchni<: nn.
l&:
U terovaginal pie
ltV" _ '"
'icsr
,
Sacral plexus P\ldendal n. - - - '"ts. ~iii
~il!!N ,,-'c."
-9t
~
J
Pudel1dal !\.
FIGURE 11.56: INNERVATION OF THE FEMALE REPRODUCTIVE ORGANS _ _ _ _ _ _ __ Autonom ic nerves supplying the female reproduc tive organs have a similar o rigin to those supplying their male counterparts. Sympathetic nerves sti mulate contraction o f the uterus, but the extent of this action depends also o n hormonal receptor responsiveness and neurotransmi tter receptor expression. Sympathetics supply the vaginal
140
arteries, the vestibul ar glands, and the erectile tissue. Parasympath etics supply the muscular and mucous coats of the vagina and the urethra, stim.. late erecti le tissue of the vestibular bulb and the> corpora cavernosa of the clitoris, and supply the vestibular glands.
.....I Co,d
REGIONAL NEUROSCIENCE Nuclear cell columns
Laminae of Rexed
,-~-----------~------------~~~-------~,------~~
N udt:us posterior margin<JHs
(mllrgin
-'
Subs tantia ge1atinosa (lamina II) N urieus propriu ~ of pCl slerior horn
'\.!uciell s do rsalis; Clarke's colu mn LT1-13 )
I ,:\',
L.;lI(:!T,ll basai lludeus ~;::>lI1 a l
\\,
reticlIl;Jr zan",
iof"mcdio lilleral cell o"iITln; sympathetic
:-:.lnglio nic neurons
~~iecliom('di
--r-------= _-1-------
mn: parasympathetic -;;:anglionic neu ro ns :_~I
Moto r
FlexOfS
neurons
of li mb, [ce rvi cal
Extensor s
-nd lumbar
D i ~I'1 1 pari of limb _-'-:t,,~,_
.lrgeme nts 01cord)
Proxim.11p.lrl of li mb Moto r neurons of trunk (Cl-3 and T2· 12)
~nd
m:c.k
RGU RE 11 .5 7: CYTOARCH ITECTURE OF THE SPI NAL CORD GRAY MATTER _ _ _ _ _ ___
~e
spinal cord gray matter is found in the interior
j the spinal co rd in a "butterfly" patte rn. It is sub
\'ided into 3 horn s: ( 1) dorsal horn-site of major ~ n sory processing, (2) intermediate gray w ith a la t
eral horn- site where preganglionic sympathetic th ora columbar) and parasympathetic (sacral) cell bodies resid e and interneuron al processin g occ urs, .and (3) ventral horn-site where lower motor neu rons (l MNs) reside and where convergi ng refiex .and descending control of lMNs occ ur. Neuronal cell groups appea r homo geneous in som e regions 01 gray matter, with some discrete nuclei (e.g., Clarke's nucl eus, su bstanti a gelatinosa). laminae 01Rexed, an alternate system of cytoarchitectural
classificatio n establi shed in the 19505, subdivides the sp in al cord gray int o 10 lami nae. Th is system is used extensively for the dorsal horn and the inter mediate gray, laminae I to VII, particularly in con junction w ith anatomical derails of nociceptive processing, and for so me reflex and cere bellar pro cess in g. Althou gh these laminae have distinctive characteri stics at each segrnentCl lleve l, they show some similarities across segments. The absolute amount of spi nal cord gray is more ex tensive in the cervical and lumbosacral en largements of the sp in al cord, wh ich co rrespond to zones associ ated \Nith limb innervation, than in th e upper cervica l, thoracic, and sacral regions.
141
Spinal Cor<
REGIONAL NEUROSCIENCE Second cervical
Fasciculus sracilis
Fa~ciCI.J lus cune;JIUS Dorso lal !!ral
~
ra$ciCulu S ~
(lis~ uer's
Zone)
"
' " .. ...-
\..
/:' /
DOlsal spinocere bella r traCI--crr"
.... ,.
/
Rostral spinocerebe llar tra ct lateral corti c[)~pi n a l traer Ruhrosplnal II
it '.." '"
Ven tral spinoc(>rebellar lIaCI
-;--'-- - --f--
-:\
Anterolah:ral system (Spinothalamic trac l ami ~p;noreljcu'a r Iracl)
.
• •
Lateral (n le
.,.,
...._
;:,
rt.'tiCulospi n.,l lfacl ---~
Arll E'rior corlicospinal trac t
Seventh cervical
r asnculus gradlisi - - -- - - Fasc.iculus cuneatvs \ .,.-.'.. ,. '\
.,/ DorSill spinocerebella r \rilCI
lCl telal cortK.ospin.1l u.lC1
.
/ /
1
Rubrosptn"lt rilCI Ve ntrill spinocere bellar
.
! ,'
~\
'r;"'~"w"""~"
"'.
, zone gelC!ti.......
-.~-------Substan\ia
.'.
- -'---- -- - --,;c,-
Nucleus proprous
v - - - -- - -
V1
x
V" \
-. . .
'.
L
Descending monoamine <1.\ (norad renl!fgic, serotonger Oesceoding fibers from hyPolhala ....... and br..in sl em 10 ~pinal Co
----~---MiI 'I~in al
tv ··
"-
trac t ~
Anterolale ral system {SpinothalamiC t.ael and
.. •
I
, "'"
", ..,- ' " __
~
\
\.~----\:.- -r---"",
Dorsolateral fasc icul us (Li5S,HI~r's Zonel
.
Anterior while commissu rE'
Medial100giludinal iJ)inal tract)
ROSlra l spinocerebellar trilCl--
Spinal accessory nucleus
- -- - - -",,"" :,.,1,'--- AnteriOf horn
u teral v~l l bu lospinal lracl Medidl (po ntine)
- - - -- - - , - Nu cleus p ro pri us
~ /J. . _ I.
!
Subslanlia gel
'x
IX
_
VHI
~~:i
~ :$ f#
)
- - ,,
i
"I
Intermediate F"; l ower malar net.: in anterior horn
"
' ~~' ~_ -~ . .,
l ateral { medu ll.u ~'l reliculospinal lraCI
"' ..,,' v.,,;bu""p;",' ".c, Medial (pOntine ) feticuiospinai lraci
.~ '- -,-' "~ #\
~
. - - •..- .-
i
I
/
,
An" ';O""';'e comm'''"''
Medial longitud inal fasciculus
Amerior corticospinal trJ ct
,. Pe rkiM MS..-o-· o,~
FIGURE 11.58: SPINAL CORD LEVELS: CERVICAL, THORACIC, LUMBAR, AND SACRAL _ _ __ The o rganization of the gray matter info laminae of Rexed is retained throughoul the spinal cord. The dorsal an d ventral horn s are larger and w ider at the levels of the cervical and lumbosacra l enlarge ments. The lateral horn is present from L1 to T2 . Some nuclei, such as the intermediolateral cell colum n w ith preganglio nic sympathetic neurons (Tl -L2 lateral horn), Clarke's nucleus IC8-L2), and th e parasympathetic prega nglioni c nucleus (S2-4), are found only in ci rcumscribed regions. The w hite
142
matter increases in absolute amount from caudal rostral. The dorsa l columns contain only fascicL gracili s be low T6; fasciculu s cu nea tus is added Ia:. erall y above T6. The sp inothalamic/ spino reticu!a anterolateral system increases from caudal to ro; fral. The descending upper motor neuron {U ,\\, pathways diminish from rostral to caudal. Th e la.... eral corticospinal tract loses more than half oi i::: axons as they synapse in the cervical segments tract Ihen diminishes in size as it extends cauc~
REGIONAL NEUROSCIENCE
Fasciculus 8r..olt5 - -- - - , FasCiculus (unealu$
\
Dorsolateral fasCiculus
\ \.. ,"
""""""/),11,,
-'
-, ,
~\:
(Llssaue,'s Zone)
'' ' ~ //
- - -- -- -'.-- - M arginal zone
~ COrl icos pinal HilCI -f''-----i''
f
Rubrospinal
h.
- - -- -- -- - -- Subslanri
A.
traCl-~\i-,o,--c" c -i t
____-------- -+1-
,\
\
-p, noct-,ebella( I,act ----"";;:"
"'"
Nud~u, dorS
I
.." !If '.e - - - - ---:::;,:!---l ower mOIOT neurons
'- >.
"'nlerolatt!ra lsystem
Nu cleu~ propriu s
- -- -- -- -- --
)
_: ' Olhal,lmic trael and
r
'--
- .enulia' y) rehcuiospin,-,Itraci
~
-~~~~ ;
'
Laleral v~hbulospina l lracl \\~' a l (pontine) reliculosplnaJ Iract
in an terior hom
Anle rior white commissure Medial longitudinal iasciculus
,
....
' ..
Anterior corticospinal lract
..
D escending monoamine axon s
(nnradrenergk, sero ton~ergic) Descending fibers irom hypot halam us and hrain stem 10 spi nal cord
thoracic
Dorw laleral folSciculus - - - ,
//A '
(U,,,,,,,', Zo", ) -~I
.~. ___ .__
Fasciculus gradli.. - - - - - ,/\ /
spinocerebellar Iract ------,~
"
l"
h.
II.
.
IV V
--;--,-----:---
~tr.J1 spinocerebellar Irao
,
~2====~~~===
I
~ ij' · "til
.,----
I . ll eral cor ticospinal lr
\
~_--------- Nucleus ool'Sdlis oi Clarke
"
t '-
VII
'
- --"'"
X"
'j~.
\
I
ISpi no thal,lmic. tract ,lnd
""
spinore tieular (fac tt
-:...: _ :.'
"metOlaleral sy51em _ ___C'''~
L.i.' ('ral (medullary) ft!liculosplnallract
Lateral vestibulospinal tract M edial (ponllnel retlcu l()sprn al tract
?
/
]
"-
/f
late ral ho rn Intermed io lateral cell column
---i"'--_"o wer motor
'"O w (j_ _
Jl~urOIlS
in ,Interior hom
Jl
'77 ,;YI'\ /
Substan ge la tino 5" Milrginaltiazone N udeu~ IJroprius
"
riiY
AnterIor while comnussurt:!
Medra110nglludlnal i:)sticulu s AnteuorcortlCospmaltract
J. Perkins M5,MfA
" lION
.,,""
143
REGIONAL NEUROSCIENCE
Spinal Cor..:.
~/_/ '~
Fasciculus gracilis
First lumbar
__. "
';j
X
Lateral corticospinal tract
.
Rubrospinal tract
h~ k . '{g;;~/ ;;~~
/ / /
r . \..- -;--; -{ A~
:,
'-.
___
.-):".
\\~\:'..' \ l~-\\ ' Ventral spinocerebellar IracI--- 'o, \\" \ .....' \
Anterolateral system
'~' -
:~
~ ....
Lateral vestibulospinal tract
,
Marginal zone Substantia gelatinosa
.~, \ '.
tJ?lt~~~_____'-'c :~
. ,~-"t:· :;>I:~_'~'>'~
, n~ "~"'\ ' ' \$, .k
~j '..
.
1
~1
_
.
__ __ .ffJjJ(" :
~ I;~
~<~ l / : ; ",:J' \.
Lateral (medullary) retlculospmal tract
.' '_.
'X
~~:: - ..J~:
splnoretlcular tract)
.,;:§'~ '
-:'%4" .;.
i '~"
\.
\,;'i:; ',-....
(SpinothalamiC tract and
\
!
/!:__,:fi:,\,,~,., .
I
'. .
~
':
Dorsal spinocerebellar tract
~,
~"
~
1/
\
(Lissauer's Zone)
-~
~
,/' Dorsolateral fasciculus
-y- ______
'
JL
,,,
, _ J"/.I,jfo"""'<
Dorsolateral fasciculus (Lissauer's Zone)
\" .' / /,"
/-" -\"-'-~r---" -
"<'
'-
~
.~
Marginal zone Substantia gelatinosa
Nucleus propriUS
\ '
t
Lateral corticospinal tract
"~
Rubrospinal trac t
~
"
Nucleus dorsalis of Cl ar>.e-
Ventral spinocerebellar trac t -----L Anterolateral system (Spinothalamic tract and spinoreticular tract)
,.....
"".\ " ,
Lateral vestibulospinal
~ ..
'
Lateral (medullary) reticulospinal tract
,
~
.; /
Lower motor neurons in anterior horn
;r.
tract~
Medial (pontine) reticulospinal tract------./
Anleriorwhite commissure Medial longitudinal fasciculus corticospinal tract
144
.
~'"'. ~
, ~~~- ·~ ·- ..... ::~luW:'$
Dorsal spinocerebellar tract
,i ..
Descending monoamine 2VP' {noradrenergic. seroton ge' f Descending fiber; from hypoth a l ~- _ and brain stem to spin21Cl
" " :" .:' . ., .;. "':",, ' .
.,
·.~ .Il.. "';;"
Lower motor neurons in anterior horn
,--
Medlallongltudmal tasoculus
Fasciculus graciliS -----~
Lateral horn
Intermediolateral cell COlli'
..
~.
Anterior corticospinal tract
Third lumbar
Nucleus dorsalis of Clarke
.;~q{'
Anterior white commissure
Medial (pontine) rctlculospmal tract
Nucleus proprius
J. Pe rlci MS, ' ''' '
C'l l@l'\l
"',"
"
REGIONAL NEUROSCIENCE
...,1Cord
filsOrulus8rac;' i~ ~
~' ,
__
/ "\
Dorsolateral fasciculu~
/"
(Ussauer's Zone)
--...
\
-'''---''', - - - Substan ti~ g elil tinOSJ
DoHill spinocere be ll ar tra ct ----~. ~
i 11-:- l.ller,,1 c()rti<."OSpinal tract ----+-~ . •
--'----l,- - --
_ Rubrospinal 'ract ___71l!.12\.-"7--. -/
V,,,,,I "
--..."
,.,,-"-,~----- Marginal zo ne
/ /_'
f
~.
- -- - ---'\;-- - - Intermediale gray
'"o<.•,.b.lI" "''''-----(\
Ante ro liJ teral
sy~lem
~' \
j
\
~I__--f_---low{' r
~)... ..:~
(Spino thalamic trar.! and spinorelicula r I racl)
~"-.
~.••" ,,,,,,,"",,,, ,,,,,,,10>00001
",0<'
'.
Nucleu~ proprius
motor ne uro ns
in an terio r horn
...:
~
latelal vestibulospinal tract MW.JI (pontinel reliculospinal tract
/
/
,_._--- ....
• •A
Amerio( while commtssure
Medial l(lfl~itul linal (asciculus
:4
:.-~- .......:
Anterior oonicospinclt Ir,let
Descendins monoamine ,1xon~ (noradrenerglc, serotongergi<:l Descending tlber$ flom hypoth'll"mu~ and I.Iraul stem to spi n~ 1 COld
F",.dculus grac ilisl - - - -_ Dorsolateral fasciculus - - - (Liss~ uer's Zone)
)<
/ Dorsalspinocerel>ellar 'r <1C'----, f'/~ lateral corticosl'ina l 1'.lCI Rurnospinal lracl Vf'ntral spinocerebellar tract
---+ ---
spinme ticular Iracl)
",'k"IO>P'"" ',"d
.I
,,
~
lateral vestibulo spin.ll lrad Medial (pontine) rel iculospin~ 1 II.KI
--c,,---- ,lvl
.
-c;-'"',--- --
",/ - I~
- - - - - ' : -- --
\V. .
/ ::' ...... ... "
Anterolateral system (Spinolhal.1mic " ad and
". llm,doII,cy)
,~-
V
VII
-
x
VI
Substan ti a gelalinosa
Nucleus p ropri us
-"----'~-- Sacral parasympclthetic nucleus
VIII
IX ;
IX ~~-----,#----lower motor neurons
\,:., ,
~ _,
in ,1ntefiOr horn
_ ~
~'
/
/
An terior while (.;ommissure
Mediili iongi ludinal faSCIculus Anlen O. corl,cosI'inallr.lCt
.
,. Perk ins MS,Mf"
'''--,''
145
REGIONAL NEUROSCIENCE
Spinal Con: Dorsal horn interneuron
mOlor neuron
'
Dorsal horn interneuron
, .
a motor axOll
Schematic representation of motor neurons " ~r~-T
,, i
i
'
\'/ In cervical enlargement o f spinal cord
In lumbar enlargement of spinal cord
~~
CON : ......:::
FIGURE IL59: SPINAL CORD LOWER MOTO R NEURON CONTROl _ _ _ _ _ _ _ _ __ Lower motor neurons are localized in the ce rvi ca l, thoracic, lumbar, and sacral segments in th e ventral (anterior) horn of th e spinal cord. LMNs also have a med ial to latera l and dorsal to ventral organization. LMNs supplying trunk musculature are found med i ally and vent rally; LMNs innervating more distal musculature are found dorsally and laterally. Thi s o rganization also is apparent in the topography of
UMN control of LMNs. UMNs regulating fi ne hand and finger movements are sent from the
146
co rticospinal system to terminate o n dorsal and lateral LMNs. UMNs regulating basic truncal ton e and posture are sent from the reticul osp in al and vestibu losp inal systems to terminate on ventral and med ial LMNs. Reflex pathways regu late LM i\. activity through monosynaptic (muscle stretch reflex la afferents) or polysynaptic (flexor or cuta· neous reflex aHerents) pathways. Superi mposed 0 :" this o rganizatio n is the descending UMN control and coordinatio n of LMNs.
REGIONAL NEUROSCIENCE
Co rd
-
-
'- '-....l ere n! inhibilion
8. Stretch reflex (reciprocal inhibition)
- -- -- 1'I-'-''----'-'--'---
...... ~O r spindle ..i. iibers)
. --
C. Realrren! inhibition
O. Tendon organ reflex
- 1' rl--'--"'-===
--'-- ' - -- -
From exte05()( spindle receptor (Ia fibers)
From eJC l ensor tendon organ (Ib ~be rs )
•
f
.
,.
.... / J
,-,, --r-j' -. . ... I \
.
.
i '. \
'.
;' ' ~ I~ . '
",
;
.
I
.
,
~ ~ \
\ Rl?OsOaw --'--F
\
'!
cell s
~ Inhibitory
\
,, ___ J
synapse
'
Excita tory
synapse
__i1~t
To flexors
To flexo rs
Collateral s
oors
To extensors
To extensors
To synergistic muscles
F. Renshaw cell bias
E. Flexor withdrawal reflex -----~
~i;ve
fi bers
\ I
l.ewrs
Toilexors
. J.
To extensors
Perkins
/tis. MfA :v~ '"
\
".Jr__ "',.;
~,
synapse
" f,
,
'""T-
r{ ' / j
'.... ~ ~
Inhibits to nic exten sors
~
-
Exdte s phas ic
O"o~
',,'h:;;
To fl exors
_ __ _ _
To extensors
URE 11.60: SPINAL SOMATIC REFLEX PATHWAYS _ _ _ _ _ _ _ _ _ _ _ _ _ __ ":Ie muscle stretch reflex, la afferents excite the lonymous LMN pool directly and inhibit the ;:a gonist LMN pool reciprocally via la inhibitory e-neurons. The Golgi tendon organ (GTO) reflex ........bits the homonymou s LMN pool disynaptically .rrl excites the antagonist LMN pool reciprocally. =aor reflex responses excite a larger pool of _ .\\!s, with reciprocal inhibition of the antagonist _., ~s, to bring about a protective w ithdrawal ~p on se from a noxious stimulus. These refl exes to
can extend throu ghout th e spinal cord. When an LMN fires an action potential, it excites a Renshaw cell, w hich inhibi ts the LMN, thereby ensuring a cl ean slate for the next set of inputs to it. Rensh aw cells receive input from axon collaterals of both fiexor and extensor LMNs to exert an inhibitory bias that is mainly directed toward inhibition of extensor LMNs and reciprocal excitation of flexor LMNs. Thus, the Renshaw cells favor flexor move ments and help to inhibi t extensor movem ents.
14 7
REGIONAL NEUROSCIENCE
Spinal
Muscle ilnd joint receptors Alpha motor nel.J ron~ 10 e)(traTusai
striated mu~cle end plates - - - -- - ---G a mma molor nellro ns [0 inl!
(Au ) iiber~ from
endi n R~ (pJOprioceptloni - -- - -- - - " 11 (AIlI fibers fwm flo w er $pray
end ings (proprioception): - - -- - - ' " /
fro m paciniiorm co rpu_Kl es (p ress ure) - . / / and pacinian c orpu scle~ (pressure) / III (Ao) fillers from free nerve endinl\s
a nd from ,orn e specialized end ings' (pain .md some press ure)
/
IV lunmve hnatedl fiht'r~ from iree
nerve e~dings (pain)
/
WI
Ib (Aa) !iber~ from G oigi tend oll organs (pro prioception) - -
1/1
An fib ers hom Golfl j-tvp e (: nd ing,
All fibe rs from pacini/orm corpu'>(;les c:md Ruffin i terminals
- - AS and C tibers irom fre!? nerve
~nd ings
Alphil illo tor r'u=uron to extrafu sal
muscle fibe r end piOlte5 Gilmma motor neuron to inlraiu ;al muscle fiber end pla tes
II
(A ~)
--Intra(u sal muscle fib ers
/"
fiber irom fl o wer spra y e ndi ngs
" - yl plilleend lngs
la IAn) tIber from annulospiral endings
- - - - s h l ? ath , - - - - l vmph . ,pace Nudear bag fil ter
Detai l of muscle sp indle
~fp c lCuN "'--;,' ,:
' Nuclear <.h ain ti ber Effere nt fibers Affe re nt fibe rs
FIGURE 11.61; MUSCLE AND JOINT RECEPTORS AND MUSCLE SPINDLES _ _ _ _ _ __ Joints are innervated by a host of afferent recep tors: bare nerve endings, Golgi-type endings, pacin iform endin gs, Ruffini-like endings, and other encapsulated endin gs. GTOs inn ervate tend ons and respo nd to stretch w ith increased discharge, causing disynaptic inhibitio n of the LMNs that con tract the homonymous m uscles. The mu scle sp in dles, com plex sensory receptors w ithin th e muscle, are arran ged in parallel w ith the extrafusal (skeletal) muscle fi bers. These receptors contain small
148
intrafusa l muscle fibers that are stretched when the muscle is stretched. The la afferent fro m the muscle sp indle excites the homonymou s LM N pool mon osynapti cally and respond s to both the length and the velocity (change in length w ith respect to time) of the extrafusal muscle fi ber. These muscle reflexes ass ist in maintainin g hom p,:", stasis durin g contraction and help to regul ate m L~ cle tone during movement.
Cord
NEGIONAL NEUROSCIENCE
-
B.-Jsetine fiung ...
Extra/usal m uscle tiber
neuron s ..........
Gam ma mo tor neurons A.
Golgi te ndo n o rgan
- - - -*It:
Pas~'~
. lretch. Both ;mra fu, ai 3r1d f'xlloru S
spindle-.; 3C[' \'';lIed. Rp,lcx\'ia 1:1 libers and ol\Pha mOtOf
noWron~ c~uses
s.eco nrlu r)' COrltrxtion (b~sis of Stfe l<;h ,eilE-xes, slI<:;h iii knee jerlo.
Stretch is too w eak to ac tivate Golg; len dOl'1 organs
Al pha activation from brain
Exlra/u sal muscle fiber ' nlTa ru~al
muscle liber
Inhibitor), intern euron
neurons -+ Gilmm
caUWi
Ge lg' tendo n olg.ln
-----
con l T~ cljon
01 "\{,,,iu!.iI1muS(le fiber s " iln tO n~ l'quenl
of inlrafuSllltihcr,; spind les nOI actj,' atE'd, Tension
j<
rel ,lx~"on
10\\; (I t'~ 1 not M!IUSI
to inut:'dsed r(>~isIJn Cf;". Tenoon organ aCli\B Ie<:! , (dUJonS fel~xation Th,s is theoretical only. Act",. (oO't ra<:1;on imol\E'~ n··! coar ln alion
~
Jbfibe r;;- _
, Alpha ;Iod 8
13 iiber5 (maintains bJseline)
Ext raru 5
-
Gamma motor C. Ad hot Contra ct ion with alpha·g~mma coactivation.l nlrJ iu s.a1as ...-ell as Io'xrraiusill tiber5 corur.J.c t spindle~ ,u:;ti..ated, reinforcing contraction Jl;muluJ ,~a 1;'1 iibers in accord with resIJlanf.t. Te ll(i()n organ ~ l iva tE'd. causi ng rr. IOIxation if load is Io n !!reJ I
fiG URE 11 .62: THE MUSClE STRETCH REFLEX AND ITS CENTRAL CONTROL VIA GAMMA _________________________________________ MOTORNEURONS ..Juring passive stretch, a muscle stretch reflex of'\ci tes ho monymou s LMN s, whi ch results in muse contraction to restore homeostasis. If active co ntracti on occurs without y.LMN activati on, th e "'1u scle spindle "unloads" and the tension in the 'f'Irrafusa\ fibers is redu ced, resultin g in diminish ed ring of bo th la and group II afferen l s. Ho\·vever, ",n en LMNs co ntract becau se of brain stem UMN activity o r voluntary corticosp inal activity, a.-LMNs :ond y-LMNs are adiva ted together. This process,
a-"fCoactivation, ensu res that the tensio n on the muscle sp indle (throu gh th e intrafusal innervati o n by y.fibers) adj usts immediately, that is, as the extrafu sal mu scle contracti o n (thro ugh a-fiber innerva tio n) occurs. In norma l physio logical cir cumstances, a-LMN s and "tLMNs are coactivated, although they can be modulated separately by cen tral nellronal circuits. If y.LMNs are differenlially activated in pathol ogical circum sta nces, increased muscle tone and spasticity ensue.
149
REGIONAL N EU ROSCIE NCE
Brain Stem and Cerebellu
Fasciculus cuneatus
~
Spinal nucle us eNv
Spinal tracl eNv
level of section
,.... -~ "\ I"
y l
'-..
DOf'NI l
I
spinocerebellar tract - -- _ __
I
" :,>;,~:J.9:
<;.~
XI "...
Spinothalamic! spinoreticu1ar Inll:;l
/
NudeusCN XI
, -
·~~~ 'X l a tera l ( on icospinal . tract
,I
Ven tral
spinocerebellar tract
FaSCI<.UIUSgracil i S
'.
~
Central canal
Decussation oi
'f:;'if '%fW
pyramids
' !?
--
IJ
j'::1J,~
__ ..cow:..., I ..,...
PyramId
"w'"
Section 1: Med ulla-Spinal Co rd Transition- Decussa ti on of the Pyra mids
Dorsal spinocere bellar tract
('~:t)
~' ,T'J' f, '.f ' .~y-
'-.
~ Nucleus gracilis
,
, ': .,
AY
i\ Level of se ction
Fasciculus cuneatus
>\,
1/
Spinal trac t
C NV ~
'iF
Nudeus cuneatus -',\
~"",--.c;'r\- Tra c tu 5 soli tanus
Spinal nucleus
CN V
,
-
---f-- D o rsal m Olor
Nucleus ambiguus ---.I. - 't-__ Ven tral spinocerebellar lrael ./
SpinOl halamiC/
nucleus of X
-J- Nucleus eN Xli
'l
V"- Medial lo ngiludinal fasd culus
'tract ",""'eli",'" /~'l' - ---', Do rsal accesso ry olive
Medial accessory o live
Py ramid
pyramids" Nucleus solilarius
.I_"COW:~ ._ I 'Wi m
Section 2: Medulla- Level of the Dorsal Column Nuclei
FIGURE 11.63: BRAIN STEM CROSS-SECTIONAL ANATOMY _ _ _ _ _ __ _ _ __ _
150
REGIONAL NEUROSCIENCE
Sie m and Cerebellum
Nucleus runeatus
External (lateral) cu nea te nucle us Inferior cerebella r peduncle ~vit do rsal spinoce rebellar trac! ~
Tractus Level of section
Nucleus gracilis
r .
Nucleus S(IIit.Jrlius
/ - (:eo,,,1canal
.
nucleus
',. ~."l'1
X
Nucleus eN XII
' , ~
SOlitar~jUs:
<;:'
Spinal tract
~'.
. ~,
(NV
"
Spi nal nucleus ,:., CNV - -J
:.)..._- Imern al arcuate fibres
;~~b~%~~J2~[
Medial lo ngi tu dinal fasciculus
Spino thala micl spinore ticular
Tectospinal tract Medial lemniscus Inferior olivary nucle us
ivledial accessory olivary nucle us
...., 3: Medu lla-level of the Obex
Exle rn')l c uneale nucleus Infe rior cere bellar ped uncle
Nucle us cu neiltus
r - N,,,I,,,, so!itari us
_ T""" " solitarius
~.
000 , 1mo tor nucleus o f X
~.;'~!"J!~~;;~;:
Choroid plexus 0-- -
fe,""" ve ntricle
Leyel of sectio n CNX Spinotha!.amic/ spinoreticula r tract
,~- , ,,,!;,l longitudinai
fasc iculus
Nucleus ambiguus Tectospinal lracl Inferior olivaI)' nucle us Dorsal ilccessory oliva ry nucleus
~ M,di,'lemniscus
CNX II
L ",,,fj, 1accessory olivary nucleus
!Clion 4: Medulla-Level of th e Inferior O li ve
1 ': 1
Brain Ste m and Cerebell lr"
REGIONAL NEUROSCIENCE
Tra c tu s so lil.)rillS
Nucleus solitariu!>
Inlerior ve sTibular
r- Medial vestibular nucle us
nucleus formation
Inferior
cerebellar
peduncle
level of sedion
Dorsal mOlo r nucleus
Dorsal m O':
nucleus 0'
longitudina
fasciculus
Spinal tract eN v Spinal nucleus eN \I
TeCiospinal tra.,.
Spino thal am ic/spinarelieular Iracl
' - Medial lemniscus
Infe ri or olivary nucleus
.,jOHN"'CI'f"'IC.~
e l(DN
I
,w·,'",
Section 5: Medulla- level of eN
x and the Vestibu lar Nuclei
Dor~3J
cochleM nucleus
Med ial ve stib ular
N ucleus prepositus
iormalion
Medi'll longitu dinal
fasciculus
nucleus
Inferior
traci
Ven lral cochleM
level of !iection
nucleus
Raphe nuclei
(NVIII
pallidm
(obs (l-~;
Spina l tract
eN v
Spln,l l nucleus eN v
~ Inferior olivary nuclew.
Inferior vestibu lar nucleus Spinothalam ic/spinoret icular tract
Med ial lemniscus Central te gmenl alu3cl Middle> cerebellar pedunde
L Pon tine nuclei
Section 6: Medullo-Pontine Junction-Level of the Coch lear Nuclei
152
Corticospinal tract
~HN ACR4.'1
e~
c.
REGIONA L NEUROSCIE NCE
. Slem and Cerebellum
l
Superior vestibular nucleus
N ucle us eN VI
Superio r cerebell.tr peduncle ~ \
Supedor o livary nucleus
Dent.}le nude us ______ _ \
Medial longitudinal
Middle cerebellar peduncle _ _ _ In(erior cerebellar
fasci cu lus
___
peduncle- -
Fibers ( NVII
Level of section
---========='
Spinal tract eNv
Spinal nucleus eN v
tract
-~"'""------
Nucleu s eN VII
CNVII" 7< CN VI I - -
Spinolhalamic/spinoretlcular Iract
"--- R,>ph,. n ucleus tmagnu!.)
Central tegmental tract
~"'- I~e,j;a' lem n i >CU5
Tr.lpezoid body
Corticospinallract
"'
Po ntine nuclei
( NVI
IOn 7: Pons-level of the Facial Nucleu s
Dentate nudeus \ Superior vestibular
nucleus Inferior
'
cerebellar ,~ pedunde _ _ _ M iddle cerebellar
Superior cerebellar peduncle
r
Globose 3r1 d emboliform nuclei
i
CNVII
~
pedunde (MCP ) _
Level of section
~ ' \fl~:; ;'?
vestibula r lateral nudeus
.
Nucleus CNVI Med ial longitudinal fasciculus Fibe rs (NVI
Spinal tract CN V Medial vesti bula r nude us
Tecto spinal Spinal nucle us C N V
tract
--C" ot,, 'l tegmenl al tract
Sp i no th ala mic/spi noreticular tract
Trape zoid body
•
Media l le mniscus
Cort icospinal lrac t Pontine nude i
Section 8: Pons-Level of th e Genu of the Facial Nerve
153
REGIONAL NEUROSCIENCE
(' r. ~··k....
l ateral para brachial nucle us
t,"
......
Brain Stem and Cerebell
Medial parabrachial nucleus
l ocus coeruleus
Fourth
ventricle
~,
Jr·· ·
-
\
Super ior
cerebellar peduncle ~~ . /'
,,,
'Yl ' f .JrT,;r--P--
Medial longituo
fascicul\..,
M iddle
cerebellar peduncle
level of section
>-'
tr;) c t
Raphe
Mesencephalic
nu deu~
nucleusCN V
(ponl lS
CNV~'~ Main !chief) §en~ly nucleus eN v J
' - Centrat legmer
.\I\olor nucleus eN
Ira e!
5pinOlha tamiC/spinoreticular Iract ' - Medial lemniscus
Crossing fibers of middle cerebellar peduncle - 1
............IC_
Pontine nuclei
. W':::: """
I
Section 9: Pons-l evel of Trigeminal Motor and Ma in Sensory Nuclei
Supe rior cerebd lar peduncle
locus coeruleus
,
-:=
~ PeriaQueductal gray maltfc:
,.
-Z!
, !,
\ l evel of section Spino thalamid spinoreticular tract
1 ;
Aqueduct
./
1, ...,
- - - - Dorsal raphe nud'h .·
i:' -,.. '< Media l longiludina j fasciculus
Medial lem ... i~cus -..../" Corticospinal tract - - -
Central supelior raphe nucleus
Pontine nudei
.-
~"CRAc..... c:
Cenlrallegmental tlael
Section 10: Pons-Midbrain Junction- level of eN IV and locus Coeruleus
154
,.......:,'
REGIONAL NEUROSCIENCE
Jain Stem an d Cerebellum
!n feri()( coUiculu ~
Brac hium 01 in ferior
Re ticular formation
Periaqu educlal gray mailer
-'_ ;::;========;'2,=~N~'Ucieus eN IV d
Oor,,,1raphe nudell'
-----A f)}~ , -
- -<--
.'vted iiliiongitu dinal fasck ul us
Superio r cerebellar peduncle ~ de( u $S
Cenlral tegmen tal tract _ _/
Interpedu ncular nuclei
Medial lernniscus Sobstanti;a nigra
Kti on 11: Midbrain-level of the Inferior Colli culus
Brachi um ot inferior colliculus
Superior culilculll S
Mesencephalic nucleus eNv /~.--_ _- -\"-
PeriQqueduClal gray mailer
I ;'¥'....- . - - - - - --Aqueduct
l evel of section
:iC'-----~"'=::-- Nucleus of [ dinger-Westph
Spinothalamid spinoreticular tract
Nudeus CN [II
Medial lemniscus Medial lo ngitud inal Cen(ral tegm ental trac t
fasciculus Ventral tegmental decussation
Substantia nigra
Red nucleus
e N II[
area
.,IOHN A"C:RA1i-"" ° II!lN "....... :"
:!Ection 12: Midbrain-Level of the Superior Colliculus
155
REGIO NA L NEUROSCIENCE
Brain Stem and Cerebel
Sr i11 0lhala mic
J
Brac hiulll oi Inferior colliculus
sp ino reti cular
tract - - Periaqueduct,,1gra y m;:ltter Medial Aqueduct
lemniscus
Nucleus of Edj l)ger-W~lphil
l evel of sec tio n
Cef~bra l
peduncle Optic Iract
SubSla,)lia nigra
Cerebe lloru b rot ha lam k IraCI
.-
Central tegmenwl v act
Red nucleus
,.jOHN A,CR4JC.,..w;'
Medial longitudin al fascicu l u~
,',w,""
Sectio n 13: Midbrain- Level of the Med ial Ge ni culate Bod y
Pul"inar
Peria<.jueduclal gr ay matter
Superior colliculus
Posterior commissure
$p rnotha: sprnorel'C::" tract
Level of secti on Laleral geniculate body (nucleu s) ~
Cerebri'll peduncle . tract O pile
lerr',""
Darksch
---'
Medial Ion:;;
Cerebelloru broth alamic tract
fascicu lu s
Re-d nucleus
~-, '?::%\ - -:;;~ Centra l tegmt:!nw,1
Subsl.1ntia nigra l(lIer.ll hypothalamic area
l
~ - tract . h}'PO thalamic area Postenor
Section 14: Midbrain·Oiencephalon Jun ctio n-level of the Posterio r Commi ss ure
156
..IOHNACAAc.
.,....., 'We:;:
m
Brain Stem a nd Ce rebellum -
Molnr fibers Se nso ry fibers
REGIONAL NEUROSCIENCE JJ[
Oculomotor
(vII eye mU$cles excep t tho se b elow. Also ci1iarr
IV Trochle ar
iris, 5phiflc1erJ
V Trigeminal
Sensory to fa ce, sinuses, teeth, gen era/ scns"tro n to ,in /errOr 2;, of o f al <:
.
Motor to muscl es of mas'ical ion
Ner v u s intermediu.q A,u/Q n(JfOlC - suu,,,.v
sublingual, )"o imal glilnds
Sensory - t.lSle 10 anterior 2/3 oi to ngue, soft palate expressi on,
stapedius VIII Vestibulocochlear
., IX G lossoph aryngeal - t.l ste to pOStNior
Sen )Qr~'
1/) 01 IOngUl?, general s e n~ ati O Il to lo nsil, pharynx, midd le eilf
Motor - styl upharynge us,
pha ryngea l rnusc:ulillu re
x Vagus Motor - to pharynx, Itlrynx
Autonomic /0 hf'an, lu ngs, bro nchi, G I tra c t Sensory - hear!, lungs bra nch;, trachea, lafrnX, p har ynx, G I tract, external ear
Sternocle idomastoid. t rapezi u~ (upper 2/ 3)
URE 11.64: CRANIAL NERVES: SCHEMATIC OF D ISTRIBUTION OF SENSORY, MOTOR, AND AUTONOMIC FIBERS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ iiIf
_ :> trac ts derived fro m the neural tube. eNs III-XII ~rge from the brain stem and supply sensory
"-5V, VII-X), motor (e Ns III-VII, IX-XI I), and auto lie (eNs III, VII, IX, X) nerve fibers to structu res ~ e head and the neck. All th e crani al nerves that ~' erge from the brain stem distri bute ipsilaterally
th eir target structures. Th e cranial nerve nudei,
except CN nucleus IV (trochlear) and some motor co mpo nents of eN nucleus III (ocu lomotor), are located ipsilateral to the pOin t of emergen ce of the cranial nerve. Th e spin al accesso ry portion of CN XI emerges from motor neuro ns in the ro stral spinal cord, but it ascends throu gh th e foramen magnum and th en exi ts w ith eNs IX and X; thus, it is con sidered a cranial nerve.
157
Brain Stem and Cerebellu-'
REG IONAL NEUROSCIENCE OcUIOnlOtOt (III) n. ~ed
/
Superior ICldo ia l1(oilicul Termina tion si te<; fo r
fibers in optic trac t,
."
-\ C
nucleus
/ ' Ed inger-Westphd l nucleus
/
OculomOIOI nucleus
-I
__ Trochlear nucleus Trochlear( IV1 n. nucleus of trigeminal n.
./ ,"'-10101
Tfigemlnal lV) n. and ga ngli()n
inalM n. ngli,
Principal (pontine)
sensory nu<:lelh
o( trigemi,lal
n.~
AbdUCMS nucleus
Geniculate ganglion of fada l n.
Facia! nucleus _ _ __ _ _ _ _ Superi or OInd inferior
Veslibulo cochlea , (VIII)
saliyatory nuclei
Ven tral (Ochl ear nucle us
:lil",;o;'''''O\lr -- Nucleus ambiguus
/"
Dorsal cochlear nucleus ----""" G los'>Oph'-lIyng~a l
............ Glossopharyngeal (I X) n.
(I X)
~ Vagus (Xl n.
Veo;tibular nuclei
........... Accessory (XI) n.
V;)gus (X) n.
Dorsal (motor) vagal nucleus
Spina l tract and spina l nucleus of trigeminal n.
Hypoglossal nucle us
;, _
Efferent fibers _ Motor
_
Affe rent fibers Effe ren t fibers _ AutOllOmic
_
~1p
c~
FIGURE 11.65: CRANIAL NERVES AND THEIR NUCLEI: VIEW FROM ABOVE _ _ _ _ _ __ Lower motor neuro ns (lMNs) of the brain stem are localized in a medial column (CN s III, IV, VI, XII I and a lateral colun1n (eNs v and VII, nu cle us ambiguu s ICNs IX, Xl, CN XI). Pregangli oni c parasy mpathetic nuclei are fou nd med ially in the Edinger-Westphal nucle us (e N III) and the dorsal vagal nucleus (e N Xl and laterally in the superior (eN VII) and inferior (eN IX) sa livatory nuclei. Secondary sensory nuclei include the main sensory and descending nuclei of eN V, the vestibular nudei and the cochlea r nuclei (eN VIII ), and the
158
nucleus sol itarius (eN s VII. IX, and X). The superior co!licul us and the lateral genicul ate body rece ive seco nd ary sensory axo nal projectio ns fro m the op tic tract; the inferior co lliculu s receives input fro m th e cochlear nu clei and o th er accessory auditory nuclei. The nuclei graciliS and cuneatus. located in the medulla, receive input from dorsa root ganglion cells, w hich convey epicritic somatosensory modalities (fine discriminative touch, vibrato ry sensation, joint position sense).
bell
REGIONAL NEUROSCIENCE
Stem and Cerebellum
;~~~I~~~"i"'~h;~;'i~"";:r "'O"'i'"
Supratroc hlear n.
~'l
I
M ed ial re
i In.
.
superi ori, m.
Superior obl iq ue m .
Nasoc:ilIi.)ry n. - - --:::::-_ Cnbifo rm pl,Ue oj ethmo id bone CommOll ..nnu!ar tendon
O pticlili n. - -- ---
Opti c .;hi a,m -
-
-
_
_
O phthalmic n
~:;;;;:==-; Maxillory n.
Pituit ary , talk (infundi bulum)
::;:
O cul omoto r (illi n.
Tm ..:t.I..ar (IVI n.
-==::::::::::~~
Tentorial (meningeal)
branch of ophthalmic Il.
-
_ _-
Abducens (V I) n . -
M~nin !l~al brMICh oi ma~ill Jry n. Ma nd ibu lar n. Men inge al brand , (ner~us
SplnOSIJ ,) of m andibul ~r n.
S;:::::::::::-G.eluer les5e' poel!osal n n.
f'~:'::~__--=::-;,~:, ~::::;: sanglio n TO! n lOriu m ({'Iebelli
- - -- \
;:.
Supratrochlear n. (cul l _ _ _ _ - ' Me dial and lateral
branlh.., oj supraorbi tal n, (cut)
Infratro chleM n.
--;:-:=====;~
An leno r ethmoi dal A.
p~l pebl ae $upenOriS m. leu !)
Ii
I
Lacrim al r"I. leut)
Short cill ~ ly r"ln .
Bllln<..h or" oeulOI'llOIOl n . to mfen"r ()1 ,lique m.
","'=--C;I;. ~ S~ngJjoo : ; : -- Mo'."p"" ym'P . ".~i,,)
l ong ciliary nn. Oplic (Ill n.
",.,,'mm oculomotor o .
Sym~lhelic ' 0 0 1 ('(>011 iOl emal
Nasociliary n. Op hlhalmi'; n.
-------"'=-'l
(e~~=====3! "
Ocu lomotor Trochlear (IV)(IIn.I) n Abducen, (VIr n.
(,]roud
ple~ u~
Sl'"f\j.QI)' ' 001 i,om nasociliary n.
Branch es 10 n-..edi.:d .:m d inferi", 1("
f ocu lomotor n.
lolemal c
Internal urotid 3.
Abducen s (VI) n. Ophthal mic n. C.",~nou s
M..,ib'1· fI .
"l- RE 11.66: NERVES OF THE ORBIT AND THE CILIARY GANGLION: DORSAL VIEW AND CROSS-SECTION THROUGH THE CAVERNOUS SINUS _ _ _ _ _ _ _ __ II ca rries visual information from the ipsilat eral :.d . Axons from th e temporal hemiretin as -'""kljn ipsilateral, wh ereas axons from the nasal retinas cross the midline in the optic chiasm. :1.\ons then enter the optic tract. eN s III (fro m ~ m otor nuclei), IV, and VI innervate the extrin m uscles of the eye. Sensory portion s of th e oph .mic division of e N supply gen eral sensation .... e cornea and th e eyeball and provide th e affer limb of the corn eal refl ex. Motor fibers of eN nnervate the o rbicularis oculi muscle, closing eye; these fibers constitute the efferent limb o f ~ corneal reflex. Parasympathetic preganglionic .:lETS irom the Edin ger-Westphal nucl eus distribute
v
to the ci liary ganglion, which suppli es the pupillary constri ctor mu scle and th e ci liary muscle (accom modati on for near vision). Prega nglionic parasy m pathetic axons from the superior salivatory nucleus distribute to the pterygopalatine ganglion, w hich supplies the lacrimal gland (tea r production). Sympath etic postganglioni c nerve fibers from the superior cervical ganglion supply the pupillary dil a tor mu scl e and the superi o r tarsal muscle (dam age results in m ild ptosis). e Ns III, IV, VI, and th e oph thalmic and maxillary divisio ns of e N V traverse the caverno us sinus and are vulnerable to dama ge fro m cavernous si nus thrombosis.
159
REGIONAL NEUROSCIENCE
Brain Stem and CerebeU......
Short ,iliary nn.
Edin8e r-W~~tphal nll cleu.
Lo ng (Wary n.
}
(autono mic)
Oculom otor (111 :1 n.
Oculomotor nucle us
SenSOly ' 001 01 ciliary SlPng!ion
Superior oblique RI. SuperiQr reclU. m .
divi5ioo of oculomOlDf n.
Abducen s nucleus
Levator
and inferim c.ollicuh
SupetlOf
p~ lpebrae
MJperia. i. m. Su perio r
tarsal m. (involuntary)
Sphincter
pup illae m.
D ilalor
pupillae m.
'\ Abducens ( VI) nerq
\TrOChl~ar{lV) nef\-e
\ Oculomoto r (JII) nerve
Inierlor oblique m.
In ternal ca rotid a. and
p lex~;
Infraorbilal n. Inferiof reclllS rn.
Zygoma tic n.
\
\ MaxilL-uy n .
la teral reetu. m. a.nd abducens n. (turned bad )
MOlo< \pa' a5~mpathetic) . 001 oi ohl)' ganglion
Common annular ten oon
Levalor palpebrae superioris m. Oculomoto r (III) nfrve
---~-
Superio r l ec tus m. - - - - Medial rec:tu s m, -
Illferior rec lus m. . 10ie li00 obItQu!;l m .
Supel'lo obliq u e m .
Trochlear { (IV) nerve
later,ll rectu5 m.
{ Abducen~
J '
~
d
I
(VI) nerve
~ ~' 112'. .Jt...~ ,','.
MOlorfib en
Sen.ory fibt>rs
Sympathetic fibers
Parasympathetic fibe,~
FIGURE 11.67: EXTRAOCULAR NERVES (III, IV, AND VI) AND THE CILIARY GANGLION: vim IN RELATION TO THE EYE _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ CN VI innervates the lateral rectus muscle; damage results in ipsilatera l paralysis of lateral gaze. CN IV innervates the superior oblique muscle; dam age results in inability to loo k in and down (most con spicu ous w hen climbing stairs, ste pping off a curb, reading in bed). eN III (ocu lo mo tor nuclei) inner va tes the medial rectus, superior rectus, inferio r rectu s, and inferior ob lique muscles (damage 160
results in paralysis of ipsilateral medial gaze}, aJ)I" the levator palpebrae superioris muscle (dama:? results in profound ptOSiS). The ciliary ganglion gives rise to postga ngli onic pa rasympathetic .l>.i. that supply the pupillary co nstrictor muscle a the ciliary muscle, Damage results in a fixed anG dilated pupil that will not co nstrict for the pup light reflex and will not accommodate to near \ ~
REGIONAL NEUROSCIENCE
Stem and Cerebellum
(VI ne rve and (sefTInuoJrl gJ ngllon
Tri!emin~1
-
MOlor fibers
Tenlorial (mening.,....tJ
- - SenSOl")' fibe" Proprio~I;"'e
t
. ... 0 10 . nun..u. o( lr ill"min~1 n.
fibers
P"'r.liY"'p"lho!lic: fobc-rs -- - - - Sympalhelicfobc-rs oi i Ii
I
SpillllllraCI and spIna l nucle us of l" gemi~1I1 n. {r~in and t(>m pcr3Iu.e)
5h"'l , 111"'1 M
Anle.IOI' ethmoidal n. - ,i-s., 1a"d mlern;ll o~S
,.
~\.u ill;lry
Move
_ • ;.m"!lcolerTll~,,1 o .
.:
~orna1lct>fxi;rl
n - - ' - - Facial (VIII n .
.... ronic hrJnch~ ""d
," -~- Chorda
- . ; opalil'ine II"nWion ~ .If alveolar
hr,"lndleS
0:>"01'. middle, post{'lior)
,finn.lOmltai n.
,... branOieS (j'ust .....ior ;I
[aler"l, n;u.opalatille
::o;.":'l"lOrsuperior ~. (.
lTIed~11)
of pterygOid canal
"i'rJrY"8t'.11 manch
Inferior d(:.'fltll '~"s,
J~p
>' Ungu'ill n.
" lil'lh;./of del'l13l ~M: '--"\~.;:.
sfnr
"""
•
6'f 011DN ,.........::
RE 11.68: TRI GEM INAL NERVE (V) _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ __ -~geminaJ
nerve (CN V) carries sensory infor n from th e face, the sinu ses, the teeth, and an terior portion of the o ral cavity. It has 3 sub ns: (I) op hthalmi c- se nso ry innervation, (11 ) ary- sensory innervation, and (III) mandibu : nsory innerva tio n. and motor innerva tion -eo mastica tory and tensor tympani muscles. :ary sensory axons from trigeminal (semilunar, -€' rian) ganglion cells that process fine discrimi •e tou ch (epi criti c sensation) terminate in the
main sensory nucleus and the rostral descendin g nucl eus of Those axons processing pain and temperature se nsation (protopath ic sensation) termin ate in th e ca udal descencling (spinal) nucl eus of CN V. The trigeminal nerve also carries proprio cepti ve in formation from muscle spindles in the masticatory and extraocular mu scles. The primary sensory cell bodies found in the mesenceph(llic nucleus of CN V are the o nly primary sensory neu· rons to reside in the CNS .
eNv.
161
REGIONAL NEUROSCIENCE Motor fibers Sensory fibers Parasympathetic fibers Sympathetic fibers
Brain Stem and Cerebellum Grea ter petrosal n.
Carotid plexus Ion internal carotid a,1 Ge niculate ga ngli on facial (VII) ncrve Molor 100\ of facial n. Internal acoustic meatus
Deep petrosal n. lesser petrosal n. Nerve o f pterygoid canal
O tic ga nglion
Nervus inlcrmedius fOI fadal n.)
Pterygopal atine ganglion
nucleus of fa cial n. Superi or salivator), nucleus
,.,..".,."
Facial muscles
':>:-.:~:
Nucleus of the solitary Iratt
OCCipitofron tali s m.
(frontal belly) - - - -, \ Orbicu laris oculi m. Corrugator supercili; m.
Zygomaticus major m. Zygomaticus minor m. ~\ j
Depressor supereil,; m. Procerus m.
Levator labi; sup eri oris m. Levator labii superioris alaeque nasi m, _
I-
LevaTor anguli orism.
Nasalis 111 .
Occipito frontalis m . (ocapi tal belly)
Depr e~sor
septim. O rbf<:ularis oris m.
D<:dpilal branch of pos teri or auri cu lar n.
J
D epressor labii inferiori s m. - - --C
Branches to auricu lar musd es
Mentalism.
Posterior auricuhu n.
Transvers us menti m.
Nerve to stapedius m.
Ri.o rius m.
Buccinato r m.
Tympanic n.
Platysma Submandibular g,mglion
II
I
Glossopharyngeal (IX) n.
Posterior belly of digastric m.
Lin gual n.
Stylohyo id m.
Chocda tympa ni
Caroti cotympa nic n.
~~~
CIIQN
:\":.":::
FIGURE 11.69: FACIAL NERVE (VII ) _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
The faci al nerve (CN VI I) has motor, parasympa thetic, and se nsory co mponents. The motor fib ers distribute to the mu scles of facial expression; the scalp, auricle, buccinato r, stapediu s, and stylohyoid muscles; and the posterior belly of the digastric muscl e. Oamage results in ipsilateral paralysis of facial expression, in clud ing the forehead (Bell's palsy). Activation of th e stapediu s dampens th e ossicles in the presence of sustained lo ud noise; damage to CN VII also results in hyperacusis. Parasympathetic nerve fibers from the superi or
162
salivatory nucleus distribute to the pterygopalatint: ganglion, which innervates the lacrimal glands, a"'" to the submand ibular ganglion, whi ch jnnervat~ Ihe submandibular and sublingual salivary gland!' Special sensory taste fibers from the anterior tv. a- thirds o f the tongue (via the chorda tympani) a M the soft palate (via th e greater petrosal nerve), axons of the geniculate ganglion, co nvey informa tion to the rostral portion o f the nucleus soli ta ri ~ in the medulla.
.lIe -
s.
[)
d
REGIONAL NEUROSCIENCE
Stem and Cerebellum
~ib ulocochlear
(VIII) Nerve
G reater petro5a1 n.
Spiral ganglion of cochlea Geniculate ganglion of facial n.
Cochlea r part of \"esli bulocochlea r n.
Facial cana l
ur Tool of facial n. "'o('fV US inte rmedius
of malleus
___ Ty m,,,n·il c cavity
.... ---- -, .'!:lllihliocochiear (VIII)
,
,~
_ _ _ Incus
;;,!.c-- - Chorda tympani
loblongata
- - -- :~~;'~i',"~u~o':f:superior duct Ampulla of la teral semicircular duct Utricle Ampulla of posteri or semicircular du ct Saccule
Superior diViSion}of vestibular pari of Inferior division
'Dc"~I} Cochle" nudei
vestibulochlear n.
" ' ' '' ibu'' " ganglion VestilxJlar pa rt oi ves tibulocochlca r n.
Inferior cerebellar
peduncle (to cerebellum)
'lGU RE 11.70: VESTIBULOCOCHlEAR NERVE (VIII) _ _ _ _ _ _ _ _ _ _ _ _ _ __ - -e vestibu locochl ear nerve (eN VII I) ari ses fro m ""'volar prim ary sensory neurons in th e vestibu lar Sc::arpa' s) ganglion and the spiral (cochl ea r) gan _ Dn. The periphera l process of th e vestibu lar gan ::ion neurons innervates hair cells in the utricle and ""'""'"e saccule that respond to linear acceleration ; "avity) and in the ampullae of the semicircular .....ets that respond to angular acceleration (move - ent). The utricle, the saccule, and the semicircular ::.... cts provide neu ral signals for coordination and ~ ui libr ation of position, and moveme nts of the
head and the neck. The ce ntral pro cesses of vestibul ar gangli on cells terminate in th e medial, lateral, superior, o r inferior vestibul ar nuclei in the medulla and th e pons and in the cerebellum. Th e periph eral processes of spiral gangli on cells innervate hair cells that lie along th e cochlear duct in the o rgan o f Corti. They convey hea ring in forma tio n into the do rsal and ventral cochlear nuclei via the central axonal processes. A lesion to CN VIII resu lts in ipsi latera l deafness and vertigo and loss of equi librium.
163
REGIONAL NEUROSCIENCE --
S~n sory
Brain Stem and c.,Jl;';ula~f\
rohe l'5
Cer e b ~ 1
g;lJlglion 01lacial n.
- - MOlu, fibe,s
.......• P3r.uympa lhelic
-~.
>.
m~rs
~
N"rvp. o f pte rygoid (JnJ~
Ptern;opdlalm e
,j
~~ n ~II ()n ~
Vi ~
l
MJncllbul.v
Intenor 5 all v~ to ry
nu cklu 5 Solj13l~ Ir./l~'
O liL
nucJ.. u~
,lnd ,I)
AUIlCulolempo'JI I '~.o"ci
nerv<:'
Nucleus ambi guu s
~'Glossophal)'ngeal (I X) nerve
,
Com m unication 10 aur iCular
'\C"..om.....m'cation to faCIal "
, r-%1 !
S u~ri(lr V~B u l
cerviCdlwmpathetic 8anlliion
(XI n.
Ph.:u yl1 gcal b'and> of va gus n.
'"
, Ph.:l, )'nllt'",I. lun< ~I",r. ,md ~ogual b,.:mche. ( ) i glrmopOJ'Y"gealll..
~l
C~rDlid $Inu s bra nch of ti cmOpMr)'l1 I'1H1n
I
Inte rn al carotid a.
', :
Comn1of> caro,id J
;f. ~p
-
, ~
c .~
FIGURE 11.71 : GLOSSOPHARYNGEAL NERVE (IX) _ _ _ _ _ _ _ _ _ __ __ __ The glo ssop haryngeal nerve (e N IX) is a mixed nerve w ith motor, parasympatheti c, and sensory compo nents. M o tor fibers fro m the nucleus ambiguus supply the stylopharyngeus muscle and may assist in innervation of pharyngeal muscles, for sw allow in g. Preganglionic axon s fro m th e inferior salivatory nucl eus travel with e N IX to the otic gan glion, whose neurons innervate th e parotid gland and the mu co us glands. Special se nsory axons from the petrosal (i nferior) ganglion convey infor mation from taste buds on the posterior third of the tongue and on parI o f the soft palate. These axons terminate in the rostral portion of th e nu cleus 501i tarius. Axons from additional primary sensory neu rons in the in ferior ganglion carry general sensation
164
from the posteri or third of the tongue and from . pharynx, the fauces. the to nsil, the tympanic C3\ the eustachian tube, and the mastoid cells. The central axon branches terminate in the descenru"'. (spinal) nucleu s o f eNv. The general sensory fibe fro m the pharynx provid e th e afferent limb of the gag retlex. Additional primary sensory nem o ns inn ervate the carotid body (chemorecepti on oi C02) and the caro tid sinus (baroceptors) and co nvey the central axons to the caudal nucleus solitarius. Primary sensory neurons in the superiOf ganglio n innervate a small regio n behind the ear and convey general se nsa tio n into the desce ndir_ nucl eus of eN Nucl eus so litarius = Solitary tract nucleu s.
v.
Stem
and Cerebellum
\')gus (X) Nerve
REGIONAL NEUROSCIENCE
Gloosopharyngeal
/
M eninge,,1br1lncn o f ,'a8u~n,
C:---c-' '::","Y, ""'"
Auricu la r branu. of ~illlLls n. Auditory
I Eu~<Jchi~n)
Levator veli
p~lalln1
' Oo ",It,,,.,,,,, nucleu~ 01X nud"us
Spi nal J r~(:1
tub
~pin,,1
nud e l' s of tn geminal n.
m.
.'
Sa lringo-.pha rvngc-u\ m, PalJ togto'lus
I.
C'~nia l r!"llli
i
oi accessory n,
Superio r constJldnl m.
af pharynx
Stylophar ynl)""-'S m. Mid dle oi
can~::"~;'~''~m:,:::::::~~Tt '
pha.yn~ :
Inle.io . ganglion o i vagus n. Phar~'n gea l
Infe"or ~on STri(:tor m. of pha.yn~ CriCO lhyroid m.
branch 01 vagus n. (mOlar to mu,d+'s 0 1 pharynx and .,a~t ~; sen so ry 10 lower p h,lrYJlX) \ C V'S"b ,,",h to <.:arct id sinu s hranc h oi glossoph aryn gea l n.
L""" ",,,,'I pl exus Su pe-r;or l.Jryn gea l n.
RighI recu.ren, laryoge.ll n.
Int"ffi.ll
branch (Hmsory) (mota. 10 c"«llh~' foid m.)
u(\em.:d branch - - Mololfo~
-
Afferenl fibers
.....
Pill,lS~'mp;'lthe lk
libers
Hep
ve ga l trunk lin I ~ss.c r omentum)
Ce liac br~n<,;h~ s (from an ter ior Jnd posterior VJ g~1 trunk~ 10 celiac plexus l
CMdidc pleXUi Esophageal ple~\Is
~. C"". b",""h,",' "'~'",""..' l .un k Vag,,1bo--aoches lparasympe.s) dccomj)ilny wperior m~nl..,.ir ,,,Icry .md it:; brand>eS to smaIl1nte5 line, cec um. appendix .md colon, "ftl!fl a~ (1)1 as left co li c i; plenlCj ftexure Sma llinies linl'l
:CU RE 11.72: VAGUS NERVE (X) _ _ _ _ __ __ _ _ _ _ _ _ _ _ _ _ _ __ \ agus nerve (eN X) is a mixed nerve w ith 'or, pa rasympathetic, and sensory components. '\, axons from the nucleus ambiguus in the \€C ulla supp ly muscles of the soft palate, the phar and th e larynx, w hi ch control speakin g and allo win g. A les ion results in hoarse ness, dys 2gJa, and decreased gag refl ex (efferent limb). £;-ganglionic para sympathetic axons from neurons me dorsal (motor) nucleus o f CN X in the -!'"Jf'dulla distribute to intramural ganglia associated -n thoracic and abdominal viscera to supply :onomic innervation to the hea rt, the lung. and --e GI tract to the descending colon. Special
sensory axons fro m the nodose (inferior) ganglion, w hich ca rry information from taste buds in the pos terior pharynx (fou nd mainly in children), send cen tral bran ches to terminate in th e rostral nucleus solitarius. Primary senso ry axons from the inferior gangli on, whi ch co nvey general sensat io n from the larynx, the pharynx, and the th oracic and abdomi nal viscera, terminate mainly in the ca udal nucleus soli tarius. Primary sensory axons from the superio r (jugular) ganglion, w hich convey general sensatio n from the ex ternal auditory meatus, terminate in the descending (spina l) nucleus of CN V.
165
REGIONAL NEUROSCIENCE Accessory (XI) Nerve
Brain Stem and
Cerebellu ~
Crania! roOl oi accessory n. (jo ins v~gu s n. to supply
muscles of larynx - excepl Nucleus
cricothyroid - via recurrent
Jugular foramen
laryngeal n.)
,/~ Superior ganglion of vagus n.
L - - Accessory (XI) nerve
Vagus (X) n.
: . . . - - - Interna l branch of accesrory n.
accessory
f-- - - 1 nferior ganglion of vagus n.
r
Foramen
~
- lstspinaln.(C1)
_ _ _ _ 2nd spinal n. (e2)
L-_ _ _ _ External branch of
accessory n. (to
sternocleidomastoid and trapezius mm.l
: - - - - - - SternoCleidomaS10id m. spinal n. {O ) ~
_ __ _ 41h spinal n. «(4) Trapezius m.
-
Moto r fibers
-
Proprioceptive fibers
4' ~:*;
FIGURE 11.73: ACCESSORY N ERVE (XI ) _ _ _ _ _ __
The accessory nerve (eN XI) is a mo tor nerve w ith cranial and spinal po rtions. The cranial portio n ari ses from LMN s at the caud al end of th e nucleus ambiguus; the axons travel through an internal bra nch that distribu tes w ith the pharyngeal and laryn geal bran ches of the vagus nerve (CN X) and th e nerves to th e soft palate, These axons are often considered to be part of CN X. The spinal portion arises from LMNs in the lateral part of the upper four or five se gments of the cervical spi nal cord.
166
...; -
_ _ _ _ _ _ _ _ _ _ __
The axons then emerge as rootlets from the lai e-~ margin of the spin al cord, ascend behind the de- ticulate li gaments, and coalesce as a singl e ner. e Thi s nerve then ascends through the foramen rna:. num and joins the vagus nerve to exit thro ugh cr jugul ar foramen. The spin al accessory LMNs su the sternocleid omastoid mu scle and the upp er two-thirds of the trapezius muscle. D amage to . division results in weakness of head rotation ar .:: shoul der elevation.
REGIONAL NEUROSCIENCE
Stem and Cerebellum
Styloglossus m.
Hypoglmsal nucleus
Meningeal branch
1tfinsic muscu lalure of tongue
_ _ _ A' -_ _ _, Hypoglossal (XII) nerve
(in hypoglossal canal) Occipita l condyle Infef iOf ganglion of vagus n. Ventral rami of C l. C2 and C) forming cef'llical plexus _ _ _ Superior ceNical sympathetic trunk ganglion Superior root ldescendens hypoglossi) of ans.a cervical is
~Jossus rn. >.c;.-;~:";~:'2
fJ'--'L----=~_ Inlernal carotid a.
Ceniohyoid m.
Inferior root (descendens hypoglossi) of ansa cervica l is
Hyoglossus m.
Thyrohyoid
m.
~_ _ _
Omohyoid m. (supefior hell y) Stern othyroid
m . _~- '
-
Ansa cervical is (ansa hypogloss i)
- - Inlernal jugular v.
_ _ _ Omohyoid m. (inferior belly)
Sternohyoid m.
Motor fibers
- - Semory fi bers
U RE 11.74: HYPOGLOSSAL NERVE (XII ) _ _ __ _ __ __ hypoglossa l nerve (e N XII) is a moto r nerve. in the hypoglossa l nucleus of the caudal t"dulla exit fro m the ventral surface of the medulla iIle preoliva ry sulcus {between the medullary '("amid and the inferior olive) to innervate the ",nsic hyoglossus, styloglossus, chondroglossus, -.d genioglossus tongue mu scl es and the intrinsic
'5
_ _ __
_ __ _ _
superio r and inferior lo ngitudinal, transverse, and vertical lingual tongue muscles. Damage to this nerve leads to weakness of the ipsilateral to ngue muscles; the protruded tongue d eviates toward the weak side because of th e un oppo sed acti on of the innervated contralateral geni oglossus muscle.
167
REGIONAL NEUROSCIENCE
Brain Stem and Cerebellu Trigeminal nerve (V)
lIary V1)
wpcriOi ,,1I'eoliu
Glossopharyngeal nerve (I X)
nerve ~
==== W/",0;
Vagus nerve (Xl '%:/'// h
ganglion ,J(la greater
Fa cial ne rve (V II )
and feS5f:f pall/ine nerves Facial (VII) (intermediate nerve)
plus gener.]1 senS
Trigemin.;a[ ( V) (mui1lary Vll Via pharyngeal /]Janeh of pterygopala tine sangJion Facial (VII ) (i ntermediate nerve)
Via Slealer pelfoS<J1 ~rvl! and pterygopalatine gang/ion
Vagus (X) Vi,) internal branch or superior larynge,li nI;fVf'
Glossopharyngeal (IX)
l:1 :"_"''l
Via pharyn t:4~Ai pJexus Via tonsillaf brandle5
Ta ste plusgeneral
Trigeminal (V)
(m~x illary V2)
- Via p terygo palaline gatlglion
sensatjon via
iJnd greater and
lillgual bran, ,
lesser palatine
Via inferior
alveolar nef~
1}0::
Facial (VII ) (i ntermediate nerve) - - TaSI~ viol cilOldd Iympani and /j~ua' nerve
~~p
. !,~
FIGURE 11.75: AFFERENT INNERVATION OF THE MOUTH AND THE PHARYNX _ _ _ _ __ Primary sensory axons of the maxillary and mandibu lar d ivisions of eN v (trigemina l ganglion) provide general sensation to the mouth, the tee th, the gums, the sinuses, and the anterior two-thirds of the tongue. General sensation to the posterio r third of the tongue, the pha rynx, and the larynx is pro vided by primary sensory axons of eN IX (inferior
168
or petrosa l ganglion) and, to a lesser extent, by eN x (inferior or nodose ganglion) for the phan ....· and the larynx. Chemosensatio n from taste buds conveyed by eN VII (genicu late ganglion ) for Ih. anterior two-thirds of the tongue, eN IX (petrosa ganglion) for the posterior third of the tongue, a"" eN x (nodose ganglion) for the posterior pharvn\.
REGIONAL NEUROSCIENCE
Stem and Cerebellum
Do,P.IT"""'skoe" groups
~ffiia n reticulilr 10m"",," -----"
~:el al l e ticula r
~>R,,'h.
formation - and nudei
nudei
"'edlal reticular ----,,L' formation
' ,jK:~r--~ Major noradrenergic and
~
adrenergic cell groups
Raphe ""'''.'. - -
Raphe nudei 1. Obscurus. pa1!idus
2. Magnus 3. Pontis 4. DOl'5alis. centralis superior
E 11.76: RETICULAR FORMATION: GENERAL PATTERN OF NUCLEI IN THE BRAIN STEM _ 'F..JCular formation (RF), the neuro nal core of _:.Il stem, consists of neurons w ith character ~e ndritic morphology. The RF extends from _<:fa l sp inal co rd through the hypothalamus "'ie se ptal region. RF neurons are large cells Z\Onal arboriza tions that terminate at a dis TOm their ce ll bodies and dendritic tree; they ~ intern eurons. The major nuclei are found in zone (sensory functions), a medial zone 'unctions), and a co lumn of raphe nuclei
(serotonergic neurons). The sero to nergic neuro ns exert modulatory influences on their targets. The catechoJaminergic neurons (locus coeruleus, tegmental noradrenergic and adrenergic gro ups) in several regions of the RF have w idespread projec tions and exert mainly modulatory influen ces on their targets. The dopaminergic neurons of the mid brain are included in this illu strati o n, altho ugh some experts question whether they are RF neurons.
169
Brain Stem and CerebeIL.:...
REG IONAL NEUROSCIENCE
,
\
•
A. Thalamus and
hYf)Othalamus
~
-
.J
l~ .' 7 .
'-#\,
.
~
.
l atera l ~ F of the mid brain _ _ __
'/'
.
I
~
~
nigra - -
Ii
-J )
Gu~f'
,
In rralamin':l1 nuclei Reticular nucleusuf thalamus
.J.\ ;_....,.,;(
. .~ . '
.'\... Sub~lanlia
Thala nlUS:
"
~. -r"(
j
'v
"'"{
t. . .
\
B. Mid brain
;'
MiOli", oct", Late ral hypothalamic arE'~ throogh septalnuclei
J./
_ -- - - Pcriaqueduclal gray mailer
R.Jphe n udei (dorsal, cenllal sureriOl l
7'
- - ' - - _ - Ventral tegmental nucleus
---41,/
Interpp.l'Iunwlal nucleus --\"'.---
,/'''' .'\. ~
_____'_ Loc,us COe ruleus
C. Pons
,<
Raphe n uclei (pontis)
/l
P'lrahrachial nucleI.JS
f. 4;--,c-c, -- - Pa.aporui nc RF (Ialeral gal.e Center)
......( _.
AS
"
.
..
ii
Po ntine RF (pon ti~, c3u d.a lis, ovalis)
L3Ieral R: F ~
A-/" O. Medulla
Z ,('
,..",'" 0 '
Medullary RF (gigimlocellularJ Raphe nudei (obscul us. pallidus, milgnus)
."
'.b
,J"'I.fo.'~ A2 "
".
~ R~~,"0'Y"""';
~~ Rostral Vl medulla (RVLM)
~
A:~Al
~
~
:
~
LUe lal felKtRill nucleus
--' E. Spinal cord-medullary junc tion
. ")
lamina 7 - caudill RF
,-
J. Perkins MS, MFA
••
'w.... "
FIGURE 11,77. RETI CULAR FORMATION : NUCLEI AND AREAS IN THE BRAIN STEM AND DI ENC EPHALON ___________________________________________ Many of the named nudei of the RF are present in the medulla, the pons, and the midbrain. Impo rtant medial RF groups include th e medull ary (giganto ce llular) and po ntine (caudal and rostral) RF, whi ch are in volved in reticulospin al regul atio n of spinal
cord LMNs; and the parapo ntine RF (PPRF), the hori zontal (lateral) gaz e center. l ateral RF areas and nuclei (such as the lateral reticular nucleus) are involved in polymodal sensory functi o ns. RF respi ratory and ca rdiovascular neurons are found in the
170
medulla. Catecho lam inergic neurons are found , the locus coeruleus and the tegmental groups. Raphe nuclei are fo und in th e midlin e and in thE wi ngs of cells that extend laterally. Th e core 01u RF co ntinues rostrall y fro m th e lateral regions 0-" the brain stem into the lateral hypo thalamic ar· and extends through the hypothalamus to the sep tal nuclei. The intralaminar, midline, and rel, lar th alami c nuclei are classified as part of th e R;
-------~
~---------
olem and Cerebellum
REGIONAL NEUROSCIENCE
Oladory input
A,.in l1(m
Trijtemin." nvcicw, vnllb..JIi, nuclt'IJ~
(<xhI~~, nucie,,!. 0Ihe< "udljO<~ nUdel. nuclo!'U! 01 the sol~arl U-iCI, ~1Qr coikullll idee!) Livers)
I. Pe,~i ns ,",w,
.,~
E 11.78: MAJO R AFFERENT CONNECTIONS TO THE RETICULAR FORMATION _ ~ e sensory information {particularly nocicep -om spinal cord somatosensory sources and all brain stem sensory modalities is sent to ..Li?ral regions of th e RF. Olfactory input arrives 5Jl olfactory tract projections int o forebrain ~ . Many li mbic and hypothalamic structures
provide input to the RF, particu larly for visceral and autonomic regulatory fun ctio ns. The cerebral cor tex/ the glob us paliidus, and the cerebe llum also provide input to th e RF medial zones invo lved in motor regulation.
H)'pOlhalamU5, Corte~
A,ou ul
SI.l atu m _ _
~ptu m
limbic fortb~in
1
...:::::;""+-
Tha lamus Inlral.amlr'l.l( nucleus
~rU'
Hrp pocamp.llrormal'on, a ~wg'Wo , d nu cieu;. N'ci eu. lcr.~ml _s. oliac lor, lubercle. d n~~ l a'~. pre irool~ l. in.u l ~r C.()tle.'
I
--'
_ __
ARAS
Iteticul~r
• _ _ _:j;>
_ _
_ _--{(j', . _ _ _•• '-. /
formallon
Nud eu. of the
-----;(i ' Spinal cord mOlor reSioo. "ia renruto;p,f\al u at:(s
•~. Fron1 i.1rteral ,tt.w!;" n ~, Nudeus '''ticui.1rns t~ e.1~ po<1 li5..
, oljt~ry
tract
Mulliple brain,tern regions for l el·point modulalion
Spinal cord ..,n,ory r~l\ion, Oors.1 oorn !or T1·Ll ;"t",rnedi<JI~ let~1 ,,,II U>iurnn, noc,rer<,ve S2·$a int.,,-m~~l;'''e ~r;,l' modlli<>,;""
G t Vi" ~i'r\ ioreb[. i~ bu ndl~. ~llongitL!(\",.lll''''''OJlu!,
h~nulop-edl.t~cul¥
locul o:letvle~ ,apl>e n"";"; wIW~llegme
•
outon<>mk re&io~s
p." ,ln.edi)M relicui.1rr tM;I""s.
.: !) (-rom locus coerule...s, raplr.. nudel.
Br~in , tern ~ ut(}f'L<>mic cenlers .};;
rnamm,II01~"""n t.lI
(4) -
tr.ct.
!racl
(5) 11X1l.tding ventrol.,,,.-.I and vcntromcd,.1 -
!egnrenl1Jm Df caudal br. ,n ,tem
:~'; Intri-fet,cd", connoection ,
From odf~n...--g;c. n()f >
J. P.. rkin •
""MtA
~ ,1I!f)!
RE 11 _79 : MAJOR EFFERENT CONNECTIONS OF THE RETICULAR FORMATION _ _ __ ascending reticu lar ac tivatin g system (ARAS) of is responsible for consciousness and ...sal. It projec ts through nonspecific nuclei of .,. ·~a lamu s to the cortex; lesions in this area lead roma. The RF sends extensive axonal projec r-! to sensory, moto r, and autonomic regions of soinal cord that modu late nociceptive input, .:.an glionic autonomic outflow, and LMN ou t respectively. The RF sends extensive connee -rs to brain stem nuclei (such as the nucleus
tractus solitarius) and to autonomic regulatory ce n ters and nuclei for modulation of visceral func ti ons. Efferent RF projections to the hypothalamu s, the septal nuclei, and the li mbic forebrai n areas help to modulate viscera l autonomic func tions, neuro endocrine outflow, and emotional responsiveness and behavior. Efferent RF projections 10 the cere bellum and the basal ganglia participate in modulat ing UMN control of LM Ns.
171
REG IONAL NEUROSCIENCE
Brain Stem and Cerebelhr
(cholinerglcs)
area
Interleukins;
other ~(}(}d-borne substances
To pin eJ I (melato nin)
lei
~~?
M '."
Areas assoCiated wi th arou sal
). p",;"
Areas assoCiated Wilh
QlmN
the induction 01 ,Ieep
Spinal co rd
!::li
Sympat hetic ch ain gangli a
FI G URE 11.80: SLEEP- W AKEFULNESS CONTROL _ _ _ _ __ __ _ _ _ _ _ _ __
Sleep is a normal physiological state involving a cyclic temporary loss of consciousness; it is readily reversed by appropriate sensory stimuli. Sleep is an active process initiated by activity in several chemi cally specific collections of neurons of the brain: locus coeruleus of the pons (noradrenergic); raphe nuclei of the medulla and pons (serotonergic); nucleus solitarius of the medulla; cholinergic neu rons of the brain stem tegmentum; lateral RG par ticularly in the pons; anterior, posterior, and preoptic areas of the hypothalamus; and reticular nucleus of the thalamus. Many of these regions actively inhibit the lateral (sensory) portion of the RF, which is responsible for maintaining a waking state and consciousness. Circulating substances
172
such as interleukin (Il)-1 ~ can act on key sites i'" the hypothalamus and the brain stem to influ€ll( · components of sleep. Illness behavior involves enhanced slow-wave sleep induced by IL-1 ~ an.:: other intlammatory mediators. Non-REM, or slcr. wave, sleep, initiated by hypothalamic neurons and other regions, is accompanied by decreasec. activity of the locus coeruleus and the cholinerg::: tegmental neurons. During REM sleep, activity if; the noradrenergic locus coeruleus neurons and _. serotonergic raphe neurons diminishes, whic h ~ vents the cerebral cortex from attending to exte"" stimuli. Dreams are likely the result of the corte\. attending to internal stimuli from stored mem ore.
REGIONAL NEUROSCIENCE
Stem and Cerebellum
LinguLl--,
I Re gions I
~u:!ra l
"Unlolded" s
hC!misph('fc
I Lobes I
P()~ l e rior
lobe
Flocn,lonodula r lobe
•• 1
· Unfolded· schematic vf t:erebel lum d emons traling regi ou~ and lobes
"
RE 11.81: CEREBELLAR ORGAN IZATION: LOBES AND REGIONS _ _ _ _ _ _ _ __
globose and embo li form, and dentate, respectively) ce-rebellum is organi zed ana tomically into -or lobes: anterior, posterior, and flocculo that help to regulate the ac tivity o f the re ticulo- spinal and vestibulospinal tracts, the rubrospinal ar. Di stin ct sy ndromes are associated with tract, and the co rti cos pinal tract, respectively. At .....age to each lobe. The functional organi za tion ~e cerebellum follows a vertical arrangement of least 3 rep resentatio ns of the body are mapped ·~p heres: (1) ve rmi s (m idline), (2) paravermis,
onto th e cerebellar cortex. The cerebell ar cortex has multiple, ord erly, small info ldings, o r co nvolu 31 lateral hemisphere. Each fun ctiona l regio n
~ ciated w ith specific deep nuclei (fastigial. tions, called folia.
173
REGIONAL NEUROSCIENCE
Brain Stem and Cerebe....
id
Posterior view
Habenu lal trigone
Pulv;nCl!
.-- Later.»)} Geniculate _ _ Medial
" !neal gland
bodies
Sup Cfior collicul us
IIi Trochlear (IV) nerve Superior medullary Velum---j
CerebeliM peduncl e~ {
Sup er;
"ddl
"'II e~. Inferiot
Lateral recess ~
Dentate nucleu s Tlmia o f 4th ventricif.
l. - lingul.. ( l -" (cnrrallo bule CUl = ( ulmen
0 '" ded ive FOl - JuUu m
TUB - luber
PYR - pyramid
UV" uvula
TON'" tonsil
Cerebellar cortex
fasciculus Woldlis
J~~
~r,~
Mttdian sagiltal section Bodv of forn ix Choroid pl",xu) of 3rd ventricle
~
Inter ventricular fo ram en
~
H.J\)e{lul.}r co mmissure
_____
. _
( OrMOnrO I ~~
{
,~. ; .
Pineal gland
-
!iplenium of corp us callosum
Thabm u~ ~
!=erebral aqueduct (of Sylviu s)
A nt. co mmissure---...,: ".
L~
Post. commissure - - ' Ma mmillOlry body~
LingulCi Cen[rall obule
'*ihor---
Vermis
i, O<:vlommor (!Ill
Stlpe,ior (ollic ulus
,11·'Mediallongitutlinal fasciculu ~ 41h veolride
,II
Median apertu re {o r MagendieJ - "\- 7 ,C
Sup. medullary velum .. medullary velum
Choroid plexu~ of 4th venlrid e
p""m'd }
I'ti"'""' Uvu la '"'-- - - Nodule
Vel mls
Central canal of spinal cord
FIGURE 11,82: CEREBELLAR ANATOMY: LOBULES _ _ _ _ _ _ _ _ _ _ _ _ _ __ The 10 lobu les of th e ce rebellar cortex are seen in both midlin e and cross-sectional views. Inputs to the 3 layers of the cerebell ar co rtex arrive mainly as mossy fibers; the inferi or oliva ry nucleus sends climbin g fibers to end on Purkinje cell dendrites, and the locus coeruleus sends diffuse varicose inputs to many regio ns o r I'h e cerebellar cortex. The deep nuclei provide the "coarse adjustment" upon w hich is superimposed the " fine adjustment" from
174
the cerebell ar cortex. The cerebellar cortex se--C. its output via inhibitory Purkinje cell projecti ons (using CABAl to deep nuclei, which in turn p" .~ to UMNs. Affe rents and efferents pass throug.'" cerebellar peduncles, w hich con nect the cere!Je lurn w ith the brain stem and the d iencephal o'L table lists the majo r afferent and efferent pro!C[ tions through the 3 cerebellar peduncles.
REG IONAL NEUROSCIENCE
- tern and Cerebellum
Pedunde 00=1
(restiform body)
Rostral
Fastigiobulbar. Undnate fasdcu lus
Cuneocerebe!lar OIive
Trigeminocercbcllar Raphe<erebellar
l evel of section
T"~'"",I~ ar>d r~ncUiaI1
Spinocerebellar
Inferior
lux tarestiform body
Vestibulospinal (primary, secorn:lary)
Middle (brachium pontis)
Pontocerebellar
Superior
Ventral Spinocerebellar
(Brachium
Trigeminocerebellar Te<:loCerebeliar
conjunct ivumJ
Superior colliculus Interior col liculus
Coeruleo-cerebellar
)
nucle;
Direct cercbellovestibular (10 lVNj
Den tatoth alamic Den tato rubrJI
Dentatoreticular
;
II
lnlerpositus·ruhral connectionS (gtobose, embolifOrml ~
nucleus
Fourth
ventricl e
CN VI
--::=-~-:---'%~---------tMedi,'II lo ngi tudinal f,)sciculus
Te ctospinJ t trac I
"""-
- - Nucleus eN VII
0'
'3(ial
" Ponline nuclei
~L R E
11.83: CEREBElLAR ANATOMY: DEEP NUCLEI AND CEREBElLAR PEDUNCLES _ _ __
deep cerebellar nuclei are found at lhe roof of ~o urt h ventricle in a cross-sectiona l view of the r:;, at th e leve l of cranial motor nucl ei for eNs VI ~ V II. The fastigial nucleus receives input from , erm is and se nds projections to reti cular and :ibular nuclei, the cell s of origin for the reticulo ~.al and vestibulospinal tracts. Some vermal and culonodular Purkinje cells project directly to the ? al vestibular nuclei, w hich some authors con·
sider a fifth deep cerebellar nucleus. The globose and emboliform nuclei receive input from the par avermi s and project to the red nucleu s (rubrospinal tract). The dentate nucleus receives input from the lateral hemispheres and projects to the ventrolat eral and ventral anterior nuclei of th e thal amus, which then project to the cells of origin for the co r ticospinal and corticobu lbar tracts. The 3 cerebellar peduncles are seen in this cross section.
175
REGIONAL NEUROSCIENCE
D ieneeph...
Thalamocortica l
radIation.
Central sulcus
, Th almic n udei
CM Centromedian LD lP
MD
late ral dorsal
l ateral posterior Medial dors.lJ
VA
VI
VentfaJ an/erior Ventral inlermedial
VL
Ventral laleral
VPl Ventral po~'efola'eral VPM Ventral postero medial
r 1ntetnal medullary lamina
An te ri or nudei
r
Intraraminar nuclei O ther medi ill nuclei
r
M idline (median) nuclei
Pulvinar
~fp CII!!N
:',';.':::
/ Medial geniculilte body From globus pallidus
and subslanliil nigra Lat~al
genkvlate body
Irael
Someslne lic from body
(spinothalamic Ifac! and medial lemniscuS)
Someslhetic from head (lrigeminal nel lie)
FIGURE 11.84: THALAMIC ANATOMY AND INTERCONNECTIONS WITH THE CEREBRALCORTEX _________________________________________ The thalamus conveys extensive sensory, mo tor, and auto no mi c information from the brain stem and the spinal cord to the cortex. Th alami c nu clei are reci procally interco nn ected wit h regions of the cortex. Specifi c thalamic nu clei project to circum scri bed regio ns o f th e co rtex; these nu clei in clude ( 1) sensory proj ecti o n nuclei (VPl- somatosensory; V PM- trigeminal; lateral geniculate body- visual; medial geniculate body-a ud itory>. (2) mo tor related nuclei (VL and VI---<:erebellum; VA and VL basal ganglia), (3) autonomic and Jimbic-related
176
nuclei (anterior and LO- cingulate cortex; MD fro ntal and cin gul ate cortices), and (4) nuclei related to association areas and l P- parietal c o'- ~ N onspecific th alam ic nuclei (j ntralamin ar nu d . [CM , parafascieularl and medial VA) send d i ffu ~ con nectio ns to w idespread regio ns of the cere cortex and to other thalam ic nuclei. The reticui.r nucleus of the thalamus helps to regulate the excitabili ty o f thalamic projection nuclei. Some : amic lesio ns can lead to excruciatin g neuropalt pain, referred to as thalam ic syndrome.
REGIONAL NEUROSCIENCE
on
Fornix ,,~potha la mic
sulcus
.;.ruerior commissure Paravenlricular
.1 Ve ntromedial
-"""'=
ArcUolte -----l~
(in fundibular)
Mil mmillary
------r
, ', ,.
,
tracl
In fund ibulum (pituitary """., ~ Hypophysis (pituitary gland)
Dorsa l longitud ina l fasci c ulu s a nd Olher
descending pathways
Lamina terminalis -
'
Hypothalamic
sukus
~-a,'cntricular hypothalamic '", ', "' - - , Supraoptic hypo"""n" "",01,",, - - -: Supraopti cohypophyseal lracl
- --"--'7--:-'
Tuberohypophyseal ""' _ _
Mammillary body
Hypotha lamohypophysea i " '" ~ Infundibulum {pituitary sta lk}
'-A""",, (infundibular) nucleus
Median eminence ·.aenohypophysis
Fibrous trabecula _ _ __
of tuber cin ~ reum
Pars i"",,~edl " _ _ __
Infundibu l.:l ' stem
lmerior lobe Of
Diluilary gland)
Pars diSlalis -
_ __
Cleft
Neurohypophysi s (p 05te rior lobe
o i pitu i lar~' gland)
Infundibul,u process
L RE 11.85: THE HYPOTHALAMUS AND THE PITUITARY GLAND _ _ _ _ _ _ _ _ __
hypothalamus is the major region of the eNS ~ ve d in neuroendocrine regulation and control .• isceral functions, such as te mperature regula· • food and appetite regulation, thirst and w ater ~ nce, reproduction and sexual behavior, parturj. and control of lactation, respiratory and cardi o· .3Scular regulation, gastrointestinal regu latio n, ~ ' ess responses, and reparative states. It is sub - .ided into rostral·to-caudal zon es (preoptic, .JI1 terior or supraoptic, tuberal, and mammillary Of posterior) as w ell as medial-ta-Iateral zones -'F
(periventricular, medial, lateral). These zones contain some discrete nudei and more diffu se "centers" or areas. The neuroendo crine portion of the hypothalamus consists o f (1) magnoceUular portions o f the paraventricular nucl eus (PVN) and the supraoptic nucleu s (SON), which send axons directly to the posterior pituitary, (2) releasing factor and inhibitory-factor neuron s, which proj ect axon s to the hypophyseal portal vasculature in the median eminence, and (3) the tuberoinfundibular system.
177
REGIONAL NEURO SCIE NC E
Diencepa llill Cor pus callosum .m:~ ".' '_ ''J'';'~~ "h:IJ.....
oc ___ : .:
,':Mecuan forebrain 1
,al
I Optic (II)
,
.
MammIllary complex
nerve
Oculomotor (III)
~hySe.a llfact
Anterior I o f pituitary
Posteri or lobe
of pituitary
,f' ,f$
4~'~oN .. :'
-,"': : ~
FI G URE 11.86: SCHEMATIC OF HYPOTHALAMI C NU CLEI _ _ _ _ _ _ _ _ _ _ __ _ Hypothalam ic nuclei and areas are associated with visceral and neuroendocrine functions. The magno cellular neurons supraoptic nucleus of the SON and PVN release oxytoc in and vaso pressin into the posterior pituitary general circulatio n. PVN parvo cellular neuron s containin g CRH project to th e hypophyseal portal system in the median eminence
and induce the release of AOH. Descending axons of th e PVN project to brain ste m and spinal cord preganglionic neurons and related nudei to regulate outflow from the ANS. The anteri or and 178
posterior areas coordin ate parasympathetic and sympathetic outtlow, respectively. Nudei OM arw4 VM, and the lateral hypothalamic area regu late appetitive, drinkin & an d re prod uctive behavio r. The preoptic area regulates cyclic n e uroe nd oc ri~ behavior and thermoregula tion. The suprachias malic nucleus receives visual inputs from the cp' tract and regulates circadian rhythm s. Several hypothalamic regio ns are involved in the regula e
of sleep.
REGIONAL NEUROSCIENCE
alon
CN V Uncus
COrliCOsp rnallract fibers Basilar artery
..
".--~
' ; . " , 8 ~.;.\ . :;;;;":wx,
Level of section (mid pons)
i.,,;,
\ ~;J!/I
. ~1
.~~
~\.~~.
\-.~" \ ..... \~ . .
,.
lateral
..
)
~.
cerebellar
Superio r cerebellar
bemisphere
peduncle
Medial lemniscus Cerebellar vermis
Pontine legmenltlm Fourth ven tri cle
RE 11.87: HORIZONTAL SECTIONS THROUGH THE FORE8RAIN _ _ _ _ _ _ _ __ ~
plates co mpare anatomical sections, MR
-"c"',,;, and ( T scans. These are cut in th e tru e hor ~J
plan e, nol in the older, 25 0 tilt. Th e most ~ a nt anatomical relationships in th ese sec center arou nd the internal capsule (Ie). The Mi oj the ca udate nucleus, medial to the anterior of the Ie, forms the lateral margin of the r-~I po le of the lateral ventricle. The thalamus is " 'al to the posterior limb of the Ie. The globus -Idus and th e putamen are lateral to the wedge ~.i.iO e d Ie. The posterior limb carries the major
descendin g corticospinal, corticorubral, and corticoreticu lar fibers, and the ascendin g se nsory fibers for the so matosensory and trigemin al sys tems. The mos t posterior portion s also ca rry the auditory and visual projections to th eir cortices. The genu carries the corticobulbar fibers. Th e ante rior limb carries cortical projections to the striatum and the po ntine nuclei (pontocerebellar system). "The MR images for the horizontal sectio ns are T2-wei ghted, with high signal intensi ty, so the ven trical s (cerebrospinal tluid) appears bright."
179
REGIONAL NEUROSCIENCE
Teleneephalcr
Amygdala C()(licospina! tract fi bf' r~
\
~,.
\
~,
...
~\
~,
i
h
level of section (rostra l pons)
L"
'\ ""',
J
.: ~fl
'·'f
"
~
t~-." , /)';,.
.' .~I\". ~... . '~ ..
'r ~
..'
'.\
/." -
I
': } ,: '
:1,
M """
~
,.
•
I
' .
'
I
},
)i"'~". ~. ,~ . . \ it ' . .,.'
! ~j.
"
Superior
cerebellar
",
,\
c.
'~'. \: .. '
•
\
lem ~
Foul1h veolride
Lateral cerebellar
..... ).
J.''''
.. 'Ii
J ....~ .·:-I
Vermis of cerebellum
'~ --. ~ ~.
0_
........c~ 1 "....·m
Rostral Pons
180
-
REGIONAL NEUROSCIENCE
ph.lon
Posterior cerebral arteries
Cerebral peduncle Amygdala
Tail o r caudate
nucleus
\ , \' \
lobe
--~
)~ :.~
\\
'\
/
level of section (mid brain)
HiPpoca mpa~~I_ _ _""::"'~_ _ _ formation Inferior horn of
lateral ventricle
fl
--~~-~'-~:_ _---.J,.--~ j!(~Q~
Entorhinal cortex
Cerebral aqueduct Occipilallobe
Decussation of superior cerebellar
pedunde Cerebellar verm is
Miilbra/n 181
l8L
5tWJ i)/\
Ji!IIOIqaJaJ
aqolll.'l!dp:>() p npanbl' Il'Kj
snln:l!llo:'l JO!Jadns
(!lnWl'Il!410d)' 4 pue U!l'Jq P !W !I!JlSOJ) UO!I~S'
JO lilA""
VO!l l' WJOJ
Il?dwC:)odd!H
sn<> pnu ,{jail\, l eJq aJ~ :)
illejn:>!ua8 Il'JaIFl
J01..Iil\Uy
sn
pa~
DN3DSOlln3N lVNOl9311
REG IONAL NEUROSCIENCE
ephalon
O rbitOLrontal cortex Putame n Claustrum
An terior limb of internal capsule Glo bus pa llidus (internal a nd external segments) H ead of caudate nucleus
Insular cortex
An teri or
commissure Colum n~
of forn ix
l evel o( section
Posterior limb o{ inte rnal capsule
(anterior commissure and caudallhalamus) Th,llamus - -, Temporal lobe ~ Choroid ple xus
~
-.:~
r ail o f cauda te
nucleus --~...;....- ---.:::::""
Atriu m of' 1 ,~t~'~"~'_.!.:..-3_-- ven lricle
Extreme capsule Extern al C<1.psuie
iormenian Pulvina r Occipital lobe
commissure
o
.JCIt'IttACRA'i .. w ::. "
Anterior Commissure and Caudal Tha lamus 183
-
REGIONAL NEUROSCIENCE
~
......, Frontal lobe
,
Anterior limb oi inter nal capsule
!
Head of caudate nudeus
Claustrum
\ '.
~
level of sect ion (head of c
Insular
and mid thalamus)
con ex
caHosum
./ \\
Extreme capsule
\\
GenuofcOf~
Genu a in tern a.
~\~
capsw
\; A nt ~
hori'" tau?... \'('n:-
Posterior limb of
internal capsule
Auditory radiations ~
Tail oi caudate nudeus ~
Tempo,," obe ~
~ '4'
Optic radialion
Third venln~
Temporal pole o f
Globus pallid;....;.
lateral ve ntricle
Putamen
Cho roid p lexus Fimbria ()f fornix
\... Spleni um of the corpu s callo sum
Oeeipilat robe
Pulvinar
Head of Ca udate a nd Midthalamus 184
-"C"4~ o~
REGIONAL NEUROSCIENCE
ph. lon
, - A" ,,,;m limb o f internal capsule Putamen
Rostru m of corpus callo su m
Claustn)m Frontal pole o f laleral
Insular
ven tricle
l evel of secti on sal ga nglia and internal capsule) latera l and ven tral thalamic nuclei Postelior limb o f
inlem al capsule
Pulvinar Tail of caudate nucleus -~_ ~-,..' .
Temporal po le of
lateral ven tricle
Head of
caudate nude;
Optic radiatiom
Chofoid plexus Medial thalamic nuclei - - -- '
'--. Goo, of in Iernal capsule Body of iarnix
Splen ium o f corpus
ollosum
O ccipilallobe
Basal Ganglia and In ternal Capsule 185
REGIONAL NEUROSCIENCE
(ingulate cor tex
Genu of corpus ca ll ~
Frontal lobe Body or caudate nucleus
level of section (dorsal caudate, splenium and genu of corpus callosum ) ,!/~ '
Insular cortex
~ ' ":i' t/;;·:;l~
Parietal lobe - - .'\;:
....,,,,.::.
~ -.
,
~"
~~
~
Frontal ~ lateral \ e""" Occipital Septum pellu cid...
lobe Spjenium of corpus callosum
..IC1HNA.C:~
C ~!N
Do rsal Caudate, Splenium, and Genu of Corpus Callosum 186
I
REGIONAL NEUROSCIENCE
halon
Ant€r jO( cin gulate
cortex
Body of caud'lI €
Fro nta l lobe Centrum se miovale
nucleus
l evel of section {body of corpus callosum)
,, ~
Parietal lobe
-----1\~.--
,"
'h '
" ,.....,.. ~
Occipita/ lobe
Body of lateral venlride Booy of corpus callosum
Body of Corpus Callosum 187
REGIONAL NEUROSCIENCE
Telencephalo<
<. 'y ;;"f~'\:. », .L
,q,._.
"
\ . ~.
Fronlal lobe
Cingulate gyrus
?'l .. 1
.~~ l evel of section (centrum semiovale)
~
)t., 4< -
-- f ""
/i I
t
<1' .
( ¢!,
.-;;, /~;
>~\W -12tW)),
~"'. '< ',:'.
·'·'.,X '
]. ~.' .~j "
~
~.
M
.j_ ,·I ,~~t "
.
'.'
. J' ~ (\· J U . ~~, .", .10> ~ .
;
"
~W~· '0; - •
:
Occipilal lobe
__ -"'.....
..... .""
Centrum Semiovale
188
I <...,.~
REGIONAL NEUROSCIENCE
ephalon
Superior Iron lal gy rus
Cingulate gyrus
Middle fro nlal gyrus Genu o f corpus callo sum
Inferior fronla! g)' rU 5
Fron tal pol e of
l evel of section
la te ra l ve nt ri cle
(gen u of corpu s callosu m)
Subcallosal
gyM
I............
Lateral
iissure
~
Tempot"a\
~
pole
Genu of Corp us Ca ll osum
RE 11.88: CORONAL SECTIO NS THROUGH THE FOREBRAIN _ _ _ __ _ _ _ __ - -.a,e pl ates co mpare coron al anatomical sections \ \R images. Th ey show impo rtant relati onships
.,. Ie. the basal ganglia, and the thalamus. Basa l "':brain structures (such as the nucleus accum i, the substantia innominata, a nd the nucle us ..I.SC!lis), thalamic nuclei, and th e important tempo
rallobe structures (amygd aloid nuclei, hippoca m pa l form ati on) and pathways (forn ix, stri a termi nalis) are illustrated. The MR images for the coronal sect io ns are T2·weighted, w ith a reversal technique (FLA IR) thal results in the ventricles (cerebrospinal
nuid) appearin g dark.
189
REGIONAL NEUROSCIENCE
~
Cingulum Para oOaCIOry gyrus
Cingulale gyrus Body o f corpus calloSl.-
Head or caudale nudeus - Nud~J 5
-
Septum pellucidL~
,
accumbens Fron tal pole (II latet"al vent~
Anleri()( limb o i internal CJpsule
b .:"
l evel of section
(head of caudate nucleus!
nucleus accumbens)
Insuldf COd ex l a tera l Ihsure
TempOial pole
(
).
--J.l : (
'J t
Amygdala
b"
Oplic nerve
".
0
-'CHN A.CIU.I:....c
,.': : .-::
Head of Ca udate Nucleus/ Nucle us Accumbe ns 190
REGIONAL NEUROSCIENCE
halon
G ngulate gyrus Columns 01 fOrnix
Cingulum Head of Ciludate nucleus
Body of corpus callosum
Septum pellucidum
lateral ven tricle An teri()( limb of iOlem al
capsule - - - -,
level of sedion (anterior commissure!
Globus pallidus
columns of fornix)
Claustrum
-~~~"""
Insular cortex --t~"'::::::;;gl...-
Pulam€'O
-:::-==~;;;;;:;;;:::f---':':;
Lateral fissure
--4~~---ll------''---''(4;'
Nucleus basalis Temporal lobe -
---.__"
Amygdala Thi(d ventricle
Extreme
capsule
Supra optic re<:ess External capsule
Anter ior Co mmi ssure/ Co lumn s of Forn ix
lelencephal
REGIONAL NEUROSCIENCE
Cingulale gyrus
Stria terminalis and terminal vein Body of caudate
nudeus AnTerior limb of intetnal capsule
Level of section (amygdala, anterior limb
of internal capsule)
Claustrum
Putamen
Insular cortex
i ; (, . df, ,","tJ . . './ Ii
-----.!
G lob us pallidus
extern al segmen t
Temporal cortex
~
,~
~
.'10
~~/'~'
'?(~.
\_
'.or.
,
'. ~i}ff..'
.ti%,~ .". ';$
." ~::;
"il. .'
~",;,~
'~~:~~Z;.' ), 'N",.
~
'1$?}:
'~ Amygdala
Colu mn s o f fo m lX
Third ventricle
G lohus p.ll1 idus inlem al segment
H ypothalamus
O ptic (ract
..I""" _ .. ......:: "
Amygdala, Anterior limb of Inte rnal Capsul e 192
C.....,..., I
REGIONAL NEUROSCIENCE
phalon
Third "en!rid e
ROSlral th.1Iam u$ Hypothalamus Posterior limb o i internal CClPsulf>
Cingulate gyr us Body of corpus callosum Cingulum Columns o f fornix
G lobus pdllidus
internal se gment
Body of lateral
Putamen
level of section (mammillary bodies)
Insular corl ex
Lateral fissu r e
( I(lustrum
:-:::::~~::::~=t :I.•
Inferior horn of
lale ral venlobe tricle Temporal
---==~'W;~:==~r",;r:.
Hippocamp:J1
Ex te rnal
formation
capsule
Inte rpedul'lcular iossa Mdmmillary body
'--. ,Vlid,jlece",,,, 1 artery Basis pontis
CNebral peduncle in basis pontis
.JOHN ....., , _ CII!JN I
....:,:"
Mammillary Bodies
193
REG IONAL NEUROSCIENCE
, ~~T~~"
Cingulate gyrus Ongulum - - - - - .
Anterior thalamus Medial dorsal thalamlJS Mammillothalamic tract
Body 01 caudate nudeus Venlfallalefal thalamus
Postelior limb oi internal capsule
,, ~
\
l evel of Section (mammi11othalamic tract/substantia nigra, rostral hippocampus)
Insular cortex
---
Tempo,, ' pole of
.,.
-(o
j.,
i·
~
-;.';
t - : : - -- ,
''N''
ventricle
7"<;:
Tail of caudate nucleus
.-\~
_ _"
...
Tempor..1 cortex --'
L Globus pa external sE' ..-
Cerebfill peduncle
Substantia nigra (ort icos pinaltraCI
fi bers in basis
pon t ~
C lobu s pallidus internal segmen·
"--- Basis pOntis
"
'-Medullary pyramids
"""'" ACR......., 011lN I ,.......,,:
Mammillothalamic Tract/Substantia Nigra, Rostra l Hipp oca mpu s 194
REGIONAL NEUROSCIENCE
Body of corpu s ca llosum Cingulale (Oriel(
Interventricular fo ramen of Munro
Third ventricle
Cingulum Suia ter mi na lis Body of ca udate
nudeus
level of section (midthalamus)
Cenlromedian thalamus Ta,1 o f the caudale nucleus
Medial
geniculate
nudeus Corle:< of cefebellum
Superio r cerebellar peduncle
Ento rhina l
Pons (floor o f
cortex - ---'
fourth ven tricle)
L_," ,,,,,, cerebellar peduncle
Medulla
Midtha lamu s 195
Teleneeph. . .
REGIONAL NEUROSCIENCE
::\~ I { ~
Cingulate gyrus
Body of corpus callosum Body of forni)!.
Pulvinar '>
level of section (geniculate nuclei) Medial geniculate nucleus Lateral geniculate nucleus
Tail of caudate nucleus Inferior role o f lalera l ventricle
.'~.:.
Ah,.... . ~r~
;-':-..::.~;;
04
-----4
comm Cerebellar cortex
Peri aQueduc.: _
gray matter
Middle cere bellar peduncle I D ecussati on o f superior
cerebellar peduncle
M edulla
,JOHN A.CRAC-or.: 0 UllN I
,.,......."
Genicu late Nu cle i
196
REGIONAL NEUROSCIENCE
Cingulale gyrus
Body 0/ corpus callosum
Cingulum Crus of fornix Superior colliculus Pulvinar
Third ventrid e
Sody 0 1caudate nucleus
Body of lateral ven tricle
Level of section c:aMial pulvinar and superior colliculus) Tail of caudate nucleus Fimbria o f hippocampal
;;~=====~~~~~;;~~"-.
Inferior pole o f forma tion laleral ventride
--j":---~:"'----II"-,~~
Hippocampal formation
lateral cerebellar
caJliculus
hemi5f)hefe
EnlOrh;nal cortex
_f--'.r
, .......l.D
Middle celebellar peduncle
\...·C,,,.i>ell,, vermis
Fourth venTricle
Super ~ cerebellar peduncle
Caudal Pulvinar and Superior Colliculus
197
Telen eeph
REGIONAL NEUROSCIENCE
(ingulate gyrus
Splenium of corpus callosum
Pineal Trigoneof lalera venlricle
Crus o f fornix
ChorOid p'
Pukinar Inferior p. ofl a te '~ ven 'nc ~
level of section (splenium of corpus callosum ) Tail of caudate nuculeus _____
Optic radiations _____ Hippocam pal formation Tempo ral
lobe
& . ---.,_~ ~ .
'
..
I...... '
4
ii$:.
~
\"
"-.J
V.
L.u eral
cerebellar
hemisphere
Denlat e nucleus Cerebellar vermis
Fourth ve ntride
....... A.CI!A.IC.-.c
' OlIN ,~,w"
Sple nium of Co rpus Callosum
198
I
REG IONAL NEUROSCIENCE
"'.-c..cl aIon
,
,
, , ,, ," , •
,
,
"," •
.. ,
RE 11 .89 : LAYERS OF THE CEREBRAL CORTEX _ _ _ _ _ _ _ _ _ _ _ _ _ __
ns of the cerebral co rtex with specific func
'-d ro les, such as the so matosenso ry cortex and ~~o tor cortex, demonstrate histological charac - cs that reflect their func tio n. TIle sensory ;;::::\ has large granule cell layers (granular cortex) "pceiving extensive input, w hereas the motor re, has sparse granule cell layers and extensive
pyramidal ce ll layers, refl ectin g exte nsive output. Specific and nonspecific afferents terminate differ entially in these structu rally uniqu e regions of the cortex. Monoamine inpu ts terminate more diffusely than do the specific inputs, reflecting the role of monoamines as modulators and enhancers of the activity of o ther neuro nal systems. 199
REGIONAL NEUROSCIENCE
I~ Key for Abbreviations 3 Horizon tal cell b Cell of Marlinotti
"
c Chandelier cell d e
f g
Aspiny granu le cell Spiny granule cell Stellate (granu le) eel Small pyramida l ce ll o f layers II. III
h Small pyramidal
association cell Small pyra midal asso ciation <J nd prOjK'l ce lls of layer V
La rge pyramida l projection cell (Bel z (;
,
v
Cortical interneurons
cen bodies and
Black { dendrites
~-v~-
~
Cortical association
Effe re nt
neuro ns
neuron
axo ns of in te rneuro ns
Bro wn { and association neurons
of efferen t Rod { axons neurons
~~p
OIlQN I·N".' : ~
FIGURE 11.90: CORTICAL NEURONAL CEll TYPES _ _ _ _ _ _ _ _ _ _ _ _ _ __ The cerebral cor tex has many anato mically unique cell types, with characteristic cell bod ies, dendritic arbo rizati on s, and axo nal distribution. G ra nul e ce lls are local ci rcuit neuro ns w ith small cell bodies, lo calized dendriti c trees, and axons that distri bute locally. Granu le ce ll s function as recei ving neuro ns for thalamic and other input, and they mod ulate the excitability of oth er cortica l neuron s. Pyramidal cell s po ssess more vari ed cell bodies, with large basolateral dendritic branching patterns and apical
200
dendritic arborizatio ns that run perpendicular ::
the cortical surface and arbo rize in upper layes.
The axons of pyramidal cells, w hich function as
projection neuro ns (e.g., corticospinal tract ne.:
ro ns), leave the cortex an d may extend for up :
meter before synapsing on target neurons. Theso
unique anatom ical characteristics give rise to b
co ncep t that neuronal structure exp lains neu r
fu nction.
REGIONAL NEUROSCIENCE Vertical co lumns (O.5 -1.Q mm wide)
Small .
' - - - Corticocorlical olfferent
--- 1 ----------
' _ _ _
l. Perkins "ti, .... r...
----1----------·
Corticocortical eflerenlS ....._ _ _ _ _ _ _ _ (."m' 10 adjacent or nearby _ _.L___________
c BN.
vertical columns)
E 11.91: V ERTI CAL COLUMNS: FUNCTIONAL UN ITS OF THE CEREBRAL CORTEX _ _ __ ~n tal
studies of sensory regio ns of the cere
cent::, provided anatomical and physiolo gical .a:'lCe that discrete info rmation from a specifi c _ ' r o r conveying specific fun ction al characteris . orocessed in a cylindrical vertical zo ne o f
in the co rtex that sp an s aU6 layers of the e'\. The se vertical units va ry (rom O. S to ""1 in diamete r. The dia meter corresponds to ~ horizo ntal e'pall se of a large r pyram ida l
",.-.;:s
arborize in the verti cal column and synapse on both stell ate (granule) cells and pyramid al neuro n dendrites. Information from a vertical column can b e sent to an adjacent or nearby column via corticocortical efferents, or it can be sent to distant structures by commissural fibers (cortex on th e o ther side) or p rojec tion fibers (s ubcortical stru c· tures). The minimal elem ents o f the vertical unit are sh own.
~:. unit. Bo th thala m ic and cortical afferen ts
201
Teleneeph.
REGIONAL NEUROSCIENCE
"
...
'-t
t
,,
- ------1 Association Fibers _______ l ong - 10 distant regio ns o f i~ilaterill hemisphe re \, .
4#
:
1.
r-~"',""
ipsilate ral hemisp ht're
Comm;,," ,,1 Fib", To cor ti ca l regio ns of (on tr
Projection Fibers Corti cos pinal tract Cortlcobulbar tract
..
<~_ "" .
""
"-.
} ..
I
r \. .: .
1 l- "
-
1
nucleus
\ _L
Putametl
\
,,#
,.
Y,
t"".
(po lysyn ilptic)
Corti coteetat fibe rs
\
~
~:: j . ~...
Corticorubrospinal system
Corticoreticulospinili system Cortlco bulbospinal system
Car lica pontine fibers (to cereb ellum) C orticostriale fiber<>
(to ba!Hl1~ngliiJ )
T /
:7
I
~~
.,..:' I I
),. ~ \ , j
Short - to nearby regions o f _______
•
. <;:
. I
III Venwce;
1"
.I
,I
",,--
J
Globus
'"
.
;
pallidus
,,:,~po'h,' ,m~ ' '-p
H ippocampus
Coniconigral and conicosublnalamic fi bers Corticonud eiJf fibers (to seco nda ry ~ensory nuclei)
Corticothalamic projec1ions
Corticohypotha lamic a nd corlicoaulo nomic fibefs Conicoo liva ry fibers Co rticoli mbic fibe rs (in subcortical ro renra in )
1 T
~
...
;,:. ,
.).
--.
'.
~.
'1~ La te ral venui~ (la teral po le
' . PMa
"".
."" ,-,
FIGURE 11.92: EFFERENT CONNEOIONS OF THE CEREBRAL CORTEX _ _ _ _ _ _ _ __ Neuro ns of the cerebral co rtex send efferent co n nedio ns to 3 majo r regions. Short o r long associa tion fibers are sen t to o ther cortical regio ns of the same hemisphere by sho rt associatio n fibers (nearby) or lo ng association fibers (at a distance), Commissural fibers are sent to co rtical regions of 202
the other hemisphere thro ugh the corpus callos. or the anterior commi ssure. Pro jectio n fibers a"E sent to numerous subcortica l structures in the telencephalo n, the diencephalon, the brain st ~ and th e spinal cord , Th e major si tes of termi na:'! of th ese co nnectio ns are li sted in th e diagram.
REGIONAL NEUROSCIENCE
...ha lon
Small pyramid.,11
,ell
Subcortical projectio ns (mainly) Some corticocorlical axons
Corticocortical axons Commissural axons
J. Perkins -U, IoI''''
Cortico cortical axons
Corticothalamic axo ns Some corlicoco rlical clXons Some commissural axon s Some ptojection
e~
E [1. 93: NEURONAL ORIGINS OF EFFERENT CONNECTIONS OF THE CEREBRAL CORTEX _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ ICia tion fibers destin ed for cortical regions of ;":1e hemisphere arise mainly from smaller .-.idal cells in cortical layers II and 111 and from ~_ d pyramidal cells in layer VI. Commissural destined for cortica l regio ns of the opposite "'Onere arise mainly from small pyramidal cells
in co rtical layer III and from some modified pyram idal cells in layer VI. Projection fibers arise from larger pyramidal cells in layer V and also fro m smaller pyramidal cells in layers V and VI. O nly a small number of projection fibers arise (rom the giant Betz cells in layer V.
203
REGIONAL NEUROSCIENCE Motor-sensory
MS I {
Ms II
PremO lar; nrien tati on;
eye arld head movements
Visual I
Preironlal; inhibitory conlrol
of be-havior;
higher intdligence
l anguage: reading; speech
MOior conlrol of speech --~I
MO lnr-sen ~fy
PremOlor
5,, 1 } Sensory-motor III
Temporocingulate and parie tocingu lilte pathwilY
Prefrontal;
inh ibitory control
of behavior;
highe r intelligence
, Visual II I ,Visual II
~ ~f:~ {I@\. ,.
,./
Fronto
cingulilte
pathwa y _ _- ,I
~?»L Corpus callosum
Cingulate gyrus (emotional behavior)
il nd ci ngulum
Hippocampal commi ssu re
OilaclOfY
'----Ante rior commissure
FIGURE 11.94: CORTICAL ASSOCIATION PATHWAYS _ _ _ _ _ _ _ _ _ _ _ _ _ _~ Cerebral cortex neurons have extensive connec· fions with other regio ns o f the brain (projectio n neurons), w ith the opposite hemisphere (commis sura/ neuronst and w ith other regions o f the ipsi lateral hemi sp here (associatio n fibers). The cortical association fibers may con nect a primary sensory cortex wi th adjacent associa tio n areas (e.g., visual cortex, somatosensory cortex), or link multiple regions of cortex into complex associatio n areas
204
(e.g., polysensory analysis regio ns), or interl.i1" importan t areas involved in language functicJo. cognitive function, and emotiona l behavio r analySiS. Damage to these pathways and a 5S ated co rtical regi ons can result in loss of spec. sensory and motor capab iliti es, aphasias (I disorders), agnosias (failure of recogni tion apraxias (performance deficits).
REGIONAL NEUROSCI ENCE
alon :;'.t)E'rior occipitofronta 'i
faSciculu~ -
....., . J...~JP"'..
-----=7"""~:::r:::::~7-
~~~III"~
·looghud'o. '"deulu,1~
ierior
;mntal
--jf--"''''''"",f' '-_
-.3
~culus
",nClnate _ _;';',-;~ ~ cul us
~{?
-
I ·~
~~
Superior occipito(ront a l - - - , fasciculus
•
I
... Superior "::'Itu d i nal ---::-i~--"
~".
;.a SC iClI llI s
q nudC'Us ~utamen
Inferior
I
fa sciculus UnCIn ate
lilSClcuius
,
I
Thalamus
-
til"
paJlidus
r,"c,
.
1' 1
Globus
oc:pl.ofro nta l~
.
,~ /~ Lateral ..,),. ~. fis sure
. Claustrum\·
Hypothalamus" - o
-~~ "" I
\."
/ ~.
_ _'"
~.
;~)
I.MP5,.."" ..... f .. o~
URE 11 .95: MAJOR CORTICAL ASSOCIATION BUNDLES _ _ _ _ _ _ _ _ _ _ __ rsociation fibers co nn ecting cortica l regions in I f hem isphere with adjacent or distant regions of S
bund les include the uncinate fascicu lus, the su perior lo ngitudi nal fasciculus, the superior and inferior occip itofro ntal fasciculi, and the cingulum. Th e cingulum is a bundl e through w hich th e major mo noa mines (dopamine, norepineph. rine, sero tonin) and par t o f the cholinergic projec tions travel to their w idespread target sites.
205
REG IONAL NEUROSCIENCE
Telencephalr
TempO f
AI.
\
FIGURE 11.96: NORADRENERGIC PATHWAYS _ _ _ _ _ _ __ _ _ _ _ _ __ __ Noradrenergic neurons in the brain stem project to widespread areas of the eNS. The neurons are found in the locus coeruleus (group A6) and in several cell gro ups in the RF (tegmentum) of the
medulla and the po ns (groups A 1, A2, AS, A7l. Axo nal projectio ns of the locu s coeruleu5 branch to the cerebral cortex, the hippoc,ampu s, the hypo thalamus, th e ce rebe llum, brain stem nuclei, and the spinal cord. The locus coeruleus acts as a mod ulator of the exci tability of other projec tion systems (including nociception), such as the glutamate sys tem, and helps to regulate attention, alertness, and sleep-wake cycles. The RF groups are interco n nected with sp inal co rd, brain stem, hypothalamic,
206
and limbic regions involved in neuroendocri ne tro l, visceral fun ctio ns (temperature regul ation feeding and drinking behavior, reproductive be-1. ior, autonomic regulation)' and emotional be A sparse set of epinephrine-containing neuron5. th e medu llary RF are similarly interconnect ed \\. each other. The RF gro ups can work in co ncer: with th e locus coerul eus during challenge or in response to a stressor to coordinate aler tn ess ,:-t appro priate neuroendocrine and autonom ic responsiveness. The central noradrenergic ana adrenergic neurons and th eir receptors are the' gets of many pharm acological agents, inclu d in~ those for depression, analgesia, and hyp ertens
REG IONAL NEUROSCIENCE
Temporal lobe
Raphe d~y" ;'
Raphe pontis centralis ",,~'i'''/
Raphe ~'"" ;< , /
Raphe pallidus and 0",,",,,, -
\ \ RE 11.97: SEROTONERGIC PATHWAYS _ _ _ _ _ _ _ _ _ __ _ __ _ _ __ nergic neuro ns (5-hydroxytryptamine ' -~ I. found in raphe nuclei of the brain stem and
en l w ings of cells, have widesp read proj ec hat innervate every major subdivision of the
.:.. '-=euro ns in the nyf le \..! s raph_~.Qp~!'l!i s and "'ltJcleus cenlralis superior projec t rostrally 10 ate the cere-brarcoriex, many limbic forestructures (hippoca mpus, amygdala ), the gangli a, many hypothalami c nuclei and areas, so me thalamic regio ns. N euro ns in the raphe ': us, pontis, pallidu5, and obscurus project r e cauda lly to innervate many brain stem _ ns, th e cerebellum, and th e spinal corcL The eclions of the nucleus raphe magnus to th e 3d1 horn of the spinal cord influence opia te ~ ~ es i a and pain processing. The ascending
seroto nergic systems are involved in regulatio n of emotional behavior and a wide range of hypothala mic functions (neuroen docrine, visceral/auto nom ic). Serotonergic neurons are involved in sleep-wake cycles and stop firing during REM sleep . Projections to the cerebral cortex modulate the processing of afferent inputs (e.g., from the visual co rtex). The descending se ratanergi c neuron s enhan ce th e effects of ana lgesia an d are essen ti al for opiate analgesia. They also modulate pregan glionic auto no mic neurona l exci tability and enhance th e excitability of LMNs. Many pharmaco logica! agents (in cl udin g drugs for treating depres sion, other cognitive and emotio nal behaviora l states, headaches, and pain) target serotonergic neuro ns and their receptors.
207
REGIONAL NEUROSCIENCE
Telencep h.,:;·
Ventra l tegmental Jre~
~Jf'
ci8!N \ FI GURE 11.98: DOPAMINERG IC PATHWAYS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ j.""",",,
,-,-,...."
Dopaminergic (DA) neurons are found in the mid brain and the hypotha lamus. In the m idbrain, neu ro ns in the substantia nigra p
basal ganglia ci rc uitry that aids in the planning and execution of cortical activities, especially in the
motor system. Damage to the nigrostriatal system results in Parkinson's disease. The antiparkin so nian
drugs, such as L-dopa, target thi s syste m and its rece ptors. DA neuron s in the ~entra l tegme~!a l area and the mesencephali c RF mesolimbi c p-rojections to the nucl eus accumbens, th e amyg dala, and the hippocampus and meso co rti ca l pro j~ctions to the frontal cortex and some cortica l association areas. Th e mesolimbic pathway to the nucleus accumbens is invo lved in motivation, reward, biological drives, and addictive behaviors,
send
208
particularly substance abu se. Projectio ns to Ii,......, struc tures can induce stereotyped, repetitive behaviors and activities. The mesocortical pro;e. tio ns influence cognitive func tions in the plam and carrying-out of frontal cortical adivities al'lQ in attentio n mechanisms. The mesolimbic and mesocortical systems and their receptors are - targets of neuroleptic and antipsycho tic agents influence behaviors in schizophrenia, obsess" €- co mpulsive disorder (OeD), attention deficit hyperactivity disorder (AOHO), and other behavioral states. DA neuron s in the hypotha form the tuberoinfundibular dopamin e path \" iJ'" which projects from th e arcuate nu cle us to til€: co ntact zone of the medi an emin ence, where dopamine acts as a prolactin inhibitory factor. Intrahypothalami c OA neuron s also influ ence other neuroendocrin e and visceral/auto nomic hypothalamic function s.
REGIONAL NEUROSCIENCE
ph.lon
(01 Meyl'left)
Bra,n, lem legmentJ! cholinergic Woup
RE 11.99: CENTRAL CHOLINERGIC PATHWAYS _ _ _ _ _ _ _ _ _ _ _ _ _ __
al cholin ergic neuron s are found mainly in the ~ s basalis (of Meynert) and in septal nuclei. deus basa lis neurons project cholinergic axo ns Ie
cerebral cortex, and septal cholin ergic neu
_ project cho linergic axons to the hippOCilmpa l lion. These cho linergic projecti o ns are . ed in corti cal activation and memory func parti cul arly conso lidation of sho rt-term r-.lOry. They often appear to be damaged in -eimer's di sease. Drugs that enhance choliner - nction are used for improvem ent of memory. -.eor chol in ergic neurons, found in th e brain stem
teg mentum, project to structu res in the thalam us, the brain stem, and the cerebellum. The proiec tio ns to the thalamus mod ulate arousal and the s!eep wa ke cycle and appear to be import.ant in the initia tion of REM sleep. Cho linergic interneuro ns are present in the striatu m and may participate in basal gangli a co ntra! of tone, posture, and initiation of movement Or selectio n of wan ted pattern s of activ ity. Acety!choline is the principal neurot ransmitter in aUprega nglio ni c au tonomi c neuron s and LMNs in th e spin a! co rd and the brain stem.
209
REGIONAL NEUROSCIENCE Internal nasal branch (la t~ral ra mus) }0, anll!n.OI Exlerna l nasa l branch _ _ _
I!lhmoidill n. \
O lfactory bulb ~Olbctory
O lfactory IraCI
nerves
M axillary n.
Pterygopalatine
ga nglion and branches '"
Nelve o f pterygoid canal
Grea ter petrosal n. Oeep pe\rosal n.
- - - - Pharyngeal branch
~ Naroopa latinc n. Cpa s ~ng
to !oqllum)
PosteriOI inferio r
nasal branch
l esser (mi no r] palatine nn.
.
O lfac torv , bulb
Cribri form 01
Olfactory nerves liil(['
(nlerna l n.lsal bra nch (medial ra mus) o f anterio r ethmoid,,] n . --_ _ __
Nasopalatine n. _ _ _ _ __ _-."
Incisive cana! __
N~I ~Ium
~~p ,
CIIQ' ....... ;.:
FIGURE 11.100: OLFACTORY NERVE AND NERVES OF THE NOSE _ _ _ _ _ _ _ __ __ The o lfactory nerves and their projectio ns into th e eN S are an important compo nent of forebrain function. Bipo lar cells found in the o lfacto ry epithe lium are the primary sensory neurons. The peri ph eral axon, a chemosensory transd uce r, responds to the uniqu e chem ica l stimuli of airborne molecu les entering the nose. The central axon s of bipolar neu rons aggregate into approximately 20 olfactory nerves that traverse the cribriform plate and end in glo meruli o f the ipSilateral olfac tory bulb. These nerves are vulnerable to tearing, resulting in anos mia. Unlike neurons in o ther sensory systems,
210
these bi po lar neuro ns ca n proli ferate and reg;:: ate. After processing in the olfactory bul b, miL-a neurons and tufted neurons project via the altar tory tract directly and indirectly to limbic for~ stru ctures, in cl udin g septal nuclei and amygd nu clei, an d thereby infiuence the hypothalam...s. and its regulatio n of neuroendocrine and viSCer:3. autonomic function. The olfactory sys tem is involved in territorial recognition and defensE' and wa ter acquisition, social behavio r, reproc _ tive behavio r, and signaling o f danger.
III. SYSTEMIC NEUROSCIENCE ... A. SENSORY SYSTEMS SO 'lATOSENSORY SYSTEMS
- -=- re 111.1 : Somatosensory Afferents to th e Spinal Cord
- =-
re 111.2: =-SU re 111.3:
Soma tosenso ry System: Spinocerebellar Pathways
Somatosensory System: The Dorsal Column System and
Epicritic Modalities
~ re
111.4:
:-_ re 111.5: - .:oure 111.6: - ..:.ure 111.7:
So matose nso ry Syste m: The Spinothalami C and Spinoreti cul ar Systems and Protopat hic M oda liti es
Spinothalamic and Spinoreticular Nociceptive Processin g
in the Spinal Cord
Mechanisms of N europa thic Pain and Sympathetically
Maintained Pain
Descendin g Co ntrol of Ascending Somatosensory
Systems
TRIG EMINAL SENSORY SYSTEM - u re 111.8:
Trigeminal Sensory and Associated Sensory Systems
ENSO RY SYSTEM FOR TASTE
- ure 111.9: Anatomy o f Taste Buds and Their Receptors
-=igure 111.10: ~
Taste Pathways
\UDITORY SYSTEM
~ ure 111.11: Ggure 111.12 : =- ure 111.13:
figure 111.14: figure 111.15: f igure 111.1 6:
Periphera l Pathways for Sound Receptio n
Bony and Membranous Labyrinths
V III Nerve Innervation of Hai r Cells o f the
O rgan of Corti
Coch lear Receptors
Afferent Auditory Pathways
Ce ntrifu gal (Effe rent) Audito ry Pathways
w. VESTIBULAR SYSTEM Figure 111.17: Figure 111.18:
Vestibu lar Receptors
Vestibular Pathways
Figu re 111.1 9:
Nystagm us
6. VISUALSYSTEM Figure Fi gure Figure Fi gure Figure
111.20: A nato my of the Eye 1IJ.21: Anterio r and Posterior Cha mbers of the Eye 111.22: The Retina and the Pho toreceptors m.23: Arteries and Veins o f the Eye 111 .24: Visual Pathways: Retinal Projectio ns to the Thalamus and the Brain
St e m Figure 111.25: Visual Pathways: The Retino-Geniculo-Calcarine Pathway
Figure 111.26: Visua l Pathways in th e Parietal and Temp oral Lobes
211
SECTION B. MOTOR SYSTEMS B.l. LOWER MOTO R NEURONS (LMNs ) Figure 111.27: Fi gure 111.28:
Lower M otor Neuron D istribution in th e Spin al Cord and the Bra in Stem Alpha and Gamma Lower Motor Neurons
B.2. UPPER MOTO R NEURONS (UMNs) Figure 111.29:
Cortical Efferent Pathways
Figure 111.30: Corli cobul ba r Tract Fi gure Figure Figure Figure Figure Figure
111.31: 111 .32: 111.33: 111.34: 111.35: 111.36:
Corticospinal Trac t
Corticospinal Tract Terminations in the Spinal Cord
Rubrosp inal Tract
Vestib ulospin al Tra cts
Reticulos pi nal and Co rti co reticular Pathways
Tectospinal Tract and Interstiliospinal Trac t
Figure 111.37: Spinal Cord Te (minations of Majo r Descending Uppe r Mo tor Ne uro n Tracts Figure 111.38: Ce ntral Contro l of Eye M ovements
Figure 111.39: Centra l Con trol of Respi ration
B.3. CEREBELLUM Figu re Figure Figure Figure Figure
111.40: 111.41: 111.42: 111.43: 111.44:
Func tional Subdivisions of th e Cerebellum
Cerebe llar N euronal Circui try
Circuit D iagram s of Affe rent Co nnections in the Ce rebell um
A fferent Pa thways fa the Cerebellum
Cerebellar Efferen t Pathways
Figure 111 .45: Vestibu loce rebe ll a r a nd Cerebe lloves tibula r Pa thways Figure 111.46:
Schematic Di agram s of Efferent Pathways Fro m th e Cerebellum to Upper Motor
Ne uronal Systems
B.4. BASAL GANGLIA Figure Figure Figure Figure
111.47: Conn ectio ns of th e Basal Ganglia
111 .48: Basic Basa l Gan glia C ircuitry and N eurotransmitters
111.49: Parall el Loops o f Circu itry Through the Basal Ganglia
111.50 : Connections of the Nucleus Accumbens
SECTION C. AUTONOM IC. HYPOTHALAM IC, AND LIMB IC SYSTEMS
C.T. AUTONOMIC NERVO US SYSTEM Figure 111.51:
General O rganizatio n o f the Auto no mic N ervou s System
C2. HYPOTHALAMUS AND PITUITARY Figure Fi gure Figure Figure Figure Figure Figure Figure Figure Figure Figure
Gen eral Anatomy of th e Hypothalam us
Sectio ns Th rough the Hyp othalamus: Preoptic and Supraop tic Zones
Sections Through the Hypothalamus: Tuberal Zone
Section s Through th e Hypothalamus: M ammi ll ary Zon e
Sc hem ati c Recon stru ctio n of the Hypoth alamus
Fo rebrain Regions Associated W ith the H ypothalam us
Afferent and Efferent Pathways Associated W ith the H ypo thalam us
Schem atic Diagram of Major Hypoth alamic Afferen t Pathways
Sc hem atic D iagram of Major Hypo thalami c Efferent Pathways
Summary of General Hypothalamic Con nections
Paraventricular N ucleus of the H ypo thalamu s: Regulati on o f Pituitary
Neurohormonal O u tflow, Auto no mic Pregan glioni c Outflow, and limbi c Acti\'i:' Figure 111.63: Mechani sm s of Cytokin e In fl uen ces o n the Hypothalamu s and Oth er Bra in Reg ion s and o n Beh avior
212
111.52: 111.53: 111.54: 111.55: 111.56: 111.57: 111.58: 111.59: 111.60: 111.61: 111.62:
111.64: 111.65: 111.66: e 111.67: e 111.68: ... e 111.69: e 111.70: re 111.71: ~ :- e 111.72: ;. e 111.73: _'.Ire 111. 74: ==-
Circumventricular O rgans Hypo physeal Portal Vasculature Regulatio n o f Anterior Pituitary Hormone Secretio n Posterio r Pituitary (Neu rohypo physeal) Ho rmones: O xytocin and Vasopressin Vasopressin (Antidiureti c Ho rm one) Regulation o f Wa ler Balance and Fluid Osmo lali ty
Th e Hypothalamu s and Th erm oregulati on
ShorHerm Regulation of Blood Pressure
Lo ng-term Regulation of Bl oo d Press ure Neural Control of Appetite and Hunger
Neural and Neuroendocrin e Rol es in th e Fi ght-o r-Fli ght Respon se
Neuroimmuno mo dulatio n
J \IBIC SYSTEM ~""'!lI re 111.75 : =-""!Ure 111.76: ~~re 111,77: - .:;ure 111 .78: :-~ure 111.79: :-~ re 111.80: - ~ure 111.81 : :-- ure 111.82: =-.,:)ure 111.83:
A nato my of the Limbic Forebrain Hippocamp al Formati o n: General A nato my Neuronal Connections in the Hippocampal Formatio n Maj or Afferent an d Efferent Co nn ecti o ns of the Hi ppocam pal Form ati o n Majo r Afferent Connections of the A mygdala Maj o r Efferent Co nn ectio ns of the A mygdala Summary o f Major Afferents, Efferenls, and Interconnectio ns o f the A mygdala Major Affere nt and Efferent Connections of the Septal Nuclei Major Connections of the Cin gulate Cortex
OLFACTORY SYSTEM ure 111.84: O lfactory Receptors ~ ur e 111.85: O lfacto ry Pathways
"0
213
SYSTEM IC NEUROSCIENCE
Sensory Systems- Somatosen sor
Proprioception
Touch and
pressure . -----...
Pain (nociceplion) { and temperature
I
--....
T
-- ' --- -~,
--.......
c".°'- '''.~
'
Dorsal spinocerebellar tract
Spinothalamic and spinoreticular tracts
Ii
---f< ; -- "' i\
J. PerbF MS• ..,..
To skeletal ( muscle 0(
...-'"
c ~.
-----
FIGURE 111.1: SOMATOSENSORY AFFERENTS TO THE SPINAL CORD _ _ __ _ __ __ Unmyelinated IUNM) and small myelinated 1M) axons that convey nociception and temperature sensation terminate in laminae I and V (origin for spinothalamic tract). Other UNM axons terminate in the dorsal horn, from which neurons for poly synaptic reflexes and for the spinoreticular system originate. M axons for touch and pressure termi
nate in the dorsal horn, where additional reflex connections and spinothalamic projections
214
originate. M axons also project into fasciculi gra:i
and cuneatus for lemniscal pathways destined
conscious interpretation. M proprioceptive ax;
terminate directly on lower motor neurons (l "'"
(via la afferents) and the la interneuronal poo;
and also terminate on neurons of origin for tr €
spinocerebellar tracts.
M = myelinated; UNM = unmyelinated.
SYSTEMIC NEUROSCIENCE
Systems-Somatosensory
/'
-....... "'-,,,,,,,... ',, ~<
~,,-
..."
" ",•. <"" "',':'
'\;Y"~
Cerebe llum
.\ 'c '\d
1.,); ~_J:.:.)?1
'7 "i / ' ""-
r~ : :;J . ;; .'
~-r~\ ' ~l~~ (above T6 )
Inferior cerebellar peduncle La te ral (accessory) cuneate nudeus Rostral spinocereb ellar tract (RS(T)
L-l
/ (
. >{ (*->.;/ \'-,..1...,,,,,.' Cuneoce rebellar trtlct
"
i~}.-I
Upper Body
,./
_~
: ':
/
! J
\
J! .. '
; .\~~l ~
.L· _ la (to cune(lce rebellar tract) -- . ·- - - - 1··-"'.:.JJJt-c-""--4-.-~-- Ib (to RSCT) Ventral spinocerebellar tract (Vscn -J, <1>- - Do.-sal spinocerebellar tract (DScn __
(1'
i
If\
"7~:';,~";'~ ) r).1 !"~ j .~ --.___.U~\\ .1__-. . ~---.~- ................~. ~\
::to.'~---'-"'-"-----'~_
Anterior w hite commissure
oscn
- Ia(10 Ib (to VSCT)
_
,. Perkins MS,M FA
OllON
'--'-"
RE 111.2: SOMATOSENSORY SYSTEM: SPINOCEREBELLAR PATHWAYS _ _ _ _ _ _ __ ocep tive pnmary soma tosen sory axons - jo ints, tendons, and ligaments (represented afferents from Golgi ten don organs) term i .R o n neurons of o rigin (border cells, dorsal .,., neurons) for the ventral spinocerebellar - ~ and the ros tral spinocerebellar tra ct from the -er and upper body, respectively (16 is cutoff). -nprio ceptive prim ary somatosen so ry axons from ""'.... e spi ndles (Ia afferents) terminate on neurons
of origin (Clarke's nucleu s, laterall external] cuneate nucleus of the medull a) for th e dorsal spinocerebellar tract and the cuneocerebellar tract from the low er and upper body, respectively (16 is cuto ff). The do rsal spinocerebellar, rostral spinocerebellar, and cuneocerebellar trac ts remain ipsilateral. The ventral spinocerebellar tract crosses twice, once in the anterio r white commissure and again in the cerebellum.
215
Sensory Systems- Somatosens.
SYSTEMIC NEUROSCIENCE
•I
\
I
Cerebrum
"
J
Po,"""' hmbor
///-'r\ f
'--"'"
"" "" I""pro _ _-'l.._~_ __
Ventral p
thalolmus
~
p
po;tcentr~1 gyru s
t
"w" "
..... )
""
/
~
'Y
\:"
~
' .j
h
e.'-.-~
CerC'h ral (Ort el( _
•
'/ L1
' ' .J
~
1;
:d'
~,~.;'
I .·.. I..,
,If.
J
J:..-J J
"d~,
J. Pe rkins
M~ MM,
"""""
.' .,.
'''.'',m,,,,
1
.~ 1;'1,. ,~
Midbrain
. 1"'
1-=~' .• 1
.
~' II~
Pons
"'
~,
Medial lem"iscus
./
'.L
trr l ''''y.'Ir'p~v
" -"'ia"\! nlni sc.u s ~l '.
, "~
L we, medun::.
.\
o
I
I' ,.
'j;
.
Gracile nucleus
~ Cu[)€a te nucl e us
/
..
,
II ~
'" .
~
Fas.clculus vae , ,s. fJscicu l u~ c.uneatus~ '\
t
I'"
c"""r' p""r ",", )f"', / \.
•~ ,\
J
IS
,
' j.
lor",,1 ,"co " ,,'"
(decu ssa tion of the me
'
lumbar spinal cordi L ·
.J~
p,"p~o,~: ~~,;,po~ilion
To", ,p
_ ..,
i
n
"b""p"
",
"
I
~m"i"",1
LateralcervICal nuc Ieus (C I -C 2 0nlyl
~ 1~ " ....::
door
\
J' ' \
_.3"-_ --
.~ -~
....-h~..-~'t~ __~.~~ '!!...
""OI"'''''P''OO, '"bSit loll n
- T-"h '''''"' pressure, VI rallO
FIGURE 111.3: SOMATOSENSORY SYSTEM: THE DORSAL COLUMN SYSTEM AND EPICRITIC MODALITIES _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Prima ry somatosensory M axo ns that co nvey fin e discriminative to uch, pressure, vibratory sensation, and co nsciou s joint positi o n se nse project directly into th e dorsal column system, w here they are topographically organi zed (fasciculus gracilis for lower body [below Tbl, fasciculus cuneatus for upper body [T6 and above)). These axons termi· nate, respectively, in nucleus gracilis and nucl eus cunea tus, from w hich the medial lemniscus o rigl
216
nates. Th is tract crOsses in th e medulla and pr to the ventral posterolateral (VPL) nucleus o f tho< thalamus. The VPl nucleus terminates topogra' ca ll y in the prim ary se nso ry co rt ex. The spin o cervical system contributes polysynaptic mechanoreceptive informatio n to supplement that in the do rsal column system. M = myelinated.
SYSTEMIC NEUROSCIE NCE
Systems-Somatosensory
Cer~brum
~
'
C~r~br al corle!C:
r
poslcenllal gyru'-
;,
\
~
"-.-J
.J~. -
~
\
'{
~
( -~"" ' .i (
PO~l enornmb of mt erna l caps ule
!
.
:.j
1\ . , \.:. ".; J I I ~ ·
',..,.
(Vr u nuc1eus of th.llamus
. \ ....
,
·4
JJ
.......
~ ,
,.
r~....
(ce ntrorn edianl
J. Perkins
,....)
Midbrain
NOMpecific
- - --'-:- --,jl-----'-- thalam ic nuclei
.~"
Deep layers of superior colliculus and
",,'''q'''''''''''Y
Pons
lower medulla
Spmothalamlc/sPIl10r~!l cular
\'R ...
u teral leticular formation
"..;
~l
sys tem (irom all spllla lleve!sl ----'
Ce rvical spinal cord
Aowk"
:I~~F'~
lumbar s.p inal cord A01erior
:s::::::::==
".i"
-.
Pain. tempe rature
Polin
,
while commiS5Ure - - ;h ; =
"",
,~:::::== Pain, tempera ture _. - Pain
" RE 111.4: SOMATOSENSORY SYSTEM: THE SPINOTHALAMIC AND SPINORETICULAR SYSTEMS AND PROTOPATHIC MODALITIES _ _ _ _ _ _ _ _ __ _ __ ~ r y somatosensory UNM (C fibers) and small
; 8 fibers) axons that convey nociceptive infor -.' n (fast, locali zed pai n), temperature sensa and light, movin g touch termi nate on neuro ns minae I and V. These neurons send crossed DOS into th e spin othalami c tract projectin g to VPL nu cle us of th e th alamus. These th alami c ...rons project to the secondary somatosensory ":ex (5 11 ), as well as to the primary sensory cor Prim ary se nso ry C fibers co ntribute to a large, .2SCading network in the dorsa l horn resu lting in
bilateral projectio ns into the spinoreticular tract. This system ends mainly in the reticular formation (R F), fro m w hi ch po lysynaptic proj ections lead to no nspeCifi c, medi al dorsal. and anterio r th alamic nuclei. Some spinoreticular fibers termi na te in the deeper layers of the superior co!li culus (spinotecta pathway) and pe ri aquedu ctal gray. Co rti ca l regio"'$ such as the cingul ate, in sular, and prefron tal regio ns then process and interpret noc icepti\ e info rmatio n related to slow, excrucia ting pain. M = myelin ated; UNM = unmyelin ated .
SYSTEM IC NEUROSCIENCE
Sensory Systems-Somatosen"' Spinal Mechanisms of Nociceptive Processing
Gating Mechanism DOrs.)I column aiierent r'
,.~--
--- '~ '
O
...
'.
\
"'\
/~
!
I
.~
/
,'.,
I
j
!
,---
f
I.
~
'j
i
I
/
\
\
\
/
i'·,
iI ~.
"
!
.
,
,j, ,
J
i ,.
~,
Spj nolhc1 l am~ spi norelicu:";' tract
!
\( ,
"
,. Perkins MS, MfA
0 1lllN "" .~"
'-..
-." -..;,
..
.q.r(J '
._".- pYi'=
~ ~ ~ ~ ~
~All'A'A. ·.AlTA.· i,
..__•... _-
FIGURE 11 1.5: SPINOTHALAM IC AND SPINORETICULAR NOCICEPTIVE PROCESSING IN THE SPINAL CORD
- --------------- - - --i
Unmyelinated primary afferents (c, AcS fibers) th at
convey "fast, localized pain" and temperature sensation terminate in laminae I and V, from w hich the crossed spinothalam ic axons originate. UNM primary afferents (C fibers) also termil'late on neu
rons in the dorsa l horn, from whi ch a cascading sys tem of recruitment, convergen ce, and po lysyn aptic interconnectio ns o riginates. Th is system con tributes to the spinoreticular trac t (ma inly crossed),
218
which projects into the RF and th en project~ synaptically to nonspecific, medial dorsal, arc an terior thalamic nuclei. It contributes to perce" tio n of excruciating pain and its emoti onal Cor-' tatfon via cortica l regions such as the cingula:? insular, and prefron tal cortices. The gatin g mea. ni sm, shown o n th e left allows prim ary dorsc.: column axon col!aterals to dampen pain proa!!l ing in the dorsal horn.
SYSTEM IC NEU ROSCIENCE
Systems Somatosensory ~s
of Neuropathic Pain - ... S 01 sympathetic postganglionic nerve fibel'> on 10 affe renl ending~ and 1 ~ sensory ce ll hodies_ :t-d ~ hre5hold for firing of C fibers (hype resthesia) and AS fibef"S (allad yn ia). ore-atio n of a-
0
Cenlral seroto ni n .md cenllal norepineph rine p ath ways
o
Preganglionic sympathetic fib er
Sym pathetic chain ganglion
~
J. Perkins .vIS, MfA
Q~
RE 111.6: MECHANISMS OF NEUROPATH IC PAIN AND SYM PATHETICAllY MAINTA INED PAIN _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ __
- cascading dorsal horn system-which receives ·-..ary afferent C fibers of nociceptive origin - projects into the spi noreticular system for the ious interpretation of excruciating and neuro - ic. pain-is illustrated. The sympathetic connec-s in ad dition to secretin g norepineph rine into oIood and activatin g the secretion of epineph € can synapse with terminals and cell bodies of
primary nociceptive neurons in neuropathi c pain syndromes. Descendin g ce ntral noradrenergic and serotonergic projectio ns are also shown. Specific mechanisms relevant to neuropathic pain, particu larly complex regional pain syndrome (reflex sym pathetic dystrophy), are described in the numbered sites.
219
Sensory Systems-Somatosen-
SYSTEM IC NEUROSCIENCE
From cer ebral from hypori1al<Jmus Stimuli from higher cortE'X and (i ncludes betacenter, (P'iydlOendorphin axonal limbic forebrain logical, pLacebo ~ projec.tions] effect, etc.)
From sensory cort ex
~ -t~ ~
.
,
..
'
'\
Eo'eph, "o ooo,,'o'o, ",''co
." - Periilqued uda l gr'IY ma il er
>.,
"
.
~_~
m~"
t \ IF ~-'K. tngen1 u1al nerve _________-.. . .. . ... . '~. L " ,"-,"-
Anee,", pa'o In
LOM
egmental
'goc " II gmups
-I
,'
~
\
• ' ;
M'db,,'o
, , , ,f' \\
~ -
' ( .,
.
\"
..!"
/
h -n-containing neuron
'okep " '
/
/ / "..;
d' /
,.'
,
4
I
.
Medu'"
:-N '
I
t
)
5 1
t \
.. -.:
Corliconudear fi ber~
!
.r.--.~ 1 , ;;' I
, f., "I ~:
"
J Llte'" cetlcul" lo,m,,'oo
•.•.
,;
.......:t;
~ . I
I
'. &
palhway~
l era l lu n iculu~
'.
,
..
~",
Serotonin
'
I
palhWay~
Descending no repi nephrine
Pos,e, o'a
)
OU'I'USY'"~ ' 11 IstJ"
",""m,,', ,m, oed ",",00
norJdrene'
."
ru,e
Sp,"llogemm"
,,,,,;tem I
L
pathway
D ecussa tio n o f the pyra mids
An terolatera l fu niculus
-~ ~
'! Il~ lI \. "" \ Sp'oa' wd ; ') ~ , :. ~".L . .-. .~· -· ~'} ~'" ~~~~ /" /'~ / ·4"''' ' ' -- ~..... :-....~,~ 7~'-"" _ ,l , ~ t - ,..-...~ , 'I,I)
Afferent pain neuron - / /
I
"',
o f dorsa roo ,gan~ho) .' n
. 'i,iiJtFJ'.
--~
. .
Spino rE'ti cular neuro n
" ".
~".;;;. , ".~~"'~ . .Y-"-'''''''''''''~~
I."";'" ".~I .
tI ,I.~
FIGURE 111.7: DESC END ING CONTROL OF ASCENDING SOMATOSENSORY SYSTEMS _ __ Descending connection s from the cerebral co rtex, the limbic forebrain structures, the hYPolhalamus (the paraventricular nucleus and the periarcuate beta-endorphin neurons), the periaqueductal gray (PAG), the RF of the brain stem, central noradrener gic neurons (of the locus coeruleus and other brain stem tegmental groups), and sero tonergic (S·Hn
220
neurons (nucleus raphe magnus) modulate the processing of nociceptive information in the c:ic:J horn of the spinal cord. The central descendirr; noradrenergic and seroto nergic pathways, inilu enced by the PAG and other higher centers. 2-e important for endogenous (and exogenous) r lation of pain.
Sensory Systems- Somat
SYSTEMI C NEUROSCIENCE From cef"ebral
r-mn1 hypothalamus
Stimuli fr om higher
From
cortex and
{indude!i beta
cen t~r s {ps~'ch o·
~enso r y
logk'
(;(lrt ex
limbic forebrain endorphin axonal ~ projections)
effect, etc.!
~. -~'~ -/ 1S¢ * , /
. ,
E"'.ph,I;"<0"" ;";"8 "'"'''''
:..._..c :>'~<-_ _
t
. .
'\
I>eriaqueductal gray m
.,
Midbra in
locus coeruleus
~f(e~ent pain ribers
\_. !" ...... '" t".'m; ~" "en', ~ '\"':"!~ SPinallrisp.nlimd7 -- ' i"l ·· ·
-,
.,/
!rJet and nucleus
:
Enkephalin-coru aining neuron
.
h
Brainst emtegment al~
no radrenergic cell groups
~ ~i -
':
•
Descending norepine Phrin.e pathw,ly
Serotonm p.lthway
7
a "" ,r,
,
I
Medulla
Coniconudear fibers
d
Posterola teral funiClJlus
j
' !=E
\.' ~
_' Latera l ret icular (orm atioc.
Spinore lic ular pathway De c u~sa ljoll
of the pyraf"1;
~ An l erolaler,,1
Enkephalin
Afferen t pain neuron o f oorsal foot ga n ~ ion
.?
1~'''''
II! t~ {
•'" " "
f-
----r-
--
\
A
·.. ··---_ _L:.:.;~"'"-
'
---f-'
..
... -;tJi/#Jt ,,
Spinoreticular neuron
funiculus
"
Spinal c(
-"
....~ .,....------' '" - ,
.\,.
'-._ ;
~~--..,
\
tf ~
".
't
FIGU RE 111.7: DESCEND ING CONTRO L OF ASCENDING SOMATOSENSORY SYSTEMS _ Descendin g connections from the cerebral cortex, the limbi c forebrain stru ctures, the hypothalamus (the pa raven tricu lar nucleus and the periarcuate beta-end orphin neuro ns), the periaqueducta) gray (PAG), the RF of th e brain stem, central noradrener· gic neuron s (of the locus coeruleus and other brain stem tegmental groups), and serotonergic (S·HT)
220
neurons (nucleus raphe magnus) modulat processin g of nociceptive information in II horn of th e spinal cord. Th e ce ntral descel noradrenergic and seroto nergic path wa~ ~ enced by the PAC and other higher cente important for endogenous (an d exogenol! lation of pain.
-
~ns
SYSTEMIC NEUROSCIENCE
- ory System s- Tri geminal
,
Cerebr,J1cortex.
1-- (:",,~ ,"j. nudc~
(ntem.ll capsule
(i nlr;,t;.,minilr)
f--- v,,,,,,
po slerolTlff:iial N PM ) ,,,-,de us ()/ th;JJ;u ,"IUS
Midbrain I mesenceph,J1rc nudeus
Dorsal tli ~mina J ~mn"j'K~~_---=~~~~ ~
(dors~l l.i8c'ninolh,)l,)mi( If.
.
Venrr"llri~emin.'1
,
(venfldl trfgen,inOlh,..l.lmic (•.act!
tl!mpl!. "IUrf - -
Pontine
Propfioctptio n ' f,om mu sd.. . pi nd l... -
. .'". ~.
<~~~s;:~'
,~.
,./
~~2~~' ~
.
\
.oot oi m.lndibul.!.r n.
r~i'~<~"'~"~~~~;:~~~~~~~
Later,,1 r
I
Medi~ lr
Medull"ry Venlral trigemin.J11 Spin,,1
(ngcmin..1
Spin. 1
,
mgemin,,1 nucleus
I
.r I
I
I
Ccrvi.cal spinal cnrd
9G URE 111.8: TRI GEMINAL SENSORY AND ASSO CIATED SENSORY SYSTEMS _ _ _ _ _ __
-
- IJ)ns of primary sensory neuro ns enter the brain -:::I"n, travel in the descending (spinal) (ract of V rid terminate in {he descendin g (spinal) nucleus of -\xons of the trigeminal ganglio n (V) supply the e, the anterior ora l cavity, th e teeth, an d th e _...ms; axons of the geniculate ganglion (VII) and e ju gu lar ga nglion (X) supply a small zone of th e ~'e rna l ear; and axons of th e petrosal gangli o n (IX) oply general sensa tion to the posterior oral cavity .-xl fhe pharynx. Axons from the descending cleus of V project into the crossed trigeminal miscus (ventral trigeminothalamic tract 1VTT11 " "1ich termi nates in the ventral posteromedial .. PM ) nucleus of the thalamu s. The V PM nucleus ojects to the lateral primary sensory cortex (51)
and to in tralaminar thalamic nuclei, w hich are asso ciated w ith nociceptive processing. The caudal descendin g nucleus of V also sends bilateral prOjections to the RF to process excruciating pai n (similar to th e spinoreticular system). Primary sen so ry axon s that carry fine discriminative modalities from V (simi lar to th e dorsal col umn) te rminate in the rostral descendi ng nucleus of V and the main sensory nucleus of V, w hich contribu te to the VTTI. A po rtion o f the main sensory nucleus also projects ipsilaterally to the VPM nucleus. The mesencephalic nucleus o f V, a primary nucleus inside the (NS, mediates muscle spindle reflexes for masticato ry and extraocular muscles.
221
SYSTEMIC NEUROSCIENCE
Sensory Systems-Taste
-
SenSi
B. Sccti(Jn through vallate papilla Foliate papillae
--.... T,,~t .. buds Duct of gusta tory (Ebner's) gland
M"""
Fun giform
t
papillae
and M of Irigi
C. Tule bud
~EPithelium
Va llate pa pillae:
Basement membra ne
M icrovilli
Taste pore
~"_.
Nerve p lexus
," # I),h T:--- Nerve fibers emerging itom taste buds
LMge nerve
fiber Intercellular
Fibroblast ~ Small nerve fiber
largE! nerve fiber
Collagen
De!tmosomes
low€" oblofl;!
Schwanncell
C ranules _ _
Basement membrane
Epithelium ----.j
Pee
o i~
D. Detail of taste pore
E. Detail of base receptor cells
~~p
OIIl!N
: ......... 1I
f iGURE 111.9: ANATO MY O f TASTE BUDS AN D THEIR RECEPTORS - - - - - - -- - IGURE III Taste buds are chemosensory tran sducers that and posterior regions of the tongue and, less fre'rimary sen consist of bundles of columnar cell s that lie within the epith elium. They translate individual molecular configurations o r combinations of molecul es for salty, sweet, sour, and bitter sensations into action potentials of both small and large primary sensory axons. The taste buds are found on the anterior
222
quently, on the palate and the epiglottis. Nerve anglion (\ /j fibers for taste show complex responses to electr~ odose (infE cal activity across populations of many nerve fibers. le anterior The integrative interpretatio n of taste takes place -'lird of the I
the e NS.
~spect ivelv
.'
irt of th e n. ,et), which
SYSTEMIC NEUROSCIENCE
ry Systems-Taste
venlral poste romedial (VPM) nucleus of thala mus
Sensory cortex (just below
face area)
Lateral hypothalamic area
Amygdala
Ponti ne taste area (parabrac hial nucleus) Trigeminal (V) n. Trigemi nal (semilunarl ganglion
;e;;encephalic nucleus _ ''Iotor nucleus - ·.,geminal n.
~~'%l~~M;n ~' ldibular n, Pons - ---"-""Pterygop alatine gan8iion
Greater petrosal n. = = = =+ - -Lf.:P"j?fll f
Ne~e ofote'",oiid canal
Geniculate ganglion Facia l (VII ) n. and Nerv us intermedius ROSlral part of nucJeus of solitary tract -~Glossopharyngeal (IXl n. - - - --f,
-
---+\.(-- -~
Lower parI of merlulla oblongata
Fungiform papillae
Foliate papillae
"
",-, " "Ihi
'"
papillae
"""
Petrosal (inferior) ganglion
of glossopharyngeal n.
Nodose (inferior) ganglion of va gus n. - - -_ _/ Vagus (X) n.
'I CU RE 111.10: TASTE PATHWAYS _ _ __ _ _ _ _ _ _ __ __ _ _ _ _ _ __ :>rimary sensory axons of neurons of the geniculate .,anglio n (VII ), the petrosal ganglion (I X), and the ~o dose (inferior) ganglion (X) supply taste buds in Ie anterior two-thirds of the to ngue, the posterior mird of the tongue, and th e ep iglo ttis and palate, ·espectively. These axons terminate in th e rostral part of the nucleus solitarius (nucleus of the solitary 'ract), which sends ipsil ateral projections mainly to
the parabrachial nucleus in the po ns. The parabrachial nucleus pro jects to the VPM nucleus of the thalamus, the hypothalamus (lateral hypo thalamic area, paraventricular nucleus), and the amygdaloid nuclei. These no n thalamic projectio ns are associated with th e emotio nal, motivational, and behavio ral aspects of taste and food intake.
223
Sensory 5ystems-Audiror~'
SYSTEMIC NEUROSCIENCE
Umhs ,,{ c bn _
front al section
Prominence of lateral semicircular CJncll
of stapes in oval (vestibular) wi ndow
Incus
Tegmen
Semicircular duCtS, ampullae, ulricle and saccule Facial nerve (VII) (cut)
Epitympanic
Vestibu lar nerve
Auricle
I acou stic meatus Veslibuloco chlear nerve (V III)
j'.
" Tv
R, \~
l
to
"
External Scala vestibuli
acoustic meatus
Cochlear duel
Cochlea
containin g spiral organ (COrti)
,
Pharyngotympanic (auditory) tube
I
Scala tympani
N o te: Ar rows inDICate course of sound wav~s
~~p CIIl!N I~·.W;~
FIGURE 111.11 : PERIPHERAL PATHWAYS FOR SOUND RECEPTION _ _ _ _ _ _ _ _ __ The sound transd uction process involves move ment of mech an ical so und through the externa l
ea r and the external acoustic meatus. across the tympanic membrane, leveraged as a mechanical force by the bones of th e middle ear (ossic1es) via the oval window to produce a fluid wave in the cochlear duct This fluid wave ca uses differential mOvement of the basilar membrane, stimulating hairs on the apical portio n of hair cells to release neurotransmitters that stimulate primary sensory
224
axons of neuron s of th e cochl ear (sp iral) ganglion. The basi lar membrane in the cochl ea shows maxi mal displacement spatially accord ing to the frequency of impinging to nes. with low frequen cies stimulating the apex (heli cotrem a) and high frequencies stimulating the base. The eustachian (pharyngotympanic) tube permits pressure equilibration between the middle ear and the outside world .
Fie
Th e
Yes !
can roUi incu
mer
SYSTEM IC NEUROSCIENCE
""6lsory Syste ms-Audito ry
Bony a nd mem branous labyrint hs: sch e ma Ampullae
Anteri or semici rcular canal and duct
,...,=~-
~o?I'io r
semicircular
- cln d duct
Dur,l mJter
Endolymph atic sac Endolymphatic duct in
ve stibular aqueduct
-" lon body and
.e-:branou s limbs
Utricle
al semicircular
and duct _ _
~
Saccule
capsule _ _ __ Ductus reuniens
"'!PeS in oval ~,:, !lula r ) window
-panic cavity _ _ _ _ _-.:::~
-".'nal acouslic meatu s - oo ------------~
- "'panic membrane Cochlear Jqueducl ••md (cochleClr) "
:occondtlry
-,J
AG URE 111.12: BONY AND MEMBRANOUS LABYR INTHS _ _ _ _ __ _ _ _ _ _ __ --~ relati onship between the cochlea and the
3tibular apparatu s (utricle, saccu le, semicircu lar -.a ls and du cts) and th e bony labyrinth that sur" ds th em is illu strated. The ossicles (malleus, "IICU S, stap es) leverage move ment of the tympanic l1brane to produ ce movement of the oval
window. M ovemen t of the oval window causes th e tluid wave to move through the scala vestibuli and th e sca la tympani of the coch lea and ricochet onto th e round window. The 3 semicircul ar can als are located at 90° angles to each other, represe ntin g tilted X, Y, and Z axes.
225
SYSTEMIC NEUROSCIENCE
Sensory
Systems-Audit ~
Seelion through turn of cochlea ves tibuli (perilymph w eakly +)
Osseous spira l lamina
Vestiblilar (Reiss n.,...-,. membrane
Nerve fibers
(endolymph + 80 mV)
Spiral ligame.-;
Modiolus of cochleus
'ic.
membra-. $pirJlga nglion _ _
Spiral Qrg-,,- (Coni)
Scala tympani - _ _- ' (perilymph 0 mY)
Cochlear nNve
Osseous cochl ea
Inner hair cell
~{p
OIl!!N
:;·:.... : 1
FIGURE 111.13 : VIII NERVE INNERVATION OF HA IR CEllS O F THE ORGAN OF CORTI _ _ _ _ Primary sensory axons of th e sp iral (coch lear) gan glion innervate inner and outer hair cells of the organ of Corti, located on th e basilar membrane. Th e axons are activated by release of neurotrans mitters from the hair celis, wh ich occurs when the
hairs o n the apical surface are moved by shearing 226
forces from movement of the fluid basilar mem brane in re lation to the ri gid tectorial membran e. This represents the complex transd uction process of the converting external sound waves to action potentials in spiral ganglion axo ns.
FIG l Fluid
the h
panll orgar
MOVE
ial mE resul t:
~m5-AuditOliensory Systems-Auditory
.al rRej ~sner's)
M
~ mV)
-- Spiral ligament
5. Short waves (high frequency, high pitch) base of cochlea
1. Sound waves impinge o n ear drum, causing it vibrate
ochlear ducl "'Idolymph 2.0ssicles vi brate as
SYSTEMIC NEUROSCIENCE
,.K'''! 3. Stapes moves in and out of oval
4. Sou nd waves transmitted up scala ves tibuli in medium or its contained perilymph
Long waves (low frequ ency, low pitch) at apex of cochlea
Distort Reissner's membrane and basilar membrane of cochlear duct and its contained organ of corti, thus stimulating hair cells which are ill contact with the tectoral memberall e. Impulses thell pass up cochlear Ilerve.
,
- Tectorial membrane
Spiralorgall Corli)
"-'ilar !embrane cochleJ
8. Impact of wave on membrane of
l:oN ";.','::
round window causes it to move in and out at round window in opposite phase to oval wi ndow
7. scala tympani in medium of its contained perilymph
6. Wave transmitted ac ross cochlear duel in medium of endolymph. from scala vesti bul i to scala tympani. (Note: wav~ may also travel around helicotrema at apex of cochlea.)
-
FIGU RE 111.14: COCHLEAR RECEPTORS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
,.
Fluid movement through the scala vestibuli, around the helicotrema, and ba ck through the scala tym pani moves the basilar membrane on w hich the organ of Corti and its hair cells reside differentially. v\ovement of hairs by shearing forces of the tector ial membrane on the apical portion of the hair cells 'esults in their depolarization and in the release of
55
neurotransmitters. This release stimulates action potentials in the primary afferent axons of spiral ganglion cells. Efferent axons from the olivo cochlear bundle that ca n modulate the sensory transduction process and the excitability of hair cells are controlled by descending central auditory pathways.
227
SYSTEMIC NEUROSCIENCE
Sensory Systems- Auditor y
/ AcouSlic ilrea oi
lemporal lobe corlex Medial geniculate body
Brachium of
inferior collkulus
Inienor colliculus--ff1.f Midbrain
"~' ,~
,, ~
L..' lerillremniSCi ~
a nd acoustic a rea oj corlex: _ low tones _ Middle tones High tones
~
Medulla oblongata
Superior o livary comp~x
Dorsal cochlear nucle us
lnle rior cerebellar peduncle ,- - - Vemral COChle
II / Cochlear division of veslibulocochlear nerve
,/ '/
~!p
Intermediate I-!elicular
acoustic slria
forma tion I
Trape zoid body Iventral acoustic stria)
.Ii
Hai, ce lls
"':',':!UN ...'::
FIGURE 111.15: AFFERENT AUDITORY PATHWAYS _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Ce ntral axon projections of th e sp iral ganglio n neurons terminate in dorsal and ventral cochl ear nuclei in several to notopic maps (shown in th e cochlea in colors). These cochlear nuclei projec t into the lateral lemniscus (LL), via acoustic stria, but many projections remain ipsilateral. The LL ter minates in the nucleus o f the inferior co lliculus. The inferior colliculus, in turn, projects via its brachium to the medial geniculate body (MGB) of the thala, mus. The thalamus sends to notopic projectio ns to
228
th e pri mary auditory co rtex on the transverse gyru s of Hesch!. Th e accesso ry audito ry brain stem nuclei (superior oli vary nucleus for lateral sound localization, nuclei of the trapezoid body Ino t shown I and the LL) send crossed and uncrossed proj ections through the Ll. Because sound is repre sented bilaterally, a unilateral lesio n in the LL, the auditory thalamus, audito ry radiatio ns, or audi tory cortex results in diminution in hearing and auditory neglect contralateral to simultaneous stimulation.
,ditory
SYSTEMIC NEUROSCIENCE
Se nsory Systems-Auditory
Excitatory e ndings Inhibitory e ndings -+ _ -+ Intermediate endings - "" ~
l
Temporal cortex
Fib~(5 may be
'nf" ' ;"rcoH;cul,, , }
eXCltdtory or
inhibitory
", Brachium o f inferior co llicu lus Inferi o r colliculus
Tympa ni c memb rane Nuclei of
lateral
.~~~_ _ _--;:~ .
lemnisci - - - -"" -
Middle ear
Stapes
(-l~~S~~~==t===T;:r~~:n:;n" ,oe"" fibers ::::::::::",,?J-;?'~l:-
n ucleus of tri geminal n.
I nerve fibers ~-C'o ,,;, '
cochlear nucleu s
<.-.\-_-",""",1 cochlear nucleus / ':ff"'enl ol ivocochlear fibers (inhibit hair cell s and afferent nerve term inals via coch lear division of vestibulocochlear nerve)
) fOfmalion
Tr,'lpezoid body
N
". "
Superior olivary complex ~IG URE
iem j j
pre
e
lr\
A"erenl nerve fibers
111.16: CENTRIFUGAL (EFFERENT) AUD ITORY PATHWAYS _ _ _ _ _ _ _ _ _ __
:Jescending pathways travel from the aud itory cortex, the MGB of the thalamus, the inferior colliculus, and accessory auditory nuclei of the '"train stem to caudal structures in the pathway to ~e r mj n a te in the cochl ea r nuclei and the superio r olivary nu cleus. These centrifugal co nn ections oe rmit descending contro l of in comin g auditory ,ionn atio n. Th e olivocochlea r bund le from the
superior olivary nuclei projects back to the hair cells in the orga n of Corti to modulate the trans duction process between the hair cells and the primary afferent axons. The moto r nuclei of V and V II send LMN axonal projec tions to the tensor tympani and stapedius muscles, respectively, to dampen refl exes of the ossicles in response to sus tained loud noise.
Dr\
n.
229
SYSTEMIC NEUROSCIE NCE
Sensory Syslems- Vestibu icr B. Position within base of sku ll
A. Me mbrano us labyrinth
Canals
Superior Vestibular
semicircular
Po~tl!rior
superior
Plane o! horiZOflld1
GllliJl a nd
V'fide
Ve stib ula r and cochlear divisio ns o f ve5tibulo
H ori zontal
/.... ' -' . ~---::-~
cochlear n.
._~ '-~ P1~nc
of sacc ule
Cochlea r duct
,
Plane of superior canal
'
Svperior
;C"!~'
Horh:onlal
("-..1 '
ampullae
r
semicircular canal
Opposite wall ~~ o f amp ulla _ _ _ _
E. Structure and innervation of hair cells
Excitation
•
Gelatinous cupula- - - Hair tufts
Hair cell s::---
Nerve fibers
t
I
)1.1)
iii,
l!2
~
Hair cell (type I)
O. Section of macula
Po~tel i or
PlMleof po51erio r canal
C. Section of crista
Affelefll nerve
,
Effe renl nerve
Basemenl
.
. 1& ;lb:~
L .Ulr.~ H air cell (rype II) Supporting cells ~
-......---Efferen t nerve endin g
~ Affe(ent nerve
""'"
. /M yelin sheadl
~~!%
CIIiiI\I ; ......; : :
FIGURE 11 1.17: VESTIBULAR RE CEPTO RS _
_ _ _ __ _ _ _ _ _ _ _ _ _ _ __ Th e ves tibular receptors includ e hair cell s in th e crista e ampuliaris of the utricl e (lin ea r acceleration · or gravity) and saccule (low-frequency vibratio n) and in th e maculae of the o rthogo nall y orien ted semici rcular canals (angular acceleratio n or move ment o f the head). Hair tufts fro m the cristae ampullaris and the maculae are embedded in a gelatinous substance, w hich is moved by gravity (utricle) exerting force on the calcium ca rbonate
230
crystals (oto liths) resting on top of the hairs, or by fluid in a se mici rcul ar canal (h ead movement). Ben ding of the kinocilium in the hair tufts depolar izes th e hair cell, causing the release of neurotrans mitters that stimulate actio n po tentials of primary sensory axons o f the vestibular (Scarpa's) ganglio n. Additio nal efferent projections fro m the e NS mod ulate this transduction process.
estibular
SYSTEM IC NEU ROSC IENCE
Sensory Systems- Vestibular
~ Su~~pe'~ : I';;O'} I
Vestibulospinal Tracts Excitatory endings Inh ibi tor y endings _ _
7-+'----f'<~-;I
-
Vt'stibular nudei Ros tral
Ascetldln8 'Ibers in medial lo ngitud in al fascicul i _ _ _ _L-<1'
Tmnk
~
Ve ntral
Caudal Somatolo jlica.1pa tte rn In la teral vestibula, nucleus
.,
Motor neuron
(oontfOliing .,,' m"'"<"'''Jt:~ Med ia l ve stibulosp inal fi bers in media l
Fibers irom c ristae
Lat era l
Vffi..i bulot p inOiI
(fOt,ltional
~Ii mu lj)
"'''
interneuron Inhibitory interneuron
~== To flexor muscl es
Lower
-
e ll)
ells
To axia l mu sdes
F iber~ from maculae (gravitatio nal ~limull )
- - -<1===:::3' I
il
ending Lumbar part of spinal co rd
To eXlensor muscl es
Inhibitory ending
To axial muscles """;',,,o ,yending
"--l"'...' vestibu\ospi J'l all r.lcI
\
~=:: To flexof musd es
-
To exten!oOf ml1S£lei
J{p
tT
01lliN , ·.·: ··.. : 1
-
FIGU RE 111.18: VESTIB ULAR PATHWAYS _ __ _ _ _ _ _ _ _ __ _ __ _ _ __
by
Primary afferent vestibular axons fro m the vestib ular ganglio n terminate in the superio r, inferior, medial, and lateral vestibular nuclei and directly in the cerebellum (deep nudei and cortex). Descendi ng axo ns are sent fro m th e medial vestibulospin al tract (medi al nucleus) to spinal cord LMN s to regul ate head and neck movements. Descendin g axons are se nt from the lateral vestibu lospinal tract (l ateral nucl eus) to all levels of spinal cord LM Ns to activa te extensor mOvements. M ultiple vestibular nuclei project to the cerebellum
lar
ans
ry Ion.
od·
to modulate and coordinate muscle activity for basic to ne and posture (shown in figure 111045) and to extraocular lMNs via the medial longitudinal fascicu lus to coordinate eye movements w ith head an d neck move ments . Some ascendin g axons from the vestibular nucl ei may reach th e th alamu s (nea r VPM and posteri or nucle i), with projection s to th e lateral postcentral gyru s (area 2, mo ti o n per ceptio n and spa tial orientati o n) and th e in sular and temporo parietal co rti ces.
23 1
SYSTEMIC NEUROSCIENCE
Sensory Systems-Vestibular
Slow phase
I'
"
~
mainT;Jin~,~~e~~~~.~Ie'ation ~ : '~ \ Hori~onlal
Ho, j2ontai semicircular
/ _-
~ ,~
.,_
(a na l excited
semi(.ircuJar canal dej)l'e~sW
,
Rapid phase (saccadic movement»-----
~
.~~ maintain~~~I~raTiun ~.# Horizoolal vi \.. H".ri~()nl" ~('mK I(c.ular
unil.' InpUT
;rP ,
_,c,'
("t-l.
tJ..
r 1 1"-.
' ";
seomlclrculJ"
-\.
canal depres~e,c
conhnues,
but is
opposed by Medial rectU $
Medial r~I US nlOlor neurons depressed
V
moto r n~~;~~s ~ exdted -------"" ~
Abducens imernudeil' neuron
Ascending tr.:ad of Deirer5
nucleus depressed
Medial rectus motor neuro ns exCited
\
"
ce nle, Medial
Abd ucen<
_ _ _ _ In/1ibi torv
Il Ucltc'Ui
intemeu(on~
depressed Vestibular nud ei
Medi..!! and lateral vestibu lar nudei, e~cited Abdu cens
inhibition imm sat:oOO::
nudeo s exdted
bun, interneu ron
depressed by saccadic cen teo'
:,t ,~
I
I
- Excitol tOI\ bur,;
"'"''''''''--'''''''''''''f''' \-- Abducen~
(VI) nerve
Parapontine reticular fo rmation
Abduc ens nucleus e};cited by saccadic
interneuron
Oculomotor (III)
nerv~
(PPRF) (III)
Laler" rectu, muscle
La teral
recws muscle
Lateral rectus
~ Eyes move in opposite direction to head; tend to prt!~t!rve visua l iixiltion: rille determin ed by degr ee oi hOri20ntal canal exci tation
Laler al rec lus muscle
---
---
Eyes sna p bac k in same direction as head
~~p
CJ I@N
:'<\"',:;
FIGURE 111.19: NYSTAGMUS Nystagmus, the alternating back-and-forth move ments of the eye, requi res central coordination of extraocular LM Ns and eye movements. O pto kinetic nys ta gmu s~ the v isually activated movement o f the eyes via tracking mechanisms, allows the eyes to return 10 a forw ard positio n by visual association cortex projections through the superior col liculus to extraocular LMNs. Vestibular nystagmus involves vestibular projections via the
232
medial lo ngitudinal fasciculus to extraocular nuclei (LMNs). The slow phase (or drih) of vestibular nystagmus results in the provocation of eye move ments as if the head were turning. It is caused by asymmetrical input fro m receptors of the semi circular canals o r from damage to vestibular nuclei o r the vestibular cerebellum. The fast phase (saccadic movement) is the provoked return to a forward pOSitio n.
:stibular
SYSTEMIC NEUROSCIENCE
ilenso ry Systems- Visual Ho rizontal sect ion ~"""" of lens
Scleralvenous sinus (Schlemm's
/Cmo" c hamber
,C'' '''I processes
--, Ciliary parI o' ,e."",_,
orizonlaJ r.icircula; epressed
IS
-eldon o f lateral rectus muscle
,Te" do, of media l rectus
muscle
motor
e.~ ciled
duc:en~ nu cleu~
lre.sed _bilOry burst ~e l.Jr O I1
ta ror)' b ur~ 1 ~ur OI1
O ptic (visual)
..ller,,1 re<:lu<
'lUsde
part
V itr eous body
Choroid Hyaloid canal
Perichoroidal m,,-p/
' -_ _ Lamina cribrosa of sclera
Sclera
i!jN
.... ,'
clei
\ e
fascial sheath of eyeball (Tenon's
~Vp"i,
,;,,,,,'el/
nerve (II)
/ ':e,",,' relinal artery and vein
Fovea centralis "0 m"
u';
O uter sheath o i optic oe,ve -"-Subarachno id '~' CP'/
FI GURE 111 .20: ANATOMY OF THE EYE _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ --"ere are 3 major layers of the eye. The outer layer, ;:he fibro us tunic, consists of the protective cornea '"ansparentJ and sclera (opaque). The middle layer, ...., ~ vascu lar tunic (uveal tract), cons ists of the
epithelium of the posterior iris. The retina contains the photoreceptors for transduction of photon en ergy into neuronal activity. Aqueous humor is secreted fro m blood vessels of th e iris into the
"'(Koid the Ciliary body, and the iris. The transposterior chamber and flows through the pupil into .p ' biconvexlens surroundedbya capsule of the dnterior chambet; where it is absorbed into P::' /5 suspended!/om tile Ciliary process the trabecularmeshwork //}/O Scillemm s canalat ~. me 1/717er layer, Me laterlldl tile Ii7dOcornealangie. Claucoma results when "'t:> neuroretli7a, the nonpigment absorption ofaqueous humor is blocked Vitreous
a..an body, and the pigment
humor fills the interior of the eyeball.
233
SYSTEMIC NEUROSCIENCE
Sensory Systems-Visual
.Posterior ~miling I~min a (Dcscemel's membrane) Endothelium of an terior cham ber
TrOlbewlar meshwork ;mo spaces o f iridOCOIfleal an gle IFonlanaJ
Cornea
St;ieral vt'nou~ ~inus (5chlemm's I
Sc.Ieral spur
Pectinate ligamen t, ........ jnr arte rial circle of
"nlerior ciliary I'ei~
~. Anlerior chamber ~FOldsof iriS
M inor
d lcle of iris
Ciliary pr0ce5S Merid iona l fibers
Circ ul ar fibers ./
....
~
( ili.ny muscle
-
Nucleus of len$
,.
Zonular fibers
~I ichnroinal
spiKe
G liill)' body
Ug.tment of le nSI
Pigment epithelium iiridial part o f retinol)
Capsule of l en~ Sphincter muscle of pupil
Notl:!: Fur daril),. Ollly single plane of zo nular fiben sh own; aau.l l ~. fibcf"s surround entire cirOJmference of lenr;
FIGURE 111.21 : ANTER IOR AND POSTERIOR CHAMBERS OF THE EYE _ _ _ _ _ _ _ __ The ciliary mu scle and the pupillary co nstri ctor mu scle are supplied by parasympatheti c post· ganglionic M nerve fibers from the cili ary gangli on (preganglionics in the Edin ger·Westphalnucieus, axons in CN III). Ciliary muscle contractio n reduces the tension on zonular fibers and ca uses the lens to curve, w hich induces accommodation for near vision. In the pupillary light reflex, light shone in one eye en ters the CNS via the optic nerve (CN II) (afferent limb) and terminates in th e pretectum . euro ns of the pretectum project bilaterally
234
(crossed axons through the po sterior co mmissure) to the Edinger-Westphal nucleus. Thi s nucl eus projects to the ciliary gangli on via e N III (effe rent limb), whi ch res ults in both direct (ipsilateral) and consensual (contralateral) pupillary constriction. The pupillary dilator muscle is supplied by sympa· thet;c postganglio nic UNM nerve fibers from the superio r cervical ganglion (preganglio nics in Tl
I
a
a
o
n
C
and T2).
a
M = myelinated; UNM = unmye linated.
a
If
Visual
SYSTEMIC NEUROSCIENCE
Se nsory Systems-Visual Re tinal lay!1"5
Visual R ~ce ptors A.. Eyeball
Nerve Iber l¥
Cells Jnner limiting me mbratl('
r
~uriJce
Inner plexiform Llyer
oi
w:niculale body
"
Inner nuclear layer
II I cell i5uppor lill!; ~d i a l ce ll ) IJipo),,.. ce ll
Oul~r
Amelre ine cell
plexiiOlm
fa\"ef
OUler nvdeal layer
choroId
PhOIOIKcplo r
I,,.,
B. Section
Pijtll)Cf1 t
,
I U'il~
i
th rOug h retina
ep'lhO!liu m
Cone photoreceptor
Rod Photoreceptor
I
Outer plexiiorm layer
O. Rod in liSh'
Nuc levs hiller
segmef1 1
!CURE 111.22: THE RETI NA AND THE PHOTORECEPTORS _ _ __ _ _ _ _ _ _ __ _ -~e
retina, a tissue-thin piece of eNS containing -.e photoreceptors, is attached to the vascular c at th e ora se rrata. The o uter segments (rods cones) of th e ph oto receptors are embedded in . ment epithelium to prevent backscatter in the ~ er part of the retina. The rods and cones con l synap tica lly with bipolar cells, which in turn nect with the ganglion ce ll s of the retin a (equ iv t of secondary sensory nuclei). Horizon tal and ;.acrine cells provide ho rizontal interco nnections ....e retina. In the macul a {3 mm in diameter), th e
fovea centralis (0.4 mm in diameter), the central point for visual focusing, consists of cones for color visio n (p hotop ic), w hich project, with very little conve rgence, to ganglion ce lls. The periphera l retinal pho to receptors, mainly rods for night vision (scoto pic), project, \-vith great convergence, to ganglio n ce ll s. Rod light tran sdu ction invo lves co nve rsio n of II -cis-retinal (fro m rhodopsin) to an all-trans form, provoking calcium influx w ith hyperpolari za tion and a decrease in sodium co nductance.
235
SYSTEMIC NEUROSCIENCE
Sensory Systems- Visual
Corn€ i I ~----"" A nterior chamber ~ ..
Minor anerial circle of iris
Major arlE'fial circle of iris
Scleral venous sinus ISchlemm's 1.:<1( 011)
Blood vessels of ciliilry body Bulbar conjunctiva and conjuncliv
IlenS
Iridocorncal angle
iii
Ora serrata MUKular artcry Clnd vein Ex trin~ic
eye- musd~
Vitreous t:h,Jmhel
~ ,. Long po sterior ciliary ar tery
H--- Vorticose vein , - - - . Episclera l artery a nd vein
" Re linal a rlery and vein
J
r
Lo ng I)Osterior ciliary artery
p t - Shorl posletiof cili ary arll!ries Central refinal
ar{~
and vein
({Ii~ .
/ Superior macular arteriole . venule
"'-'--''-- OPl ic ner ve (II) Superior n3sill ret inal ar teriole and venule
Superior tempor...1retinal arte rio le and venule - -
Optic d isc
Macula and iovea centralis
~ I rl ferior rl;lSJJretinal
Inferior temporal (etinal ____ Jf\eriole and venule - - - -
Right retin al vessels: ophthalmoscopic vi ew
ar teriole and venule
Inferior macular arteriole and venule
~J~
° n·.·..:: 1!!iN1
FIG U RE 111 .23: ARTERIES AND VEINS OF THE EYE _ _ _ _ _ _ _ _ _ _ _ _ _ __
The ce ntra! retina! artery and its branches supply blood to the retina. Thi s arterial system, derived from the ophthalmic artery (the first branch o ff the interna l carotid artery), is often the site w here ischemic or embolic events (transient ischemic attacks) herald the presence of serious vascular disease. Cili ary arteries supply the middle vascular
tuni c, w hich also contribu tes blood to the retina. Blood supply to the retina can be disrupted if the retina becomes detached. Vessels enter and exit the retina at the optic disk (nerve head), loca ted nasally and slightly inferiorly fro m the geometric midpo int of the eyeball. The macula is located terr porally and slightty inferiorly from this midpoint.
C(
kl
rl< ~ .
<
-,
~
236
ls-Visu a
SYSTEMIC NEUROSCIENCE
..ory Systems- Visual
_ _-
To visual cOflex From visua l cortex To Vi5Uili cortex
_ _ Pulvin ar
Supra chiasmatic
nucleus - - -____
sUp€ r ior colliculus
Nucleus of accessory optic tract l a le ral geniculate
body _ _ _- '
Pontine
tegmen tal reticul,ir
nucleus
Infeliorolive
-------~l_
To pleg
sympathetic neurons
(ll - T2) that project to the superior cervical ganglion and regula te melalonii""~"'C ~:,e~l~iO: "_ _ _ _ _ from the p ineal gland -
,p
!;N ; . ::
-
a. 'e it j
FI GU RE 111.24: VISUAL PATHWAYS: RETI NAL PROJECTIONS TO THE THALAMUS AND THE BRAIN STEM _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ ::eti nal projections travel through th e optic nerve, 21iasm, and tract and terminate in several regions. -;he lateral geniculate body mediates conscious nterpretation of visual input. The superior (olliculu s, a seco nd pathway through the pu lvinar m th e associa ti ve visual cortex, provid es loca li zing n iormation for visu al stimu li. It also provid es desce nding co ntralatera l connections {tectospina l '~ac t} to cervical LMNs to mediate reflex visual erieds o n head and neck movements. The
pretectum mediates th e pupillary light reflex. The suprachiasmatic nucleus of the hypoth alamu s inte grates light flux and regulates circadian rhyth ms and diurnal cycles. The nucleus of the inferio r accesso ry op ti c tract may help to mediate brain stem responses for visual tracking and may inter co nn ect with sympath eti c preganglio ni c neurons in T1 and T2 (regu latin g the superi or cervical gangli on).
237
SYSTEMIC NEUROSCIENCE
Sensory Systems- Visu al
Centra l darker eirde represents macular .:co ne
O verlapping vi'S...,,[ fi elds ,
Lighte51shades repr~n l monocular fields Each qu adrant a different co lor
Projec tion on leli l f lin.:!
Projection on right re tina
Projection on left
dmsa[ lateral gemculate nucleus
Ipsila , lehll
:
--::- (;:.-"- --,
:.;•• +
I, :,jr.
s
4 '
t ::. .:· .... :;
, !. _____ . : ·2 1
."_,,,"l
•
Projection on right M eyer's
loop
Contralateral
Projection on 1£011 occipita l lube
.,.
Calcarine
do rsalla!"",,1 geniculate nucleus
Meyer's
loop
,, "
Ipsilateral
,..",. """ " " ~ 6'"
'
,,--------- ' ' ,, ,, , ,,, ,
' .40
, L-~ _ _"'_.• ;"::,,"i,", . ;I . , . , 2
.... .. I L
.. -,.-; I
-) ';: "
,
Co ntralateral
" ."
~ '
,
Projec tio n on right
-
occipital
lobe
FIGURE 111.25: VISUAL PATHWAYS: THE RET INO·GENICULO·CALCARINE PATHWAY _ _ __ Th is visual pathw ay co nveys info rmatio n fo r fi ne. grained conscious visual analys is of the o utside world. It is organi zed topographically (retinotopic) th rough its course to the calcarine cortex in the occipital lobe. The nasal hemiretinal gangli o n cell axons cro ss the midline in the optic chiasm, whereas the temporal hemiretinal ganglion cell axons remain ipSilateral. Thus, each optic tract con veys information from the contralateral visual field, and damage produ ~es a contralateral hemian o pia. 238
The op tic tracts terminate in the lateral gen iculate body o r nucleus, w hich is organized in 6 layers. The optic radiatio ns project to the calcarine (striate cortex (area 17). The portion of the optiC radiations that loops throu gh the tempo ral lobe (Meye(s loop) can be damaged by a tumor o r mass; such damage results in a contralateral upper quadran tanopia (quadrant defici t). Bilateral convergence from the right and left retinas takes place first in the primary visual co rtex, area 17.
SYSTEMIC NEUROSCIENCE
)elso ry Systems-Visual
Parietal lobe
Spa tia l vis ua l pathway: p
vis ual scene, analysis oi motion Fron tal lobe
,
I
direction motion responsive
Occipital lobe
shape and color
• Temporallobe
,
percep tion
Obje<:1 recognilion p athway:
high r~olu tion and form
' IGURE 111.26: VISUAL PATHWAYS IN THE PAR IETA L AND TEMPORAL LOBES _ _ __ _ __ ' eurons in the primary visual cortex (V1, area 17) send axons to the association visual cortex (V2 and .'3, areas 18 and 19). V2 and V3 also receive input ~'o m the superior callieulus via the pulvinar. Vl , '2, and V 3 project to th e middle temp oral area .and V4. Middle temporal neurons are directi on ~ electiv e and motion respo nsive and furth er project .:lto the parietal lobe for spatial visual processing.
Th e parietal neurons provide analysis of motion and of positio nal relatio nships between objects in the visual field. V4 neurons are involved in shape and color perceptio n. V4 projects in to the temporal lobe, in wh ich neurons provide hi gh reso lu tion object recognition, inclu ding faces, an imate objects, and classification and o rientation of objects.
239
SYSTEMIC NEUROSCIENCE
Motor Systems-lower Molor Neurons (LM
Oculomolor \III) n.
gji
"
Q:
.;I
Red nucleus
,
~ QculomolOr n ucleu~
:"-'- - - Trochlear nut .<-:.
'--- - -- - --
Tri geminal M n. and ganglion
%;,
_ ~
..
Trochlear (IV
f"
Trigemin.-.' (V and jjaflgl ion
"
MOlor n ucleL;
--
trigeminal n.
----:;;:-- Abducens nu·
;;: Facial (V II) n.
Faci
•~ Fada l nucleus Clossophar\ !IX) n.
Glossopharyngeal (IX) n. ----i
Vagus (X) n.
Vagus (Xl n. - - - - '
'-----'-:::.- - ACf;essOty (XI) n.
"Hypoglossal (X II) nucleus
~ Spinal nucleus of accessory n.
i - - -- Spinal cord vel1 tral horn (at all spina l levels)
FIGURE 11 1.27: LOWER MOTOR NEURON DISTRIBUTION IN THE SPINAL CORD AND THE BRAIN STEM _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Lower motor neurons (l MNs) are found in the ventral (an terior) horn at all levels of the spinal cord and in motor cranial nerve nuclei in the medulla,
pons, and the midbrain. These l MNs send axons into the ventral root and then in to spinal nerves
240
from the spinal cord ventral horn, and into cranial nerves from the brain stem. The LMN axons ter minate as neuromuscu lar junctions on skeletal muscle fibers.
SYSTEMIC NEUROSCIENCE
:o r Systems-lower Motor Neurons (lMNs)
1<1
:>erkins 06, ' IF'"
Iri':i
Ne uro musculdr junctions on ex!r aiu ~~ 1
ske letill m uscle fibt-rs
Trail and plate endings on contractile elements (intraiusal fibers) oi muscl e spindles
Skeletal muscle fibers (extrafusal)
la afferent
Nuclea r bd~ Nuclear ch
'"'''-+ --ffl"
nerve
, ,, ,,-tlii jl~
Muscle spindle
FlGURE 111.28: ALPHA AND GAMMA LOWER MOTOR N EURONS _ _ _ _ _ _ _ _ __ ~
LMN groups, except the facial nerve nucleus "'13t supplies the muscles of facial expression, con tim both alpha motor neurons (a~LMNs) that sup~ - , th e skeletal muscle fibers (extrafusal fibers) and :-2lll ma motor neurons (y-LMNs) that supply the ;;;m all contractile elements of muscle spindles (intra J5al fibers). The muscles of facial expression do
not have muscle spindles and are not supplied by "tLMNs. The a-LMNs regulate contraction of the skeletal muscles to produce movement. The "tLMNs regulate the sensitivity of the muscle spindles for la and group II afferent modulation of a-LMN excitability.
241
SYSTEM IC NEUROSCIENCE
Motor Systems- Upper Motor Neurons (UMNs
Cerebral Cortex: Effere nt Pathways
From {mntal cortex to tha laml)s, ba ~a l g~ngli a.
pontine nucl ei and
reticular form
Corticobulbar, cortioorub.al,
parietal (orte~ to thalamus, pon lin e
cortlconuciear, an d co rt icos pinal
--~"""'r
pathways
nuclei an d reticular iormation
r ~i
c..uda le nucleus .- -- -~ -.;:: A.nte-rior limb of internal ca psule - - -
Lentiform J Glob us pa lli du s nucleus
,
~~i'!'
in terstitial nucleus of Cajal
Posterior limb o f irllernal capsule From occipital eye fi elds to
';111 1_
From fron tal eye liekl~ 10
-
~uperior co lli c ulu~
From audilory cortex to in ferior colliculus
Sup",nor coJliculi ?~ ." . ~,t -.,.,___ In~erstilial nucleus of Caial ~
Inlerior
Ce rebral peduncle
co lli CLJ lu~
Red nucleus CorticuS{)inal Corticonucleaf
formation
For pontocerebellar connections ambiguLJs
Facial nerve nucleus of oppoSIt e
side for lower fa ce I nudeus
Upp er (MI l o f medu lla oblongata
(ormation
? yramkl s ile nucleus
Lower p.l rt o f medu lla oblonttala
Derussation o f py.-amids Anterior (d irect) co rticosp inal tract
Spinal cord Anteri or (ven tral) horn s
Re ticular formation
r~t$-t ~
l ateral (cro ssed) cortic ospin allract Posterior (dorsal) hom
~~ft% ° lrnN ",'."."/' l
FIGURE 111.29: CORTICAL EFFERENT PATHWAYS _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Neurons in the mo tor cortex (area 4) and the sup plemen tal and premOlar cortices (area 6) send axons to the basal gangli a (caudate nucleu s and putamen), the thalamus (ventroa nterior IVAl and ventrolateral [VLJ nucleO, the red nucleus, pontine nuclei, moto r cranial nerve nucl ei o n both sides, and th e spina l cord ventral horn mainly on the con tralateral side. These axons form the corticospinal tract, the corticobulbar tract, corticostriate projec tions, corticopontine proj ection s, corticoth alamic projections, and cortical co nnectio ns to upper mo tor neuro ns (UM Ns) o f the bra in stem (reticular formation IRFJ, red IlUdeus, superior co11iculu sl.
242
Neurons of the sensory co rtex (areas 3, ' ,2) send axons mainly to secondary sen so ry nuclei to reg u late in coming lem niscal sensory projections des- tined for conscious interpretatio n. Neurons in the frontal eye fields (area 8) project to the superior co lli culus, the horizontal and vertica l gaze centers of the brain stem, and th e intersti tia! nucleus of Caja/ to coordinate volun tary eye movements and associated head moveme nts. Other region s of the sensory cortex project axo ns to th alam ic and brain stem structures that regu late incoming lemniscal sensory info rmatio n.
SYSTEMIC NEUROSCIENCE
to r Systems-Upper Motor Neurons (UMNs)
f>rimary mOlor co rteK (Are... 4)
larynx
/
Midbrain
' \
,
til IV
)0
111 Upsilateral and conjralilteral) IV l ip~ ila l c ra l Jnd contralateral)
IV
VI Pons
';;;t
•
III
\)si, .
Lateral ilspecl oi ceteb,a l cortex 10 show topogtaphic proJec1io n oi motor (enU~fS o n precentral gyfUS and puomulor and supple mental molor cortex
\1
VI Iip<;ilMeral and oonlralateral)
V
V
U""".
VII 10 uppt'! lace (ip~larernl a nd contralatera l)
lower
VII
V(ipsilJ lefal and amtralateral)
VII 10 lower iace (contr
VII
XII (ipsil ate ral a nd contralateral)
IX,X,XI
LX. X, XI
IX X. and XI (psilateral and contralateral)
~~p ..
eiil
FIGURE 111-30: CORTICOBUlBAR TRACT _ __ _ _ _ _ __ _ _ _ __ __ __
o
j
,
The corticobul bar tract (CBT) arises mainly from the lateral porti on of the primary motor co rtex area 4). CBT axons project through th e gen u of the internal capsule into the cerebral peduncle, the basis ponti s, and the medullary pyramids o n the ipsilateral side. The axons distribute to mo tor cranial nerve nuclei on the ipsilateral and contra lateral sides, e)(cept for the portion of the facial nerve (eN VII) nucleus that supplies the muscles of
facia l expressio n for the lower face, w hich receive contralateral prOjections exclu sively. CST projec tion s to th e hypoglossal nucl eus are mainly contralateral; projections to th e spinal accessory nucl eus are mainly ipsilateral. In con tra st to Bell's palsy (CN VII palsy), in which th e entire ipsilateral face is pa ralyzed, CST lesions result mainly in a contrala teral drooping low er (ace that is paretic to volun tary co mmands (central facia l palsy).
243
SYSTEMIC NEUROSCIENCE
Motor Systems-Upper Motor Neurons
(UM" ~
Prima ry motor cor1ex (Area 4)
l ateral aspect 0 1cerebral (Orlex showi n. Posterior
limb
topograph ic lucali zation o t" mOlo r een le", on prece ntral gyrus arid premo tor .l r :,
~ '~ >~
w
supplemental moto r ((Jfle-.
"%.,
Intt'rnal
Po. lerior ~..,....... ~.
ca psul e / Anl erior lim b
~ ,~ '
__I
Visual .md audito:.
__ ,.~
'-
Temp oropontU1e
~
,:?{' ~:;"
Midbrain
"-/fA:~
Corl icospmal
Co rlicobulba r f rnnloponline
; ~~)
.-.-.
Sensory
Ho rizontal set:tion Itnough internal capsule show ing location of principal palhw av5
,~ 1'
)
Pons
Fron tolna lamic
Anterior
Ve ntrilJ aspe-c -
brai n stem shon .,...:;; decuSS31io r pyl a !T1~
' Ir tI\"'
fiE-
~ l _""~ """
~ "-i'!.~
Spinal
.1"
cord
",.
,d
Decussation of pyramids (approxitTlalety 80% of CST fibers)
-,
\
. ",
~~:,~/
J ~t;~ tT l , ,,;:..
Lateral (crow~dJ
corticospin al tracl
Anle.i()f (direct) corlicospinal lr,}ct
.:>~
FIG URE 111.31 : CO RTI COS PI NAL TRACT _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Th e motor portion of th e co rticosp inal tract (CST) originate s fro m neurons of many sizes mainly from the primary motor cortex (a rea 4) and the supple mental and premo tor cortices (area 6). The primary sensory cortex (areas 3, 1, 2) contributes axons to the CST tha t terminate mainly in secondary sensory nucle i to regulate in comin g lemnisca l sensory infor mation processing. The CST travels through the posterior limb of the intern al cap sule, th e cerebral ped uncle, th e basi s po ntis, and the medullary
244
pyramid on the ipSilateral side. Most CST axom decussate in the decussation of the pyramids a: meduUary-spinal cord junctio n and descend in lateral CST to synapse o n a-LMNs and y.LM i\ 's both directly and indirectly through interneur()(i"" CST axons th at do not decussate continue as . ~ anteri or CST and th en decu ssa te at the appropn&: level to terminate direc tly and indirectly o~ L , ', contralateral to the cell s of o ri gin.
IU MNs)
SYSTEMIC NEUROSCIENCE
-·'olor Systems-Upper Motor Neurons (UMNs)
I.-. ing
fllNS
rand
!lfll."\
....... eral . : "llc05pina l - - - - - : - - - '"><, 'i
Minor component of
1""""",- - - - - ---,1--
""",;OC corticospinJI tract (ipsilatera l)
-=dIal muscles
-
Anterior white commissure
An terior corti cospinal tracl
J. Perkins MS.MF'\
.~
URE 111.32: CORTICOSPINAL TRACT TERMINATIONS IN THE SPINAL CORD _ _ _ _ __ ~ ~ed CST axons in the lateral CST, intermixed :- axons of the rubrospi nal tract, travel in the
ear j'unicul us. Most of these CST axons termi
di rectly and indirectly on LMNs associated - distal musculature, especially for skilled hand
2
ringer move ments. The uncrossed anterior CST ~ decussate predominantly in the anterior :e commissure and terminate directly and indi
mainly o n LMNs that supply medial muscula - .; small number of anterior CST axons
termina te ipsilateral to the cortical cells of origin. An isolated lesion of the CST in the medullary pyra mids results in weakness of contralateral fine hand and finger movements. All lesions involving the CST intermixed w ith other descending mo to r sys tems (internal capsule, cerebral peduncle, po ns) produce contralateral spastic hemiplegia w ith hypertonia, hyperreflexia, and a plantar extensor response. Lesio ns of the lateral CST produce similar symptoms ipsilaterally below the level of the lesio n.
245
SYSTEMIC NEUROSCIENCE
Motor Systems-Upper Motor Neurons (UMNs)
<4f~~~ , } ~ ~ ~~!il-
"b",p'",1 T" Pnmary rnocttor cortex (area 4)
I,
7
,
""' ...
~\ ~
'm,IIpy,.m'd, ' oell,
)
Giant pyrarnidil l ceils
V;c -
'~
.
r
Fibers from glo bose and
emboli/arm, ~ m e from
dentate dee p nvdei via
,"pe"~co,,bell"pe""oc~ ~
~'.. .
Red nuclei
~ Helps 10 hold flexor actions of RST on UE in check
Helps \0 drive Bexor actions of RSTfOl l E
Crossed robrospinal and ~
rubromoou1lary fibers -
Mid brain
To pyramid
nI,...
Fildal nerve nudeus
Ul"ICrossed
rubr om~u ll ary
Irubr obulbar) fi bers
Medu ll a oblongate Lateral reticular nucleus
Ru brospinal lraC!
M edullary reticul ;lr
formation
-----------.Ji
Inferior olivary rlUcieU5 '~_~ \
Inhibitory Interneuron
;-..
ExcitaTo ry i nterneuron
Cervical part of spinal cord l ,l(eral (crosse d ) corticospinal lraC I
Rubros pinai lraci Pos terior (dor sal) ho rn !Iltemeurons controlling afferent input 10 spinal cord
~
To extensor mu scles To flexor
muscles
~ , _O?
-, ,_
.
,J ,\ 1(
)
lUmbar pall of spinal cord
-I"hibi ,o", iote,~",on
Excil.atory interneuron
~~p
01lDl\l ;,',,-:;;
FIGURE 111.33: RUBROSPINAL TRACT _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ __ Th e red nucleus receives ipsil atera l topograph ical input from the motor cortex and fun ctio ns as an indirect corticospinal system. Axons of the rubrospinal tract (RST) decussate in the ventral tegmental decussa tion and descend in the lateral brain stem and the lateral funiculus of the spinal cord, w here they are intermixed ex tensive ly with axons of the lateral CST. The RST terminates directly and indirectly on a,-LMNs and y-lMNs in the spinal co rd, particularly those associated with flexor movements of the extremities. Th e RST helps
246
to drive fl exor movements fo r th e lowe r extremity but helps to hold flexor move men ts in check for the upper extremity, RST lesions usually occur in conjunction w ith the CST in the spinal cord; corti corubral lesions also occur in conjunctio n w ith the CST in the internal capsule and the cerebral peduncle, These lesions result in contralateral spastic hemiplegia. Brain stem lesions ca udal to the red nucleus result in decerebration (extensor spasticity).
-
MNs)
SYSTEMIC NEUROSCIENCE
Molor Systems-Upper Motor Neurons (UMNs)
h:citatory endings - - Inhi bitory ~ ndings ..... _
V~s tibu lolr
nuclei
Rostral
Upper lirl1,
Ve ntr.,1 cerebellum
;X
Trunk
./:"
Oors ,,1
t;
l ower limb
Caudal Soma totopic..' pattern in lateral ve stibu lar nucleus
!\ Ves tibu lar :, ganglion ,"d
MOlo<"e~l~~'"
•
(cont rolling _ (\ neck muscles) ~
,
Fib ers from cristae
(rotatio nal sti muli )
tract
Excita tory endings 10
Interneu ron
l ower pari of
Fibers from macula e (gravitati onal stimuli)
~=:: T;:O l1ex(I( muscles :... ~)(tensor muscles
cervica l spinal
cord
t~-l~~:'T;:O::;Uial mu~cles
Lum b
,,,'''''''' ending '+-'''"''''1 vestibul O$ pinal tract
spinal co rd
-........,., {
Inhibitory iniern eulOn
~--'TO
' - --
H exorm uscles
To .,," "'" muscles
F CU RE 111.3 4: VESTIBULOSPINAL TRACTS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
-"e la teral vestibulospinal tract (LVST) arises from ·e lateral vestibular nucleus (LVN ) and terminates ectly and indirectly o n ipsilateral a-LMNs and LMNs associated w ith extensor musculature, especially proximal mu scu lature. If thi s powerful antigravity extenso r system were not kept in check by descendin g co nn ecti ons fro m the red nucl eus and the cerebellum, it wo uld prod uce a co nstant state o f extensor hypertonia. The medial vestibu lospinal tract (MVST) arises from the medial
vestibular nucleus (MVN ) to provide inhibiti on of the a-LMN s and the y-LM N s that control neck and axial musculature. The MVST terminates mainly o n interneuro ns in the cervical spinal cord ventral ho rn. Th ese 2 ves tibulospinal tracts stabilize and coo rdin ate th e pos iti o n of the head, th e neck, and th e body and provide important refl ex and brain ste m co ntrol ove r tone and posture. The vestibu lospinal tracts work w ith the reticulospinal tra cts to con trol tone and posture.
247
SYSTEMIC NEUROSCIENCE
Motor Systems- Upper Motor Neurons (UMNs)
Re ticulospinal and Corlico~tjcuJar Pathways
Ex citato ry endings Inhibitory endings
p,';e,,1
T nickness o f blu~ l ine.
Frontal ____/" .1:....'"
indi ca! i!s deo~ty ot
r
~~
cortica l proj ec tion { O rb ito
---
ironlal
--
MecJial pon tine relicular fo rma tion ________ f.
pon s ~ Receives input from multiple
,en$ury
Tri geminal mOlor nucleus
.
1
"'-----" Receive excitatory
,.
S~' stCIllS
fibers irom pontine,
via laleral RF
inhibito ry fi bers from medullary
Medial
reticular formation
medullary relicul¥ form ation -
~
k
I
,
Medulla oblonga(J
F"cial nerve nucl eus
""'"
Exerts slro ng d rive over medullary RST
l ateral reticulo-spina l Ira c t (pa rt ially ClOSSed ); excites ~nd inhibits axial (neck and back) motor neurons and moclula l ~ affe rent inpu t 10 sp ina l cord
"it ":r~~l
M ecJiill (anterio r) ret iculospinal trac ti I)roduces direct t:.'(ci ta tion oi motor neurons
-..
@'*
..,
~ 1r:%
-,-- - - Ce-rvical part oi spinal cord
-:>--- Pos te-rim (dorsa l) horn inte-rneurons
re-gulating se nsory inpu t to spinal cord M otor neurrlnS (alpha and g
(
I
_____
~
};':. I ,
Excitatory inte-rneuron
Inh hibito ry Interne-uron Lumb.,r part of spinal corr!
~~p
OII9N \\'0•••:::
FIGURE 111.35 : RETICULOSPINAl AND CORTICORETICUlAR PATHWAYS _ _ _ _ _ _ __ The pontine reticulospinal tract (RetST) arises from neurons of th e medial pontine RF (nu clei po nti s caudalis an d orali s). Axon s descend as th e po ntine (medial) RetST mainly ipSi latera lly and terminate directly and indirectly o n a-LMNs and y-LMNs at all levels. This tract has a distinct extensor bias w ith axial musculature, and it rein forces the action of th e lVST. Th e ce rebral cortex exerts minimal influ ence on the pontine RetST; it is driven by po ly sensory input from trigeminal and somatosensory
248
sources. The medullary RetST o riginates from the medial RF (nu cleus gigantoce llularisl and is heavily driven by corti cal input, especially from the motor and pre molor/supplementa l motor cortices. Axons o f the medullary (lateral) RetST terminate bilaterally, directly and indirectly, o n a-LMNs and y-LMNs at all levels. The medullary RetST exe rts a flexor bias, reiniorcing the CST and the RST. The reti cu lospi nal tracts are important regulato rs of basic tone and posture. They are no t organi zed somatotopically.
'UMNs)
'----;f
Motor Syslems-Upper Motor Neurons (UMNs)
"'II. ------
Midbrain
e .ilv
or
}n s
aliI'.
s, .al
Superior colliculus Interstitial nucleus of Cajal
!
11\ ./' Itt
1-------
Mediallo ngiludillal fasciculus
Pons
\
".,..,..-
"
'" :p .. I\. \ :"\
(~f
Upp" """,' spmal cord ) /
. . ---.-
~. To neck • _ _ _;;_:::::::;;;;::::::;.::.:: --- ._ _ .::~_ _ ;:-:::_ musculature
~
v,.. ...,~
/ .,...-
j
~....'-\ '\
I
.ptf
_ ~_.l'
To axial muscles of the trunk fo r
...~__.,
,:::::.~~;:;. .. :~._ .::::;::;:;::-:: __ .~;::; ::. :: •..:......_
_
_
,;.
Perkins
M§,M.FA
'\
0 10N ." :::::
'\ \
. =__
,! ......-. . ...
J.
\.
........
.~,,:: _:::~:::~;; - _.~:;:~ . _:;.~.:.... .--~
rotation al movement
~~~ J.
~"-
iii\! . .'. :;
-
SYSTEM IC NEUROSCIENCE
___
To axial muscles
of the trunk for
ro tational movemen t
FIGURE 111.36: TECTOSPINAL TRACT AND INTERSTITIOSPINAl TRACT _ _ _ _ _ _ _ __ The tectos pinal tract (r ST) arises from neuron s in deep layers of th e superior colli cui us, decussates in the dorsal tegmenta! decussation, descends con tralaterally near the midline, and terminates directly and indirectly o n a -LMNs and y-LMN s in the cervi cal sp in al co rd associated with head and neck movements. This pathway mediates reflex and visual tracking infiuences for positi oni ng the head
with regard to visual input. The interstiti ospinal tract (1ST) arises fro m the interstitial nucleus of Cajal, a region that helps to coordinate eye move ments and gaze centers. The 1ST descends ip si laterally in the medial lo ngitudin al fascicu lu s (MLF) and terminates directly and indirectly on a-LM Ns and y-LMNs associated with axial muscu lature of the trunk involved in rotatio nal movement.
249
SYSTEMIC NEUROSCIENCE
Motor Systems-Upper Motor N eurons ( UM I\ ~
A. Corticospinal tracts
B. Rubrospinal tract .-- -.-~-", -:-
r""",
l ate ra l (crossed) cortico~pinal !r
'C<.1!:G;.
Anterior (d irect) corlicospinaltracl
~.
is
~
;;;J ~
;~:f.:" Fibers from
leit mOlOr COf1ex
;:::;::;:~ Fibers I'rom left red nucleus
:;i;ii~;: Fibers from lell seOSOfY cortex
C. Reticulospina llracts .... .. j:" ,
'l1i'::.
l ateral reticulospinal tract
/ .
1,
/~ C;;'
j ' .
A
v,": . f I
l"
~ {~ o
\ v",
vill.
.&
.~
Medial re ticulo spinaJ tract .:~;:;:;, F i be~ from
I
"N ,
J. .~I f-~l.IJ;:!). t
". .
j
lefl pontine reticular formaiion
:;iiiii~i Fibers h om lef! medullary relicular formation
II!IN :', ';": ::
Medial ves tibulospinal fibe rs
l ateral vestibulospinal tract
;~:~,:, f ibers (rom lett lateral (Deiters') nucleus
;;iiiiW f ibers from leit medicI! and inferior nude; (only 10 cervical and Ihora
FIGURE 111.37, SPINAL CORD TERMINATIONS OF MAIOR DESCENDING UPPER MOTOR NEURON TRACTS __________________________________________
f
C The lateral C ST and RST terminatio ns are directed mainly toward LMN s associated w ith di sta l limb mu sculature. The anterior CST, the retic ulospinal
tracts, and the vestibulospina l tra cts are directed m ainly toward LMN s associat ed w ith m o re proxi mal and axial mu sculature.
C
P< ~
"
250
(UMI\,
-
SYSTEMIC NEUROSCIENCE
or Systems-Upper Motor Neurons (UMNs) b ci.alo r)' endings --.. -
-
-
-- _
_
_
Frorllal eye iields (Brodmann ared 8)
lnhibitoryending5 -
Occipital eye fields
,.
IBrod mann areas 17, 18, 19)
~ :e fS!il i a l
...., cleusOf----fl~~ ,. (.aja!
'"'f""l
- , - - + i " - M"dlj , ,( longitudinal fascicu lus Superior oblique m.
~ucem
Superior
~"'ur on
r;Xlu S m .
lateral Medial re1: lus
" uci eus
~---jc-:i-- Modli" longi!udin;:tl iasciculi
'l.ledialloo,,"odlo,,' _"=:::= 'asciculi
~-Jt"~~1-
__
Ascending Irael ofOielers
SOP",m} Medial
Ve'itibulaf
Lateral
nuclei
i obliq ue m.
rect us m.
Inierior
. GURE 111.38: CENTRAL CONTROL OF EYE MOVEMENTS _ _ _ _ __ _ _ _ _ _ __ Ce ntral control of eye movements is achi eved
- 'ough the coo rdination of extrao cu lar motor -ucJei for cranial nerve eN III (oculomo tor), C'J IV (trochlear), and eN VI (abducens). The ~ra pontjne reticular fo rmation (PPRF) (horizontal ;aze center) receives input from the vestibular - .uclei, the deep layers of the superior colliculus 1pUt from Vl, V2, V3), the cerebral co rtex (frontal ,?>. e field s), and the interstitial nucl eus of Cajal nput from th e vestibular nuclei and th e frontal eye
fields). Th e PPRF supplies the ip sil ateral eN VI nucl eus and the co ntralateral eN III nucleus (via intern eurons in the eN VI nucl eus) for th e medial rectu s, thu s coordinating horizontal eye move men ts. The interstitial nucleus o f Caja l helps to coordinate vertical and oblique eye mOvements. Secondary sensory vestibular projections also ter minate in the extraocular motor cranial nerve nuclei. Axons interconnectin g the extraocular motor cranial nerve nuclei travel thro ugh the MLF.
251
SYSTEMIC NEUROSCIE NCE
Motor Systems- Upper M oto r Neuron s (UMt\ s Descending Coolro! from higher centers
Superior ce,ebt:!:II
Mf;'dia l pa' olJbrachiaJ
nueIeus
Cerebral corte"
.............
'\
...'
r
Pilcemaker Ventral ~
respira tory
nudeus
<±>
Oor&ll
respiratory
ffi
RelSu lil le~
pan:maker
funclion
nucleus
~
/'" Dor~1 mOlor nucleus oiCN X
Pcms ____ D o rsal resp irvl Ory nudeus
nucleus
{ventrolateral nucleus solitarius}
nude us solitariu!>}
Mutual inhibition
eN IX chemorecep tor
chemoreceptor
zone
zone {Pc02 1 neaf ior
Ven tr al
o f luschka
respir atory
Nucleu s
nll cieu.
ambigulis tral respiratory nucleus
bo dy
(,elfOambiguus nucleus) Ca wtid body
'-
/
lower mo to r neurons oi phrenic nucleus
Tu lower mOll'lr neUf()n s for
expi'
r~.
~ 1._ _........
,:z. 'iIJdI..P""""
folysyna phc
Spinal cord
conne<..1ions
To lower motor neurons iar
cb
( 0 , (4 ,(5)
in~l,irJl or y
lower mo tor neurons for inlercostal dnd ilCCesSOlY
l
muscles
~muscles
,.-J.-,-,
oi respiration
tfJ'
Sp inal cord
(T6 - 12)
FIGURE 111.39: CEN TRAL CONTROL OF RES PIR ATI ON _ _ _ _ _ _ _ _ _ _ _ __ _
f Inspiration and expi ra lion are regulated by nuclei of the RF. The dorsal respiratory nucleus (DRN) (la t eral nucleus solitarius) sends crossed axons to ter· minate on cervical spinal cord lMNs of the phrenic nucleus and on thoracic spinal cord lMN5 that supply intercostals and accessory respirato ry musculature associated with inspiration. The ventral respiratory nucleus (VRN) (nucleu s retro ambiguus) se nds crossed axo ns to terminate on thoracic spinal co rd lMNs that supply accessory
252
mu sculature associated w ith expiration. Th e DR(\.. receives input from the carotid body chemosensl)t'3 (via CN IX) and the aortic body chemosensors (\ ia CN X) and from the central chemoreceptive zon€'5 of the lateral medulla. The DRN and the VRN mutually inhibit each other. The medial parab rachial nucleus (P BN ) acts as a resp iratory pacemaker to regulate the DRN and the V RN. Tht medial PBN recei ves input from higher centers such as the amygdala and the cerebral cortex.
.,.
J M Ns)
Motor Systems-Cerebellum
SYSTEMIC NEUROSCIENCE
Lingula --~
Vermis
Lateral h",,,,,h,ce
PrimJry fissure
"Unfolded" schematic oi cerebellum demOnSlrJling
body map areas
Poslerlor
lobe
Flocculoflodular
;v----.,0,;,}.'---__J
lobe
"Untoldcd" schema lie of cerebellum demonstrating rH1.iou ;. and lobes
:'C.lW_\\\e.
0\
\.rll':me'i\ca\ "unioldln'1," niccereoeliaf sUr/an: In
derivation or
above clr'awam
"'G URE 111.40: FUNCTIONAL SUBDIVISIONS OF THE CEREBE LLUM _ _ _ _ _ _ _ __ _ - ....e cerebellum is classically subdivided into ante 'lOr.
middle (posterior), and flocculonodular (FN)
lobes. Damage to each lobe is associated with ipsi Jaie ral syndromes such as stiff legged gate (anterior Dbe), loss of coordination with dysmetria, action "'e mor, hypotonia, ataxia, decomposition of move --en t (middle lobe), and truncal ataxia (FN lobel. n e cerebellum is also classified according to a -ongitudinal scheme, based on cerebellar cortical
regions that project to deep cerebellar !luclei, which in turn project to and coordinate the acti\ it' of UMN cel! groups. This scheme includes the vermis and the FN lobe (projecting to the fastigial nucleus and the LVNl, the paraverrnis (projectin¥ to globose and emboliforrn nuclei), and the lareral hemispheres (projecting to the dentate Ilu cl eus·. Each cerebellar subdivision is interlinked w ith circuitry related to specific UMI"i system).
2 53
SYSTEMIC NEUROSCIENCE
Motor Systems-Cerebellum
Cerebellar Cortex GoIgi (inner stella It» cell (inhibitory)
Exrit.1lory endi ngs -
Inhibilory endings _
_
G ranule cells (excitato ry)
Parallel fibers (a)(Ons of gra nule cell Parallel fibe r, ICU!)
PurkinJ e ce ll s (inhibito ry)
Dendri le~ 01 Pu' kinje
ce ll ..........
011.
G ranular layer
Basket cell
White matter
:limbing filler (excitatory)
Gl om eru li
,
r.bers (e)(citatory) Verkose axon of locus coeruleus (nOfadrenergic )
...... Purbni., cell axon
~~f!% ......
· I"~N '::
FIGURE 111.41 : CEREBElLAR NEURONAL CIRCUITRY _ _ _ _ _ _ _ _ __ __ __ The ce rebellum is organized into an o uter
3-l ayered cortex, w hi te matter, deep ce re be ll ar nuclei. an d cerebe ll ar ped uncles th at co nnect with the spina l cord, the brain stem, and the thalamus. In the cortex, the Purkinje cells (the Inajor output neurons) have their d end ri tic trees in the molecular layer (a rranged in parall el "p lates"), th eir ce ll bo dies in th e Purkinje cell layer, and their axo ns in th e granu lar layer and the deeper w hite matter. Inputs to the cerebellar cortex arrive as climbing fibers (from the inferior oliva ry nucleus) or mossy fibers
(all other inputs). The mossy fibers synapse o n granule cells, whose axons form an array of paralle l fibers that extend through the dendritic trees of several hundred Purkinje cells. Additio nal inter neurons modulate interconnectio ns in the molecu lar layer (o uter stell ate ce ll s), at the Purkinje cell body (bas ket cells), and at granule cell and molecu lar layer associations (Go igi cells). Noradrenergic axo ns of the locu s coeruleus neuro ns te rminate in all 3 layers and modu late the excitabili ty o f o ther cerebellar connectivity.
FIG
Aff, d im
fibe, and
arOl
drer: cell I
SYSTEMIC NEUROSCIENCE
or Systems-Cerebellum ~
Gene ral Scheme
_- +
B. Deep Nuclei Relationship With Afferents
Cerebell ar COlle>.:
~
, - _ Deep nuclei
~
Purkinje cell
Uppe r m OTor
neurons
Granule cell
II
D,,,,
l ower mOTo r neurons
Afferents
Ske letal muscle
C. Circuitry of Cerebellar Neurons· M o~sy Fibers
Gran ule cell
Mossy llber
nucleus
Mossy fib er
Climbing fib er
D. Cirruitry oj Cerebellar Neurons - Climbing Fibe rs
Deep
Goigi cell
nuc;leu s
Clim bing fiber
J. Perlo:ins M~ .
MfA
I!) lmN ,',-: .
,,,
'IG URE 111.42: CIRCUIT DIAG RAMS OF AFFERENT CO NN ECTIONS IN THE CEREBElLUM _ _ "erents to the cerebellum include mossy fibers, dimbing fibers, and locus coeruleus no radrenergic ':'..bers. The mossy fibers synapse in the deep nuclei .snd on granule celis. The climbing fi bers intertwine o!: ound the Purkinj e ce ll dendritic tree . Th e nora drenergic locus coeruleus axons terminate with all :ell types in th e cere bellar cortex. Th e loops and
circuits in C and 0 show interneuronal modulati on of ah'erent co nnections and Purkinje cell outflow. The entire circuitry of the cerebellar cortex pro vides fine-tuning of the original processing in the deep ce rebel lar nuclei. The en tire Purkinje cell out put to th e deep nuclei is medi ated by inhibiti on, usin g GABA as the neurotransmitter.
255
SYSTEMIC NEUROSCIENCE
Cortical inpul ____
Motor Systems-Cerebellum ~ uperior
<,..... ~
cerebellar ped uncle
. _~ ,l " ..\
Nucleus reticular.s legmenl! pon tis
con tr
Ponline nuclei (contral ~Prim(lry fi~u, e
,Ii, Upper part of
meduna oblongata,
Spinal Ves tibular nerve
Inferior ce rebellar pednu de
and gan gli
tract tract
Spinal input __
(relilY lor cutaneous informati on)
"'External cune;!te nucleus (relay for propfioceplive ;nro rmalioo)
Ro str al
spinoce rebellar trac t
~ \
:": ~ ,.
' Spinal borde r cells____ MOlo. in terneuron
_".
k)
_~. ,-
.
IFrom • y
'"
skin (Io uch
Frommusde Ispindles and golgi tendon organs)
~~From skin and deep tissues 11 - '
(pain and Golg; tendon organs)
Lumb ar
skin (tooch and pressure)
.:and ['o m musee (spindles and Golg; tendon o rgans) Ventral spinocerebellar tr ..et
\Oocsal spinocerebella r trac t
~~p
c ~N
FIGURE 111.43; AFFERENT PATHWAYS TO THE CEREBELLUM _ _ _ _ _ _ _ _ _ _ __
H
Afferents to the cerebellum terminate in topo graphically organi zed zones in both the deep nu clei and the cerebellar cortex. The body is repre
nu
sented in the cerebellar cor tex in at least 3 separate regions, Afferents traveling through the inferior cerebe llar pedun cle include spinoce rebellar path
ways (dorsa l and rostra l spin ocerebellar tracts, cuneocerebellar tfacO, the inferior olivary in pu~ RF input (rom the lateral reticular nucleus and other regions, vestibular input from th e ganglion and vestibular nuclei, and so me tri geminal input. Th e
256
dorsal spinocerebellar tract and cun eo cerebellar tract derive mainly from mu scle spindl e output, whereas the ventral and ros tral spinocerebellar tracts derive mainly from golgi tendon o rgan o ut put. The middle ce rebellar peduncle co nveys mainly pontoce rebellar axo ns that carry crossed cortico pontocerebeliar inputs. A fferents traveling thro ugh the su perior cerebellar ped uncle include the ventral spinocerebellar tract, visual and audi tory tectocerebell ar input, some trigemin al input, and noradren ergic locus coeru leus inpu t.
EfJ
m,
ter
ve~
re fl
retj
ane ally bell
SYSTEMIC NEUROSCIENCE
. to r Systems-Cerebellum
--
Excit;atory endings
Inhibitory
e ndings of
Purkinje cells
cerebral
~-""" ,"'l capsule
Ve ntral ante rio r and ventral late r..l nuclei o/thalamus Mesenc.ephillic retiCU!ilr formalion
- - - - -fi
Reu nucleus Fasti!,;ial nucleus
r II
I
1_
Descending fi ber~ iwm supe rior cerebellil r p ed unde~ Hook bundle oi Russell
Emboli/orm nucle us
Dentate '"'
I" ",
Cerebellar co rtex
Section A - B viewed irom
below
Section B - C viewed from
above Vestib ular nuclei
Inferior cerebellar peduncle
In(erior o live
f'on to m<.>
- C URE 111.44: CEREBELLAR EFFERENT PATHWAYS _ _ _ _ _ _ _ __ _ _ _ __ _ ~-ere nt s
from the cerebellum derive from the deep oJC!ei. Projec tions rrom the fastigial nucleus exit .linly thro ugh the inferior cerebellar peduncle and Fminate mainly ipsilaterally in the LVN and other :tibular nuclei, and in pontine and medullary ocular nuclei, regulating the vestibulospinal and nKulospinal tracts. Proj ections from the globose .n:i embol ifo nn nuclei project mai nly contra later . through the decussatio n of th e su perior cere ellar peduncle to the red nu cleus, with a smal!er
con tributio n to the VL nucleus of the thalamus, and mainly modulate activity of the RST. Projectio ns ~rom the dentate nucleus project mainly con tralat era lly through the decussa tio n of the superior cere bellar peduncle to the Vl nucleus and, to a lesser extent, the VA nucleus of the thalamus, and mainly modulate activity of the CST. A small projec tio n from the dentate nucleus also projects to the con tralateral red nucleus and to brain stem reticu lar formation.
25 7
SYSTEMIC NEUROSCIENCE
Motor Systems-Cerebellum
Cerebellovestibulllr pathways Excitatory endings Inhibitory endings __ -
Vesti bulocerebellar pathways /Fastigial nucleus
- - --
/ Globose nuclei
/Emboliform
nucleu~
/Dentale nucleus
~~p CIIDN ~\ '.',".';
Vesti~ular
nudel
:
{ L" Medial- - Inferior-----
/~;hn.< from cristae
Nodule
Vestibular nerve
Fibers from maculae
FIGURE 111.45: VESTIBULOCEREBELLAR AND CEREBElLOVESTlBULAR PATHWAYS _ _ _ __ Primary sensory vestibular inputs terminate in the
4 vestibular nuclei and in the fastigial nucleus and the cerebellar co rtex of th e vermis and th e FN lobe. The vestibul ar nuclei also proj ect to the cerebellar cortex of the vermis and the FN lobe. Purkinje cells
in the vermis and the FN lobe, in turn, projec t back to the vestibular nuclei and the fastigial nucleus. The fastigia/ nucleus proj ects to the vestibular
nuclei and to the pontine and medullary medial RF. Thus, primary and secondary vestibular neuron s project to the fasti gial nucleu s and the cerebellar cortex, and both the cerebellar cortex and the deep nuclei project back to th e vestibular nuclei. This extensive reciprocal vestibulocerebellar cir cuitry regulates basic spatial pOSition and body tone and posture.
fl
n
th th, of
SU i
be
en 0';
th, rna
258
SYSTEMIC NEU ROSCIENCE
tor Systems- Ce rebellum
/ ..
....._ ; ,
.;
~"),
-r--_..-' ': -- -_ ~ "
J
.
IF
:~
Cerebra l co rtel(
. :)' ,
",. 1
.., Cerebellar ( corte"
~,
r
., /
~
~
./
,/ l ateral
h,m;'Ph~
~/
r~
7·
..,',..,-
.
!
I
.'
""---
Dentate nucleus
;
/ y',\ ; , j
" ,j
.
~"'._./
'.-
P,,,"~; :,;=~c-;"ob~""'::::'"~d=~ ~ ~ ~~ ;:::~======::::::~J
"
embolifOfm nuclei
Skeletal
muscles
Pontine nu cleus
Red nucleus .,
,
l ower motOl" ~,~
/
~/
.......
','~-"/'
:;.,..--C
'-."
Cerebellar cortel(
r= - .
Aocc ulu~
~~
T
TO r T1OCCUlo-ooduiar lobe Spinocerebellar tracts
Vestibular afferen ts and secondary sensory projections
lowl'f motor neurons
~. ~, ..~t
~-
t
1:1.' -
Skeletal
Ii ~ -.of I: muscles
J. Perkins loiS, MfA
CI ~
FIGURE 111.46: SCHEMATIC DIAGRAMS Of EffERENT PATHWAYS FROM THE CEREBElLUM TO UPPER MOTOR NEURO NAL SYSTEMS _ _ _ _ _ _ _ __ - ne lateral cerebellar hemisphere connects thro ugh -1? dentate nucleu s with VA and VL nucl ei of the -'al amus, the major tha lamic inputs to th e cells .; origin of the CST in th e motor and premotor! supplemental motor cortices. The pa raverm al cere- oellar co rtex connects through the globose and : boliform nuclei w ith the red nucleus, cells of origin for the RST. The cerebellar connections to -ne cell s of origin for the CST and the RST are "'1ainly crossed, and th ese UMN systems cross
again before terminating on LMNs. Thus, the cere bellum is associated with the ipsilateral LM Ns through 2 crossings. Th e vermi s and the FN lobe connect with the fasti gial nucleus and lateral vestibula r nuclei. The fastigial nucleus projects mainly ipsilaterally to cells of origin for the vestibu· lospinal and reticu lospinal tracts, exerting mainly an ipsilateral influence o n spinal cord LM Ns through these UMN system s.
2 59
SYSTEMIC NEUROSCIENCE
Motor Systems-Basal Gan glia
Connedions of Basal Ganglia Fro ntal Precentral cerebr al cortex
Caudate {Head nucleus Body Tail
Postcentral cerebral corle).:
Cla ustrum
A&
,l>" ,
Temporal cone'
"m
,"
Lenti for r-
External segmen t} Globus Internal segmeOl
Ansa lentic ularis
Hypothalamus
nigra
~- Corticorubral, conicobul bar
Pars compacta { Pars reti c ularis
nucl eu~
'Fasciculus lenticulari s
Sub thala mus
Substantia
paliidus
}
and cort icospinal fibers
---
===:'
nudei from upper pons and midb rain tshown separiltely)
-' ~----. Projections back 10 cortex a nd basa l ga nglia
---...,•• Dopa minergic projection of substantia nigra Thalamic and subthalamic projections
~
~
-'
Projections from cortex and basal ganglia pro jection .. Cortical Corticoslrial.ll projection '" Slriatal projection ----,~ Pall idal projection
=
~~~
OIIl!N :;.: -":;:
FIGURE 111.47: CONNECTIONS OF THE BASA L GAN GLIA _ _ _ _ _ _ _ _ _ _ _ __ The basal ganglia consist of the striatum (caudate nucleus and puta men) and th e globu s pa llidu s (GP), The substantia nigra (SN) and the su bthalamic nucleus (STN), w hich are reciprocally connected with the basal ganglia, are often included as part of the basal ganglia. Inputs to the basal ganglia from the cerebral cortex, the thalamus (intralami nar nuclei), the SN pa rs compacta (dopamin ergic input), and the rostral raphe nuclei (sero to nergic input) are directed mainly toward the striatum, and
260
the STN projects mai nly to the globus p allidus. The striatum projects to the GP" The GP in ternal segment projects to the thalam us (VA, VL, and centrom ed ian nuclei), and the external segment projects to the STN. Thal am ic VA and VL nu clei provide input to the cells of origin for the CST. D amage to basal ganglia com pon ents often r esu lt~ in movement disorde rs. Damage to the dopam in e neuro ns in the SN pars compacta results in Parkinson'S d isease.
FI<
Inr to
SIr;, inh exc driv cosl tory baSe
segr
~anglia
Motor Systems-Basal Ganglia
SYSTEMIC NEUROSCIE NCE
"OrtE'X
:ortE'~
:rforrr
em
SN - Sub5tantia nig ra STN - Subthalami<: nucleu5 GLUT .. Glu tama te GABA .. Gamm a aminoburyric acid DA .. Dopamine
3HT - 5-Hydroxytr yplamine (serotonin) PC '" Pa r~ compacta PR =- Par~ reti cutala ACh '" Ac etylcholine G P = Glob~ pallidus
SUB P '" Subs tan ce P
FI GURE 111.48: BASIC BASAL GANGLIA CIRCUITRY AND NEUROTRANSMITTERS _ _ __ _ Inputs from the cerebral cortex and the thalam us to the striatum are excitatory (glutamate). Th e stria to pallidal and pallidothalamic connedions are inhibi tory (C ABA). The combination of th ese excitatory and inhibitory influ en ces resu lts in a net drive over the thalamocortical (and resultant corti cospinal) output. Extensive inhibitory and excita tory circuitry that produce complex modulation of basal gan glia output also derive from the in ternal
segment of the GP, the SN, and the STN. Th e
dopaminergic nigrostriatal con nection s can e\ ert bo th inhibi to ry and excitatory effec ts on ' :1€' striatum. In Parkinson's disease, the lo ~! o ~ nigro stri atal dopamin e axons aJlows bot;'" .... '2 ~.? {i ve symp to ms (bradykinesia) and posit;\ €, ~\'"'1ptom 5 (resting tremor, muscular ri gidity, posture "' ~ ~abil i ty ) . Ad ditional intern eurons such a3 .:--e e"\citatory cho linergic interneurons in e ':;·rl.3:tum are foune in so me basal ganglia s tr uctJ~e--
SYSTEMIC NEUROSCIENCE
Motor Systems-Basal Ganglia
b. limbic loop
SfN
c. Cognitive loop
d. Oculomotor loop Cortex
Cortex
SN = Substantia n;grd PC .. Polr5 compacta
PR .. Pa rs relicuta la
5TH " Subthalamic nucleus
--~
-----11~,Onlai ~"~
Vl .. Ventfolateral nucleus VA = Ventral anterior nuclcu5 eM .. Cel'womcdian nucleus
MD '" Medial dorsal nucleus
p.arvo .. Parvocel'ular
magno .. Magnocellular
C PI .. Globus pallidus !nlemal segment
CII!!N
w..··;, :
FIGURE 111.49: PARALLEL LOOPS OF CI RCUITRY THROUGH THE BASAL GANGLIA Th e co rticostriatal, striatopallidal, and pallidothala mic con nections form parallel loops for motor, lim bic, cognitive, and oculomotor circu itry. The motor
circuitry is processed through the putamen, the limbic circuitry through th e ventral pallidum and the nucleus accumbens, the cognitive circuitry through the head of the ca udate nucleus, and the oculo mo tor circuitry through the body of the caudate nucleus. Connections through the GP and
262
the SN pars reticulata or ventra l tegmental area then project to appropri ate regions of the thalam u ~ to link back to the cortical neurons of ori gin for the initial corticostriatal proj ections. These parallel loops through th e basal ganglia and the co rtex modulate specific subroutin es of cortical activity distinct to the appropriate fun ctio n. The SN pars compacta may act as the principal interconnec tions among these parallel loops.
FlGUI
The nu
end of rostral structu/ nUcleus
tegmen
The nu(
Is-Basal Gan,btor Systems- Basal Ganglia . _
-
nus the
SYSTEMIC NEUROSCIENCE
Hippocampal
ionnation
Precommi S5urai forn ix
Ven tral amygdalo rugal
pat hway
OA median
FIGU RE 111 .50: CO NN ECTIONS O F THE NUCLEUS ACC UMBE NS _ _ __ _ _ _ _ _ __ Th e nucl eus accumbens is located at th e anterior
states and addictive be havio rs.
end of th e striatum in th e int erior of th e ventra! and
a prin cipa l region in brain reward circuits associ ated w ith joy, pleasure, an d gratification . The involvem ent o f the nucleu s accumbens w ith a specitic limbic basal ganglia loop helps to provide m o to r ex pression o f emo tional responses and acco mp anying gestures and behaviors.
rostral forebrain. Inputs are derived fro m limbic structures (amygdala, hippoca mpal fo rmatio n, bed nucleus o f the stria terminal is), and the ventral tegm ental area, via a ri ch dopaminergic projectio n. The nucl eus accum be ns is central to mo tivational
[t
also appears to be
263
Autonomic, Hypothalamic, and Limbic Systems- Autonomic
SYSTEMIC NEUROSCIENCE
Nervous System Input ' 10 i!u tOll om ic pr!;!ga nglionlc neururlS ui sympathetic Jnd p,)rasyrnpathl'tic nerv o us sys tems: limbic iorl'brain ~tructures So me corticJ I .egions ~Iypolh.:lli)mic .egiuns Brain St!:'m ce nte rs
Inpu t, to dut onomic
pr e-g ~n 8Iionic neuron,
PreS
- - - - - sy",p~t het i c
POSI&~ nglioJlic
+ - -- .. _- .. s\'mp.:lIhel ic <••- - - - .
Jnd nuclei
Sensory inputs
Preg.lnslionic
pari)Fynlpathelic
Po~tsansliOrliC
"" " "'" ~ parasvmpathe tic
Ed in ge r.Wes tphdl
Ciliary g.J np,lion PupilJa.v (on~trlctor m . .... . . ~~ ___ _ ~ ••• __ ~
CiIr"lIym.
~
Plelygop.:lL:it int' ~ns~on
OWomotor III I! n.
Wcttmalgland s"'••••• __ •• • ___ • • Glands Ot nasill mUCOSil
Sall.,ary
gl~n(b
Supe,io. .. ·Ii· nucleU5
.
"
Submandib~lar SJ ngl lOll
[S"bm""",,, ."d•....__ .......... . S ubltngu~ 1 gland
\::
Faoal tV II ) fl .
GlossophJ rvngeJI (IXI n.
otlC ga~g l' O n
Parot'dgla nd ...·-·--· ••
····.·-!~
Smoot h m, c~ .d ia( m., ~ec.eto.\' ... ••• -;!' .~it gl.mo~ in heart lung, ,';see' a, G t l.aCllu de~cendjn g coJon ganglid
\ ,
____
---"
V
X agusl)n
!
~::.
'-' ..~
..-#.~3.:
~
"" ""
\
.
Dorsa l mo tor (au\ onom i
\
nucil;u> of X
L..lIer al ho rn (intermt'(\iol,lterJI cell column)
....\ White U)mmunic.1tls
Se cretion oi
e pine phrrne and
Infel lor
sJ.liv~ t p r )'
i
~
To ~"SUlldr smooth muscle 111
5kin and mus<:lc~. "'flector .... -- p ill 111m" 1\\,<;.11 glands in limb s
"\
Th OfJcic sp in ~ 1
Gray rJmu s fOO l communi ca ns
co rd
(Tl ·L2 J
o.
no replnephrrnr'
gJnglia
Into blood
. ~' ~ .r./ " "",'........• .. j
__ " '~'--""""" ~ ,f$ \- ~"~:~>
"""O''''"Od;·.:::~"o.,y'''m
To "'"'" . m.. ,moolhm . II., · '
L _______
"boh " " . "o,h, IIi"". ''''. ,.11'0 . S mooth m., <;ccre 10", ,'.~'O"' 'I',er'"~ < Intramural 'wi! , ,Je lower G( Ir"'c , &~ngliJ '~l"
>
.
"
"
•• '"
_
PohK 00. . -.,
4r~ I ~1)l, ~~' . _
,'"
""'"
• •.•
,j
Sacral spinal cord (S2·S4)
«
FIGURE 111 .51 : GENERAL ORGANIZATION OF THE AUTONOM IC NERVOUS SYSTEM _ __ The auto no mi c nervous system is a 2-neuron chain connecting preganglionic neurons Ihrough ganglia to visceral target tissues (cardiac muscle, smoo th mu scle, secretory glands, metabolic cells, cells of th e immune system ). Th e sympath etic division (sympathetic nervous system rSNSJ) is a thora co lumbar (T1-12 ) system arisin g from the inter med io late ral cell column of th e lateral horn, actin g thro ugh chain ganglia an d collateral ganglia; it is a system for fight-o r-flight, designed for reactions in an emergency. The parasympathetic division (parasym pathetic nelv ous system IPsNSJ) is a
264
_
craniosacral system arising fro m brain stem nud e associated w ith cranial nerves (CNs) III, VII, IX, a-.... X and from the intermediate gray in the 52-54 spinal cord. Connections from eNs III, VII, and 1\ act through cranial nerve ganglia; connecti ons ircr eNX and 52-54 act through intramural gan gli a in or near the target tissue. The PsN5 is a hom eosta· reparative system. Central connections from the limbic forebrain, the hypo tha lamus, and the brain stem regulating 5NS and PsNS o utflow to the bcx::t. act mainly through connections to vagal and s~ rr~ pathetic preganglionic neurons.
Jl onom ic
-\ utonom ic, H ypo th alami c, and Limbi c Systems-H ypothalamus and Pitui tary
SYSTEMIC NEUROSCI ENCE
iotlic
, """
t('fTIS;
lIJres
""",
'"",
r!lers udei PUTS
~I
• " ,
•
Preoplic nudei 2 Poraventri aJlJ.r nucleus J Anterior hypothalamic area 4 SupraoPllc nucleus 5 Lat eral hypothalamic J.rea f) Dorsal hypolnalamic area 7 D orsomed ial nucleu. B VenlromediJ.1nucleus
9 Postt'l'iof hypo th alamic area
10 Mafllmlllary!xxh'
TT Opticchi,ul1l 12 Lamina terminalis 13 An terio!" commisWle 14 Hypotl\;llamlC wkus I S Intel thalamic adhe~ 1& Fol nix 17 Seplum pellocidtlm
;:>i
pd
Jm
:ic
\
..oro region
18 Intel'Pf'"
19 Thala.~ 20 Tube!
21 Opoe "'I!l"O
"
22 Infu"","_
23 Ante...
24 POSIerG'
FIGURE 111.52 : GENERAL ANATOMY OF THE H The hypo th alam us, a collection of nuclei and fiber tracts in the ventral diencephalon. regulates vis ce ral autonomi c functi ons and neuroendocrin e fun cti on, parti cularly from the anterio r and poste rior pituitary. Many nuclei are fou nd between the posteri or bound ary (mamm illary bodies) and the anteri or bo un dary (lam in a terminalis, anterior com mi ss ure) o f the hypothalamu s; these nuclei are subdivided into 4 general hypot halam ic zones: (1 ) preopti c, {2) anteri or or supraoptic, (3) tuberal,
....'IUS _ _ _ _ _ __ _ _ __ "'"'-Cmmillary or posterior. From the medial at th e eN III \ entricle to the lateral the nuclei are s-_ ooi\ ided into 3 general perive ntricular ] medial, and (3) lateral. ...:..-lfy gland is attacfled at the base of the ;..amus via the media ""' em inence and the m (p ituita!) sta,· ·.. . The med ian emi· M1 important zone of neuroe ndocrine
n.
265
Autonomic, Hypotha lamic, and Limbic Systems-Hypothalamus a nd Pituitary
SYSTEMIC NEUROSCIENCE
Sections Through Hypothalamus I
1
Plane 1 COI'PlJS <:allow m
,
~~~~~~~~~~~~~~~~.·i'·~~~sePtum
:i'J,
'"
~i
Anteri o r horn o f lateral ventricle
Head ofpellucidum caudate nucleus Septal area
-,;."
Column of fornix
!Ii.
AnteriOT limb of inl ernal capsule
~;~==:==~===~~~'.~~~~?~~
.
,~~~~~~!t~=]~==::~~~~~~~~~~ l
'-.~_ _~:;;;".._ _-\;;--_ __
""
~~p Cl:oN ~
PUTamen
3rd ventp
Anlygdala
.
commis ~Jle
Lateral preoptic ilrea
Medial pleoplic are.t Amerior
Substantia innomina la Optic chiasm
•.•.•.•: : : Plane 2 ~,/
Interventricular foramen (of Monro)
lrd ...cnllide Column oi iornix Perivennicul,)! nucleus An$,llenllcularis
~
,
_ Paraventriculilf nucleus
-
_
JI'_"~~~~;:::~=::::::::::=,~==
!' e r '-
..
-===--
)
~J
. .-.,~./
7 ..
~
mfer;or thal".mic peduncle
La leral hypoth.,l.,mic .lIea Ante rior hypothala mic area
S"p"opHm" "" ISON) OptiC
tract
O pfic chiasm
FIGURE 111.53: SECTIONS THRO UG H THE HYPOTHALAMUS: PREOPTIC AND SUPRAOPTI C ZON ES _ _ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ The major nuclei in the preop tic zone include the medial and lateral preoptic areas. The organum vas culosum o f the lamina terminalis (OVLT). a circum ventricular organ, is presen t in this hypothalamic area. The major nudei in the supraoptic (anterior) zone include the supraoptic nucleus (SON ), the paraventricular nucleus (PVN ), the suprachiasmalic
266
nucleus, the anterior hypo thalamic area, and the lateral hypo thalamic area (LHA). Some nuclei, such as the PVN, have many subregions (magnocellular and parvocellular) that contain collections of chem ica lly specific neuro ns w ith disc rete projectio ns and functio ns. These gro ups o f neurons sometimes in termingle w ithin o ne subregio n o f the nucleus.
lothalamus
IS
Autonomic, Hypothalamic, and limbic Systems- Hypot halamus and Pituitary
I
SYSTEM IC NEUROSCl E1\C
Sections Through Hypothalamu s II
~~~§~~~~~~~~§~~~;
Plane 3
, of caudate nucleus callosum of laleral ventr icle _horn Septum pellucidum " - - - - _- -- - - - -- ---i, - Body of fornix
-r-~------__..---t-- Thalamus Mamilio tha lamic twCl 3rd ventricle
POSl- lim b 0 1 internal capsule Pul.amen
pallid us Dorsal hypoth al amic area i I nu cleus of fornix
Ansa lenticularis nucleus l aleral hypothalamic area I i hypothalamic area Supraoplic nucleus Pementricular arcuale nucleus
Plane 4 Thalamu s Mamill(')fh"lamic tract Post. limb of IIlIE'rnal cap~ule f'u tamen
Zona incerta and fields of Forel Fasciculu s lenticularis Dorsa l hypo thalamiC area Perjvenlricuiar nu cleus Dorsomt.'dial nucleus Aberrant pallidoiugal fibers l atelal hypothalamic area Ven tromedi al nucleus
Oplic Iract SupraoptiC nucl eus
<:.::::::::::;:.-~__ '"
-
Ie
iuch
Jlar lelll
and
Tub",ral nucl ei Periventr icul,)f arcua te nucleus
FIGURE 111.5 4: SECTIONS THROUGH THE H YPOTHALAMUS: TU BERAL ZONE _ _ _ _ __ The major nuclei in the tuberal zone include the dorsomedial (OM) nucleus. the ventromedial (VM) nucleus, the PVN, the arcuate nucleus, the peri arcuate area (~ndorphin cells), the tuberal nuclei, th e dorsal hypothalamic area, and the LHA. Some nuclei from the supraoptic zone (PVN, SON, LHA) extend cauda l~ into the tuberal zone, The median
eminence extends (rom this region, and axo ns from releasing..factor and inhibitory-factor neurons that control th e release of anterior pitui tary hor mones funnel down to th e co ntact zon e, v,,'here they release th ese factors into the hypophysia l portal system, whi ch balhes the cells of the anterio pituitalY,
26'
Autonomic, Hypothalamic, and limbic Systems- Hypot hal amu s
SYSTE MIC NEUROSCIENCE
and Pituitary Sections Through Hypothalamus fit
r:
)
;
Plane 5 Corpu s ca llosum
'\
f
'I·
lail of caudal~ nucleus
Anl_ horn of taler,,-I venllicle Body oi forni:- 3rd vO;: r1 lrid~ Th.Jla rn us Post. limb of i nl~rna l capsule Field H, of Forel
i/I
Id H, of forel Marnmillotll.llamfc Ifact
'.:
....
PUlamen Globu~
pallidus Post. hypothalami!..: ;lIea $uulhalJmic nucleus (aprulupechmcvlar Iransilion zone l ,l\e ral nypoth,JlCln lic area Opli<:tract p,uts o f medial
Column o f tOn'll);
mamm il1 Jry nucleus
j nterc ~ l a tus
~~~...
i
l ale ral m
nude u~
ClliiN ', .-:, : ~
i
Plane 6 Thalamus 3rd \'entr icle
Field H, of Forel
Field t-L~ oi Forel Putamen G lohus pallidus MammilioThalamic trac l PO$L hYllothaJaOl ic ':lIea Subthalamic nud E-US
~ _c_" ~ !" ~ ~
_
~ ma mml'" ary
In{. norn of laleral IIl!'ntricie
Laleral hvpolhalilmic are.,)
"ii-"
""
b
n ucleus
. -
Amygdala Jv1.amm iliary peduncle Supramammillary decussa\lon
FIGURE 111.55: SECTIONS THROU GH THE HYPOTHALAMUS: MAMMILLARY ZONE _ _ __ The major nuclei in the mammillary zone include the medial and lateral mammillary nuclei, the pos terior hypo th alam ic area, and the LHA. The LHA
268
extends thro ughout most of the length o f the hypo thalamus and shom neuronal characteri stics seen in the brai n stem reticul ar formatio n.
Ilam ~
. ...... o nomic, Hypothalamic, and Limbic Systems- Hypothalamus Pituitary
SYSTEMIC NEUROSCIENCE
1';.~~~~~~:".\: lamillothalamic t;:ao
..,,~- p,,,,,,,·;o,
area . · . I ~ Perrven\ncu ar
Jr----""W- nucleus
'\!uclcus
iotcrcalatus
Ventromedial nucleus nerve
\'1.!mm,ILlr. comple\' /
Tuberohypophyseal
[rad
OculomOlOr ! I!! no:> r. 0:>
h (irom
Irac t
Pons
-~- Posterior
lobe o! pituitary
FIGU RE 111 .56: SCHE MATIC RECONSTRUCTIO N OF THE HYPOTHALAMUS _ _ __ _ __ -\ schem atic 3·0 recon stru ctio n of the hypotha la mus in sagitta l section shows the nuclei, th e areas, and the zo nes that occupy this small region of the diencephalo n. Many pathways are represented, including the fornix, the mammiliothaiamic tract, the median forebrain bundle, the supraopticohy pophysial tract, the tu berohypop hysial (tuberoin
fundibular l trac t, and bra in stem co nnections w ith th e hypothalamu s. wh ich include th e dorsallongitu din al fasciculus, th e descendin g med ian forebrain bundle, the mammillotegmental tract, and descend ing connections irom the PVN to preganglionic autonomic nuclei.
269
Autonomi c Hypothalamic, and limbic Systems-Hypothalamus and Pituitary f
SYSTEMIC NEUROSCIENCE
Supplementary mOtor (premo!Of) ;lrea
Molor area
som"o"oro,y,,,, ~ Corpus C;;Iliosum ' - / / ,J.......... , .;,' ' ".
.......... ( ingula te gyrus Fornix
.
Hyp
I
Orbital cortex Amygdala Hippocampal formation
~~p °lION
Parahip pocamp;'ll gyrus
:\".':;: 1
FIGURE 1i1.5 7: FOREBRAIN REGIONS ASSOCIATED WITH THE HYPOTHALAMU S _ _ _ __ A number of forebrain region s are intimately co n
nected with th e hypothalamu s, some through d irect fiber projections and some through indirect co nnections. Important cerebral cortex region s include the prefron tal cortex, the orbitofrontal (orbital) co rtex, the cingulate cortex, the insular
cortex, th e parahip pocampal cortex, an d the
peria mygdaloid co rtex. Important subcortical regions of th e limbic forebrain include the hippo campus (a three-layered co rtex), the amygdaloid nuclei, and the septal nu clei. Important thalamic con nectio ns include the medial dorsal and anterio r nudei. Important olfactory connections inclu de the o lfactory tract, nu cle i, and cortex.
r j
5
~
h tl a c
P B
d
270
la _
-
onomic, Hypothalamic, and limb ic Systems- Hypothalamus -:) Pituitary
SYSTEM IC NEUROSCIENCE
II i ( inlwlille)o:\ rus
Cor pus cilllo~um
I ~>(;:::::~' ,:~I dorsal : nucleiJnd ~ 01thalamu) Septal nuclei
From s~pta" subtallosal, preoptic.. and frolllotempCll3! Jr~JS
Hypothalamic nu clei
ii~~~~~
S"iJ. ,.,-mif'1a lis
Olfactory bu lb Orbiloj, ontJI cortex prOJl"Ctlon )
Hippocampal formation
H'·pophvsls
:;-~tic ular
\
ent,~1
am\ gdaloiugal pathway
Oors.ll Iongit ucinal 1.1 ;.c ICU:U'
" ,Me.li," to",b",'" " " ",,,Ie rdeKenclm1;l - ,vled",""y C.lrdio vascular cente~ ,
,,,",,, IX) nc,,'(:
FIG URE 111.58: AFFERENT AND EFFERENT PATHWAYS ASSOCIATED WITH THE HYPOTHAlAMUS __________________________________________ -\pot hal amic co nnections are numerous and com ex. Some regions of th e ce reb ral cortex (pre -·onta l, orb itofr ontal) and th e thalamus (anterior) x nd axo nal projections directly to the hypo ,....,alamus. Diverse afferent pathways arise from the - ·ppocampal formation and the sub icu lum (fornix), ':'1e amygdaloid nudei (stria term inalis, ventral
o71ygdalofugal pathway), and the habenula Ifasc> cul us retroflexus). The retina sends direct retinohy pothalam ic fibers to the suprachiasmatic nucleus. Srain stem projectio ns, some compact and some diffuse, ascend to the hypothalamus th rough multi
pie pathways (not shown here). Efferent connec tion s fro m th e hypoth alamu s include those to the med ian emin ence (from multiple nuciei), the poste rior pituitary (suprao pticohypophys ial tract), the septal nucl ei and the anterior perforated substance (median forebrain bundle); those to the thalamus (mammillothalami c tract); and those to many brain stem and some spinal co rd sites (dorsal longitudinal fascicu lus, median forebrain bundl e, mammil lotegmenfal tract, direct co nnections from the PVN to preganglio nic neuro ns, and o thers).
2 71
SYSTEMIC NEUROSCIENCE
Autonomic, Hypothalamic, a nd limbic Systems- Hypoth ala mus and Pituitary Dien cl!'ph~ron
Brain Stem and Blood·Borne I
no SeN)
I
LHA. lateral prl'oplic .Jll!a))
I
-----------+j• l 1lof11lOr'leS, (glucose. Na.-, cyloi.:ines, others)
L
and Telencephalon Inpuls
H:etino hyp olh al..ulic Ihlihway
Assoc. RF polysenSOl)' information
(to lateral
Mammillary peduncle
• Dlf
d
I
(to
____...J
Mam millary nucleus)
. I Ito medial areas)
Hypothalamus
MF8
(to PVN)
"'rB I1\\
MD m idline nuclei
~_.::.:::..::=:::::,",,:::oo:.
(t~ lHA, Lateral
I
• (lo lHA )
po-eoptlC .Jrea.. other)
E 'h""
~
1 ·....;A::::"t"·orioO,t"
I.
Posterio r orbito(ronlal corre)!,
Olfactory bulb, rel ated region s
1-+-+---1'I (to PVN, lHAJ \\ 7I
•
I
I (to PVN )
(to
~d i a l preoptic area, AHA, SON)
Stri a termina lis ,
(to preoptic, medial areas)
I, I,
V6r'ltralam ygdalo fugal pillhwily
\to mediill milffiITlill.uy nucleus)
I_
Postoommissurill fornix
(via MFR, ST, VAFP)
Dors.al and ventral NA bundles (via MfB, Olfr •
I
O lfactory-re lated projection
(to widespread an:as)
_"
(to .... ] zones)
I
,
Pre
L----------'!"""-,.JI {IO widespread iI/east OlF .. KF lHA .. MFB =
Dorsal longitod ina l lasciculus Retic ular for ma tion Lu e ra! hypo thillamic area Median foreb ra in bu nd le NTS "' NucieuSlla ctUS50li(ariu s
PVN .. Polraveotricular nucleus
CA .. catechobm ine NA .. "'Ofadl~ic 5HT .. :;·Hy~oxytrypt amine. ser()(onin AHA - An tetio4" hypoth alamic area
SON - Supraop tic nucleus Sf - Su ia (erm in-Ollis VAf.P = Ventral amygdalofug.l1pa lhwoly MO = Medial dorsal f1udelJS 01 thalam us
ClmN H':·", :
FIGU RE 111 .59: SCHEMATIC DIAGRAM O F MAJOR HYPOTHALAMI C AFFERENT PATHWAYS _ The hypothalamus receives extensive input from many regions of the eNS. Descending inputs arrive from limbic forebrain structures (hippocampal for~ mati o n, subicu lum, amygdala), the cerebral cortex (anterior (ingu late, orbitofrontal, prefrontal), and the thalamus (medial dorsal). Ascending inputs arrive from extensive areas of the autonomic brain stem (tegmental nuclei, periaqueductal gray, parabrachial nuclei, nucleus tractus solitarius
272
[NTS]); the locus coe ruleu s and tegmental ca te cho!amine nucl ei; raphe serotonergic nuclei; and the brain stem reticular formation. Th e retina sene: input directly to the suprachiasmatic nucleus, a ~ lion of the hypothalamus that modulates diurna rhythms. Blood·bo rne substances (cytokines, ho," mones, glucose, Na+, o thers ) influence the hvpc thalamus via numero us ro utes and mechanism::..
amu s
-
.\utonomic, Hypothalamic, and limbic System s-Hypothalamus an d Pituitary
SYSTEMIC NEUROSCIENCE Diencephalon, Telencephalon, and Pituitary Efferen t Pathwa ys
Brain Ste m Efferent Pathways
Irom Ol agnoccllular PVN, SON) Anterior pill.litarv
" om RF and IF neuron s)
(t rom arCLlil[C, pt.:. '1\ enlriClJI<Jf nuclei)
_ (irom LHA )
H) pothalamus
'" !.lI"O
(irOn! medial periventriculaf area )
1":'"<e63J m.lmmHlar y nuclei)
"orr,
ill
I,
O!"". efl\ncular nucleus) f - - - - - -
iirom !oeptal nuclei. p reopti c Mea) (from periarCUilli: ,1 fC,]
(from p.uvo<eliular PVN
RF - Releasin g faClor I F " Inhibitory facto r PVN ., P,uaventricu!;u nud€\.lS SON - SUPfilOplic nucleus MfB " Media n foreb rai n bundle
SHT :
5-Hvd rox~ lr\p!amin" ~""' o'.){1-'l
SNS - Sympa thetic nt'J' 01.1."" ,:"''" Dlf " Dor.<,,)1 longi tudinal ra ,,,-ocu ,, ~ ILC - Int ermed:oI,H",ral ce'! c(>.'-"" DM N of X : OmSill malar tautOnomic nue;,,:.!, of \
M Teg T " Mammilioleg merllal tract FilSc. RelrOO exu s " F,lsci cu lu s Re troflexus (HilbenuloPf>duncu lar Tract) S1 " Stri;) termirldlis CA - Ca tt'cholaminf>
FI GURE 111.60: SCHEMATIC DIAGRAM OF MAJOR HYPOTH ALAMIC EFFERENT PATHWAYS _ _ Th e hypothalamus gives rise to ex tensive effe rent prOjectio ns. Ascending efferents are sent to the limbic forebrain structures (amygdala, septal mlele', anteri or pe rforated substan ce), the cerebral co rtex (orbitofrontal cortex and tem pora l associ atio n cortex), and the thalamus (medial dorsal, anterior). Extensive projections are sent to the median emi nence (releaSing and inhibitory factors for control of anterior pituitary ho rmones; dopamin e projec tions from the arcuate nucleus and the PVN) and
to th e posteri or pituitary. O ther efferent projections are sent directlv and indirectly to the preganglionic neuro ns a t the SNS and the PSNS (median fore brai n bu ndl e, dorsal lon gitudinal fasciculus, mammill otegmenta l tract, d irec t project ions from the PVN), to \.videspread autonomic and visceral nuclei (noradrenergic neurons, serotonergic neurons, parabrachial nu clei, NTS, per iaq ueductal gray, tegmental nuclei, in terpedu ncul ar nucleus), and to the brain stem reticular formatio n.
273
SYSTEMIC NEUROSCIENCE
Autonomic, Hypoth ala mic, and Limbic and Pituitary
Sys te m s-H yp o th a l am u~
(orIel(
Papez circuit
limbic {()(ebra;n structures
MD Thalamus Amerior thal amus
Midbrain te8rnenturn Brain stem autonomic structures
Brain stem autonomic struClures
Hypophysea! porlal system _ _ _., An terior
Posterior pituit,uy
Spinal cord SNS pregangllonics
SupraopticohYDo phY5t'al traCI - - - -
Dl F .. eorsallonglludinal i a$Cicu lus
MO - Medial dor5al nucleus of thalamus
M f B .. Median forebrain bundle ST '"' Stria termin alis
f'X - Forni" MTT .. Mammilk)(ha lamic ' r;let
VAFP .. Venval amygdalofugal pathWolY
SNS .. Sympathetic nervous system
C ~.~N
FIGURE 111.61 : SUMMARY OF GENERAL HYPOTHALAMIC CONNECTIONS _ _ _ _ __ _ The lateral, medi al, and periventri cuiar zo nes of th e hypotha lamus have specific connectio ns with the cerebra l cortex, the limbic fo rebrain structures, the thalamus, and w idespread areas of the brain stem. Extensive efferent projections of the hyper thalamus are directed toward regulation of pre-
274
ganglio nic sympathetic and parasympathelic neuro ns and toward release and regulation o f hormo nes of the anterio r and posterior pituitary_ The anterior pituitary hormones regulate hormone secretio n and functional activities of many target structures throughout the body_
-
.\ utonomic, Hypothalamic, and limbic Systems-Hypothalamus -:- nd Pituitary
SYSTEMIC NEUROSC IENCE
-,
\J loc~s
coe ruleus
Parabrachial nuclei
Hypophyse:a l porla l , },stem in th e median eminence
/
Antefio,
pituitary
,:,c' ~::::~~l
Nudeu! SOhLlrius To rntramura l gan glia
i
, \
Do!';al mo tor
nucleus oi X •---,v;;:;;-;-:;Jiiiiii~:".!'A:+-+--\i-\ Va gu> \ comp lex (au tonomic)
Interm Nliolater 31 cell column In laleral hom To sy mpaThetic chain ganglia, • _ colla te ral gan gli a, ad renal medu lla
_
--::==:---_~
Too racic
spinal cord
(lH2)
FIG URE 111.62: PARAVEN TRI CULAR NUClEUS OF THE HYPOTHALAMUS : REGULATION OF PITUITARY N EU RO H ORMONA L OUTFLOW, AUTONO MI C PREGANGLI ON IC O UTF LOW, AN D LI MBIC ACT IVITY _ _ _ _ _ _ __ _ _ __ _ __ The PVN has man y projectio ns that help to coordi na te pituitary neuro ho rmo nal o utflow, auto nomic pregangli o niC outflow, and limbic activity. Magno cell ular neurons send axon s to the posterior pitu itary, rel eas in g oxytocin and vasopressin into the general circulation. Cortico tropin-releasing factor (CRF) neurons and some vasopressin neurons send axons to the median eminence; these axons release thei r hormon es into th e hypophyseal portal
system, influencing the release of ACTH , PVN parvocellular neurons send direct descending pro jections to preganglio nic neurons o( the parasym path etics (d orsal moto r nucleus of CN X) and the sym pathetics (interm ediolateral cell co lumn in the Tl -L2 lateral horn) and to the NTS. These neurons also send axons to several important limbic-related struc tures, such as the amygdala, the parabrachial nuclei, and the locus coeruleus. 2 75
SYSTEMIC NEUROSCIENCE
Autonomic, Hypothalamic, and Limbic Systems- Hypothalamus and Pituitary ~"
Behaviors Iniluenc:ed by Cytokines;
y -""~,. .,>'< ..,.-~
Illness hr.havior Affective b ehavior Cognitive beh avior Autonomic an d neuroendocrine
-
"- ,.
regulation
bloocJ.brain oo.mer (BBB)
~~ ,
O rg.lnum vil K ulafum of the lamina
VasCl,jlature to hypothalamu s
e
G = Inlerle ukin-l !3 {ll-1~l
Other cytokine~ actin g on brain:
®
IL 6 {inlerleu kin-6)
TNF-o. (tumor nt'cr()!;is faClor-o )
Se"""" g;eog!ion or X
IL-2 (inlerJeukin-2) irIviscera
h----l+- Nudeus tf"dCTus solil.1r'us
".'Ujl
Vag.l l arierenlS
~
~~~
•
y- _ _ _ _...
~
1-' ,, \
Dorsal mOto r [a utonomic)
nudeusorx
,I ellerents to intramural ganglia
associated with vagal aife.-enls
Periphera l
Somalic
nl?rve
Sympathetic
Spinal cord
. ganglion
® e - ~ -"'0 \;II' Target
CD
's'
Cytokin es tr~ n s ported directl)' acrm s th e 888.
a> C)'to kincs cros&ing IntO Ctlrebmsp in,d fluid at OVlT. thai release PG E2 01 neurons thai projeCt to
Of .lC lingon cells visct'fa~aulonomic Wuelvre'>-
C!l Cylo kine-stimulated r~l eas(> o f small mol ecu les (su ch as NO) Ihat directly cross in (() th e brain and act as mediators. Cytoki ne stimulalion 0 1 vagal afferetlts (t hr o ugh p.>raoeurons] thai
@ modulate aCllvity in nucleus Iradus ~Iitariv:o. iniluendn!! the mvlliple
Cy tokin e activation oi o ther afferents tha t modu late
\V dorsa l horn sensory plOce!...~ng tv m.:my site'>..
®
o
C~'lokine modulation o f norepinephrir'le release from sy mpatheti c: !'lerv e termilla l•.
Cytokin e modu lation of ne uro transmitt e r intracellul Jr Signalin g in t.arse t cells.
® C~·tokine mo dulation o i p ituitary hOlmonc release.
FIGURE 111.63: MECHANISMS OF CYTOK INE INFLUE NCES ON THE HYPOTHALAMUS AND OTHER BRAIN REGIO NS AND O N BEHAVIOR _ _ _ _ _ _ _ _ _ _ __ Cytokin es, including interleukin (IL)- '~, IL-6, tumor necrosis factor-ex, and IL-2, ca n influ ence central neuronal activity and behavior. This diagram illus trates IL-l access to the brain: (1) directly cross ing the bl ood-brain barrier into the brain, (2) acting on circumventricular organs (OVLT), releasing small mediato rs such as PGE2, (3) acting o n vascular endoth elial cells, releasing nitric oxid e (NO), which
P
276
acts in th e CNS, (4) activatin g vaga l afferents into th e NTS via paragan gli on cells, and (5) activating o ther afferent nerve fibers. IL-l can evoke illness behavior (fever, indu ction of slow-wave slee p, decreased appetite, lethargy, classic illn ess symp toms), influence autonomic and neuroendocrine regulation, and influence both affective and cogni tive function s and behavior.
p
~mus
-
Autonomic, Hypothalamic, and Limbi c S) s:lems- H\-pothaJamu s and Pituitary
SYSTEMIC NEUROSCIENCE
) Pineal gland
<,,.,;~
"'\ Organ um vascularum of the lamina terminalis (O VU )
/
Median eminence
. .-"'"
. <~.~
~
~
FIGURE 111.64: CIRCUMVENTRICULAR 0
/
~
\
Area postrema
\ ,, I
G.-
Circumventri cular organs are "windows o n
endothelial appositions and instead have leoes- trated vasculature. Thus, the circumventricu;ar organs have no blood-brain barrier. Som e oj-
organs- th e OVLT, the subfornical organ, a nd ' ~ area postrema-have associated neurons \\ ; ... projec tions to hypothalamic and other viscera. structures. They also have cells that can release small molecules, such as PGE2, into the CSF affectin g target structures at a distance. The
~
.::. ~ i te of axonal release (from PVN neuro ns) of oxytoci n a'iOpressin into the general circula ~'1 eminence is a zone of neuro "ra1Sdu ctio n for the secretio n of ~ and inhibitory factors into the - oonal vasc ulature; th ese facto rs influ -~.€' or anterior pituitary hormones. ::;and synthesizes and releases the ho r ~~ '"1()cel kdar
n,
277
SYSTEMIC NEUROSCIENCE
Autonomic, Hypothalamic, and limbic Systems-Hypothalamu-s and Pituitary
Blood Supply of Hypothalamus and Pituitary Gland
"
".
. ,
"J>- J
K
Hypothalamic \'esseis
nucleus
lans h ypophysea l portal veins
Anterior brOl.nch} Superior
Posle.'"ioo branch hypophy>eal
\1k
'"ery
Short hypophy>eal
portal veins ~
~
Artery of trabecul~ Trabelnu>
,~
tr;;.~ Anterior lobe
Secondary pl ex us of hypophyseal port al ,ystem
l ate ral branch """"" ,cd
Simil ar >ecl ion through supraopti c nucleu>
Efferent vein to
caverl10us sinu~
M ed ial branch /
(.wernOU 5 si nu s
cf Infer ior hypophysea l
Internal ca ru tid arter"
~
Superior hypophyseal artery
Portal·v,,;n >
~!p
Lateral hypophyseal vein ~ / Inferior hypophyseal ~05te rior
FIGURE 111-65: HYPOPHYSEAL PORTAL VASCULATURE _ __ The hypophyseal portal vascula r system derives from arterioles that enter the med ian em in ence at the base of the hypothalamus. The primary capi l lary plexus is a site where releas ing and inhibitory factors that influence the secretion of anterior pitu itary hormones are released from axons w hose
Q '~N
lor
_ _ _ __
_
_
_ _ __
neuron s reside in the hypothalamu s and other Ci\. ~ sites. These releaSing and inhibitory factors th en travel th rough venu les into th e seco ndary caprl lan plexus in very hi gh concentrations and act directl\ on anterior pituitary celi s, w hich synthesize and secrete th e hormones of the anterior pi tuitary.
.
• c
~
o
278
un
>\utonomic, Hypothalamic, and limbic Systems- Hyp othalamus
-
a nd Pituitary
SYSTEM IC NEUROSCIENCE Emotional and extt'TOCepliv/:!
j;,iluences via afferen t nerves
nucleus
\0 hypothalamus .:.-.:.-~~-~~
. : ,.-..:
Blomi-borne mol ~cutar
mnu ences on CRF neurons
Specific secretory cell s of ante riOI lohe (adenohypo physis) influenced by neuroseoetion5 from hypothalamus
Skin (melanocytes)
Thyroid hormones
Adrenocor tica l hormones
Es trogen
Testosterone
Progestero ne
FIGURE 111.66: REGULATION OF ANTERIOR PITUITARY HORMONE SECRETION _ _ _ __ _ Neurons that synthesize releasing and inhibito ry iactors for control of anterior pituitary hormones send axons th at termi nate on the primary capillary plexus of the hypophysea l portal system (the zo ne of neuroendocrine transduction) and release these factors into th e hypop hyseal portal blood. Th ese factors then flow into the seco ndary hypophyseal portal plexus and regulate the release of anterior pituitary hormones. These hormo nes ac t o n target organs to affec t the release of target organ
hormones or to intluence metabo lic and functiona l ac tivities. For example, CRF neurons release CRF into the hypophyseal portal blood, regulating the release of ACTH, which in turn regu lates th e release of cortisol from th e adrenal cortex. M agnocell ular neuron s of the PVN and th e SON send axons directly to the posterior pituitary; th ese axons release oxytocin and arginine vasopressin directly into the systemic circulation.
279
SYSTEMIC NEUROSCIENCE
Systems-Hypothalaml.i ,~
Autonom ic, Hypothalamic, and limbic and Pituita ry
Ne uros.ecrelory En ding (pos te rior pituitary)
"'' ' Jll ' t'( 'rf.,·jji~ t '/~z'1' /d" t %ll I: "tr,~
Pi tuicvte processes
:>.:
~ ,
""
" '.~ :>
l'
,z~t '!'fa "I Iiit
.
'<"~
..
.
I
:,,,~'t
~
~
"f" ! ' -, ,- , to'! ~
'~I, i d I"
I:
'"
{I,'
I',
·t\ I.,
,\ -1"
•
" ' ,: l t,-,
i~~!"\!f;)-~·-~~d'~..\ ~ '. 2\ ;J~ ~ "'M '0/-
".
~,11.
---. .'
.,11
BrWFl -s\cm t patnways I
J-,; .,-
Axon
"''HI
~;o~
/1
~
"
1;
I,
[}Ii
iiw'
.,
(
i?:
\ ~.
..
\ .-"~\
:."
~I'"
,,('''''.
l'
\i
V
~i
:'
.~ .. ~ ~-~
."J.,~ -<;~-', fZ.... -'/0
"".. ::'''~
"'" "'r-· --".,',' ''
M
~rti · .
C.~pillJ.ry-
.,- . .?O: '~~
;it:~I<,st
-... -
Neurosecretory
Endothelium M;l51<:ell
~es id(-'S
Collagen space ~
:.ulsr Arlerial
O rigin uf Y;lsopf"('ssin
tohvpCl
Supriloplic nucl eus
Cell of sli praop lil
Neurolw p() p h y~ eJ I II
nucleus
,/'"
tran ' f10 rt
P05lerior lobe
Anterior
.j
/~! e of~'J
produf l " ,j
Po,terlor lobe -
Fenestrated
JJ '
of se(re l olY
Ineumoypophy!>i s)
I'"ij ~
Axonal
He rri,\ S bod le , _ __________.---1( • I,
c.lpillary
.~
• ..
~~~ O'Il!N vi
~\·:.·: :I
FIGURE 111.67: POSTERIOR PITUITARY (NEURO HYPOPHYSEAL) HORMONES,
OXYTOCIN AND VASOPRESSIN _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
F
Magn ocellular neuron s in the PVN and the SON send axons directly through the infundibular region and th e pituitary stalk, to tenTlinate on th e vascula tu re in the posterior pituitary. Neurons from borh nuclei syntheSize and release oxytocin and arginine vasopress in in to the systemic vasculature. Brain stem and forebrain pathways terminate on the magnocellular neurons and regulate th eir secretion of oxytoci n and vasopress in. Th ese ma gnocellul ar
\
280
neurons possess extensive protein synthetic capac ity and transport the vesicles in w hich their hor mo nes are packaged to the axon terminals with very fast axoplasmic transport The hormo nes are released fro m the termi nals and di ffuse through the fenestra ted capillari es directfy into the systemic v a~ culature (inset: Neurosecretory Efferent Endings From Magnocellular Neurons in PVN an d SO N).
b b u
it
al
u
n,
l am ~.
~utonomic,
-
and Pituitary
Hypothalamic, and Limbic Systems-Hypothala mu s
SYSTEMIC NEUROSClE' CE MKHANISM OF ANTIDIURETIC HORMONI IN IItc.llIAIINC. tJlIlNI V{IIIJM! ANI> (ON(
ADH IS produced In >upraoplic and I'Jravenln<.;u.
lar nuel .. i of hypolha lamu~ and d"""end~ along nerve fibers
10 neuruh~1K)l'hy,,;,
~NJRAJION
0;m01Jr.~~j'~"di::· ! ~;\]i~~~~j~:~
; n I J~e 1
0r,,1 or Blood ""chJnS,,\\Jth
I) . : 1'
,ec!emJ lI0 55 " J gut I ' i loss Into bod\ cJ\ltie s IJ scites, efiu· ...ont or loss o!'.lernall\ Ihcmm m,lge s"!"!ai
whe r.. it i •• to red
for sub-5eq uent
rele.J.>e
, hypoth.llamic ~more (eplOl$ and by low. blood \'oIume aifec!ing
loor.>(;( and c~ r otid volume recep tors; low
"''''''3j
osmo llao
In presen ce of ADH, blood flow to rena l med ulla is dimi"i~ h ed, th us augmentin g hypertonici!)' oi medull ary il1lers!ilium by minimi z· ing depletion oi solutes via bl ood-
ADH cause, \vall s 01 co ll ectin g duc ts to become mOle permeabl e 10 "'01(1; ' ond thus permits 0" mo lal equil iblation arid Jbsorption of walei' into the hypertonic intersti tium: a Ima MvoIunle o i hishl~ CQnCCf1lra ted Ur~le is excreled
o
/
--.J I
,
,
270
290
310
Plasma o~mol ali.y (mO~m ;kg Hp)
- 30 - 20 -1 0
0
10 20
% ( h;lnge in blood volume o r pte»u' e
FIGURE 111.68: VASO PRESSIN (ANTIDIURETIC HORMON E) REGU LATION OF WATER BALANC E AND FLUID OSMOLALITY _ _ _ _ _ _ _ _ __ _ _ _ _ __ __ Vasopress in regu lates the vo lume of water secreted by the kidneys. Vasopressin secretion is regulated by the osmola li ty of body fluids and by blood vol um e and pressu re, Changes in body fluid osmolal ity of a few percent are suffi cient to significantly alter vasopressin secretio n. Decreases in blood vol ume and pressure of 10% to 15% or more are needed to affect va sopressin secretio n. The blood
vo lume and pressure sensors are found in the pul monary vessels, ca rotid sinu s, and the ao rti c arch. These baroreceptors respond to stretch of the ves sel wall, which is dependent on blood vo lum e and pressure. The diagram shows th e mechanisms of action of vasopressin o n th e kidney, with resultant effects on urin e vo lu me and concentration.
281
~
._ ...
_.......,..... ........,,~.:-....,..-~=~~-=~~.-.?,S::_""'-~_._~.~"'.,:'''.;;,;,;.~....s.........._ .
Conservation a-f!
regulation
o
,., 0
production oihe~-
loss .' . -j{.
.
::
;.:
«.-.k···/<;0¥-;...;,;.. C:';.<~.,~,~" _J:f~.'N_ """"&Q.0_
Inflammatory cylokines,
Neurohumcral mechanism fot- increasin8 ~ thyrotropic activity of anteliOf lobe " fO
elevate metabolism
'(
~!and
, t--- R e~pil a tion
t
regulation
37°C (98.6 °f )
l
Cutaneous blood vessel constricti on (dilation)
Perspiration
t
~~? o.._•.
-
~
M"'''
FIGURE 111.69: THE HYPOTHALAMUS AND THERMOREGULATION _ _ _ _ _ _ _ _ __ The preoptic area of the hypothalamus contains wa rmth-sensitive neurons. The posterior hypothala mic area (PH A) contains cold-sensiti ve neurons. The preoptic area an d the anterio r hypothalamic area initi ate neuronal responses for heat dissipation (parasympatheti c); the PHA initi ates neuronal respon ses for heat generation (sympathetic). Neu ro nal pathways arisi ng (rom the brain stem and the limbic forebrain areas can modulate the activity of these thermoregulatory systems. The preoptic
282
area is responsive to pyrogens and the inflamma tory cytokine IL-l p; thi s area can generate an increased setiJoint for temperature regulation, thu s initi ating a disease-associated fever. Extensive hypo th alam ic connectio ns with the brain stem and th e sp in al cord are used to initiate ap propriate heat-d issipa tion or heat-generati o n responses. App ropriate behavioral responses also are initiated to op timize thermoregu latio n (e.g., going to a warmer or cooler location).
=\utonomic, Hypothalamic, and Limbi c Systems-H\ pothalamus and Pituitary PARASYMPATH ETIC
SYSTEM IC NEUROSCIE',CE SYMPATHETIC
SmaU aneries; and "'le
Spinal
(ord
II
Change in posturE' (sitling to s tandi~
I
+
Venou~
return
0 '-r-_ _ _~~~-~...",! o ·1 00· 200 .\-IA P (n1m rig)
'P. . .asyrn~theli( I efferent QUtpul \
cs;:;;;;;;:
I MAP
•
, Firing rate of barOfE'Ceplor .me.en! fi~
- -~
t
t
.HE'aft rail' -
Qudiac output
tMAP
.
L.
FIGURE 111. 70: SHORT-TERM REGULATIO N OF BLOOD PRESSUR E _ _ _ _ _ _ _ _ __ Both the sympathetic and parasymp athetic divi sions of the autonomic nervous system are involved in maintaining blood pressure on a seco nd-by-second basi s. Many descending path ways from the brain stem (including the NTS, tegmental catecholamin e nucl ei, the locus coeruleus, raphe nuclei, the rostral ventrolateral medulla, other medullary reticular regions, parabrachial nuclei, angi otensin II-containing neurons) and the hypothalamus regulate the auto nom ic preganglionic neurons associated "',fith
short-term bl ood pressure reg ulatio n. Th e hypo
thalamu s. and the NTS are the key sites integrating
limbic forebrain dnd cortica l inf1uences over th e
brain stem regions that regulate blood pressure.
These brain stem sites have extensive interco n
nections w ith each other. Th e examp le of blood
pressure regulalion in this plate is based on a
chan ge in posture. (ACh == acetylcholine,
E = epinephrine, NE = norepinephrine,
MAP = mean arterial pressure.)
283
Autono mic, Hypoth alamic, and Limbic Systems- Hypothalamus and Pituitary
SYSTEMIC NEUROSCIENCE Rt'S ponse 10 Decre a sed Blood Volume and
t
Pres~utt
RI,'~ponse
S~'mp~ thetic
to Incn'Olu d Blood Vo lume and P' l'ss u re
I SylTlpilthetie
Ile'VI' ;Klivity
I - - - - - ADH ------.,
_ ~ ADH
, nerve activity
eN IX. X
Angiotensin
HeJrt
,lnd
lung,
eN IX, X
"
,it"
~Ild
r~
A" .'
~ }
-"'..;:'
I Ao,'o,"o,'oo,,, TAO"O'' ' 'O ,
ANt>
,---~
-":.1_,::,/'
Liver
lungs
Adrenal;
,\drenals
I
, AldoslerollC
I Renin
, .md
Renin
L r.; ! im(,I;Jle~
angiofen$in n
'cC°::.) Aldosterone ...~"'c":'cec'o
renin
~I'u{'rion
:m(/ decreAse! NaCi excretIon)
J. Perkins
L
- ;'':.l0
IdeCleas(>s waler
Ki dneys
{'.>:netion l
I
t
Blood
v()Jum~'
l inneMed I f~O inrdkt:j
,Ifld prt'Sstlrl'
..
I Bloud \ " Iun ...
,
and pr('~~u,,'
!.IS, MfA
o.~
FIGURE 111.71: LONG·TERM REG U LATION OF BLOOD PRESSU RE _ _ _ _ _ _ _ _ __ When blood volume and blood pressure change, the kidneys respond by retaining or excretin g NaCl and water in order to resto re blood volum e to its normal homeostatic state. With increased sympa-
2B4
thelic aCfivatio n, no repinephrine and epinephrine secretion from sympathetic nerve terminals and the adrenal medulla in crease in the ci rculation and act on the kidney to red uce NaCI excretion.
M onomic, Hypothalamic, and limbi c S\ ste ms- H\ pothalamu s ill d Pituitary
SYSTEMIC
EUROSCIE CE
c::::;';,lJ~
Ca lc.:Inne II:;W""
Taste QfiQod
.:
Heilring (sounds 01 food pr~par-ation, call to dinner,
O ('Cl" a...~
bell,etc.)
oiCo.. ClP· and Jep:,.,
Thoracic Dorsal rool
0., .,# . ·~"'H ~
Deplt'riOll of body rnJtri~nl Slore5 ,",10d" QI
inducin,!t hun!,,,,
-
<EV Symp,llhelic efier~ls
-
Pat"iympa l hel ic~.f ferrnts
r
- - ....fie1enh land CNS connec:tion~1 - - - - lodell"il" palhs
H unger ( 011111< .,...... - ,.
FIGURE 111 .72: NEURAL CONTROL OF APPETITE A" D H l " GE R _ _ _ _ __ _ _ _ __ Th e sensa ti ons of hunger and sa ti ety are comple, and include multiple neural pathways and cirCldal ing hormo nes_ Depicted here are pathways invo lved in the sensatio n of hunger. Altho ugh o ur understandin g is incomplete, the hypothalamus is known to pl aya critica l rol e in co ntrollin g appe tite and food intake_ When food is ingested, chol ecys tokinin and glucagon-like peplid e-l are released irom neuroendocrine cells in the intestine. These
hormones :::uppress ap petite and give the sensation oi ~at j el;\. In the absence of food, the level s of the::€' hormones are low. Long-term regulatio n of iood intake il1\ olves the ho rmone leptin, w hich is produced b~ fat cells, \lVhen fat stores are hi gh, leptin is re leased and appears to act on the hypo thalamus to sup press appeti te. When body nutrient stOres are depleted, leptin levels are lowe red.
285
SYSTEMIC NEUROSCIENCE
Autonomic, Hypothalamic, and limbic Systems-Hypothalamus and Pituitary
Ne ural, Neuroendocrine and Systemic Components of Rage Reaction paMrn released ~nd cortex and
Or!);t"ffon,all-on"~ ~-"\';'
11 ",,~i
l'- """C""l -
Median iO
•
~
"~Ii
"T ,root Id"f
il iWi
""
"
Pe!. ic""""fl....-.- '
~~p ' ·'~N
FIGURE 111.73: RESPONSE NEURAL AND NEUROENDOCRINE ROLES IN THE FIGHT-OR-FLIGHT ____________________________________________ The classic sympathetic fight-or-fligh t response, shown here CI S a rage response, invo lves the secre tion of neuroendocrine "stress hormon es," whi ch include cortisol fro m the hypothalamcrpituitary adrenal (HPA) axis and norepinephrine and epi nephrine from symp ath etic nerve terminals and the adrenal medulla. Sympathetic connectio ns with the viscera ini tiate physiological changes to support th e in tegrated fight-or-flight response. Th ese changes include diversion of blood (rom th e viscera and the skin to the muscles, increased hea rt
286
rate and cardiac o utput and contractili ty, bra n chodilation, pupillary dilation, decreased gastroin testin al activation, decreased renal activity, and glyco genolysis from th e live r. Inputs from th e limbic forebrain, the co rtex, and the brain stem regulale th e hypothalamic co ntro l of neuroen docrin e an d autonomic outflow and are key in initiating the classic fight-or-flight response_ In the fight-or-fli ght respon se, the brain stem parasympathetic neurons are inhibited.
omic, Hypoth a lamic, and limbic Systems-H ypotha lamus Pi tuitary
( -
SYSTEM IC MUROSClE'JCE
, -
- - --limbjc forebra,n
J · .,.2 ;
(cingu la!e (0."1"', anly gd J I~
Cytokin .. a nd inflam matory mediator ieedb Kk to th" bra in and Bra in nud el
e minenn~
Va o;c ular de live ry of nellfOEndoc:rine hormone~
R"'!':.J.;;ing a"d "irY' ·btllflg factor s
, Thymus
I
t r~ctw;
.'- ------ ---.~ ,, ,, ,,
Balle
>olitariu,
,
rn ~rrow
Vagu~
\
(,'\) n.
... "0'''' motor l ~lJ!onomk:)
nu de lJ ~
---------- ..
Pulmoll ar y
MALT
Spleen
G J 1·J _~s()( i ateci
.• "Tl pnoid li$sue
(GALT) Skin lym phoid tissue
c
=-----,~ Pr("l!~nglio"ic
>m ph nooes
.I
Collateral sympathetic ganglion
"' -
;\mp ,11 hetic
f ,., , tw ................. ', ............ =>-~ .... -_ .
~
01X
-.
~, ;;,.-- - ---- ------ --------- -------------
~~?
--
~ ,<.u..
~ ~~
- IGU RE 111.74: NEUROIMMUNOMODULATIO N _ _ _ _ __ _ _ _ _ __ _ __ _ ,... '1 nections from the cerebral cortex, the limbic ;-t"brain, th e hypo thalamus, and the brain stem ~rt extensive modulation over autono mic pre .......:;:glionic outflow and neuroendocrine outflow. ?J rohormones and neuro transmitters fro m this
...d ow target lymphoid orga ns and cel ls of 'he
'"'llune system. Thi s ci rcuitry provides th e sub n.te for behavi or, emotional responsiveness,
..... ro nic stressors, and positive complem entary
·erven tion s to influ ence immune resp onses. ~ m pathetic postgan glionic noradrenergic fibers
direct/\ innervate virtually all organs of the immune system. Vagal postganglionics innervate pulmonary and gut-assoc iated lymphoid tissue. Pituitary hor mones in the circula tion, and their ta rget organ hormones. modulate immune reactivity in all lymp hoid organs. Co rtisol, norepinephrin e, and epinephrin e are partic ularly important in mediating chronic stress respo nses related to immun e reactivity. Circul atin g and local cyrokin es and inflammatory mediators act on the brai n and th e pituita ry to provide immune-neural signaling.
28 7
SYSTEMIC NEUROSCIENCE
Autonomic, HypothaJamic, and Limbic Systems- Limbic
Major limbic Forebrain Structures
(inguLu{'
Intef"ventn c;ul.lr fO fJmen
g~'fUS
Anterior nucleus of thalamus
Indu, ium gri,(':um
In tertha lam ic adhesion
CorpU$ callo,um Septum pellucirlum
Precommissur,ll iornl:ot" Stria
Seopt,ll nuclei
medu llarl5
Subca llosa l H\,pot l1alamus Paraterminai gyrus .............
Calcarine sulcus
l amina termin alis
med i3l st fia
O lfacto ry
laterill stria {
tr~ct
------~ ~ ~~ -,
bulb:----· ---..
~
(fissure)
.. ~"
~ ,I _ ;i Gyrus "
,
·
-,.~:(
J;N#H':..::;,..
•.
fasciolari>
Anterior perforated
substJnce OptiC chiasm Pus\commissural fornix
De nIa lI' gyru s
:? \ ',
imbriaof hippocampus
Mammillary body and mammillotnalamic tract
Medial forebrain bondle ---1 A m~'gdaloid
(nuclei)
,p~p
tT
0 llliN '~ '.'.': ;~
Pa. ahippocampa l gyrus body
/ Uncus
Inlerpedun(.u/<;)r nucleus
Descending conne(tions to rt'ticular and tegmental nuclei of braIn ste m (dorsallongilUdi nal iasciculus)
F.:lsciOJlus rel rollexu>
FIGURE 111.75: ANATOMY OF THE LIMBI C FOR EBR AIN _ _ _ _ _ _ _ _ _ _ _ _ __
FI Struc tures of the limbic forebrain are found in a ri ng (limbus) that encircles the diencephalon. Two major temporal lobe structures, the hippocampal formation w ith its fornix and the amygdala w ith its stria terminalis, send (-shaped axonal projections .....J-hrou gh the cortex, around the diencephalo n, and into the hypothalamus and the septal region. The amygdala also sends a more direct pathway (vent ral amygdalofugal pathway) into the hypothal am us. The septa l nuclei sit just rostral to the hypo thalamus and send axons to the habenular nuclei ~
2BB
via the stria meduUaris thalami. The cin gulate, prefro ntal, orbitofrontal, ento rhinal, and periamyg daloid areas of the co rtex interconnect with sub cortica l and hippoca mpal components of th e limbi c forebra in and are often co nsidered part of the li mbic system. Th e limbic system is thought to be a major substrate for reglilation of emotional responsiveness and behavior, for individu alized reactivity to se nsory stimuli, and for integrated memo ry tasks.
n g)
Ie ar
er
sh th, th, pc
da
Autonomic, H ypothalamic, and limbi c 5 ,,"rc-~~ -
SYSTEMIC NELJROSCIE' CE
Body of
caudate nudeus
'.;'.
Basal ganglia.
Temporal horn of the lateral ventrid e CA regio ns of
hipPocampal formation
(pyramidal cells)
J. Pericins MS,MFA
:I '·~·N
FIGURE 111.76: HIPPO CAMPAL FQRMATI O
The hippocampal forma tion consists of the denU1ie gyru s, the hippocampus proper (cornu am rnonis [CAl region s), and th e subiculum. These structures are in tima tely interconnected w ith the adjacen: entorhin al cortex. The hippocampus is a seahor* shaped structure found in the medial portion 0: the anterior temporal lobe. II bul ges laterally into the temporal horn of the latem] ventricle. Th e hip pocampus is divided into several zones of p) ra m:"" dol cells, called CA regio ns (CA1-CA4). Granule
, ----------------
_ ce ntate gyrus. The dentate gyrus ~ pus are three-layered cortica l - "'""'OOQm pal formation has extensive ;:;=1:1: _ ~·.th cortical association areas ~ebr a in structures su ch as the iiI"C :"l"le ci ngulate gyrus. It is invo lved :"':::::=:=~ a rt· term memory into long - 'unc tio n with extensive regions
,.,.-
"1 89
SYSTEMIC NEUROSCIENCE
Autonomic, Hypothalamic, and limbic Systems-Limb ic
of late ral ventricle
CA3--'--
- -
Mossy fiber
._:'/'
. !
/ 1..
- ,>---- r
d J
.
'" , fi
Subiculu m
. .
.
\','
;.~
\ \
~
CAl
_~ Inputs to subiculum from
\ \
~~ -'- ;:::::'::::::::;=:;=\;X'::::'=:---:-:-":7.:-::- J ~. "", '
J'
Schaffer coUaterals
...--
c ingul,lte cortex, amygdala
~ Inp uts to ento rhinal corle", (cingu i,lte cortex, se nsory ,lssociation cortices, baso lateral dmygdala . in sular cor tex, olfactory bulb, and
preiro ntaJ cortexi Perfora n t pathway./"" from en torhin al cortex
to dentate gyrus, CA 1 and CA3, and the sub iculum
Eniorhina i corlex
J, Perkins MS. MFA
c~
FIGURE 111.77: NEURONAL CONNECTIONS IN THE HIPPOCAMPAL FORMATION _ __ The hippocampal formation has an internal cir cuitry interco nnected with the en torhinal cortex. Pyramidal neurons of the entorhi nal cortex send axons to granule cell dendrites in the dentate gyrus. These granule cell axons (mossy fibers) synapse on pyramidal cell dendri tes in CA3. Pyra midal cells in CA3 project to pyramidal cell dendrites in CA 1 (Schaffer collat erals) and CA2. CA 1 pyra mi dal axons project to pyramidal neuro ns in the subicu lum. The subicu lum sends axonal projections back
290
_
_
to the pyramidal neurons of th e entorhinal cortex. This in formatio n fl ow represents an interna l circuit. Superimposed o n this circuitry are a host of inter co nnections with associatio n regions of neocortex and other limbic forebrain structures. Neurons of th e subi culu m and CA neuron s of CA 1 and CA3 send axons into the forn ix as efferent projections to target structures. Th e subicu lu m also sends axons to the amygdala and the association areas of the tem poral lobe.
.\utonomic, Hypothalamic, and limbic Systems-limbic
-===:
-\jjerenl connections : iierenl connections _
?os1I;ommhsural o,ecommissural 'omix MammJlio tegmen t;,1 Iract
(Of pus
callo sum
-\«ociiltion ~ r"ilS of _--.0,. "onta l lohe
W _J-;;...-......-::;:-
Input5 to hippocampus and dentate
gyru5:
5eptal nuclei - -- - - -:;;
Raphe nuclei
(SHD . Loc us coe ru leus (NE)
Fimb ria
c ortex Efferems of suhio:: ulu m
Denta te
\0 amygdala, association
g)' rus
areas of te mpvralluhe
(A rellion_
of h ippocaMpI..,
Periof.Jnt o.a:h,·. a'
Inputs to entorhinal cortex: Sensory associatioll cortices Polysellsory association cortex Prefrontal cortex Insular corte,\ Amygdala Olfactory bulb Inputs to subiculum: Amygdala
FIGURE 111.78: MAIOR AFFERENT AND EFFERE'T CO , 'ECTIONS OF THE HIPPOCAMPAL FORMATION __________________________________________ Pyram idal neurons in the subiculum and the hip poca mpal regions CA 1 and CA3 give rise to the efferent fornix. The subiculum projects to hypo thalamic nuclei (especially mammillary nuclei) and thalam ic nuclei via the postcommissu ral fornix. CA 1 and CA3 neuro ns send axons to the septal nuclei. the nucleus accumbens, the preoptic and anterior hypo thalamic regio ns. the cingulate cortex. and the association areas of the fronlal lobe. Afferent cholinergic axons from sepia I nuclei traverse the fornix to supply the dentate gyrus and
tr.e ... ppocampal CA regions. Massive inputs arrive in me hippocampal formation from sensory associ ation cortices, polysensory associatio n co rtices, the preironta.l cortex, the insular cortex, amygdaloid nud ei, and the olfactory bulb via projection s !o the entorhinal cortex. The ento rhinal cortex is fully integrated into the internal circuitry of the hippocampal formation. The subiculum is con nected reciprocally w ith the amygdala and also sends axons to cortical associa tion areas of Ihe lemporallobe.
19 1
SYSTEMIC NEUROSCIENCE
Autonomic, Hypothalamic, and limbic Systems-Limbic TnalJmvs
Bed nucleus of th e slri
i Cingulate cortex
In lrJI ~m inar
I M edial dorsal
Stria lermina hs
Brain stem inputs; Parabrac hial nuclei
M
"$.
>;.«'_
Periaqueduclill gray Ve ntral tegmental area (DA ) Raphe nud ei (5Hn
.4#"
j/
Locus coeruleus (NEI Nucleus trac Lus solitarius
/.;'J1"
Corpus callosum
1/
,,-:,j::
'\
Anteri o r
!/
'""'~
Sept;!1 nudei
' ,_ _ .""",
Prefrontal cor tex
_
- -~ ~,o_" ,
I
---...
. 4."
~{!' ,
Hypothalamic inputs: l ate r",1hypo thalamic. area Ventromedi al nucleus
. ~-
~
Corticomedial nuclei /'
of the amygdala
Basolateral
(hippocampal formati on)
of the amygdala Sen sor y
Te mporal lobe ,enso ry associatio n cortex En(Qrhin;)1 cortex Insular ( Ollex
Medial frontal lobe
FIGURE 111.79: MAIOR AfFERENT CONNECTIONS OF THE AMYGDALA _ _ _ _ _ _ __ Th e amygdala is an almond-shaped co ll ection of nuclei in the medial portion of the anterior tempo rallobe. It is involved in the emotional interpreta tion of external sen so ry information and internal states. It provides individual-specific behavioral and emotiona l responses, particularly for fear and aver sion. The amygdal a is subdivided into cortico medial and basoJateral nuclei and the central nucleus, w hich mainly provides efferent projections to the brain stem. Afferen ts to the cortico medial
292
nuclei arrive mainly fro m subcorti cal limbic sources, including the o lfactory bulb, septal nuclei, hypothalamic nuclei (VM, LHA), th e thalamu s (intralaminar nuclei), the bed nucleu s o f the stria terminalis, and extensive autonomic monoamine nuclei of the brain stem. Afferents to the baso late ral nu d ei arrive mainly from cortica l areas, including extensive sensory association cortices, the prefrontal cortex, the cingu late cortex, and the subicu lum .
-
SYSTE M IC '\EL.,ROSClE'CE
Autonomic, Hy pothala mi c, and Limbic Systems-limbic Bed ("1\.'( .,,""... ; o· ~i1f: SIre.;
.~-
ilL ,
To ~~
Stria " onio, li,
"uC~""j :.~"' ~ ~~
Dorsa l ~
Rapre Stri atum (rostral areas) Cauda te nucleu s
Putamen
nt.;C..;- _~
r:i ..
-~ ~.....-
'=
l o cuscO€'"l.t"_> Parabf01d1&ai rvoea
Periaqueduct.l.l $-7_
Reticul ar forma:iof'
#
Corpo . C2~
Fro ntal lobe regions: Fron\31cortex
Prefro nta l cortex
nuclei
Nudeus - ------- --- __~~'-_'b acc umben~
SubStolOti.1 inno mina ta (w ith
nucleus w sa1is ACh neuro ns) Ventral amygd alo fu gal
pathway (VAf P)
earlico rnedial o" lei / o f th e amygd al a
cortex
Baso latera l nuclei of th e amygd a l
(e.g., visual are as)
Central nuc:leus Of t.'""f' a"Tl'o .,;:dala H - Hypothalamus: Preoptic area Anterior hypothalamic area Ventromedial nucleus
Th " Tha la m us: M
Laleral hypothalamic a rea Paraven tricular nucleu s
co rt ex
~ff ..-... ~~
FIGURE 111.80: MAJOR EFFERENT CO NN ECTIO\,S OF THE AM YGDALA _ __ _ _ __ _ Efferents fro m the corticomedial nuclei project through the stri a te rminalis and are directed mainly tow ard subcortical nu clei such as septal nuclei, the MD (DM) nucleus of the tha lamu s, hypothalam ic nuclei, the bed nucleus of the stria te rminalis, the nucleus accumben s, and the rostral striatum. Efferents from th e basolateral nuclei project tnrough the ventral amygdalofugal pathw ay to =i\t ensive cortical regions, including the frontal cortex, the ci ngulate cortex, the inferior temporal cortex, the subiculum, and the en torhinal cortex;
and to subco rti cal limbic regio ns, includin g hypo thalamic nucl ei, septal nuclei, and the ch olin ergic nucl eus basa li s in th e substanti a inno min ata. The central amygdalo id nu cleus receives input mainl y from internal amygdaloid connections and sends extensive efferents thro ugh the ventral amygdala fugal pathw ay to extensive auto no mic nuclei and monoaminergic nuclei of the brain stem, m idline thalamic nuclei, the bed nucleus o f the stria termi nalis, and the cholinergic nucleus basalis.
293
SYSTEMIC NEUROSCIENCE
I_~?'
Olfactory bulb Se ptal nLfcie l Hypo(h~l
Autonomic, Hypothalamicl and Limbic System5 -1.im2
-~
nudei (lH A. VM )
Thalami c nud E' i (inlrillaminar)
I
{.~, Jiit
~ ~:~t~IU~~:ll : i Oi ST
. - Thala mu. (MD I \-- - - - - - - - _ H yp ol h.l l am u_~ PreOI)Lic area
----- -1.
Red nucleus o( ST
AHA
8 rain stem
YM
Pa rabrolchial nucleu s
LH A
PeriaquedU
Ra phe nud ei (5HT) locus seruleus (N EI NTS
PYNp .Nucleus atTumb~n~ : Stri a tum (f()~tra ll +---------~-
Ca udate Pu tamen
@Fa
:
Mi~li ne Ih~l amic Olld ei
Kliilf-------- - - 81 aln stem Red nuclNI$ or ST Sub~ tanna
innomin,lla
I nuci\;" us b,19lis)
NTS OMNofx fl.aph~
nud ei (SHn
Lo cu >l:ue rulu s (N EJ
P
Th ala mu s (MDI Pre fron tal corl ex Cingul ate corte)!;
Subiculum
--------------1
Seno:.ory associ,llion curtex C b I ere fa
Temporal lobe sensory assac CO rlex Enlorhinal corlex
corlex { Ensul.:u cortex Med ial fro nlal cortex
DA .. Dopamine 5HT - 5·Hydroxyn ypl amine (Serotonin) NE - I~ ore pin<:!p hri n e
©lmN ... " ".
..." ..
5T - St ria terminali s VTA .. Ven tral 'e~men t al are a NTS = Nud eus tractu s solilMiu s
~,
Su b.tanti a inn omln " t~
};
Sept
~;
(n ucleus ba ~li5J
>~~.
'~'J---------- H ypo thitlamus
;."
Frontal cortex
J---------~~ En lorhinJI co rtex
\-- - - - - - - _
Subic ulum
r------- - (i nRula te (o rlex r---------
Infcrio r te mporal (orteJC
M D - Medial Ull rSillllucleus o llha l;;mlU5 AHA - Anterior h)'poth al amic (If!:'
lHA - l ateral hypulnaJamit area PVNp " f'a ravenlricu lar nu c1eu ~. parvocellular DM N of X '" Dors al moto r (autonomic) nucleus of X
fiGURE 111.81 : SUMMARY Of MAJOR AffE RENTS, EFFERENTS, AN D INTERCONNECTIO NS OFTHEAMYGDALA ________________________________________ The corticomedial amygdala is connected recipro cally mainly with subcortical lim bi c forebrain struc tures, w ith ex tensive additional inputs from brain stem autonomic and monoaminergic nuclei. Th e basolateral amygdala is connected reciprocally with extensive regio ns of limbic and association cortex, w ith additio nal efferen ts to subcortical limbi c fo rebrain regions. Both the corticomedial and the basoJateral nuclei send axons to the central nucleu s of th e amygdala. The ce ntral nucl eus has
294
massive descending efferen ts to extensive au to nomi c and mon oamin ergic nuclei of the brain stern as well as to some subcortical limbic forebrai n regions. These in terconnectio ns provide the inte grated circuitry that permits analysis of both exter nal and internal inform ation, w hich provides an emotional and interpretative context for the initia tion and control of appro priate behavioral and emotional responses.
Autonomic, Hypothalamic, and Limbi c S..-s1
SYSTEMI C NELROSCIE'CE
'-5.
AFFER ENTS Major Olfferents fmlll. HippocamPJI CA pyramidal ct' ll s A mygciai()id 11ucit'i
Corilcoml!diili nuclE'i \·i " stria Termlnalis
Basolatcral nudei via venTr,,1
ilm \, grlil lofugal path way
Vent ra l tegme nta l JreJ
Hypothalamus
Preop tl<- ,lrc')
Anteri or h\·pothai amir Mea P;u,lVE'nlricui
l ater,,1hypolh;damic
l ocus cO Nule(ls (NE; no t show n I
•e'11rJI I{'gmenlal alea
,.,• •• ";,,1111,,,; th alami
EF FERENTS Majorc(fe ren'~
nuclei
roc
Hippocamp JI CA regiOnS }
DenTilTe g~'ru~ (ACh path)
. .
.
Via ltlrnlX
Habenular nuclei } Via sui., ( Medial dors al nucleus medullaris (ithe tha lamus tha lami Vemral tegmental Mea - Via median I , H~'Poth alamu s forebrain bUI1{lie
~
Preop tic area A nterior hYPOlhillilmic area Ventromedial nucleus
laleral hypo th" l,l miC are~
(medial dQrsalJ
r
-
_~ .e
FI G U RE 11 1.82: M AJOR AFFERE NT AND EFFERE TCO"ECfION S OFTHE SEPTAL NUClEI _ _ The septal nuclei are subcortical nudei implicated by earl y ablatio n and stimulatio n stu di es in the regulatio n of emotio nal responsiveness (such as: rage be havior) , In experim ental studies, the septal nuclei app ear to playa ro le in emotional beha\ iors. sexual behavior, aggressive behavior, modulation of auton o mic function s, and aLtention and memor\' functions (from the cholinergic neuro ns). At1erents to the septa! nuclei arrive mainly from th e hippo-
carnpo!o the corticomedial and basolateral aFl1\ goala. the ventral tegmental area in the mid bra-n and several hypothalamic nudei. Efferents (rom the septal nucl ei proj ect mainly to th e hippocampus and the dentate gyrus (via the iorni"\ ·, th e habenular nu clei and th e M D (OM) nucleus 01 the thalamus (via th e stri a medullari s thalami ), the ven tral tegmental area (via the median io rebrain bundle), anel several hypotha lamic nuclei.
295
SYSTEMIC NEUROSCIENCE
Autonomic, Hypothalamic, and limbic Systems-limbic
( inguJ3te cortex
Afferent con nections - - - _ Efferent connections - - -_
Association areas o f parietal cortex
.,,,.
",,; " ,'
-{.
"
,.t/'(,'
"""',>.~".",-.,;
.. .Ao
-Ij}.·;:t'''-
Corpus callosum
~
Asr.ocialion
areas of homal corteK
Mammillary body
Amygdala (basolate ral nudei) A NT = AnteriOl' nudei OJ the thalamus
MD = Medial dorsal nucleus oi the thalamus
~~f' •. l ~U" . ~
o~
FI GU RE 111.83: MAIOR CONNECTIO NS OF THE CINGUlAT E CO RTEX _ _ _ _ __ _ __ The cingulate cortex is lo cated above the corpus callosum. This cortical region is involved in the reg ulation of autonomic functions (respiratory, di ges tive, cardiovascular, papillary), so me somatic function s (motor tone, ongoing movements), and emotion al responsiveness and behavior. Lesions of the cingulate cortex result in indifference to pain and o ther sensations w ith emo tional connotation and social indifference. Afferents to the cingu late cortex arrive fro m association areas of th e frontal, parietal, and temporal lobes, the subiculum, septal
296
nuclei, and thalamic nuclei (MO, anterior). Efferents from cingulate cortex neurons pro ject to associa tion areas of the frontal, parietal, and temporal lobes and to lim bic forebrain region s such as the hippoca mpus, th e sub iculum, th e ento rhinal cortex, the amygdala, and sep tal nuclei. These limbic fore brai n regions send extensive projectio ns to the hypothalamus for regulation of the autono mic and so matic regi ons of the brain stem and the spinal co rd.
-
SYSTE M IC :-'EL.ROSCIE' CE
4utonomic, Hypoth alamic, and limbic Systems-olfactory
Olfactory Receptors
;;;:~::bulb
~
A. Oi ~t ri bulion oi oliado r.... epithelium t b _~c ':;',,"'"
Septum B. Schema of section through
~ olf.cto., muw" ... .
Cribriform plate
.;-- - -- - - Schwann cell
Ii
t
axons _____ Basement membrane
~
-
>
- --'- -- - ViUi
.-"
FIGU RE 111.84: O LFACTORY REC EPTO RS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Olfactory receptors are found in a patch of o lfac
tory e pithelium that lines the medial and lateral w alls of the roof o f the nasal cavity. They are primi tive specialized bipolar neuro ns w hose nuclei are in the base of the epithelium. A dendritic process extends toward the epithelial surface, w idening into a rod w ith 10 to 30 motile cilia that project into the mu cous cover. Odorants act on receptors (G-protein- cQup led) on th ese cilia and bring abou t a slow depolarizin g generator potentia l. O dorant
in teraction wi th receptors is complex, often req uir ing odo rant-binding proteins to carry the odorant through the mucosa. The bipolar neurons of the oliacto ry epithelium are e NS neurons; they are unusual beca use they undergo continuous replace ment and turnover from basal stem cells in the epilhelium. The UNM olfactory axons cl uster IOgelher in groups (enwrapped by a Schwann cell) before passing Ihrough the cribriform plate. Inj uries to th e cribriform plate can result in anosm ia.
297
SYSTEMIC NEUROSCIENCE
Autonomic, Hypothalamic, and Limbic Systems-olfactory
:::~} Efferent r,b ers (; : : ; : : ; ) A"",o, "b",
~~
' '::::
Granule <::oell Ie.><eited by
Fibers from con tralateral o lfactor y bulb
and inhibitin g 10 miffal
I
to contralateral olfactory bulb
Mitralc:ell
..JH.e/ 1>.....-1
er ulMcell
~
~
O lfaclory nerve~
,y..P~"
Tuited cell I"erig(om
'I
-;"-'
.~
Re>current plOCeSS
An terior
oommis~ure
Med ial olfacto ry stria
/ ' i!
G'om,,,'"
,/ Anterior perforated substan ce
O lfactory
""V< fib",
I olfactory stria
lateral olfactory tract nucleus
,
, Anterior olfac1ory nucleus
Crib riform plale of ethl'llOid bone
~~p
° l~
"'...... n
FIGURE 111.85: OLFACTORY PATHWAYS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Primary sensory axons from bipolar neurons pass
through the cribriform plate and synapse in the olfactory glo meruli in the glomerular layer of the olfactory bulb. The glomeruli are the functional units for processing specific odor information. The olfactory nerve fibers synapse on the dendrites of the tufted and mitral cells, the secondary senso ry neurons that give rise to the olfactory tract projections. Periglomerular cells are interneurons that in te rconnect the glomeruli. Granule cells modulate excitability of tufted and mitral cells.
298
Centrifugal co nnections (from serotonergic raphe, nor adrenergic locus coeruleus) modulate activity in the glomeruli and o n peri glomerular cells. The o lfacto ry tract bypasses the thalamu s and projects to the anteri or olfa ctory nucl eus, the nucl eus accumben s, the primary o lfactory co rtex, the amygdala, the peri amygda Jo id co rt ex, and the lateral entorhinal co rtex. Th e o lfactory cortex has interco nn ectio ns with th e orbitofrontal co rtex and th e insular cortex, th e hippoca mpu s, and the lateral hypothalamus.
tor\'
d
IN DEX A
de~ e opm€ m ,
Abdominal nerves, 129
Abducens nerve, 157. 158, 160.2 51
ACA. See Ante rior cerebra l arte ry
Accessory nerve, 15 7, 158. 166
Acetylcholine
enteric nervous system a nd. 132
synapses. See Cholinergic synapses
Ac tion poten hals. 16
conduction velocity, 17
propagation. 17
Adenohypophysis. 177
AOH (a ntidiuretic hormone). See
Vasopressin
Adrenal gland, 135
Adrenergic distribution, 120
Adrenergic synaps5, 118, 120
Afferent pathways. 294
amygdala, 292
audi tory system. 22 8
brain stem, 118
cerebenar pecluncles. ' 74
cerebellum, 255, 256
ce rebral cortex. 201
cingulate conex, 296
classification, 18
cranial ne rve nuclei, 15 7
enteric, 133. 134
eye, 124
heart,. 128
hippocampa l formation, 29 1
hypothalamic, 271, 272
intestinal, 131
kidney and upper urete r, 137
mouth and pharynx, 168
Olfactory, 298
reproduc tive o rgans
femal e, 140
male, 139
septal nudei, 295
spinal cord, 118
somatosensory, 114
tracheo bronchial tree. 12 7
urinary bladder and lower ure ter, 138
vagus ner ve and. 165
AICA (anterior inferio r cerebellar ,merY),55 Alar plate
as brain stem deriva tives. 80
in early brain development
28-day stage, 72
36<1ay stage, 73
embryo nic vs. adul t comparisons. 78
neura l tube development ar'ld, 69
(l-iower motor neurons. 241. 245, 24&. 24 7, 248,249
Amacrine cells, 235
Amino dcid synapses, 12
Amygdala, 275
afferents, 292
basolateral,294
corticomedial.29 4
enerentconn ec~,1 9 3
75
interconnections. 2Q ..:
Am)'gdaloiugai pa lh\,a... 293
AmygdaJo,d nudei, ]O ]93
AnastolT\O
arte rial ~uppk. 10 br<;irl 50
veno u" rings around \ er..ebr.:.t'!. 66
Anenceph.aJ... 68
Anesthesla_ den--...r()('l" 3- <;1,3
Aneurysm. cere!:lra. 5 :
Anions. l -J.
ANS. See AIJl()!'lQl'l""C "E'I"\ O~~~, ~iem
An teri()( c er~.;r;:;:""\ .!,?
circle oj \ \ 'iIis and j(
occlu sion. 5]
separalion,50
ID'les suppi'ed 0.. 53
_ Anterior lobe, cerebel..a: ~ B Anterior whit e cOllL....,~~· = -;. :?\ .l spinocere .?J' tr"iId and ~ 15
Antidi uretic hornone. ~ '.2:X)OI'e-;SIn
Antid ro mic co nduction. 'of>. - ' 9
Aortic bodv, 25]
Appetite, 285
APs. See Action po:~ "a ' ;
Aqueous humo r, 13]
Ara chnoid
meninges a nd. -12 spinal cord. 39. .;0
Arachnoid cells. , 1
Arachnoid gran ulatioru . .!2
cerebrospinal l1uid e:"Ct.,...a'q 2'1d ..: ;; ventricular de\·elopmen~.:.'1C - ARAS (ascendi ng re ocu1ar <=<;""'.,,'-1'13 5~lem J. 171
Afea postfema. 277
Arousal, brain areas assocated Iqlh, 1-2
Artery!ies)
to brilio, 50
lateral and medial "e".'.~, 5 2
carotid,47
cerebral, 48. 49
cervical cord, 64
communicating, circle oi \ \ ~1Ii ;; and. 51
eye, 236
hypophyseal. 56
meningeal. 42, 46
~o( st roke, ~ 49
pOSterior cranial iossa '€ . 55
radicul.. r, 63, 65
skull base fOfamina and. 22
spinal cord, 64
cro.ss-sectional view, 65
diwibulion, 64
loogiludinal view, 63
verte bral,4 7
ASA (anterior spinal artery ). 63, 64, &5
Ascending pathways, spinal cord. 41
Ascending reticular activating system, 171
Association fibers, 204
cerebral cortex, 202
Associational cortex, : '?'? ~ Cacd <Jssoc[ation
Astrocvtes, 7 8, 71
Athe rosclerosis, 47
Auditory cortex, 24
Auditory system
afferent pathways, 228
bony and membranous labyrinths. 21 ';:
centrifugal (efierentl pathways, 229
cochlear receptors, 22 7
frontal section, 224
ne rve innervatioll of hair cells in, 226
ves tibular recepiors, 230
Auerbach's (myenteric) plexus, 132, 133
Autonomic channe ls, 91
Autonomic nervous system, 116
cnoJirler gic and adrenergic distribution/synapses, ' 19, 120
enteric. See Enteric nervouS syste m
eye. 124
head and neck. 123
l ateraJv i~w, 122
medial view, 121
innervation. See Innervation, autonomic
orga nization, 264
reTle>:; pathways, 118
Autonomic neurons
postganglionic, 71, 86, 264
preganglionic, 74. 86
as basal plate de rivatives, 80
development in brain stem and spinal
cord,79
o utflow regulation. 275
Axillary nerve, 103
above e lbow, 104
Axoaxo nic synapse, 4
Axodendritic synapse. 4. 5
Axon hillock, 4
Axon membrane, bare, 10
A..xons, 4, 7
autonomic, 82
central, 10
commissural, 203
conicobuJbar tract, 243
corticoc:ortical, 203
corticothalamic, 203
ensheathment, 9
glossopharyngeal nerve and, 1b4
lower motor neuron, 96
myelination of, 8
peripheral. 82
projection, 203
synaptic morphology and, 1 I
terminal. 96
unmyelinated vs. myelinated, 214
Axosomatic synapse. 4, 5
Axosomatic !ermmal, 11
•
Bare axon membrane, 10
[3arorece pto r~, 94
Basal gangha, 29
199
