f:N-i,4I}TIA I APPENDIX
INTRODUCTION SURFACEANATOMY OF THE BRAIN An Illustrated THE LATERALSURFACE OFTHE BRAIN /o) CrossFeotures Guide to Human (b) SelectedGyri,Sulci, ond Fissures Neuroematomy (c) CerebrolLobes ond the Insulo (d) Mojor Sensory,Motor, ond AssociotionAreos of Cortex THE MEDIALSURFACE OF THE BRAIN FT & (o) BroinStem Structures (b) ForebroinStructures (c) Ventricles THEVENTRALSURFACE OF THE BRAIN THE DORSALSURFACE OFTHE BRAIN (o) Cerebrum (b) CerebrumRernoved (c) Cerebrumond CerebellumRemoved CROSS.SECTIONALANATOMY OF THE BRAIN CROSSSECTION | : FOREBRAINAT THALAMUS-TELENCEPHALON JUNCTION (o) GrossFeotures (b) SelectedCell ond FiberGroups CROSSSECTION 2: FOREBRAINAT MID-THALAMUS (o) GrossFeotures (b) SelectedCell ond FiberGroups CROSSSECTION 3: FOREBRAINATTHALAMUS-MIDBRAIN JUNCTION (o) GrossFeotures (b) Se/eaedCell ond FiberGrouPs CROSSSECTION 4: ROSTRALMIDBRAIN CROSSSECTION 5: CAUDALMIDBRAIN CROSSSECTION 6: PONSAND CEREBELLUM CROSSSECTION 7: ROSTRALMEDULLA CROSSSECTION 8: MID-MEDULLA CROSSSECTION 9: MEDULLA-SPINALCORD JUNCTION THESPINAL CORD THE DORSALSURFACE OF THE SPINAL CORD AND SPINALNERVES THE VENTRAL-LATERAL SURFACE CROSS-SECTIONALANATOMY THEAUTONOMIC NERVOUS SYSTEM THECRANIAL NERVES THEBLOOD SUPPLY OF THE BRAIN VENTRALVIEW LATERALVIEW MEDTALVTEW(BRA|N STEM REMOVED)
SELF.QUIZ
j:' :: \) fi:; "i'- ,1,.., 206 C HAPTE R 7 . APPENDIX:ANILLUSTRATED GUIDETO HUMAN NEUROANATOMY
W INTRODUCTION
As we will see in the remainder of the book, a fruitful way to explore the nervous system is to divide it up into functional systems. Thus, the otfac- tlry systemconsists of those parts of the brain that are devoted to the sense of smell, the visual systemincludes those parts that are devoted to vision, and so on. while this functional approach to investigatingnervous sys- "big tem structure has many merits, it can make the picture,,-how all these systemsfit rogether inside the box we call the brain-difficult ro see. The goal of this Illustrated Guide is to help you learn, in advance,atrout some of the anatomy that will be discussedin the subsequentchapters. Here we concentrateon naming the structuresand seeinghow they are related physically;their functional significanceis discussedin the re- mainder of the book The Guide is clrganizedinto six main parts. The first part covers the sur- face anatomy of the brain-the structures that can been seen by inspection of the whole brain, as well as those parts that are visible when the two cerebralhemispheres are separatedby a cut in the midsagittalplane. Next, we explore the cross-sectionalanatomy of the brain, using a seriesof slabs that contain structuresof interest.The brief third and fourth partscover the spinal cord and the autonomic nervous system.The fifth part of the Guide illustratesthe cranial nerves and summarizestheir diversefunctions. The last part illustratesthe blood supply of the brain. The nervoussystem has an astonishingnumber of bits and pieces.In this Guide,we focuson thosestructures that will appearlater in the book when we discussthe various functional systems.Nonetheless, even this abbrevi- ated atlas of neuroanatomy yields a formidable list of new vocabulary. Therefore, to help you learn the terminology, an extensive self-quiz review is provided at the end, in the form of a perforated workbook with labeling exercises.
'W SURFACEANATOMY OF THE BRAIN
Imagine that you hold in your hands a human brain that has been dis- sectedfrom the skull. It is wer and spongy and weighs about 1.4 kg (3 lb). Looking down on the brain's dorsal surfacereveals the convoluted surface of the cerebrum. Flipping the brain over shows the complex ven- tral surfacethat normally restson the floor of the skull. Holding the brain ,,ram.s up and looking at its side-the lateral view-shows the horn,, shape of the cerebrum coming off the stalk of the brain stem. The brain stem is shown more clearly if we slice the brain right down the middle and view its medial surface.In the part of the Guide that follows, we will name the important structures that are revealed by such an inspection of the brain. Notice the magnificarionof the drawings: lx is life-size,2X is twice life- size,0.6X is 60"/. of life-size.and so on.
205 Lateral view Medialview 208 c HApTER 7 . AppENDTX:ANTLLUsTMTED GUTDETo HUMAN NEURoANAToMy
The Lateral Surface of the Brain
(a) Gross Features. This is a life-size drawing of the brain. Gross inspection reveals the three major parts: the large cerebrum, the brain stem that forms its stalk, and the rippled cerebellum. The diminutive olfacrory bulb of the cerebrum can also be seen in this lateral view.
Cerebrum
Olfactorybulb
Cerebellum
: i,- " SURFACEANATOMYOFTHE BRAIN
(b) Selected Gyri, Sulci, and Fissures. The cerebrum is central gyrus lies immediately posterior to the cenlral sr.rl- noteworthy for its convoluted surface. The bumps are cus, and the precentral gyrus lies immediately anterior to called gyri, and the grooves are called sulci or, if they are the central sulcus. The neurons of the postcentral gyrus especially deep, fissures. The precise pattern of gyri and are involved in somatic sensation (touch; Chapter 12), sulci can vary considerably from individual to individual, and those of the precentral gyrus control voluntary move- but many features are common to all human brains. Some ment (Chapter l4). Neurons in the superior lemporal of the important landmarks are labeled here. The post- gyrlrs are involved in audition (hearing; Chapter ll).
Centralsulcus
Lateral(Sylvian) fissure
(c) Cerebral Lobes and the Insula. By convention, of the cerebrum, bordering both parietal and temporal the cerebrum is subdivided into lobes named after the lobes. A buried piece of the cerebral cortex, called the "island"), bones of the skull that lie over them. The central sulcus insula (Latin for is revealedif the margins of dividesthe lrontal lobe from the parietallobe. The tem- the lateral fissure are gently pulled apart (inset). The pural lobc lies immediately ventral to the deep lateral insula borders and separatesthe temporal and frontal (Sylvian)fissure. The occipitallobe lies at the very back lobes.
Frontallobe
Occipitallobe
'i'..'.;'"1':,',:'i,.,,i;,,,,:11..rt.r,lr:: .: r',i,,':\irir,i:..4 t,:1,i : . .1,..':rij !l 210 cHAprER 7 . AppENDTX:ANTLLUSTRATEDGUTDEToHUMAN NEURoANAToMy
(d) Major Sensory, Ivlotor, and Association Areas of and auditory areas4l and 42 (Chapter lI) are in the Cortex. The cerebral cortex is organized like a patch- temporal lobe. On the inferior surface of the parietal work quilt. The various areas, first identified by Brod- lobe (the operculum) and buried in the insula is gusta- mann, differ from one another in terms of microscopic tory area 43, devoted to the senseof taste (Chapter 8). structure and function. Visual areas L7, 18, and l9 In addition to the analysis of sensory information. the (Chapter l0) are in the occipital lobe, somatic sensory cerebral cortex plays an important role in the control of areas l, l, and 2 (Chapter 12) are in the parietal lobe, voluntary movement. The major motor control areas- primary motor cortex (area4). the supplementary motor area, and the premotor area-lie in the frontal lobe, an- terior to the central sulcus (Chapter I4). In the human brain, large expanses of cortex cannot be simply assigned to sensory or motor functions. These constitute the as- sociation areas of cortex. Some of the more important areasare the prefrontal cortex (Chapters2l and 24), the posteriorparietal cortex (Chapters12, 21, and 24), and the inferotemporalcortex (Chapter24).
Brodmann'smao Primarymotor cortex (area4) Supplementarymotor area Somatosensorycortex (area6) (areas3, 1,2) Posteriorparietal cortex Premotorarea (areas5, 7) (area6)
Visualcortex (areas17,18, 19)
Prefrontalcortex
Inferotemporalcortex (areas20,21,37) Auditorycortex (areas41, 42) I Motorareas ffi Sensoryareas Gustatory (area43) ! Associationareas
:
r.l ffil ji ..:] SURFACEANATOMYOFTHE BRAIN
The Medial Surface of the Brain (a) Brain Stem Structures. Splitting the brain down the middle exposesthe medial surface of the cerebrum, shown in this life-sizeillustration. This view also shows the midsagittal cut surface of the brain stem, consisting of the diencephalon(thalanrrrs and h1'llotlralarrrrrs).the rtticltrrairt(teclrrrn and lcgnrentrrrrr),the llorrs,and the nrctlrrlla.(Some anatclmists define the brain stem as con- sistingonly of the midbrain, pons, and medulla.)
Thalamus Y(
Pinealbody b*^
Hypothalamus
Cerebellum 212 c H A pr ER 7 . AppENDtX:ANILLUSTMTED GUIDETo HUMAN NEURoANAToMy
(b) Forebrain Structures. Shown here are the im- Some of the axons in the fornix regulate memory portant forebrain structures that can be observed by storage(Chapter 24). viewing the medial surface of the brain. Notice the In the lower illustration, the brain has been tilted cut surfaceof the corpus callosum,a huge bundle of slightly tcl show the positionsof the anrl,gdalaand hip- "phantom axons that connects the two sides of the cerebrum. pocanrpus.These are views" of these struc- The unique contributions of the two cerebral hemi- tures, becausethey cannot be observeddirectly frclm the spheresto human brain function can be studied in surface. Both lie deep to the overlyinll correx. We will patients in which the callosum has been sectioned see them again in cross section later in the Guide. The "almond") (Chapter 20). The lornix is another prominent fiber amygdala (Latin for is important for regulat- bundle that connects the hippocampus on each side ing emotional states(Chapter l8), and the hippocampus "arch.") with the hypothalamus. (Fornix is Latin for is important for memory (Chapters 24 and 25\.
'(
Cingulategyrus t*'\ Corpuscallosum ,,ffi,f^*, (cut edge) /'rp-
'v 2* Olfactorybulb/
Calcarinefissure Opticchiasm
(0.7x)
;\-
(0.7x)
Amygdala Brainstem and cerebellum (beneathoverlying cortex) removedand brain rotatedslightly Hippocampus (beneathoverlying cortex) V SURFACEANATOMYOFTHE BRAIN 2'3
(c) Ventricles. The lateral walls of the unpaired parts of The lateral ventricles are paired structures that sprout the ventricular system-the third ventricle, the cerebral like antlers from the third ventricle. A phantom view aqueduct, the fourth ventricle, and the spinal canal- of the right lateral ventricle, which lies underneath the can be observed in the medial view of the brain. These overlying cortex, is shown in the lower illustration. are handy landmarks, because the thalamus and hypo- The two cerebral hemispheres surround the two lateral thalamus lie next to the third ventricle; the midbrain lies ventricles. Notice how a coronal section of the brain at next to the aqueduct; the pons, cerebellum, and medulla the thalamus-midbrain junction will intersect the lie next to the fourth ventricle; and the spinal cord forms "horns" of the lateral ventricle of each hemisphere the walls of the spinal canal. twice.
Thirdventricle
Cerebralaoueduct
Fourthventricle
Spinalcanal
(0.7x) Lateral ventricle (beneathoverlying cortex) Brainstem and cerebellum removedand brain rotatedslightly 214 c H A pr ER 7 . AppENDtX:AN TLLUSTRATEDGUIDETo HUMAN NEURoANAToMv
The Ventral Surface of the Brain of the eyes, are the oplic ncrvcs. The bundles lying pcls- The underside of the brain has a lot of distinct anatomi- terior to the chiasm,that disappearinto the thalamus, are cal features.Notice the nerves emerging from the brain calledthe optic tracls(Chapter l0). The pairedrrr.rrrrrrril- "nipple") stem; theseare the cranial ucr\'('s,which are illustratedin larl' boclies(Latin for are a prominent feature of more detail later in the Guide. Also notice the X-shaped the ventral surface of the brain. These nuclei of the hy- oplic chiasnrjust anterior to the hypothalamus. The chi- pothalamus are part of the circuitry that storesmemory asm is the place where many axons from the eyesdecus- (Chapter 241 and are a major target of the axons of the sate (cross)from one side to another. The bundles of ax- fornix (seenin the medialview). Noticealso the ollrttorv ons anterior to the chiasm,which emerge from the backs trtrlbs(Chapter 8) and the rnirlbr.tin,l)()ns, and rnt'rlrrlla.
Olfactorybulb
Opticchiasm *!ffi-
.ar*\
-{
Optictract
Optic nerve
Hypothalamus
Mammillary body
Midbrain
Cranialnerves SURFACEANATOMY OF THE BRAIN 2t5
The Dorsal Surface of the Brain (a) Cerebrurm. The dorsal vicw of the Llrain is don'ri- nated by the large cerebrunr.Noticc the paireclcerebral hemispheres.Thesc are connecteclby thc axons of the (()r'l)Ll\r.rllosurl (Chapter 20), which can bc sccn if the hemispheresart: retracteclslightly. Thc rncclialview of the brain, illustratedpreviotrsly, showccl tlte calkrsurl in crosssectiolt.
Corpuscallosum
hemisphere Righthemisphere
--t
Centralsulcus
Longitudinalcerebral fissure 2,5 c H A pr ER 7 . AppENDtX:ANILLUSTRATED GUIDETo HUMAN NEURoANAToMy
(b) Cerebrum Removed. The cerebellum dominates the dorsal view of the brain if the cerebrum is removed and the brain is tilted slightly forward. The cerebellum, an important motor control structure (Chapter I4), is di- vided into two hemispheres and a midline region called the vermis (Latin for "worm").
Lefl cerebellar Rightcerebellar hemisphere hemisphere
Spinalcord
(c) Cerebrum and Cerebellum Removed. The top sur- (Chapters l7 and l9). The superior colliculus receives face of the brain stem is exposed when both the cerebrum direct input from the eyes (Chapter l0) and is involved in and the cerebellum are removed. The major divisions of the control of eye movements (Chapter l4), while the irr- the brain stem are labeled on the left side, and some spe- ferior colliculusis an important component of the auditory cific structures are labeled on the right side. The pineal system (Chapter Ill. (Colliculzsis Latin for "mound.") The body, lying atop the thalamus, secretesmelatonin and is cerebellarpeduncles are the large bundles of axons that involved in the regulation of sleep and sexual behavior connect the cerebellumand the brain stem (Chapter l4).
Thalamus Pinealbody
Superiorcolliculus Midbrain Inferiorcolliculus
.t, -'! Cerebellarpeduncle (cut i{ surface)
Fourthventricle (floor) 'rr.
\
E. i, v cRoss-sEcroNALANAToMyoFTHE BRATN 247
V CROSS.SECTIONALANATOMY OF THE BRAIN the junction of the midbrain and thalamus. Conse- quently, the best plane of section depends on exactly Understanding the brain requires that we peer inside it, where along the neuraxis we are looking. and this is accomplished by making cross sections. Cross In this part of the Guide, we take a look at drawings sections can be made physically with a knife or, in the of a series of cross-sectional slabs of the brain, showing case of noninvasive imaging of the living brain, digitally the internal structure of the forebrain (cross sections with an MRI or a CT scan. For learning the internal or- l-3), the midbrain (crosssections 4 and 5), the pons and ganization of the brain, the best approach is to make cerebellum (crosssection 6), and the medulla (crosssec- cross sections that are perpendicular to the axis defined tions 7-9). The drawings are schematic. meaning that by the embryonic neural tube, called the neuraxis. Tll'e structures within the slab are sometimes projected onto neuraxis bends as the human fetus grows, particularly at the slab's visible surface.
ForebrainSections
@(
BrainStem Sections 2t8 C HA PTE R 7 . APPENDIX:ANILLUSTRATED GUIDETO HUMAN NEUROANATOMY
Cross Section l: Forebrain at Thalam us-Telen cephalon Junction (a) Gross Features. The telencephalonsurrounds the lateralventricles, and the lltalanrrrssurrounds the third ventricle. In this section, the latcral vcntriclt's can be seen sprouting from the slitlike tlrird vcntriclt'.The lr1'- pothalarrrLrs,forming the floor of the third ventricle,is a vital control center for many basic bodily functions (Chapters15-171. The insrrla(Chapter 8) liesat the base of the latcral1Si'lvian) lisstrrr', here separating the lronlal Iobc from the lerrrporallobe. The heterogeneousregion lying deep within the telencephalon,medial to the in- sula and lateralto the thalamus.is calledthe basalIorr'- brain.
Lateralventricle
Thalamus lnsula
Lateral(Sylvian) fissure
Thirdventricle
Temporallobe
Hypothalamus " CROSS-SECTIONALANATOMYOFTHEBRAIN 219
(b) Selected Cell and Fiber Groups. Here we take a more detailed look at the structuresof the forebrain. The intcmal capstrleis the large collectionof axons connect- ing the corticalrvhile nraner with the thalamus,and the corl)uscall Fibergroups: Putamen Globuspallidus C HAPTE R 7 . APPENDIX:AN ILLUSTRATEDGUIDETO HUMAN NEUROANATOMY Cross Section 2: Forebrain at Mid-Thalamus (a) Gross Features. As we move slightly caudal in the neuraxis,we see the heart-shapedthalarrrtrs (Greek for "inner chamber") surrounding the small llrird vcntricle at the brain's core. Just ventral to the thalamus lies the h1'pothalarrrus.The telencephalonis organizedmuch Iike what we saw in cross section l. Because we are slightly posterior, the lateral fissure here separatesthe parictallobc from the tenrporalklbc. s S fr*F ,s /, I ldv ,f,-. .\Cb l.)' Lateralventricle Jt Thalamus Lateral(Sylvian) fissure Thirdventricle Temporallobe Basalforebrain Hypothalamus (1x) g CROSS.SECTIONALANATOMYOFTHE BRAIN 221 (b) Selected Cell and Fiber Groups. Many important are labeled.The thalamus provides much of the input to cell and fiber groups appear at this level of the neuraxis. the ccrebralcortcx, with different thalamic nuclei pro- One new structure apparent in the telencephalon is jecting axons to different areas of cortex. The ventral the arnygclala,involved in the regulation of emotion p Fornix Corpuscallosum Caudatenucleus Putamen Internalcapsule Globuspallidus Corticalwhite matter Amygdala Substantianigra (1x) Subthalamus Mammillarybody CHAPTER7 APPENDIX:AN ILLUSTRATEDGUIDETO HUMAN NEUROANATOMY Cross Section 3: Forebrain at Thalamus- Midbrain Junction (a) Gross Features. The neuraxis bends sharply at the junction of the thalamus and the midbrain. This cross section is taken at a level where the teardrop-shaped tl.rirclventriclc communicates with the ct'rr'[rralaqrrr'- dtrct.The brain surrounding the third ventricle is tlrala- Ittus,and the brain around the cerebralaqueduct is rrritl- brain. The latcralverrtriclcs of each hemisphereappear twice in this section.You can seewhy by reviewing the phantom view of the ventricle,shown earlier. Thirdventricle ?r, Lateralventricle Thalamus W \ Temporal,"r"A (1x) Midbrain Cerebralaqueduct V CROSS.SECTIONALANATOMYOFTHE BRAIN 223 (b) Selected Cell and Fiber Groups. Notice that this sectioncontains two more important nuclei of the thal- amus: the medial and lateral geniculatenuclei. (Genicu- late is Latin for "knee.") The lateral geniculatenucleus relaysinformation to the visual cortex (ChapterI0), and the medial geniculatenucleus relaysinformation to the auditory cortex (Chapterlt). Also notice the location of the hippocampus,a relatively simple form of cerebral cortex bordering the lateral ventricle of the temporal lobe. The hippocampus(Greek for "seahorse")plays an important role in learning and memory (Chapters 24 and25). Corpuscallosum Cerebralcortex Lateralgeniculate nucleus W Hippocampus Medialgeniculate nucleus i iiii CHAPTER 7 . APPENDIX:ANILLUSTMTED GUIDETO HUMAN NEUROANATOMY Cross Section 4: Rostral Midbrain We are now at the midbrain. The plane of section has earlier, the superior colliculus is a part of the visual been angled relative to the forebrain sections, so that it system (Chapter i0) and the substantianigra is a part of remains perpendicular to the neuraxis. The core of the the motor system (Chapter t4). The red nucleus is also midbrain is the small cerebral aqueduct. Here, the roof a motor control structure (Chapter l4), while the peri- "roof"), of the midbrain, also called the tectum (Latin for aqueductal gray is important in the control of somatic consists of the paired superior colliculi. As discussed pain sensations(Chapter l2). Superiorcolliculus Cerebralaqueduct Periaqueductalgray Substantianigra Rednucleus Cross Section 5: Caudal Midbrain The caudal midbrain appearsvery similar to the rostral midbrain. At this level, however, the roof is formed by the inferior colliculi(part of the auditorysystem; Chap- ter I I ) instead of by the superior colliculi. Review the dorsal view of the brain stem to see how the superior and inferior colliculi are situatedrelative to each other. Inferiorcolliculus Cerebralaoueduct Periaqueductalgray ;]\. (2x) Substantianigra ti v cRoss-sEcloNALANAToMyoFTHE Bn,lIN 225 Cross Section 6: Ponsand Cerebellum This section shows the pons and cerebellum, parts of the (reticulumis Latin for "net") runs from the midbrain to rostral hindbrain that border the fourth ventricle. As the medulla at the core of the brain stem,just under the mentioned earlier, the cerebellum is important in the cerebralaqueduct and fourth ventricle. One function of control of movement. Much of the input to the cerebel- the reticular formation is to regulate sleep and wake- lar cortex derives from the pontine nuclei, while the fulness(Chapter l9). In addition,a function of the pon- output of the cerebellum is from neurons of the deep tine reticular formation is to control body posture cerebellar nuclei (Chapter 14). The reticular formation (Chapterl4). Fourthventricle Cerebellarcortex Deepcerebellar nuclei Pontinenuclei Cross Section 7: Rostral Medulla As we move farther caudally along the neuraxis,the which are involved in the control of voluntary move- brain surrounding the fourth ventricle becomesthe ment (Chapter14). Severalnuclei that are important for medulla. The medulla is a complex region of the brain. hearing are also found in the rostral medulla: the dorsal Here we focusonly on those structureswhose functions and ventralcochlear nuclei and the superiorolive (Chap- are discussedlater in the book. At the very floor of the ter ll). Also shown are the inferior olive, important for medulla lie the medullary pyramids,huge bundlesof ax- motor control (Chaptert4), and the raphenucleus, im- ons descendingfrom the forebrain toward the spinal portant for the modulation of pain, mood, and wakeful- cord. The pyramids contain the corticospinaltracts, ness (Chapters12, 19, and 22\. Dorsalcochlear nucleus Fourthventricle Ventralcochlear nucleus Raphenucleus Superiorolive Inferiorolive Medullarypyramid CHAPTER 7 . APPENDIX:ANILLUSTMTED GUIDETO HUMAN NEUROANATOMY CrossSection 8: Mid-Medulla The mid-medulla contains some of the same structures serving the senseof taste (Chapter 8), is part of a larger labeled in cross section 7. Notice also the medial lemnis- nucleus of the solitary tract, which regulates aspectsof "ribbon"). cus (Latin for The medial lemniscus contains visceralfunction (Chapters l5 and l6). The veslibular axons bringing information about somatic sensation to nuclei serve the senseof balance (Chapter it). the thalamus (Chapter 12). The gustatory nucleus, Fourlhventricle Vestibularnucleus Nucleusof the solitarytract (gustatorynucleus) Medullaryreticular------tl-"il formation Inferiorolive Mediallemniscus Cross Section 9: Medulla-SpinalCord Junction information from the spinal cord (Chapter l2). Axons As the medulla disappears,so does the fourth ventricle, arising from the neurons in each dorsal column nucleus now replacedby the beginning of the spinal canal.Notice crossto the other side of the brain (decussate)and ascend the dorsal column nuclei, which receive somatic sensory to the thalamus via the medial lemnisctrs. Dorsalcolumn nuclei Spinalcanal Mediallemniscus (2.5X) Medullarypyramid ,/ V THE SPINAL CORD lumbar, and those within the pelvic area are called The Dorsal Surface of the Spinal Cord sacral. and Spinal Nerves The spinal nerves and the associatedsegments of the spinal cord adopt the names of the vertebrae; eight cer- The spinal cord lies within the vertebral column. The vical nerves are associatedwith seven cervicalvertebrae. spinal nerves, a part of the somatic PNS, communicate Also. the spinal cord in the adult human ends at about with the cord via notches between the vertebrae. The the level of the third lumbar vertebra. This disparity vertebrae are described according to their location. In arisesbecause the spinal cord does not grow after birth, the neck, they are called cervical vertebrae and are whereas the spinal column does. The bundles of spinal numbered from Cl to C7. The vertebrae attached to ribs nerves streaming down within the lumbar and sacral are called thoracic vertebrae and are numbered from Tl vertebral column are called the cauda equina (Latin for "horse's to T12. The five vertebrae of the lower back are called tail"). **,:+;ir.rfiiiili_i**r " THESPINAL CORD 227 lst cervicalnerve 1stcervical vertebra (C1) 7th cervicalvertebra (C7) 8th cervicalnerve 1st thoracicvertebra (T1 ) 1st thoracicnerve 12ththoracic vertebra (Tl 2) 12ththoracic nerve 1stlumbar vertebra (L1 ) 1stlumbar nerve Caudaequina 5thlumbar vertebra (L5) sthlumbar nerve 1stsacral vertebra (S1) 1stsacral nerve 228 c HApTER 7 . AppENDtX:ANILLUsTMTED GUIDETo HUMAN NEURoANAToMy The Ventral-Lateral Surface of neuronal cell bodies. The gray matter is divided into This view shows how the spinal nerves attach to the the dorsal, lateral, and ventral horns. Notice how the spinal cord and how the spinal meninges are organized. organization of gray and white matter in the spinal cord As the nerve passesinto the vertebral notch (not shown), differs from that in the forebrain. In the forebrain, the it splits into two roots. The dorsal root carries sensory gray matter surrounds the white matter; in the spinal axons whose cell bodies lie in the dorsal root ganglia. cord, it is the other way around. The thick shell of white The ventral root carries motor axons arising from the matter, containing the long axons that run up and down gray matter of the ventral spinal cord. The butterfly- the cord, is divided into three columns: the dorsal shaped core of the spinal cord is gray matter consisting columns, the lateral columns, and the ventral columns. Dorsalcotumns Dorsal A horn /l /l DORSAL Lateralcolumn Spinalcanal /l,/l I )-=- Ventralhorn Lateralhorn Ventralcolumn Dorsalroot filaments Dorsalroot Dorsalroot ganglion Spinalpia mater Spinalnerve Subarachnoid space Soinalarachnoid Ventralroot Soinaldura mater Ventralroot filaments (6x) VENTRAL V THESPINAL CORD C ross-Sectional Anatomy Illustrated in this view are some of the important tracts portant for the control of movement (Chapter I4). The of axons running up and down the spinal cord. On the names of the tracts accurately describe their origins and left side, the major ascending sensory pathways are in- terminations (e.9.,the vestibulospinal tract originates in dicated.The entire dorsal column consistsof sensoryax- the vestibular nuclei of the medulla and terminates in ons ascending to the brain. This pathway is important the spinal cord). The descending tracts contribute to two for the conscious appreciation of touch. The spinothala- pathways: the lateral and ventromedial pathways. The mic tract carries information about painful stimuli and lateral pathway carries the commands for voluntary temperature. The somatic sensory system is the topic of movements, especially of the extremities. The ventro- Chapter 12. medial pathway participates primarily in the mainte- On the right side are some of the descending tracts im- nance of posture and certain reflex movements. AscendingSensory Pathways DescendingMotor Pathways Dorsalcolumn \ Corticosoinal' tract \ v Laleral \ pathway Rubrospinaltract \ Medullaryreticulospinal tract Soinothalamictract Tectospinaltract Pontinereticulosoinal tract Ventromedial Vestibulosoinaltract pathway 230 c HApTER 7 . AppENDtX:ANILLUsTMTED GUIDETo HUMAN NEURoANAToMy V THE AUTONOMIC NERVOUSSYSTEM In addition to the somatic PNS, which is devoted largely to the voluntary control of movement and conscious skin sensations,there is the visceralPNS, devoted to the regulation of the internal organs, glands, and vascula- ture. Because this regulation occurs automatically and is not under direct conscious control, this system is called the autonomic nervous system, or ANS. The two most important divisions of the ANS are the sympathetic and parasympathetic divisions. The illustration on the facing page shows the cavity of the body as it appearswhen it has been sectionedsagit- tally at the level of the eye. Notice the verrebral column, which is encasedin a thick wall of connective tissue.The spinal nerves can be seen emerging from the column. Notice that the sympathetic division of the ANS consists of a chain of ganglia that runs along the side of the ver- tebral column. These syrnpatheticganglia communicate with the spinal nerves, with one another, and with a large number of internal organs. The parasympatheticdivision of the ANS is organized quite differently. Much of the parasympathericinnerva- tion of the viscera arises from the vagus nerve, one of the cranial nerves emerging from the medulla. The other major sourceof parasyrnl)atheticfibcrs is the sacralspinal nerves. The two divisions of the ANS exert opposite effects on body physiology. For example, the sympathetic nerv- ous system speeds heart rate, while the parasympa- thetic nervous system slows it down. In general, the sympathetic division is activated to prepare the body for stressful conditions, such as escaping danger, whereas the parasympathetic division is most active under vegetative conditions, such as digesting a large meal. (The functional organization of the ANS is dis- cussedin Chanter 15.) ' t, r. ;'i;11:Il 1'-111;'1 ir - .';" il 11.",,:l :al :i.,.:r'tr' triii:; ;iiii'l rr'.r'-r V THEAUTONOMIC NERVOUS SYSTEM 231 Vagusnerve Spinalnerves Vertebralcolumn Ribsof the rightside (cut) Kidney Smallintestine Sympatheticganglia Urinarybladder Prostategland Sympatheticfibers Parasympatheticfibers 232 c HAprE R 7 . AppENDtX:ANILLUsTRATED GUIDETo HUMAN NEURoANAToMv g THE CRANIAL NERVES TWelvepairs of cr.trrialn('rves emerge from the baseof is important to recognizethat the cranial nerves have "nerves" the brain. The first two are actually parts of the associatedcranial nerve nuclei in tl-remidbrain, pons, CNS, serving olfaction and vision. The rest are like the and medulla. Examplesare the cochlearand vestibular spinal nerves,in that they contain axons of the pNS. As nuclei, which receive information from cranial nerve the illustration shows, however, a single nerve clften has VIII. Most of cranial nerve nuclei were not illllstrated fibers performing many different functions. I(nowledge or labeled in the brain stem cross sections.however. of the nervesand their diversefunctions is a valuableaid becausetheir functions are not discussedexnlicitlv in in the diagnosisof a number clfneurological disorders. It this book. --{ l. Olfactory I lV Trochlear V.Trigeminal Vl. Abducens Vll.Facial VlI l. Auditory-vestibular lX.Glossopharyngeal X.Vagus Xl. Spinalaccessory Xll.Hypoglossal w' THEcRANTAL NERVES 233 NERVENUMBER AND NAME TYPESOF AXONS IMPORTANTFUNCTIONS L Olfactory Specialsensory Sensationof smell ll. Optic Specialsensory Sensationof vision lll.Oculomotor Somaticmotor Movementsof the eye and eyelid Visceralmotor Parasympatheticcontrol of pupil size lV.Trochlear Somaticmotor Movementsof the eye V.Trigeminal Somaticsensory Sensationof touch to the face Somaticmotor Movementof musclesof mastication(chewing) Vl.Abducens Somaticmotor Movementsof the eye Vll. Facial Somaticsensory Movementof musclesof facialexpression Specialsensory Sensationof taste in anterior two-thirds of the tongue VlI L Auditory-vestibular Specialsensory Sensationof hearingand balance lX. Glossopharyngeal Somaticmotor Movementof musclesin the throat (oropharynx) Visceralmotor Parasympatheticcontrol of the salivaryglands Specialsensory Sensationof taste in posterior one-thirdof the tongue Visceralsensory Detectionof blood pressurechanges in the aorta X.Vagus Visceralmotor Parasympatheticcontrol of the heart,lungs, and abdominalorgans Visceralsensory Sensationof pain associatedwith viscera Somaticmotor Movementof musclesin the throat (oropharynx) Xl. Spinalaccessory Somaticmotor Movementof musclesin the throat and neck Xll. Hypoglossal Somaticmotor Movementof the tongue 234 c HApr ER 7 . AppENDTX:ANTLLUSTRATED GUTDETo HUMAN NEURoANAToMy g THE BLOOD SUPPLY OF THE BRAIN VentralView Two pairs of arteries supply blood to the brain: the vcr- branch to form the rtriddler'r'rr'[rral .rr.lcrics and the tcbralartcrics and the inlcrrralcarotitl artcrics. The ver- anterior ccrc[rralartcric's. The anterior cerebralarteries tebral arteries converge near the base of the pons to of eachside are connectedby the antcrior(onlntrinl(..1- form the unpaired lrasilari]11cr]'. At the level of the ing arlc'r1'.Thus, there is a ring of connected arteries at midbrain, the basilar artery splits into the right and left the base of the brain, formed by the posterior cerebral srrpt'r'iorc'crr'[rellar arlt'rics and the posterior cerebral and communicating arteries, the internal carotids, and arteries.The postt'rirlrccrc[rral arte rics send branches, the anterior cerebral and communicating arteries. This called llostcriorr'ornntrrnicatinq arlcrics, that connect ring is called the circleof Willis. them to the internal carotids. The internal carotids Anteriorcerebral artery /\ Posteriorcerebral artery Superiorcerebellar arrery Basilarartery (1x) Vertebralarteries V THEBLOOD SUPPLY OFTHE BRAIN 235 LateralView Most of the lateral surfaceof the cerebrum is supplied by the middle cerebralartery. This artery also feedsthe Terminalcortical branchesof anterior deen structuresof the basalforebrain. cerebralartery Terminalcortical Middlecerebral artery branchesof oosterior cerebralartery MedialView (Brain Stem Removed) Most of the medial wall of the cerebralhemisphere is suppliedby the anterior cerebralartery. The posterior cerebralartery feedsthe medial wall of the occipitalIobe and the inferior part of the temporal lobe. Anteriorcerebral Posteriol 236 CHAPTER 7 . APPENDIX:ANILLUSTMTED GUIDETO HUMAN NEUROANATOMY v SELF-QU|Z This review workbook is designed to help you learn the neuroanatomy that has been presented. Here we have reproduced the images from the Guide; instead of labels, however, numbered leader lines (arranged clockwise) point to the structures of interest. Test your knowledge by filling in the ap- propriate names in the spacesprovided. To review what you have learned, quiz yourself by putting your hand over the names. This technique greatly facilitates the learning and retention of anatomical terms. Mastery of the vocabulary of neuroanatomy will serve you well as you learn about the functional organization of the brain in the remainder of the book. THE LATERALSURFACE OFTHE BRAIN (a) GrossFeatures 'i, F I 2. 5 t t f q. 1 4. P,l t' i *l l. '{:I . T il ii ii,' (b) SelectedGyri, Sulci,and Fissures /' , [.,, s._ [r Jl.l 6_ { S',ri 7_ [i lt; 8.8._ tFi [:1gj ,f," t,$'r {.r i.r ti til |il ft f,:, ffi. i" V SELF.QUIZ 237 THE LATERAL SURFACEOFTHE BRAIN (c) CerebralLobes and the Insula t. 7. 3. 4. 5. (d) Major Sensory,Motor, and AssociationAreas of Cortex 6. 7. 8. 9. t0. ll. t2. t3. t4. 15. i. 238 c H Apr ER 7 . AppENDTX:ANTLLUsTMTED GUTDETo HUMAN NEURoANAToMy THE MEDIAL SURFACEOFTHE BRAIN t. (a) BrainStem Structures 2. 3. 4. 5. 6. 7. 8. 9. (b) ForebrainSrructures t0. il. 12. t3. t4. t5. 16. t7. V SELF.QUIZ THE MEDIAL SURFACEOFTHE BRAIN (c)Ventricles t. 2. 3. 4. 5. 6. THEVENTRAL SURFACEOFTHE BRAIN (a) GrossFeatures 7. 8. 9. r0. 11 12 lt. 13 t2. 14 15 r3. t4. t5. CHAPTER 7 . APPENDIX:ANILLUSTMTED GUIDETO HUMAN NEUROANATOMY THE DORSAL SURFACEOFTHE BRAIN (a) Cerebrum t. 2. 3. 4. ). (b) Cerebrum Removed 7. 8. 9. t0. il. (c) Cerebrum and Cerebellum Removed t2. 13 t3. 14 15 t4. 16 t5. 17 t6. i: :i t7. 'i:, ! j {..;I il :-: I ,:i SELF-QUIZ 241 FOREBRAINAT THALAMUS-TELENCEPHALONJUNCTION (a) GrossFeatures t,^ - / c------l-\-- | ,' *' r /'"-- - { + L --t \-- \! ^r" \ J (b) SelectedCell and FiberGroups t0. il. tc t2. 16 t3. 17 t4. t5. t5. t7. t8. 242 c H A pr ER 7 . AppENDTX:AN TLLUSTRATEDGUTDETo HUMAN NEURoANAToMy FOREBRAINAT MID.THALAMUS (a) GrossFeatures ,>. 9 +" + l\tl /' \.rA 6. 8. 9. t0. il. (b) SelectedCell and FiberGroups t2. t3. t4. t5. t6. t7. t8. t9 20. al 22. 23 t., il::;;-rrl;,:;'a r:;i|\,'::i! ij,i V SELF.QUIZ FOREBRATNAT THALAMUS-MtDBRA|NTUNCT|ON (a) GrossFeatures l. 2. 3. 4. 5. 6. 7. (b) SelectedCell andFiber Groups 8. 9. t0. il. t2. t3. C H A PT E R 7 . APPENDIX:AN ILLUSTMTEDGUIDETO HUMAN NEUROANATOMY ROSTRAL MIDBRAIN t. 2. 3. 4. 5. CAUDAL MIDBRAIN 6. 7. 8. 9. PONSAND CEREBELLUM t0. il. t2. r3. t4. V SELF-QUIZ ROSTRAL MEDULLA t. 2. 3. 4. 5. 6. 7. MID.MEDULLA 8. 9. 12 t0. 11 il. 10 t2. t3. 14. MEDULLA-SPTNALCORD TUNCTTON t5. t6. 17. ,u/'" t8. C H A PT E R 7 . APPENDIX:AN ILLUSTMTEDGUIDETO HUMAN NEUROANATOMY SPINAL CORD,VENTRAL.LATERAL SURFACE t. 2. 3. 6 4. 5. 12 6. 13 7. 14 8. 9. 10. il. 12. t3. I t4. VENTRAL t5. t6. 17. t8. t9. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. v SELF-QU|Z THE CRANIAL NERVES t. 2. 1 3. 2 4. 3 5. 4 6. 5 7. o 7 8. 8 o 9. 10 11 t0. 12 il. t2. CHAPTER 7 . APPENDIX:ANILLUSTRATED GUIDETO HUMAN NEUROANATOMY THE BLOOD SUPPLY OFTHE BRAIN t. 2. 3. 4. 5. 6. 7. 8. 9. t0. il. t2. t3. t4. t5.