Chapter2Central Nervous System ·303 .the early stages ofthis condition,dcussatingmosifxousebers for pain and temperature in the ventral whitetcocommissure are damaged selectively; this resultsdnahwyadin a loss of pain and temperature sense. Becausebowelfunctionsarnlongerunderoluntaryof the location of the cavity, the axons of the dor-control.sal columns are spared, and therefore touch and(2) spinal cord hemisection Complete he-limb position senses are unaffected. It is calledmisectionofthecord produces aBrown-Sequarddissociated anesthesia. Syringomyelia interruptsyndromaesultobuletorstabwoundsdecussating axons from both sides of the body,ygmyinmhence, the sensory loss that occurs is usuallyetc.bilaterally symmetrical. Cavity formation occursThe main signs and symptoms include:most commonlyin the cervical and upperthorac1) Ipsilateral spastic paralysis of the musclesic spinal segments,therebyproducing a cape-likebelow the level of the lesion;distribution of sensory loss on the arms, shoulder,2) Ipsilateral loss of proprioceptive, vibrato-and upper trunk (Fig. VI-2-13) .y and twopoint discriminationsense below thelevel of the lesion;3) Contralateral loss of pain and temperaturesense below the lesion.The motor deficits of distal limb are all ex-pressed on the ipsilateral side because the lateralcorticospinal tract (descending motor pathways),which target distal limb muscle motor neurons,decussate in the brain stem. Because the medialdescendingpathwaysterminatebilaterally,axialmotor function is usually not seriously affectedwith unilateral spinal cord lesions.Axons in the dorsal columns are uncrossedin the spinal cord; hence deficits in touch andlimb position sense are present ipsilateral to thespinal cord lesion. In contrast, the axons of theventrolateral system decussate in the spinal cord.Therefore, pain and temperature senses are im-paired on the side ofthe body that is contralateralto the lesion.(3) Ventral horn lesion It produces theFig.VI-2-13 Distribution of loss of pain andtemperature sense over body insyringomyeliasigns of LMN lesions described as above. Typi-involving the cervicothoracic portion of the spinalcal causes include poliomyelitis, in which a viruscordselectively attacks ventral horn cells or equiva-lent neurons in the brain stem, with no sensorySun Jinhao（孙晋浩）modalities being involved.(4) Lesions in the central portion of theSection2:Brain Stemspinal cord Asmall central lesion of the spi-nal cord occurs, for example, in syringomyeliaThe brainstem is made up of the medulla oblonga-whichisonetypeofthedegenerativediseasesofta, the pons, and the midbrain. It is stalklike in shapethe CNS.In this pathological process,acavityand connects the narrow spinal cord with the expand-fomthntralrininaoded forebrain. The superior boundary of brainstem is扫描全能王创建
·304·PART VI NERVOUS SYSTEMoptic tract, while its inferior boundary is the upperborder of the first cervical nerve roots.I . External AppearanceThe brainstem participates in three broad func-tions: @ It serves as a conduit for the ascending anddescending tracts connecting the spinal cord to theMedulla oblongatadifferent parts of the brain. It contains importantreflex centers associated with the control of respira-The medullaoblongataconnects the pons superi.tion and the cardiovascular system; it also is associ-ly with thespnalcodiferoy(Fig214,)ated with the control of consciousness.③It containsThe junction of the medula and spinal cord is at thethe important nuclei of cranial nerves II through XIlevel of the foramen magnum.The medlla oblongataThe purpose of this section is to review the struc-is conical in shape, its broad extremity being directedture of the different parts of the brainstem so that thesuperiorly.The central canalofthe spinalcord continstudent can understand the spatial relationships ofues upward into the lower half of the medulla; in thethese parts to one another;thevarious connections ofupper half of the medulla it expands as the cavity ofthese parts are dealt with elsewhere as indicated in thetext.the fourth ventricle.orticopinal tractOpitic chiasmagOculomotorn.Trigeminal n.Abducent nFicial n.Vestibulocochlearn.Hgpoglosal nAccessorgnPyramidal decussationLateral corticospinal tracVentral corticospinal tract.to limb musclesto proximal musclesFig. VI-2-14 The ventral surface of the brain stem扫描全能王创建
Central Nervous System·305 .Chapter 2Internal capsuleCaudate nucleusDorsal thalamusTerminalstriaThird ventricleHabenulartrigonePineal bodyPulvinarlateral geniculateSuperior colliculusbodyInferiorcolliculusandbrachium of inferior colliculusSuperior(Anterior)Locus ceruleusmedullary velumMedialeminence_SuperiorcerebellarpeduncleSulcus limitans-Middle cerebellarpeduncleFacial colliculusStriae medullaresVestibular areaMedian sulcusInferior cerebellar peduncleHypoglossal triangleVagal triangleCuneate tubercleAreapostremaGracile tuberclePosterior median sulcusFig. V-2-15 The dorsal surface of the brainstemthe midline there is an elongated swelling, the gracileFrom anterior view, on the anterior surface oftubercle, produced by the underlying gracile nucleus.the medulla is the anterior median fissure,which isLateral to the gracile tubercle is a similar swelling,continuous inferiorly with the anterior median fissurethe cuneate tubercle, produced by the underlying cu-of the spinal cord.Oneach side of themedianfissureneate nucleus. Superior to the gracile tubercle is thethere is a swelling called the pyramid. The pyramidsinferior cerebellar peduncle.are composed of bundles of corticospinal nervefibersthat originate in large nerve cells in the precentralgyrus of the cerebral cortex.The pyramids taper infe-Ponsriorly,and it is here that the majority ofthe descending fibers cross over to the opposite side, formingThe pons is anterior to the cerebellum and con-the decussation of the pyramids. Posterolateral to thenects the medulla oblongata to the midbrain. It ispyramids are the olives, which are oval elevationsabout2.5mmlong.Theponsis superiortotheme-produced by the underlying inferior olivary nuclei. Indulla oblongata and is separated from it by bulbopon-the groove between the pyramid and the olive emergetine sulcus (Fig. VI-2-14, 15) .therootletsofthe hypoglossalnerve.PosteriortotheThe anterior surface is convex from side to sideolives are the inferior cerebellar peduncles, whichand shows many transverse fibers that converge onconnect the medulla to the cerebellum. In the grooveeach side toform the middle cerebellar peduncle.Thebetween the olive and the inferior cerebellar peduncleshallow groove in the midline, the basilar groove,emerge the roots of the glossopharyngeal and vaguslodges the basilar artery.On the anterolateral surfacenerves and the cranial roots of the accessory nerveof theponsthetrigeminal nerveemerges on eachside. Each nerve consists of a smaller, medial motorfrom superior to inferior.'The posterior surface of the superior half of theroot and a larger,lateral sensory root. In the bulbo-medullablongata,thecentralcanalofspinalcdpontine sulcus, there emerge,from medial to lateral,openstofoms thelowerpartofthefoorofthfourththe abducent, facial, and vestibulocochlear nerves.Ventricle (rhomboidfoa)The posteriorsurfaceThe posterior surface of the pons is hidden fromtheinferiorhalfofthemedulla iscontinuuswiththeview by the cerebellum. It forms the upper half of theposterior aspect of the spinal cord. On each sideof扫描全能王创建
·306·PARTVI.NERVOUSSYSTEMfloor of the fourth ventricle and is triangular.colliculusthlaeralgnculatebyandtheoctract.Theinferorbrachiumonnectstheinferioroliculus to the medial geniculate body.3.MidbrainOn the anterior aspect of the midbrain(Fig V-2.14)threisadeedression inthemidine, theinThe midbrain measures about 2 cm in length andteduncularossawhhibunddonithersconnects the pons and cerebellum with theforebrain.by the crus cerebri.The oculomotor nerve emergesThe midbrain is traversed by a narrow channel, thefrom tile medial side of the crus cerebri and passescerebral aqueduct, which is filled with cerebrospinalforward in the lateral wall of the cavermous sinus.fuid (Fig. VI-2-14, 15).On the dorsal surface of brain stem, there areOn theposterior surface of the midbrain,theretheepairs of cerebellar peduncles: superio, middeare twopairs of rounded eminences, which are fourand inferior, which connect the brain stem with thecolliculi (termed quadrigeminal body, corpora quad-cerebellum.rigemina) , They are divided into superior and infe-rior pairs by a vertical and a transverse groove. TheRhomboid fossasuperior colliculi are centers for visual reflexes, andthe inferior are lower auditory centers. Inferior to theIn the upper part of medulla oblongata and theinferior colliculus is the superior (anterior) medul-laryvelum,from which the trochlearnerveemerges.lower part of pons, the central canal of spinal cordThe trochlear nerve is the only one cranial nerve thatopens to form the fourth ventricle, which floor is theemergesfromthedorsal surfaceofbrain stem.Theserhomboid fossa (Fig. VI-2-15, 16). Its rostral angle isare delicate nerves that wind around the lateral aspectcontinuous with mesencephalic (cerebral) aqueductof the midbrain to enter the lateral wall of the cavern-The aqueduct pierces the midbrain and connects theous sinus.third ventricle with the fourth ventricle. At certainOn the lateral aspect of the midbrain,the superiorsites of the fourth ventricular walls, the cerebral piaand inferior brachia ascend in an anterolateral direc-mater and its blood vessels combine with the ependy-tion. The superior brachium passes from the superiorma to from the choroid tela. The blood vessels of theSuperior colliculusMedial geniculate bodyLateral geniculatebodyBrachium of inferior colliculusInferior colliculusTrochlear n.Cerebral peduncleTrigonum lemnisciSuperiormedullaryvelumSuperior cerebellar peduncleFourth ventricleMiddlecerebellar peduncleInferior(posterior)Inferior cerebellarmedullaryvelumpeduncleLateralforaminaChoroid plexusChoroid tissueMedian foramenCuneate tubercleGraciletubercleFig. V-2-16 The choroid of the fourth ventricle扫描全能王创建
Chapter2 Central Nervous System · 307 .otahtbararmedullares, on each side of the median sulcus, theremeraddyahelnare two triangular areas. The medial one is the hypo-sesooiiohebglossal triangle (contains hypoglossal nucleus), thelateral one is the vagal triangle (contains dorsal nucle-esoexwhastrrestoprothecbralpnalus of vagus nerve) (Fig. VI-2-15).The striae medllaresruntransversely betweenmidlinanthlaralanglethoaII . Internal Structureposerorsurfamitedlaterayythuerereearpedunclesadisdividdsym-halves byamediansulcus. Lateral tothis suleusisGeneral descriptionnngatedatiomdialmnwhLsboundedlateralybysulcuhesulcuslmtan.As in the spinal cord, the brainstem consists ofAdjacenttothetopofthesulcuslimitans isthelocuswhite matter (ascending and descending tracts)graycerlus.Neartheupperborderofthe striaemedulmatter (cranial nerve nuclei and non-cranial nervelares, the inferior end of the medialeminence isnuclei),and reticularformation,buta studyof trans-slightly expanded toform the facial colliculus, whichverse sections of this region shows that they haveisproduced by theroot ofthefacialnerve windingbeen extensively rearranged.around the nucleus of the abducent nerve (genu offacial nerve) and abducent nucleus. The floor of the(1) Nuclei of cranial nervessuperior partofthe sulcus limitans isbluish-gray andis called the substantia ferruginea; it owes its color toThe nuclei of cranial nerves of brain stem are re-a group of deeply pigmented nerve cells. Lateral tolated to the I-XII thpairs ofcranial nerves andformthe sulcus limitans is the area vestibuli produced bylongitudinalfunctioncolumns inthebrain stem.Accord-the underlying vestibular nuclei. On the lateral angleing their characters (functions and fiber connections),of the vestibular area is the auditory tubicle, whichthey are divided into 7 groups (Fig. VI-2-17, 18):contains the dorsal cochlear nucleus. Below the striaeAccessorynucleusofoculomotorn.Nucleus of oculomotor nerve(Edinger-Westphal's nucleus)Mesencephalic nucleus ofNucleus of trochlear nervetrigeminal nervePontine nucleus oftrigeminal nerveMotor nucleus of trigeminal n.Nucleus of abducent nerveNucleus of facial nerveCochlear nucleiSup.and inf. salivatory nucleiVestibular nucleiNucleus ofhypoglossal nerveNucleus ambiguusNucleus of solitary tractDorsal nucleus of vagus nerveSpinal nucleus of trigeminal nerveSpinal cordAccessory nucleusFig-henuceraaesithebainstem (dorsalw扫描全能王创建
·308·PARTVINERVOUSSYSTEMfomthetrocharner,whh iatesthesupe1) Somatic motor nuclei The somatic motorrbiquandithqucrananmegngnuclei gives off somatic motor fibers to innervatefrom the dorsal surface of the brain stem.skeletal muscles derived from somites (includingc.Abducent nucleusIt lies deeply inthe facialglossal and extraocular muscles)and have 4pairs:colieulus andgives offfbersrunningventrllyanda, Oculomotor nucleus It is located at theemerging at medial part of bulbopontine sulcus tolevel of the superior colliculus and gives off fibersfomabducent nerve,whichinnervatesthlateralrtotake part in forming theoculomotor nerve,whichtus.innervates the superior, infrior,medial recti, inferiod.Hypoglossal nucleusIt is located deeply inobliquus and levator palpebrae superioris.the hypoglossal triangle and gives off fibers torunb.TrochlearnucleusItis situated atthelevelventrolaterally and emerge between the pyramid andof the inferior colliculus and sends fibersrunningtheolivetoformhypoglossalnerve,which innervatesdorsally to the rostral and of the superior medullaryall the muscles of the tongue on same side.velum, where they decussate to opposite side andemergefromthedorsal surfaceofthebrainstemtoorynucleusofoculomotorn.Red nucleusAccessNucleusofoculomotorn.OculomotornMesencephalic nucleus of trigeminal n.TrochlearrNucleus of trochlear nOphthalmic nPontinenucleusoftrigeminalnMaxillarynMandibulaMotor nucleus of trigeminal n.Nuclsofabducen.Abducent n.Nucleus of facial n.Facial n.Spinal nucleus of trigeminal n.Inferior olivary nucleuSuperior and inferiorsalivatory nucleiGlossopharyngeal n.NucleusambiguusVagus n重-Nucleus of hypoglossal n.Hypoglossal n.-Dorsal nucleus of vagus n.Cranialrootofaccessoryn-Nucleus of solitarytractCAccessorynucleu具O.Fig. V-2-18 The nuclei of cranial nerves in the brainstem (a stereogram)2) Special visceral motor nuclei The speciala. Motor nucleus of trigeminal nerve It lies invisceral motornucleigivesoff special visceral motorthe pons andgivesofffbers toform themotorrot offibers to innervate the skeletal muscles developedtrigeminal nerve. They travel in the trigeminal nervefrom branchial arche, including masticatory, facialand innervate mainly the masticatory muscles, tensorand pharyngolaryngeal muscles etc.tympani etc.扫描全能王创建
Chapter 2Central Nervous System · 309 .b.Nucleus offacialnerveItis situated at thethetic preganglionic fibers, the postganglionic fiberspontinreticularmatioThebersarisingminnervate smooth muscles and glands in the visceralthe facialnucleusfom thefacialnerve,andemergeiorgans of neck,thorax and the most visceral organsthebulbopontinesulcus lateraltotheabducentnerveof abdomen (the digestive canal before the left colicflexure and the parenchymatous organs),and the car-Theupperportionofthenucleusreceivesfbersfromthe corticonuclear tract of both sides and gives offdiac muscles of the heart.4) General and special visceral sensory nucleusnervefibers to innervate the facial muscles aboveThe general and special visceral sensory nucleus con-hpabassurewhileiswerorteivsists of just one nucleus, the nucleus of solitary tract.fibersonlyfrom theopposite corticonuclear tract andIt extends from the lower part ofthe pons to the levelgivesffnervefberstoinnervatesthefacialmusclesofmedial lemniscus decussation ofmedullaoblonga-below the palpebral fissure.ta, and receives primary visceral sensory fibers fromc. Nucleus ambiguousIt is placed in the retic-the facial, glossopharyngeal and vagus nerves. It isular formation of medulla oblongata and sends nervegenerally believed that the upper part of the nucleusfbers to take part in three cranial nerves: glossopha-is the gustatory nucleus, which receives the specialryngeal, vagus and accessory nerves, and to innervatevisceral sensory (gustatory)fibers.the skeletal muscles of pharynx, larynx, sot palate5) General somatic sensory nuclei General and upper part of esophagus.somatic sensory nuclei receive the primary somaticd. Accessory nucleusIt is located in the areasensory fibers from the skin of head and face, andlateral to the anterior horn of spinal grey matter frommucosa of oral and nasal cavities (Fig.VI-2-19)the level of pyramidal decussation to the fifth or sixthSpinal nucleus of trigeminal nerve is medial tocervical segment of spinal cord, and gives rise to fi-the spinal tract of trigeminal nerve, and receives thebers toform theaccessory nerve,and supplies stemo-primary somatic sensory fibers of trigeminal nervecleidomastoid muscle and trapizus.andgives off fibers to decussate to the opposite side3) General visceral motor nuclei General vis-and take part in forming thetrigeminal lemniscus.Itceral motor nuclei give off the general visceral motoris related to the conduction of pain and temperaturefibers (parasympathetic preganglionicfibers)and sup-sensations from the area of head and face where theply the smooth muscles and glands of the head, neck,trigeminal nerve distributes.thorax and most of abdomen, and the cardiac muscles.Pontine nucleus of trigeminal nerve is located ina. Accessory oculomotor nucleus It is alsothe pons,and receives theprimary somatic sensorycalled Edinger Westphal nucleus or E-W nucleus andfibers of trigeminal nerve that conduct the tactile andat the level of superior colliculus. The nucleus givespressure sensations of the skin, mucous membrane ofoff the parasympathetic preganglionic fibers, whichhead and face,cornea, conjunctiva and the meninges,travel in the oculomotor nerve and relay in the ciliaryand sends fibers to decussate to the opposite side andganglion. The postganglionic fibers innervate the cili-takepart in forming the trigeminal lemniscus.ary muscle and the sphincter pupillae.Mesencephalic nucleus of trigeminal nerve isb. Superior salivatory nucleusIt is located incomposed of pseudounipolar primary sensory neu-inferior part of the pons and sends parasympatheticrons. The peripheral processes of the neurons in thispreganglionic fbers, which run in the facial nerve andnucleus distribute to the masticatory muscles,fascialrelay in the pterygopalatine and submandibular gan-muscles and teeth etc.,their central processes termi-glia.The postganglionicfbers control the secretionofnatethepontine and spinal nuclei oftrigeminal nerve.the lacrimal, submandibular, sublingual glands, andThe mesencephalic nucleus of trigeminal nerve con-the mucous glands in the nasal and oral cavities.ducts the deep (proprioceptive) sensation of the headc. Inferior salivatory nucleusIt is situated inandface.the upper part ofthe medulla oblongata and sends6) Special somatic sensory nuclei The specialparasympathetic preganglionicfbers, whichtravelisomatic sensory nuclei receive the primary sensorythe glossopharyngeal nerve and relay inthe otic ganfibers of auditory and equilibrious sensations fromglonThepostganglioniberssupplythesecretioninternal ear, and include the cochlear nucleus and ves-of parotidgland.tibularnucleus.d. Dorsal nucleus of vagus nerve It lies undersIt is at the level of thea. Cochlear nucleusthvagaltriangleandgivesrsetohparasympa扫描全能王创建
·310·PARTVI NERVOUSSYSTEMconducts and relays the auditory informationfrom thebulbopontine sulcus and is divided into dorsal andspiralorganofoneear to the bilateral inferiorcollicuventral cochlear nuclei,and receives primary auditoryli and auditory centers.fbers from the cochlear nerve,gives offfbers to takepart in forming the lateral lemniscus of both sides,Mesencephalic nucleus of trigeminal nerveTrigeminal thalamic tract-Motomucleus oftrigeminalnerve光Pontinenucleusof trigeminalnervTrigeminal ganglionFacial nucleusSpinaltractofteminal:Hypoglossal nucleusSpinal nucleus of trigeminal nervFig. VI-2-19The trigeminal nuclei and the connection with central nervous systemb.Vestibular nucleus It is under the vestibularcuneatus respectively on the same side.They sendarea and receives the primary afferent fibers of equi-axons to form the internal arcuate fibers, which curvelibrious sensation of vestibular nerve and thefibersventromedially around the central grey matter andfrom cerebellum, and is the important relay station ofdecussate to the opposite side,and then turn upwardsthe afferent and efferent pathways of cerebellum.Theto form the medial lemniscus beside the median line.main functions of the nucleus are to harmonize theThe decussation is called the decussation of medialmovements of eyeballs and head, to regulate the to-lemniscus (Fig.VI-2-20,21)nicity ofmuscles,tokeep thebalance ofthebody etc.2) Inferior olivary nuclear complex is deep to theby these tracts.olive and receives the fibers from the spinal cord,sensory relay nuclei of brain stem, cerebral cortex,(2) Non-cranial nerve nucleithalamus, basal nuclei and red nucleus etc. and givesrise to olive-cerebellar fibers, which decussate to theThe non-cranial nerve nuclei of brain stem haveopposite side, and together with the posterior spinoc-no direct connection with the cranial nerves. The im-erebellar tract form the inferior cerebellar peduncle.portant non-cranial nerve nuclei are as follows:The complex takes part in the cerebellum to regulate1) Gracile and cuneate nuclei are deep to the grac-and control the movements, and takes part in theile and cuneate tubercles respectively, and receivelearning and memory of movements etc (Fig. VI-2-22,afferent fibers from fasciculus gracilis and fasciculus23).扫描全能王创建
Chapter 2 Central Nervous System · 311 .Fasciculus gracilisGracile nucleus1Fasciculus cuneatusCuneatenucleusSpinal tract of trigeminal n.Central greymatterPosterior spinocerebellar tractSpinal nucleus of trigeminal n.-CentralcanalRubrospinal tractAnterior spinocerebellar tractVReticularformationAccessory nucleusLateral spinothalamic tractMedial longitudinal fasciculusDecussation of pyramidMotor cell of anterior homVestibulospinal tracTectospinal tractFig, V-2-20The transverse section through the medulla oblongata at the levelofthe pyramidaldecussationFasciculus gracilisGracile nucleusFasciculus cuneatusCuncate nuclcusDorsal nucleus ofvagus n.Nucleus of solitary tract00Spinalnucleus oftrigeminal n.Spinal tract of trigeminal n.-Hypoglossal nucleusMedlial longitudinal fasciculuReticularfomationTectospinaltractDecussationofmedial lemmniscusHypoglossaln.PyramidaltractThe transverse section through the medulla oblongata at the level of the decussation of medialFig. VI-2-21lemnisciNucleus ofVestibular nucleiDorsal nucleus of vagus nhypoglossal n.Nucleus of solitarytractReticularformationNucleus of solitary tract,Spinal nucleusoftrigeminaln.Inferior cerebellar peduncle00NucleusambiguusMedial longitudinal fasciculus福Inferior(nodose)ganglionTectospinal tracVagusrMedial lemniscusInferior olivary nucleusPyramidal tracthraugvassharr扫描全能王创建
·312·PARTVINERVOUSSYSTEMAcousftictubercleDorsal cochlearnucleus-Medial vestibular nucleusInferior cerebellarpeduncleLateral vestibular nucleusNucleus of solitary tract5Root of glossopharygealn.Spinal nucleus of trigeminal n.-Ventral cochlearnucleusSpinal tract of trigeminal n.Root ofvestibulocochlearnNucleus ambiguusInferior olivary nucleusPyramidal tractFig. VI-2-23The transverse section through the rostral end of the olives3) Pontine nuclei are placed throughout the bas-of sounds at the same time. It is also the auditory re-ilar part of pons,comprise all themasses of neuronsflex centers. It sends fibers to the nucleus of superiorwhich are in different size, and scatter in the spacescolliculus and takes part in finishing the visuoaudito-between fibers arranged in a crisscross pattern.Theyry reflex caused by sound, namely the head and eyesreceive the fibers from the broad areas of ipsilateralturning to the direction of sound source (Fig.VI-2-26)cerebral cortex,give off pontocerebellar fibers to5) Nucleus of superior colliculus is beneath thedecussate to the opposite side to form the middlesuperior colliculus, receives fibers from theopticcerebellar peduncle, which enters the contralateraltract, visual cortex and the nucleus of inferior collic-cerebellum. The pontine nuclei are one part of extra-ulus etc. and integrates the information from thesepyramidal system and the main relay stations on theparts. It sends fibers to the thalamus, lateral genicu-pathway from cerebral cortex to cerebellum (Fig. VI-latenucleus,somenucleiofbrain'stemandthe spinal2-24,25).cord. The nucleus serves as visual reflex center, takes4)Nucleus of inferior colliculus is deep to thepart in the cerebral cortex to control the rapid move-inferiorcolliculus,and receivesfibers from thelateralments of eyeball in vertical and horizontal directions,lemniscus andgivesoff thefibersto medial genic-such as rapid scaning, and takes part in harmonizingulate body via the brachium of inferior colliculus.the movements ofhead and eyes, so as to localize andThe nucleus is an important relay station of auditoryfollow visual stimuli (Fig.VI-2-27)pathway,and has thefunction to localize the sourceGenu of facial n,Nucleus of abducent n.Facial colliculusVestibular nucleiSpinal nucleus oftrigeminal n.Nucleus of facial nSuperior olivary nucleMiddlecerebellarpeduncleFacialn.MediallemniscusandTrapezoid bodyPyramidal tracAbducent n.Fig. VI-2-24The transverse section through the pons at the level of facial colliculus扫描全能王创建