北大神經(jīng)生物學課件神經(jīng)系統(tǒng)對運動的調節(jié)

北大神經(jīng)生物學課件神經(jīng)系統(tǒng)對運動的調節(jié)Introduction生命在于運動……運動是動物維系個體生存和種族繁衍的基本功能之一2Howdoesacoordinatedmovementachieved?3Thementalbodyimageseemstobegeneratedbysomatosensory,proprioceptive,andvisualinputstotheposteriorparietalcortex(area5,area7)Abaseballpitcherplanningapitch…4Thehighestlevel－strategyRepresentedbytheassociationareasofneocortexandbasalgangliaoftheforebrainIsconcernedwithstrategy:ThegoalofthemovementandthemovementstrategythatbestachievesthegoalThemotorcontrolhierarchyhavethreelevels5Themiddlelevel－tacticsRepresentedbythemotorcortexandcerebellumIsconcernedwithtacticsThesequencesofmusclecontractionsArrangedinspaceandtimeRequiredtosmoothlyandaccuratelyachievethestrategicgoalThemotorcontrolhierarchyhavethreelevels6Thelowestlevel－execution

RepresentedbythebrainstemandspinalcordIsconcernedwithexecutionActionofthemotorneuronandinterneuronpoolsthatgeneratethegoal-directedmovementandmakeanynecessaryadjustmentsofpostureThemotorcontrolhierarchyhavethreelevels7Overview脊髓內(nèi)的“下運動神經(jīng)元(Lowerneurons)”，除了受到脊髓內(nèi)局部環(huán)路的影響外，還受到大腦皮層運動區(qū)及腦干中許多“上運動神經(jīng)元(Upperneurons)”的支配和協(xié)調基底神經(jīng)節(jié)和小腦則向那些上運動神經(jīng)元提供某種感覺、認知或感性的信息，使運動更加精確和協(xié)調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

支配上肢的神經(jīng)元集群位于頸膨大處，支配下肢的則在腰膨大處ThedistributionofmotorneuronsinthespinalcordThemotorneuronsthatinnervatedistalandproximalmusculaturearefoundmainlyinthecervicalandlumbar-sacralsegmentsofthespinalcordWhereasthoseinnervatingaxialmusculaturearefoundatalllevelsSegmentsC3-T1haveaswollenventralhornthatinnervateskeletalmusculatureinarmsSegmentsL1-S3haveaswollenventralhornthatinnervateskeletalmusculatureinlegs18MotorneuronscontrollingflexorsliedorsaltothosecontrollingextensorsMotorneuronscontrollingaxialmusclesliemedialtothosecontrollingdistalmuscles支配軀干部肌肉的神經(jīng)元位于脊髓前角灰質最內(nèi)側，由此向外排列的神經(jīng)元則支配肢體由近及遠分布的肌肉Thedistributionoflowermotorneuronsintheventralhorn19Muscleweaknessandparalysis－所支配的骨骼肌癱瘓、肌張力下降、腱反射消失(軟癱)肌萎縮、纖維顫動或肌束顫動見于如肌萎縮側索硬化癥(amyotrophiclateralsclerosis,

ALS)：Selectivedamagetoalphamotorneurons(degeneration)－脊髓-運動神經(jīng)元的進行性潰變?yōu)橹飨逻\動神經(jīng)元的損傷表現(xiàn)20LouGehrigFarewellSpeech:"Fans,forthepasttwoweeksyouhavebeenreadingaboutthebadbreakIgot.YettodayIconsidermyselftheluckiestmanonthefaceofthisearth.……SoIcloseinsayingthatImayhavehadatoughbreak,butIhaveanawfullottolivefor."LouGehring,astarbaseballplayerwithNewYorkYankees,whodiedofALS(amyotrophiclateralsclerosis)in193621InputstoalphamotorneuronsThisinputisimportantfortheinitiationandcontrolofvoluntarymovementThisinputmaybeexcitatoryorinhibitoryandispartofthecircuitrythatgeneratesthespinalmotorprogramsThisinputprovidesfeedbackaboutmusclelength22SPINALCONTROLOFMOTORUNITSHowtheactivityofthemotorneuronisitselfcontrolled?23ReflexReceptorEffectorSpinalMotorNeuron(center)SkinMuscleJointMusclecontractionHigherCenterVoluntarymovementsNociceptivestimulusStretchmusclesPosturemaintenance24Themyotaticreflex(stretchreflex)Twotypesofmyotaticreflex

－TendonreflexandmuscletonusA.Tendonreflex

—快速牽拉肌腱而發(fā)生的牽張反射Clinicapplication：了解脊髓不同節(jié)段的功能狀態(tài)

reflexmothedCentralsiteeffect肘反射扣擊肱二頭肌肌腱頸5-7肘部屈曲膝反射扣擊股四頭肌肌腱腰2-4小腿伸直跟腱反射扣擊跟腱腰5-骶2腳向足底方向屈曲單突觸反射潛伏期很短，約0.7s只夠一次突觸傳遞時間延擱25+26B.Muscletonus

肌肉受到緩慢而持續(xù)的牽拉而發(fā)生的收縮－使骨骼肌能保持一定的肌肉張力意義:維持身體的姿勢(posture)，而不表現(xiàn)明顯的動作表現(xiàn)：extensor(伸肌)和flexor(屈肌)都發(fā)生肌緊張直立時，以伸肌緊張為主，因重力作用于關節(jié)，使關節(jié)趨向彎曲，伸肌受到牽拉，引起肌緊張反射，肌緊張度增加以對抗關節(jié)屈曲因重力持續(xù)作用于關節(jié)，肌緊張也就持續(xù)發(fā)生。使直立姿勢得以維持多突觸反射潛伏期較長，經(jīng)過多個突觸傳遞27

Musclespindles:ConsistsofspecializedskeletalmusclefibersInthismiddleregion,groupIa

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

是一種可感受肌肉長度變化或感受牽拉刺激的本體感受器梭內(nèi)肌感受部裝置位于中間,收縮成分位于兩端,梭內(nèi)肌收縮時或牽拉梭外肌時,感受裝置對牽拉敏感性增高

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這種現(xiàn)象可以持續(xù)１h或更久，被稱為長時程抑制(long-termdepression,LTD)，是學習的一種神經(jīng)基礎SpinalcircuitrycontrolofmovementIfthemusclespindlebecomesslack,itgoes“offtheair”andnolongerreportsthelengthofthemuscle(Primarymotorcortex)TheeffectsoflateralpathwaylesionsLowermotorneuronsGammamotorneuronsThemiddlelevel－tacticsJoinincorticospinaltractinthelateralcolumnofthespinalcordHelpsmaintainastandingposturebyresistingtheeffectsofgravityOne:Projectsbilaterallydownthespinalcordandactivatesthecervicalspinalcircuitsthatcontrolneckandbackmusclesandguidheadmovement刺激藍斑可以加強浦肯野細胞對苔蘚纖維和攀緣纖維傳入的反應LTD本質上是介導平行纖維浦肯野細胞突觸興奮性傳遞的促離子型AMPA受體對突觸前末梢所釋放的遞質谷氨酸的長時程失敏(desensitization)Themotionofthefluidinthislabyrinth,whichaccompaniesmovementsofthehead,activateshaircellsthatsignalthevestibularnucleiviacranialnerveVIIIMossyfiberProprioceptionfromGolgitendonorgansGolgitendonorganActslikeastraingauge,itmonitorsmuscletension,ortheforceofcontractionLocatedatthejunctionofthemuscleandthetendonandareinnervatedbygroupIbsensoryaxonsthatareslightlysmallerthantheIaaxonsinnervatingthemusclespindles33GolgitendonorgansrespondtoincreasedtensiononthemuscleandtransmitthisinformationtothespinalcordviatypeIbsensoryafferents.Becausetheactivatedmuscledoesnotchangelength,theIaafferentsremainsilentinthisexample當肌肉等長收縮時,腱器官傳入沖動頻率,肌梭傳入沖動頻率不變;當肌肉等張收縮時,腱器官傳入沖動頻率不變,肌梭傳入沖動頻率GolgitendonorganslieinseriesbetweenthemusclefibersandtheirpointsofattachmentMusclespindlesarearrangedparalleltotheextrafusalfibers34TheIbafferentsenterthespinalcord,branchrepeatedly,andsynapseoninterneuronsintheventralhornSomeoftheseinterneuronsforminhibitoryconnectionswiththealphamotorneuronsinnervatingthesamemuscle.ThisisthebasisforthereversemyotaticreflexCircuitryofthereversemyotaticreflex＋-Musclespindlesituatedinparallelwiththemusclefibers,GolgitendonorgansaresituatedinseriesIaactivityfromthespindleencodesmusclelengthinformationWhileIbactivityfromtheGolgitendonorganencodesmuscletensioninformation腱器官是張力感受器,其傳入沖動對同一肌肉運動神經(jīng)元起抑制作用肌梭是長度感受器,其傳入沖動對同一肌肉運動神經(jīng)元起興奮作用當肌肉被動牽拉時,二者傳入沖動頻率均：首先興奮肌梭發(fā)動牽張反射,肌肉收縮,牽拉力大到一定程度,興奮腱器官而抑制牽張反射牽張反射的特點：反射弧簡單，感受器和效應器在同一塊肌肉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來自高級中樞的下行投射對腦干和脊髓環(huán)路的運動控制主要影響隨意運動和朝向目標的運動發(fā)出下行投射的中樞位于腦干某些部位以及大腦皮質的運動區(qū)域腦干內(nèi)的兩個主要結構－前庭核和網(wǎng)狀結構對維持姿勢很重要皮質主要運動區(qū)和次要運動區(qū)(運動前區(qū))主要對運動進行計劃并使運動高效率執(zhí)行，皮質的這種作用是通過對腦干內(nèi)的某些高級中樞以及腦干、脊髓中運動神經(jīng)元和環(huán)路中間神經(jīng)元的控制來完成的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運動皮層對軀體運動的調控特點：交叉性：但頭面部肌肉的支配是雙側性的有精細的功能定位：大體呈身體倒影:在4區(qū)內(nèi)側近中線部位是下肢代表區(qū)，向外側依次為軀干、前臂、手指，最外側靠近外側溝處為面部和舌代表區(qū)頭面代表區(qū)內(nèi)部為正立的運動精細部位其代表區(qū)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初級運動皮層和前運動區(qū)運動皮層(motorcortex)初級運動皮層(primarymotorarea)，即4區(qū)次級運動區(qū)或稱前運動區(qū)輔助運動區(qū)(supplementarymotorarea)，位于初級運動皮層前面的6區(qū)皮層的內(nèi)側部分，大部分在大腦半球的內(nèi)側面外側前運動區(qū)(lateralpremotorarea)或稱前運動皮層(premotorcortex)，位于6區(qū)的外側部分64皮層神經(jīng)元運動皮層中的神經(jīng)細胞可分為兩大類錐體細胞，特征是具有向皮層表面伸展的頂樹突。其軸突離開運動皮層到其他皮層或皮層下結構，是主要的傳出神經(jīng)元非錐體細胞，包括星形細胞、籃狀細胞和顆粒細胞，多數(shù)屬于抑制性神經(jīng)元65第Ⅵ層的錐體細胞投射至丘腦，它們也有上行軸突側支至皮層的各層

皮層各層中錐體細胞的投射第II、III層中的錐體細胞投射至其他皮層區(qū)，位置較淺的細胞投射至同側皮層(如輔助運動區(qū)、前運動皮層、中央溝后的感覺皮層)，較深的投射至對側皮層大多數(shù)向皮層下結構的投射起源于第Ⅴ層的錐體細胞，皮層脊髓神經(jīng)元在第Ⅴ層的深部，其中包括最大的錐體細胞即Betz細胞。較淺的第Ⅴ層錐體細胞則投射至延髓、橋腦和紅核，最淺的第Ⅴ層細胞投射至紋狀體66皮層脊髓束和皮層延髓束大腦皮層通過皮層脊髓束和皮層延髓束控制運動皮層延髓束終止于延髓的顱神經(jīng)運動核，控制面部肌肉的活動皮層脊髓束則支配脊髓運動核，控制軀體肌肉的活動67皮層脊髓束和皮層延髓束走行皮層脊髓束和皮層延髓束一起經(jīng)內(nèi)囊下行到中腦腹側，分散地穿過橋腦核，在延髓集合成錐體繼續(xù)下行至延髓和脊髓交界處，約3/4的纖維交叉至對側而在脊髓的背外側束下行，稱為外側皮層脊髓束，另1/4纖維不交叉而在脊髓腹側下行，稱為腹側皮層脊髓束68皮層脊髓束和皮層延髓束走行外側皮層脊髓束主要終止于脊髓腹角外側的運動神經(jīng)元和中間區(qū)內(nèi)的中間神經(jīng)元，腹側皮層脊髓束則主要投射至雙側腹角腹內(nèi)側的運動神經(jīng)元和中間區(qū)內(nèi)側的中間神經(jīng)元，支配軀干中線肌肉和肢體近側肌肉的皮層延髓束終止于腦干的顱神經(jīng)感覺和運動核69

運動皮層通過兩條獨立的通路分別影響脊髓運動神經(jīng)元一條經(jīng)過錐體束的直接通路直達脊髓灰質外側和內(nèi)側的運動神經(jīng)元一條間接通路，即經(jīng)過紅核和網(wǎng)狀結構的接替70皮層脊髓纖維和運動神經(jīng)元的聯(lián)系皮層脊髓神經(jīng)元對脊髓的

運動神經(jīng)元有直接突觸聯(lián)系，起到強烈的直接興奮性影響皮層脊髓神經(jīng)元間接影響運動神經(jīng)元皮層脊髓束的主要功能是控制肢體遠端肌肉的活動，特別是手指的活動通過腦干神經(jīng)元間接地控制脊髓運動神經(jīng)元。在初級運動皮層、前運動皮層和輔助運動區(qū)，均有神經(jīng)元投射至腦干的網(wǎng)狀脊髓神經(jīng)元及其他下行神經(jīng)元而間接影響脊髓運動神經(jīng)元皮層脊髓神經(jīng)元經(jīng)過上頸段脊髓中的脊髓固有神經(jīng)元，再影響位于頸膨大中的支配前臂肌肉的運動神經(jīng)元經(jīng)過抑制性中間神經(jīng)元以施加抑制性影響71次級運動區(qū)的運動功能初級運動皮層主要和運動的執(zhí)行有關次級運動區(qū)主要與運動的準備（策劃）有關使用PET影像研究局部腦血流與運動的關系：執(zhí)行簡單動作如單指按壓彈簧，則4區(qū)(S1)的手代表區(qū)血流增加；執(zhí)行復雜動作如輪排手指，則輔助運動區(qū)(S2)的血流亦增加；若只默想復雜動作，則僅有輔助運動區(qū)的血流增加72次級運動區(qū)的運動功能次級運動區(qū)是選擇正確的運動戰(zhàn)略所必需和初級運動皮層相比，損毀次級運動區(qū)(前運動皮層、輔助運動區(qū)和后頂葉皮層區(qū))引起更為復雜的運動異常，主要影響制定正確運動策略的能力一側的輔助運動區(qū)和前運動皮層被損毀后，猴不會使用對側前臂繞過擋在前面的透明塑料板，并通過側面的洞去取所看見的食物，相反，猴總是試圖直接去取食物而一再撞到塑料板上這種運動缺損和人的前額葉聯(lián)絡皮層或后頂葉皮層受損時引起的失用癥(apraxia)相似。這種病人能正常進行簡單的運動，但喪失了做需要有次序地收縮肌肉的較復雜的動作的能力，例如刷牙和梳頭等73Thebasalgangliacontrolofmovement74基底神經(jīng)節(jié)(basalganglia)是從端腦衍生的一些皮層下神經(jīng)核團的總稱，位于大腦兩半球的深部?；咨窠?jīng)節(jié)中與運動功能有關的主要是紋狀體(striatum)尾核與殼核是基底神經(jīng)節(jié)的主要輸入核(inputnuclei)，蒼白球的內(nèi)側部、腳內(nèi)核和黑質網(wǎng)狀部是基底神經(jīng)節(jié)的主要輸出核(outputnuclei)，后兩者的結構和機能也很相似75Asummaryoftheloopfromthecortextothebasalganlgliatothethalamusandbacktoarea6Cerebralcortex(SMA)CaudatenucleusPutamenNewStriatumGlobuspallidus(OldStriadum)StriadumThalamus(theventrallateralnucleus,VLo)Frontalcortexneuron(Input)(Output)紋狀體的主要傳入沖動來自大腦皮層廣泛的區(qū)域(運動區(qū)、體感區(qū)、聯(lián)合區(qū)、邊緣區(qū)甚至頂葉)傳出沖動經(jīng)過丘腦返回皮層，主要是輔助運動區(qū)(supplementarymotorarea)和運動前皮層(premotorcortex)，而與脊髓沒有直接的聯(lián)系76基底神經(jīng)節(jié)與大腦皮層的纖維聯(lián)系，與運動有關的主要為三條回路皮層

新紋狀體(尾、殼核)

蒼白球(內(nèi)側部)

丘腦

皮層皮層

新紋狀體(尾、殼核)

蒼白球(外)

丘腦底核

蒼白球(內(nèi))

丘腦

皮層皮層

新紋狀體(尾、殼核)

黑質

丘腦

皮層基底神經(jīng)節(jié)與與大腦皮層之間主要的回路聯(lián)系771.皮層

新紋狀體

蒼白球(內(nèi)側)

丘腦

皮層回路大腦皮層(包括運動區(qū)、體感區(qū)、聯(lián)合區(qū)、邊緣區(qū)甚至頂葉)

新紋狀體(包括尾核和殼核，即紋狀體的輸入核)

蒼白球的內(nèi)側部

丘腦(包括腹前核、腹外側核、內(nèi)側背核和中央中核)

大腦皮層(主要是運動區(qū)和輔助運動區(qū)皮層)782.皮層

新紋狀體

蒼白球(外)

丘腦底核

蒼白球(內(nèi))

丘腦

皮層回路大腦皮層相當廣泛的區(qū)域

新紋狀體

蒼白球的外側部

丘腦底核

蒼白球的內(nèi)側部

丘腦

皮層運動區(qū)和運動前區(qū)793.皮層

新紋狀體

黑質

丘腦

皮層回路大腦皮層相當廣泛的區(qū)域(包括運動區(qū)、體感區(qū)、聯(lián)合區(qū)、邊緣區(qū)甚至頂葉)

新紋狀體

黑質網(wǎng)狀部

丘腦的腹前核和腹外側核

大腦皮層(運動區(qū)和輔助運動區(qū))紋狀體(尾殼核)

黑質間存在具有局部定位特征的往返纖維聯(lián)系從黑質的致密部有纖維投向新紋狀體，它組成多巴胺能神經(jīng)元系統(tǒng)；但黑質除有纖維至上丘和腳橋被蓋核外，沒有其他向下投射的纖維 所以，基底神經(jīng)節(jié)的運動功能是通過大腦皮層中與運動控制有關的區(qū)域而間接實現(xiàn)的80直接通路易化運動直接通路包括通路1和3從皮層到新紋狀體(輸入核)的遞質是谷氨酸，是興奮性的；從新紋狀體到蒼白球內(nèi)側部及黑質網(wǎng)狀部(輸出核)的遞質是GABA和P物質，是抑制性的；從這些輸出核到丘腦的遞質也是GABA，也是抑制性的；再由丘腦返回到皮層的輔助運動區(qū)，則是興奮性的。當皮層有興奮沖動下行到紋狀體的輸入核使它興奮時，就會使輸出核中的抑制細胞抑制，從而激活(去抑制)了丘腦的神經(jīng)元，再通過輔助運動區(qū)和運動前區(qū)激活運動皮層和向腦干及脊髓的投射神經(jīng)元，從而起易化運動的效果81間接通路抑制運動間接通路包括通路2從皮層到新紋狀體(輸入核)的遞質是谷氨酸，是興奮性的；從紋狀體輸入核到蒼白球外側部的遞質是GABA和腦啡肽，是抑制性的；從蒼白球外側部到丘腦底核的遞質是GABA，也是抑制性的；從丘腦底核到蒼白球內(nèi)側部(輸出核)的遞質是谷氨酸，是興奮性的；從蒼白球內(nèi)側部到丘腦的遞質是GABA，抑制性的；再由丘腦返回到皮層的輔助運動區(qū)，則是興奮性的當皮層與紋狀體輸入核興奮而使蒼白球外側部抑制時，轉而使丘腦底核產(chǎn)生興奮(去抑制)，也就興奮了紋狀體的輸出核，抑制了丘腦，從而降低了輔助運動區(qū)的興奮性，產(chǎn)生抑制運動的效果82黑質－紋狀體多巴胺能投射易化運動從黑質中的多巴胺能神經(jīng)元發(fā)出纖維到新紋狀體，易化運動興奮直接通路而易化運動，也就是使新紋狀體通過GABA與P物質等抑制紋狀體的輸出核，興奮丘腦，最后起易化運動的作用。抑制間接通路而易化運動，就是使新紋狀體抑制，致使GABA與腦啡肽的抑制作用降低，因而興奮了蒼白球的外側部，抑制丘腦底核，從而抑制紋狀體輸出核，興奮了丘腦，最后也起易化運動的作用。所以，多巴胺能投射通過直接通路或間接通路，最后對運動都起易化作用83+-Parkinson’sdiseaseHuntington’sdisease-84Thecerebellum

controlofmovement85Overview小腦(cerebe