Central Nervous System · 321 Chapter2roughthhamnueianfuentrIV . Blood Supply of thesavcerebri.Brainstem(5) Influence on the biological clocksBlood supply of the medullaThe reticular formationby means of is mulipleoblongataafferent andefferent pathways tothe hypothalamusprobably infuences the biologicalrhythmsThe vertebral, anterior and posterior spinal,pos-terior inferior cerebellar, and basilar arteries all send(6) Ascending reticular activating sys-branches to the medulla oblongata.temBlood supply of the ponsIt includes the sensory imput to the reticularfomation ofbrain stem,the projectionfrom thereThe pons is supplied by the basilar artery and theticularformation to diencephalons,and theextensiveanterior, inferior,and superior cerebellar arteriesprojection to cerebral cortex from the diencephalons.Almost allthe ascending specific sensory pathways3.Blood supply of the midbraingive off collateral branches in the brain stem intothe reticular formation, in which the specific sensoryThe midbrain is supplied by the posterior cerebralinformation is relayed in the “multi-synaptic" patternthe superior cerebellar, and the basilar arteries.by a series of the nuclei of the reticular formation.Then the information are farther relayed to the non-Luo Tao（罗涛）WangHuaqiao（汪华侨）specific nuclei of thalamus from the reticular forma-tion and become nonspecific.Finally the nonspecificinformation is extensively projected to the areas ofV.Cerebellumthe cerebral cortex.Multiple ascending pathways carrying sensoryThe cerebellum, literally means “little brain", isinformation to higher centers are channeled throughsituated in the posterior cranial fossa of the skull andthe reticular formation, which in turn projects thecovered superiorly by the tentorium of cerebellum.Itinformation to different parts of the cerebral cortex,lies posteriorto thefourthventricle,thepons and me-causing a sleeping person to waken, in fact it is nowdulla, anchored there by three pairs of fiber bundlesbelieved that the state of consciousness is dependentcalled cerebellar peduncles.Although the cerebellumon the continuous projection to the cortex of sensoryis mainly concerned with sensory information andinformation. Different degrees of wakefulness seemhas fewwaysto affectmotorneuronsdirectly,it isto depend on the degree of activity of the reticularconsidered part of the motor system because it coor-formation.dinates the voluntary movements.The lesion ofthe reticular formation of brain stemofen lead tothe disturbances ofconsciousness in dif.Gross appearance of the cere-ferent extent, which may range from feeting unconbellum (Fig.VI-2-28)sciousness to deep sustained coma.From the above description it must be apparentThe cerebellum consists of two cerebellar hemithat thenetworkofneurons inthe cerebrospinal axisspheres joined by a narrowmedian vermis.It has twoalmostoally ignoredinthe past,isnowbeing showsurface superior and inferior. The superior surfacetofuencepracticallyallactivitiesohebdy扫描全能王创建
·322·PARTVINERVOUSSYSTEMthe superiorand inferior surfaceof cerebllum areis convex, while the inferior surface shows a deepdrawninone plane.The surfaceofthe cerebellumismedian notch. The tonsil of cerebellum is a roughlyindented by fine slitlike sulci,between which lie morespherical lobule on the inferior aspect of the posteriororlessparllelcerebllarfoliaBasedontheposterlobe.The tonsil of cerebellum may be displaced downlaeredfssureandthe primaryfissure, cerebellumsthrough the foramen magnum in conditions of severedivided into three lobes:raised intracranial pressure. There are many fissures1) The flocculonodular lobe consists of noduleon the surface of cerebellum. Out of the numerousand attaches floccules.It lies on the inferior surfacefissures, three deep ones, primary fissure, posterlater-in front of the posterlateral fissure. The flocculonod.al fissure and horizontal fissure, indent the cerebellarular lobe is also called archicerebellum or vestibulo-surface, with the result that the entire cerebellar sur-cerebellum because it is the oldest part of cerebellumface is made up of cortical ridges called folia. Theand is functionally corrected to vestibular nucleus.parts of cerebellum are show in figure, where bothPrimary fissureVermisSuperiorsemilunarlobuleCerebellar hemisphereHorizontal fissureInferior semilunar lobuleA.superior aspectVermisMiddle cerebellar peduncleSuperiorcerebellarpeduncleFlocculusNodulUvula of vermiBiventral lobuleTonsil of cerebellumPyramid of vermisB. inferior aspectFig. VI-2-28 The cerebellum扫描全能王创建
Chapter 2 Central Nervous System · 323 .2)Theanterior lobe, which isseparatedfrompos1) The cerebellar cortex It consists of three lay-omsresoers molecular, piriform cell, and granular layers. Thethesuprorsufacehanteroboethmolecular layer lies immediately below the surface,withthyramdanduulaothinferormiscontains few cells and consists principally of unmy-nexprlluppaeivesselinated fibers. Among its cells are distinguished thenaliputsandsocaldsinocereellmorpalerouter stellate cells (lying ncar the surface) and theebellum.inner stellate or basket cells.The narrow piriform cell3)Theposteriorlobe, which isthe largestofthelayer consists of the larger ncrve cells ofthe cerebel-thmyrmlum, the Purkinjc cells. The next layer is the granular(onthe superferior surface)and bythe posterolcoterullayer. It is very rich in cells and consists of denselyfssure (on the inferior surface)packed small nerve cells, the granular cells, as well asThe posterior lobe (minus the pyramid and uvula)occasional larger cells,the Golgi cells.made up neocerebellum or cerebrocerebellum be-Different areas of the cerebellar cortex are prefer-cause it is thenewest part ofcerebellum to appear andentially related not only to particular inputs but alsoitreceives the corticocerebellar projections from theto particular cercbellar nucleus.The dentate nucleuscerebral cortex through the pontine nucleus.receives projcctions mainly fromthelateral partsofthe cerebellar hemispheres, the emboliform nucleus2.Internal structures of the cere-and globose nucleus from the paravermal cortex,andthe fastigial nucleus from the vermis.bellum2) The cerebellar nuclei (Fig. VI-2-29) Thereare four pairs of cerebellar nuclei in the medullaryThe cerebellum is composed of an outer coveringcenter of each side of the cerebellum. From lateral toof gray matter called the cerebellar cortex and innermedial these nucleus are the dentate, the emboliform,white matter called medullarycenter.Embeddedthe globose, and thefastigial nucleus.within the white matter are four pairs of nucleus.astigialnuclensCerebellarcortexGlobose nucleusDentatenuclerEmboliformnucleusMedullary centerFig. V-2-29 Internal structures of the cerebellumcortex is a mass of white matter, the medullary centerThe fastigial nucleus lies near the midline in theof the cerebellum. It is made up of three groups ofvermis and close to the roofofthe fourth ventricle.fibers:@intrinsic,@afferent,and③efferent.The emboliform nucleus is oval and situated me-The intrinsic fibers do not leave the cerebellumdial to the dentate nucleus.but connected different folia of the cerebellar cortexThe globose nucleus lies medial to the'emboli-and vermis on the same side,whileothers connecttheform nucleus.two cerebellar hemispheres together.The dentate nucleus, the largest ofthe cereblarThe afferent fibers form the great part of the whitenucleus,hastheshapeacrmpledbagwihmatter and proceed to the cerebellar cortex. Here, theyopeninfaingmedillyhinriortblose their myelin sheath and end as either climbing orllewiwhiemattemadrshatmossy fibers.The afferent fibers enter the cerebellumleavethenucleusfomargpartsupemainly through the inferior and middle cerebellar pe-cerebellar peduncle.duncles.3Thewhite matteroferebellumBeneaththe扫描全能王创建O
·324·PART VINERVOUSSYSTEMThe efferent fibers constitute the output ofthe cer-with increased muscle reflexes.3) The neocerebellum (cerehrocerehellum) re-ebellum and commence as the axons of the Purkinjeceives input from the cerebral cortex via a relay incells of the cerebellar cortex. The great majority ofpontine nucleus and sends fibers to the dentate nu-Purkinje cell axons passes to and synapses with thecleus. Axons of neurons in the dentate nucleus travelneurons of the cerebellar nuclei. The axons of thethrough the superior cerebellar peduncle and end byneurons then leave the cerebellum.synapsing with cells in the ventralintermediate nucleTheefferent and afferentfibers of cerebellum areus of the thalamus. The axons of the thalamic neuronsgrouped together on each side into three large pedun-terminate in the primary motor area of the cerebralcles, which connect the cerebellum to the midbrain,cortex. By this way, the neocerehellum can influencepons and medulla.The inferior cerebellar pedunclemotor neurons of the cerebral cortex, impulses from(or restiform body) is composed mainly of afferentsto cerebellum from the spinal cord and brainstem. Itthe motor cortex are transmitted to spinal segmentalarisesfromthe superiorhalf of the medulla oblon-levels through the corticospinal tract,and it representsgate.The two peduncles diverge as they ascend andthe apparatus for fine synchronization of voluntarypass into their respective cerebellar hemisphere.movement. Lesions of these region results in hypoto-The middle cerebellar peduncle (or arm of the nia, diminished or pendulum muscle jerks, intentionpons)is the largest of the three peduncles. It is com-tremor,clumsymovements and nystagmus.posed of afferents to cerebellum from the pontine nu-cleus of contralateral side.It arises from the pons andVI.Diencephalonenters cerebellar hemisphere on each side.The supe-rior cerebellar peduncle (or brachium conjunctivum)The diencephalon lies between midbrain and ce-contains the major efferent pathways from the cerebel-rebrum, almost entirely surrounded by cerebral hemi-lum to thered nucleus and thalamus.It runs superiorly,sphere, and therefore hidden from surface view.It islateral to the upperhalfof thefourthventricle,toentercavity forms the third ventricle. The diencephalon ac-the lower part of the midbrain on each side.counts for less than 2% of the weight of the brain, butit isextremely important.Eachhalf of the dienceph-3.Connections and functions of thealon is divided into dorsal and ventral part by hypo-cerebellumthalamic sulcus, extending from the interventricularforamen to the cerebral aqueduct. The diencephalon1) The archicerebellum (vestihulocerehellum)can be divided into five parts: the dorsal thalamus,mainly receives input from vestibular nucleus and②themetathalamus,③the epithalamus,the sub-primary fibers of vestibular nerve, and sends fibersthalamus, and the hypothalamus. (Fig VI-2-30).to the vestibular nucleus and other nucleus of themedulla oblongata. Axons of these neurons influence.Doral thalamus (Fig.VI-2-31)spinal segmental motor activity through the vestibulo-spinal tract and the medial longitudinal fasciculus. Itis involved in eyemovements and maintains balance.The dorsal thalamus is a larger, ovoid mass ofLesions of this part lead to disturbances with no alter-gray matter that forms the major part of the dien-ationof spinal reflexes.cephlon. There are two dorsal thalami and one is sit-2)The paleocereellum (spinocerehellum)receivesuated on each side of the third ventricle. The anteriorsomatic sensory information via spinocerebellar tractsend of the dorsal thalamus is narrow and roundedand sends fibers'to the fastigial nucleus and inter-called the anterior thalamic tubercle. The posteriorposed nucleus. The fibers end by synapsing with cellsend of the dorsal thalamus is expanded to from theof the vestibular nucleus, reticular formation of brainpulvinar. The surface of the dorsal thalamus formsstem and red nucleus, which give rise to axons of thepart of the lateral wall of the third ventricle and arevestibulospinal tract,reticulospinal tract and rubrospi-usually connected to the opposite dorsal thalamus bynal tract. The paleocereellum play an important rolea hand of gray matter, the interthalamic adhesion. Thein control of muscle tone and coordination of muscledorsal thalamus is covered on its lateral surface by amovement on the same side of the body. Lesions ofthin layer of white matter, called the external medulthis part cause disturbances of postural mechanismslarylamina.扫描全能王创建
Chapter 2Central Nervous System · 325 ·AnteriorhomoflateralventricleSeptum pellucidumCaudate nucleusColumnoffomixTeminal striaAnteriorcommissureThalamic medullary striaInsular lobe-Internal capsuleInterthalamicadhesionLentiformnucleusTenia choroideaaminaaffixaDorsal thalamusThird ventricleChoroid plexus ofHabenulartrigonelateral ventricleHabenular commissurPineal bodyPosteriorcommissureFig. VI-2-30 The dorsal view of diencephalonIntralaminarnucleargroupMediodorsa nucleusInternal medullary laminaMedian nucleusAnteriornucleargroupInterthalamicadhesionThalamicreticularnucleusLateral dorsal nucleusCentromedian nucleusVentral anterior nucleusVentral posteromedial nucleusLateral posterior nucleusNuclei pulvinares.Globus pallidus thalamicfibersBrachium of inferior colliculusEVentral intermediate nucleusVenrtal posterolateral nucleusMedial geniculate bodyFibersof super cerebellarpeduncleLateral geniculate bodyMedial lemniscus and spinothalamic tractOptictractTrigeminothalamic tract(Trigeminal lemniscus)Fig. VI-2-31 Astereogram of nucleus of dorsal thalamusthe Y. Each of the three nuclear groups of the dorsalThe gray mater of the dorsal thalamus is divid-thalamus contains groups of thalamic nucleus.Thedbyialswhmae,inelateral nuclear group is subdivided into a dorsal tiermamaladahand a ventral tier. The dorsal tier includes the lateralmemamedularymonsissnrberthatdorsal nucleus, the lateral posterior nucleus, and theasfmthceusthupulvinar. The ventral tier consists of the followingin a craniocaudal sequence: ventral anterior nucleus,tuiventral intermediate nucleus and ventral posterior nu-inohararocleus. The ventral posterior nucleus is subdivided intoesedmdithe ventral posteromedial nucleus and the ventral po-es扫描全能王创建O