北大神经生物学课件神经系统对运动的调节

北大神经生物学课件神经系统对运动的调节Introduction生命在于运动……运动是动物维系个体生存和种族繁衍的基本功能之一2Howdoesacoordinatedmovementachieved?3Thementalbodyimageseemstobegeneratedbysomatosensory,proprioceptive,andvisualinputstotheposteriorparietalcortex(area5,area7)Abaseballpitcherplanningapitch…4Thehighestlevel－strategyRepresentedbytheassociationareasofneocortexandbasalgangliaoftheforebrainIsconcernedwithstrategy:ThegoalofthemovementandthemovementstrategythatbestachievesthegoalThemotorcontrolhierarchyhavethreelevels5Themiddlelevel－tacticsRepresentedbythemotorcortexandcerebellumIsconcernedwithtacticsThesequencesofmusclecontractionsArrangedinspaceandtimeRequiredtosmoothlyandaccuratelyachievethestrategicgoalThemotorcontrolhierarchyhavethreelevels6Thelowestlevel－execution

RepresentedbythebrainstemandspinalcordIsconcernedwithexecutionActionofthemotorneuronandinterneuronpoolsthatgeneratethegoal-directedmovementandmakeanynecessaryadjustmentsofpostureThemotorcontrolhierarchyhavethreelevels7Overview脊髓内的“下运动神经元(Lowerneurons)”，除了受到脊髓内局部环路的影响外，还受到大脑皮层运动区及脑干中许多“上运动神经元(Upperneurons)”的支配和协调基底神经节和小脑则向那些上运动神经元提供某种感觉、认知或感性的信息，使运动更加精确和协调8

9SensorimotorcortexBasalgangliaCerebellumBrainstemSpinalcordInterneuron

-MotorneuronMotorunit(finalcommonpathway)Receptorsmuscle,skin,joint12345Theseprogramsareaccessed,executed,andmodifiedbydescendingcommandsfromthebrainThebrain’scommandandcontrolofthemotorprogramsinthespinalcordThemotorsystemconsistsofallourmusclesandtheneuronsthatcommandthemThespinalcordcontainscertainmotorprogramsforthegenerationofcoordinatedmovementsThemotorcontrolcanbedividedintotwoparts:Thespinalcord’scommandandcontrolofcoordinatedmusclecontraction10Part1

SpinalControlofMovement11Introduction“runningaroundlikeachickenwithitsheadcutoff”

Therhythmicmovementscouldbeelicitedinthehindlegsofcatsanddogslongaftertheirspinalcordshadbeenseveredfromtherestofthecentralnervoussystem–CharlesSherington&GrahamBrown(English)Theimportanceofcircuitrywithinthespinalcordforthecoordinatedcontrolofmovements12Spinalcircuitry

controlofmovement13Spinalmotorneurons

Alphamotorneurons

Innervateskeletalmuscle(extrafusalmuscle)

Function:directlycommandmusclecontractGammamotorneurons

Innervatemusclespindle(intrafusalmuscle)

Function:regulatingthemusclespindleInterneurons

AllowscoordinatedmotorprogramstobegeneratedFinalcommonpathway(directlycommandmusclecontract)Compare:UppermotorneuronsLowermotorneurons14TheLowerMotorNeurons

－AlphamotorneuronsAlphamotorneuronsaredirectlyresponsibleforthegenerationofforcebymuscleMotorunit:onealphamotorneuronandallofthemusclefibersitinnervatescollectivelymakeupmotorunit,theelementarycomponentofmotorcontrolMotorneuronpool:Thecollectionofalphamotorneuronsthatinnervatesasinglemuscle15ThemotorunitisanalphamotorneuronandallofthemuscleAmotorunitandmotorneuronpoolThemotorneuronpoolisallofthealphamotorneuronsthatinnervateonemuscle16Muscleinnervationbylowermotorneurons30mixedspinalnervescervical1-8thoracic1-12lumbar1-5sacral1-5TheventralhornofthespinalcordcontainsmotorneuronsthatinnervateskeletalmusclefibersVentralroots+Dorsalroot=Spinalnerve17Thecervicalenlargementofthespinalcordcontainsthemotorneuronsthatinnervatethearmmuscles

Thelumbarenlargementcontainsneuronsthatinnervatethemusclesoftheleg

支配上肢的神经元集群位于颈膨大处，支配下肢的则在腰膨大处ThedistributionofmotorneuronsinthespinalcordThemotorneuronsthatinnervatedistalandproximalmusculaturearefoundmainlyinthecervicalandlumbar-sacralsegmentsofthespinalcordWhereasthoseinnervatingaxialmusculaturearefoundatalllevelsSegmentsC3-T1haveaswollenventralhornthatinnervateskeletalmusculatureinarmsSegmentsL1-S3haveaswollenventralhornthatinnervateskeletalmusculatureinlegs18MotorneuronscontrollingflexorsliedorsaltothosecontrollingextensorsMotorneuronscontrollingaxialmusclesliemedialtothosecontrollingdistalmuscles支配躯干部肌肉的神经元位于脊髓前角灰质最内侧，由此向外排列的神经元则支配肢体由近及远分布的肌肉Thedistributionoflowermotorneuronsintheventralhorn19Muscleweaknessandparalysis－所支配的骨骼肌瘫痪、肌张力下降、腱反射消失(软瘫)肌萎缩、纤维颤动或肌束颤动见于如肌萎缩侧索硬化症(amyotrophiclateralsclerosis,

ALS)：Selectivedamagetoalphamotorneurons(degeneration)－脊髓-运动神经元的进行性溃变为主下运动神经元的损伤表现20LouGehrigFarewellSpeech:"Fans,forthepasttwoweeksyouhavebeenreadingaboutthebadbreakIgot.YettodayIconsidermyselftheluckiestmanonthefaceofthisearth.……SoIcloseinsayingthatImayhavehadatoughbreak,butIhaveanawfullottolivefor."LouGehring,astarbaseballplayerwithNewYorkYankees,whodiedofALS(amyotrophiclateralsclerosis)in193621InputstoalphamotorneuronsThisinputisimportantfortheinitiationandcontrolofvoluntarymovementThisinputmaybeexcitatoryorinhibitoryandispartofthecircuitrythatgeneratesthespinalmotorprogramsThisinputprovidesfeedbackaboutmusclelength22SPINALCONTROLOFMOTORUNITSHowtheactivityofthemotorneuronisitselfcontrolled?23ReflexReceptorEffectorSpinalMotorNeuron(center)SkinMuscleJointMusclecontractionHigherCenterVoluntarymovementsNociceptivestimulusStretchmusclesPosturemaintenance24Themyotaticreflex(stretchreflex)Twotypesofmyotaticreflex

－TendonreflexandmuscletonusA.Tendonreflex

—快速牵拉肌腱而发生的牵张反射Clinicapplication：了解脊髓不同节段的功能状态

reflexmothedCentralsiteeffect肘反射扣击肱二头肌肌腱颈5-7肘部屈曲膝反射扣击股四头肌肌腱腰2-4小腿伸直跟腱反射扣击跟腱腰5-骶2脚向足底方向屈曲单突触反射潜伏期很短，约0.7s只够一次突触传递时间延搁25+26B.Muscletonus

肌肉受到缓慢而持续的牵拉而发生的收缩－使骨骼肌能保持一定的肌肉张力意义:维持身体的姿势(posture)，而不表现明显的动作表现：extensor(伸肌)和flexor(屈肌)都发生肌紧张直立时，以伸肌紧张为主，因重力作用于关节，使关节趋向弯曲，伸肌受到牵拉，引起肌紧张反射，肌紧张度增加以对抗关节屈曲因重力持续作用于关节，肌紧张也就持续发生。使直立姿势得以维持多突触反射潜伏期较长，经过多个突触传递27

Musclespindles:ConsistsofspecializedskeletalmusclefibersInthismiddleregion,groupIa

sensoryaxonswraparoundthemusclefibersofthespindleThespindlesandtheirassociatedIaaxons,specializedforthedetectionofchangesinmusclelength(stretch):proprioceptorsandpropriceptionIaaxonsarethethickestmyelinatedaxonssotheyconductactionpotentialsveryrapidlyIaaxonsenterthespinalcordviathedorsalroots,branchrepeatedly,andformexcitatorysynapsesuponbothinterneuronsandalphamotorneuronsoftheventralhornsProprioceptionfrommusclespindlesMusclespindle

是一种可感受肌肉长度变化或感受牵拉刺激的本体感受器梭内肌感受部装置位于中间,收缩成分位于两端,梭内肌收缩时或牵拉梭外肌时,感受装置对牵拉敏感性增高

28Musclecontraction(finalcommonpathway)Flexorreflex:usedtowithdrawalimbfromanaversivestimulus,suchasthewithdrawalofyourfootfromthethumbtackMotorneuronscontrollingflexorsliedorsaltothosecontrollingextensorsStretchmusclesThevestibulospinalandtectospinaltractskeeptheheadbalanceontheshouldersasthebodymovesthroughspace,andtheyturntheheadinresponsetonewsensorystimuliWhenthesubjectswereaskedonlytorehearsethemovementmentallywithoutactuallymovingthefinger,area6remainedactivebutarea4didnotTheeffectsoflateralpathwaylesionsHigher-ordermotorplanningStellatecell(finalcommonpathway)Theseprogramsareaccessed,executed,andmodifiedbydescendingcommandsfromthebrainThementalbodyimageseemstobegeneratedbysomatosensory,proprioceptive,andvisualinputstotheposteriorparietalcortex(area5,area7)BasketcellIaaxonsarethethickestmyelinatedaxonssotheyconductactionpotentialsveryrapidly+29GammamotorneuronsExtrafusalfibersareinnervatedbyalphamotorneuronsIntrafusalfibersreceivetheirmotorinnervationbyanothertypeoflowermotorneuroncalledagammamotorneuronGammamotorneuronsinnervatetheintrafusalmusclefiberatthetwoendsofthemusclespindleActivationofthesefiberscausesacontractionofthetwopolesofthemusclespindle,therebypullingonthenon-contractileequatorialregionandkeepingtheIaafferentsactive30ThefunctionofgammamotorneuronsActivationofalphamotorneuronsshortenstheextrafusalmusclefibers.Ifthemusclespindlebecomesslack,itgoes“offtheair”andnolongerreportsthelengthofthemuscleActivationofgammamotorneuronscontractsthepolesofthespindle,keepingit“ontheair”31TheGammaloopChangingtheactivityofthegammamotorneuronschangesthesetpointofthemyotaticfeedbackloopTheGammaloopGammamotorneuronintrafusalmusclefiberIaafferentalphamotorneuronextrafusalmusclefibersAlphaandgammamotorneuronsaresimultaneouslyactivatedbydescendingcommandsfromthebrain32这种现象可以持续１h或更久，被称为长时程抑制(long-termdepression,LTD)，是学习的一种神经基础SpinalcircuitrycontrolofmovementIfthemusclespindlebecomesslack,itgoes“offtheair”andnolongerreportsthelengthofthemuscle(Primarymotorcortex)TheeffectsoflateralpathwaylesionsLowermotorneuronsGammamotorneuronsThemiddlelevel－tacticsJoinincorticospinaltractinthelateralcolumnofthespinalcordHelpsmaintainastandingposturebyresistingtheeffectsofgravityOne:Projectsbilaterallydownthespinalcordandactivatesthecervicalspinalcircuitsthatcontrolneckandbackmusclesandguidheadmovement刺激蓝斑可以加强浦肯野细胞对苔藓纤维和攀缘纤维传入的反应LTD本质上是介导平行纤维浦肯野细胞突触兴奋性传递的促离子型AMPA受体对突触前末梢所释放的递质谷氨酸的长时程失敏(desensitization)Themotionofthefluidinthislabyrinth,whichaccompaniesmovementsofthehead,activateshaircellsthatsignalthevestibularnucleiviacranialnerveVIIIMossyfiberProprioceptionfromGolgitendonorgansGolgitendonorganActslikeastraingauge,itmonitorsmuscletension,ortheforceofcontractionLocatedatthejunctionofthemuscleandthetendonandareinnervatedbygroupIbsensoryaxonsthatareslightlysmallerthantheIaaxonsinnervatingthemusclespindles33GolgitendonorgansrespondtoincreasedtensiononthemuscleandtransmitthisinformationtothespinalcordviatypeIbsensoryafferents.Becausetheactivatedmuscledoesnotchangelength,theIaafferentsremainsilentinthisexample当肌肉等长收缩时,腱器官传入冲动频率,肌梭传入冲动频率不变;当肌肉等张收缩时,腱器官传入冲动频率不变,肌梭传入冲动频率GolgitendonorganslieinseriesbetweenthemusclefibersandtheirpointsofattachmentMusclespindlesarearrangedparalleltotheextrafusalfibers34TheIbafferentsenterthespinalcord,branchrepeatedly,andsynapseoninterneuronsintheventralhornSomeoftheseinterneuronsforminhibitoryconnectionswiththealphamotorneuronsinnervatingthesamemuscle.ThisisthebasisforthereversemyotaticreflexCircuitryofthereversemyotaticreflex＋-Musclespindlesituatedinparallelwiththemusclefibers,GolgitendonorgansaresituatedinseriesIaactivityfromthespindleencodesmusclelengthinformationWhileIbactivityfromtheGolgitendonorganencodesmuscletensioninformation腱器官是张力感受器,其传入冲动对同一肌肉运动神经元起抑制作用肌梭是长度感受器,其传入冲动对同一肌肉运动神经元起兴奋作用当肌肉被动牵拉时,二者传入冲动频率均：首先兴奋肌梭发动牵张反射,肌肉收缩,牵拉力大到一定程度,兴奋腱器官而抑制牵张反射牵张反射的特点：反射弧简单，感受器和效应器在同一块肌肉35SignificanceofthereversemyotaticreflexInextremecircumstances,thisreflexarcprotectsthemusclefromoverloadThenormalfunctionistoregulatemuscletensionwithinanoptimalrangeAsmuscletensionincreases,theinhibitionofthealphamotorneuronslowsmusclecontractionAsmuscletensionfalls,theinhibitionofthealphamotorneuronisreduced,andmusclecontractionincreasesThistypeofproprioceptivefeedbackisthoughttobeparticularlyimportantfortheproperexecutionoffinemotoracts,suchasthemanipulationoffragileobjectswiththehands,whichrequireasteadybutnottoopowerfulgrip36SpinalinterneuronsMostoftheinputtothealphamotorneuronscomesfrominterneuronsofthespinalcordInterneuronsreceivesynapticinputfromprimarysensoryaxons,descendingaxonsfromthebrain,andcollateralsoflowermotorneuronaxonsTheinterneuronsarethemselvesnetworkedtogetherinawaythatallowscoordinatedmotorprogramstobegeneratedinresponsetotheirmanyinputs37Reciprocalinhibitionofflexorsandextensorsofthesamejoint+++-InhibitoryinputContractionofonesetofmusclesaccompaniedbytherelaxationoftheantagonistmusclesiscalled

reciprocalinhibitionReciprocalinhibitionisalsousedbydescendingpathwaystoovercomethepowerfulmyotaticreflex38(A

&Cfibers)ExcitatoryinputFlexorreflex:usedtowithdrawalimbfromanaversivestimulus,suchasthewithdrawalofyourfootfromthethumbtackThepainfibersenteringthespinalcordbranchprofusedlyandactivateinterneuronsinseveralspinalsegments.Thesecellseventuallyexcite

thealphamotorneuronsthatcontrolalloftheflexormusclesoftheaffectedlimb(andinhibitoryinterneuronsarealsorecruitedtoinhibitthealphasthatcontroltheextensors)++++Circuitryofthepolysynapticflexorreflex39Circuitryofthecrossed-extensorreflexSpinalcordIpsilateralextensorsinhibitedContralateralextensorsactivated(contract)Ipsilateralflexorsactivated(contract)ContralateralflexorsinhibitedIpsilateralkneejointclosesuptoremovefootfromtackContralateralkneejointopensuptosupportgreaterweight40ThegenerationofspinalmotorprogramsforwalkingHeadlesschickens;behaviorAcompletetransectionofacat’sspinalcordatthemid-thoraciclevelleavesthehindlimbscapableofgeneratingcoordinatedwalkingmovementsWhenyouwalk,youalternatelywithdrawandextendyourtwolegs

Whatisthemechanismtocoordinatethetiming?Thiscouldbedescendingcommandsfromuppermotorneurons?No!Thiscontrolisexertedfromwithinthespinalcord?Yes!4142CentralpatterngeneratorswithinthespinalcordThecircuitforthecoordinatedcontrolofwalkingmustresidewithinthespinalcordIngeneral,circuitsthatgiverisetorhythmicmotoractivityarecalledcentralpatterngeneratorsHowdoneuralcircuitsgeneraterhythmicpatternsofactivity?Thesimplestpatterngenerators,aresingleneuronswhosemembranepropertiesendowthemwithpacemakerproperties(pacemakerneurons)43Rhythmicactivityinaspinalinterneuron(Pacemakerneuron)SomeneuronsrespondtotheactivationofNMDAreceptorswithrhythmicdepolarization(a)Intherestingstate,theNMDAreceptorchannelsandthecalcium-activatedpotassiumchannelsareclosed(b)GlutamatecausestheNMDAreceptorstoopen,thecellmembranetodepolarize,andCa2+ionstoenterthecell(c)Theriseinintracellular[Ca2+]causestheCa2+-activatedpotassiumchannelstoopen.K+ionsleavetheneuron,hyperpolarizingthemembrane.ThehyperpolarizationallowsMg2+ionstoenterandclogtheNMDAchannel,arrestingtheflowofCa2+(d)As[Ca2+]falls,thepotassiumchannelsclose,resettingthemembraneforanotheroscillation44Apossiblecircuitforrhythmicalternatingactivity(walking)Walkingisinitiatedwhenasteadyinputexcitestwointerneuronsthatconnecttothemotorneuronscontrollingtheflexorsandextensors,respectively.Theinterneuronsrespondtoacontinuousinputbygeneratingburstsofoutputs.Theactivitiesofthetwointerneuronsalternatebecausetheyinhibiteachotherviaother(inhibitory)interneurons.Thus,aburstofactivityinoneinterneuronstronglyinhibitstheother(Pacemakerneuron)(Pacemakerneuron)45Part2

BrainControlofMovement46Howdoesthebraincommunicatewiththemotorneuronsofthespinalcord?47Overview来自高级中枢的下行投射对脑干和脊髓环路的运动控制主要影响随意运动和朝向目标的运动发出下行投射的中枢位于脑干某些部位以及大脑皮质的运动区域脑干内的两个主要结构－前庭核和网状结构对维持姿势很重要皮质主要运动区和次要运动区(运动前区)主要对运动进行计划并使运动高效率执行，皮质的这种作用是通过对脑干内的某些高级中枢以及脑干、脊髓中运动神经元和环路中间神经元的控制来完成的48Thedescendingspinaltractscontrolofmovement49ThedescendingspinaltractsControlpostureandunderbrainstemcontrolContolvoluntary

movementsofthedistalmusculatureandunderdirectcorticalcontrol50(Pyramidaltract)ControlfinemovementsofthearmsandfingersTheeffectsoflateralpathwaylesions(inmonkeys)－byDonaldLawrence&HansKuypers(inthelate1960s)TheLateralPathwaysXJoinincorticospinaltractinthelateralcolumnofthespinalcordTerminateinthedorsolateralregionoftheventralhornsandintermedialgraymatterWheremotorneuronsandinterneuronscontrolthedistalmuscles,particularlyflexorsInputfromfrontalcortexX51TheVentromedialPathwaysContainfourdescendingtracts

thevestibulospinaltractthetectospinaltractthepontinereticulospinaltractthemedullaryreticulospinaltractOringinateinthebrainstemTerminateamongthespinalinterneuronsControllingproximalandaxialmusclesUsesensoryinformationaboutbalance,bodyposition,andthevisualenviromenttoreflexivelymaintainbalanceandbodyposture52Thevestibulospinalandtectospinaltractskeeptheheadbalanceontheshouldersasthebodymovesthroughspace,andtheyturntheheadinresponsetonewsensorystimuli(midbrain)RecivedirectinputfromretinaReciveprojectionsfromvisualcortex,aswellasafferentscarringsomatosensoryandauditoryinformationConstructamapofthewordaroundusThemotionofthefluidinthislabyrinth,whichaccompaniesmovementsofthehead,activateshaircellsthatsignalthevestibularnucleiviacranialnerveVIIIOne:ProjectsbilaterallydownthespinalcordandactivatesthecervicalspinalcircuitsthatcontrolneckandbackmusclesandguidheadmovementRelysensoryinformationfromthevestibularlabyrinthintheinnerearAnother:ProjectsipsilaterallyasfardownasthelumbarspinalcordIthelpsusmaintainanuprightandbalancedposturebyfacilitatingextensormotorneuronsofthelegsStimulationatonesiteinthismapLeadtoanorientingresponsethatdirectstheheadandeyestomove…53ThepontinereticulospinaltractenhancetheantigravityreflexesofthespinalcordByfacilitatingtheextensorsofthelowerlimbsHelpsmaintainastandingposturebyresistingtheeffectsofgravityThemedullaryreticulospinaltracthastheoppositeeffect:itliberatestheantigravitymusclesfromreflexcontrolActivityinbothreticulospinaltractsiscontrolledbydescendingsignalsfromthecortexControlpostureofthetrunkandtheantigravitymusclesofthelimbs54AsummaryofthemajordescendingspinaltractsandtheirpointsoforiginMotorcortexdirectlyactivatesspinalmotorneuronsandliberatesthemfromreflexcontrolbycommunicatingwiththenucleioftheventromedialpathwaysSo,thecortexiskeyforvoluntarymovementandbehaviorTheventromedialpathwaysoriginatefromseveralregionsofthebrainstemandparticipatemainlyinthemaintenanceofpostureandcertainreflexmovementsInitiationofavoluntarymovements,requiresinstructionsthatdescendfromthemotorcortexalongthelateralpathways55ourattention56MotorCortexMotorCortex(Primarymotorcortex)(Premotorarea)(lateralregion)(Supplementarymotorarea)(medialregion)AreasofneocortexintimatelyinvolvedintheplanningandinstructionofvoluntarymovementThemotorcortexisacircuscribedregionofthefrontallobeArea4liesjustanteriortothecentralsulcusontheprecentralgyrusArea6liesjustanteriortoarea45758Asomatotopicmap

ofthehumanprecentralgyrus运动皮层对躯体运动的调控特点：交叉性：但头面部肌肉的支配是双侧性的有精细的功能定位：大体呈身体倒影:在4区内侧近中线部位是下肢代表区，向外侧依次为躯干、前臂、手指，最外侧靠近外侧沟处为面部和舌代表区头面代表区内部为正立的运动精细部位其代表区大：如手指和面部59Area5PosteriorparietalcortexPrefrontalareas:inhumansarethoughttobeimportantforabstractthought,decisionmaking,andanticipatingtheconsequencesofactionArea6and4togethercontributemostoftheaxonstothedescendingcorticospinaltractArea6liesatthejunctionwheresignalsencodingwhatactionsaredesiredareconvertedintosignalsthatspecifyhowtheactionwillbecarriedoutPrefrontalareas,alongwiththeposteriorparietalcortex,representthehighestlevelsofthemotorcontrolhierarchy,wheredecisionsaremadeaboutwhatactionstotakeandtheirlikelyoutcomeBoththeprefrontalandtheparietalcortexsendaxonsthatconvergeoncorticalarea6Area5,receivesinputsfromprimarysomatosensorycorticalarea3,1,2Area7,receivesinputsfromhigher-ordervisualcorticalareas(MT)ThecontributionsofposteriorparietalandprefrontalcortexPrimarysomatosensorycorticalarea3,1,2Higher-ordervisualcorticalareas(MT)Area7PrefrontalareasForabstractthought,decisionmaking,andanticipatingtheconsequencesofactionArea6Area4Descendingcorticospinaltracts60Theinput-outputorganizationofM1PyramidalcellIncorticallayerV(Motorcortex,M1,Area4)Area6(anterior)Area3,1,2(posterior)Lowermotorneuronsofspinalcord

Thalamus(VLc)CerebellumBrainstemBasalgangliaThalamus(VLo)Somatosensoryinputs61Higher-ordermotorplanningUsingPET(positronemissiontomography)tomonitorchangesinthepatternsofcorticalactivationthataccompanyvoluntarymovementsWhenthesubjectswereaskedtoperformaseriesoffingermovementsfrommemory,thefollowingregionsofcortexshowedincreasedbloodflow:thesomatosensoryandposteriorparietalareas,partsoftheprefrontalcortex(area8),area6,andarea4－PlayaroleingeneratingtheintentiontomoveandconvertingthatintentionintoaplanofactionWhenthesubjectswereaskedonlytorehearsethemovementmentallywithoutactuallymovingthefinger,area6remainedactivebutarea4didnot－PerRolandandhiscolleagues(Danishneurologist)62Thedischargeofacellinthepremotorarea(PMA)beforeamovementArea6(SMAandPMA)playsanimportantroleintheplanningofmovement,particularlycomplexmovementsequencesofthedistalmusculature(a)Ready:Amonkeysitsbeforeapaneloflights.Thetaskistowaitforaninstructionstimulusthatwillinformhimothemovementrequiredtoreceiveajuicereward,thenperformthemovementwhenatriggerstimulusgoeson.TheactivityofaneuroninPMAisrecordedduringthetask(b)Set:theinstructionstimulusoccursatthetimeindicatedbytheupwardarrow,resultinginthedischargeoftheneuroninPMA(c)Go:shortlyafterthemovementisinitiated,thePMAcellceasesfiring63初级运动皮层和前运动区运动皮层(motorcortex)初级运动皮层(primarymotorarea)，即4区次级运动区或称前运动区辅助运动区(supplementarymotorarea)，位于初级运动皮层前面的6区皮层的内侧部分，大部分在大脑半球的内侧面外侧前运动区(lateralpremotorarea)或称前运动皮层(premotorcortex)，位于6区的外侧部分64皮层神经元运动皮层中的神经细胞可分为两大类锥体细胞，特征是具有向皮层表面伸展的顶树突。其轴突离开运动皮层到其他皮层或皮层下结构，是主要的传出神经元非锥体细胞，包括星形细胞、篮状细胞和颗粒细胞，多数属于抑制性神经元65第Ⅵ层的锥体细胞投射至丘脑，它们也有上行轴突侧支至皮层的各层

皮层各层中锥体细胞的投射第II、III层中的锥体细胞投射至其他皮层区，位置较浅的细胞投射至同侧皮层(如辅助运动区、前运动皮层、中央沟后的感觉皮层)，较深的投射至对侧皮层大多数向皮层下结构的投射起源于第Ⅴ层的锥体细胞，皮层脊髓神经元在第Ⅴ层的深部，其中包括最大的锥体细胞即Betz细胞。较浅的第Ⅴ层锥体细胞则投射至延髓、桥脑和红核，最浅的第Ⅴ层细胞投射至纹状体66皮层脊髓束和皮层延髓束大脑皮层通过皮层脊髓束和皮层延髓束控制运动皮层延髓束终止于延髓的颅神经运动核，控制面部肌肉的活动皮层脊髓束则支配脊髓运动核，控制躯体肌肉的活动67皮层脊髓束和皮层延髓束走行皮层脊髓束和皮层延髓束一起经内囊下行到中脑腹侧，分散地穿过桥脑核，在延髓集合成锥体继续下行至延髓和脊髓交界处，约3/4的纤维交叉至对侧而在脊髓的背外侧束下行，称为外侧皮层脊髓束，另1/4纤维不交叉而在脊髓腹侧下行，称为腹侧皮层脊髓束68皮层脊髓束和皮层延髓束走行外侧皮层脊髓束主要终止于脊髓腹角外侧的运动神经元和中间区内的中间神经元，腹侧皮层脊髓束则主要投射至双侧腹角腹内侧的运动神经元和中间区内侧的中间神经元，支配躯干中线肌肉和肢体近侧肌肉的皮层延髓束终止于脑干的颅神经感觉和运动核69

运动皮层通过两条独立的通路分别影响脊髓运动神经元一条经过锥体束的直接通路直达脊髓灰质外侧和内侧的运动神经元一条间接通路，即经过红核和网状结构的接替70皮层脊髓纤维和运动神经元的联系皮层脊髓神经元对脊髓的

运动神经元有直接突触联系，起到强烈的直接兴奋性影响皮层脊髓神经元间接影响运动神经元皮层脊髓束的主要功能是控制肢体远端肌肉的活动，特别是手指的活动通过脑干神经元间接地控制脊髓运动神经元。在初级运动皮层、前运动皮层和辅助运动区，均有神经元投射至脑干的网状脊髓神经元及其他下行神经元而间接影响脊髓运动神经元皮层脊髓神经元经过上颈段脊髓中的脊髓固有神经元，再影响位于颈膨大中的支配前臂肌肉的运动神经元经过抑制性中间神经元以施加抑制性影响71次级运动区的运动功能初级运动皮层主要和运动的执行有关次级运动区主要与运动的准备（策划）有关使用PET影像研究局部脑血流与运动的关系：执行简单动作如单指按压弹簧，则4区(S1)的手代表区血流增加；执行复杂动作如轮排手指，则辅助运动区(S2)的血流亦增加；若只默想复杂动作，则仅有辅助运动区的血流增加72次级运动区的运动功能次级运动区是选择正确的运动战略所必需和初级运动皮层相比，损毁次级运动区(前运动皮层、辅助运动区和后顶叶皮层区)引起更为复杂的运动异常，主要影响制定正确运动策略的能力一侧的辅助运动区和前运动皮层被损毁后，猴不会使用对侧前臂绕过挡在前面的透明塑料板，并通过侧面的洞去取所看见的食物，相反，猴总是试图直接去取食物而一再撞到塑料板上这种运动缺损和人的前额叶联络皮层或后顶叶皮层受损时引起的失用症(apraxia)相似。这种病人能正常进行简单的运动，但丧失了做需要有次序地收缩肌肉的较复杂的动作的能力，例如刷牙和梳头等73Thebasalgangliacontrolofmovement74基底神经节(basalganglia)是从端脑衍生的一些皮层下神经核团的总称，位于大脑两半球的深部。基底神经节中与运动功能有关的主要是纹状体(striatum)尾核与壳核是基底神经节的主要输入核(inputnuclei)，苍白球的内侧部、脚内核和黑质网状部是基底神经节的主要输出核(outputnuclei)，后两者的结构和机能也很相似75Asummaryoftheloopfromthecortextothebasalganlgliatothethalamusandbacktoarea6Cerebralcortex(SMA)CaudatenucleusPutamenNewStriatumGlobuspallidus(OldStriadum)StriadumThalamus(theventrallateralnucleus,VLo)Frontalcortexneuron(Input)(Output)纹状体的主要传入冲动来自大脑皮层广泛的区域(运动区、体感区、联合区、边缘区甚至顶叶)传出冲动经过丘脑返回皮层，主要是辅助运动区(supplementarymotorarea)和运动前皮层(premotorcortex)，而与脊髓没有直接的联系76基底神经节与大脑皮层的纤维联系，与运动有关的主要为三条回路皮层

新纹状体(尾、壳核)

苍白球(内侧部)

丘脑

皮层皮层

新纹状体(尾、壳核)

苍白球(外)

丘脑底核

苍白球(内)

丘脑

皮层皮层

新纹状体(尾、壳核)

黑质

丘脑

皮层基底神经节与与大脑皮层之间主要的回路联系771.皮层

新纹状体

苍白球(内侧)

丘脑

皮层回路大脑皮层(包括运动区、体感区、联合区、边缘区甚至顶叶)

新纹状体(包括尾核和壳核，即纹状体的输入核)

苍白球的内侧部

丘脑(包括腹前核、腹外侧核、内侧背核和中央中核)

大脑皮层(主要是运动区和辅助运动区皮层)782.皮层

新纹状体

苍白球(外)

丘脑底核

苍白球(内)

丘脑

皮层回路大脑皮层相当广泛的区域

新纹状体

苍白球的外侧部

丘脑底核

苍白球的内侧部

丘脑

皮层运动区和运动前区793.皮层

新纹状体

黑质

丘脑

皮层回路大脑皮层相当广泛的区域(包括运动区、体感区、联合区、边缘区甚至顶叶)

新纹状体

黑质网状部

丘脑的腹前核和腹外侧核

大脑皮层(运动区和辅助运动区)纹状体(尾壳核)

黑质间存在具有局部定位特征的往返纤维联系从黑质的致密部有纤维投向新纹状体，它组成多巴胺能神经元系统；但黑质除有纤维至上丘和脚桥被盖核外，没有其他向下投射的纤维 所以，基底神经节的运动功能是通过大脑皮层中与运动控制有关的区域而间接实现的80直接通路易化运动直接通路包括通路1和3从皮层到新纹状体(输入核)的递质是谷氨酸，是兴奋性的；从新纹状体到苍白球内侧部及黑质网状部(输出核)的递质是GABA和P物质，是抑制性的；从这些输出核到丘脑的递质也是GABA，也是抑制性的；再由丘脑返回到皮层的辅助运动区，则是兴奋性的。当皮层有兴奋冲动下行到纹状体的输入核使它兴奋时，就会使输出核中的抑制细胞抑制，从而激活(去抑制)了丘脑的神经元，再通过辅助运动区和运动前区激活运动皮层和向脑干及脊髓的投射神经元，从而起易化运动的效果81间接通路抑制运动间接通路包括通路2从皮层到新纹状体(输入核)的递质是谷氨酸，是兴奋性的；从纹状体输入核到苍白球外侧部的递质是GABA和脑啡肽，是抑制性的；从苍白球外侧部到丘脑底核的递质是GABA，也是抑制性的；从丘脑底核到苍白球内侧部(输出核)的递质是谷氨酸，是兴奋性的；从苍白球内侧部到丘脑的递质是GABA，抑制性的；再由丘脑返回到皮层的辅助运动区，则是兴奋性的当皮层与纹状体输入核兴奋而使苍白球外侧部抑制时，转而使丘脑底核产生兴奋(去抑制)，也就兴奋了纹状体的输出核，抑制了丘脑，从而降低了辅助运动区的兴奋性，产生抑制运动的效果82黑质－纹状体多巴胺能投射易化运动从黑质中的多巴胺能神经元发出纤维到新纹状体，易化运动兴奋直接通路而易化运动，也就是使新纹状体通过GABA与P物质等抑制纹状体的输出核，兴奋丘脑，最后起易化运动的作用。抑制间接通路而易化运动，就是使新纹状体抑制，致使GABA与脑啡肽的抑制作用降低，因而兴奋了苍白球的外侧部，抑制丘脑底核，从而抑制纹状体输出核，兴奋了丘脑，最后也起易化运动的作用。所以，多巴胺能投射通过直接通路或间接通路，最后对运动都起易化作用83+-Parkinson’sdiseaseHuntington’sdisease-84Thecerebellum

controlofmovement85Overview小脑(cerebe