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1CentralNervousSystemControlofMovementXING,GUOGANG(邢国刚),MD.Ph.D.NeuroscienceResearchInstitute,PekingUniversityEmailaddress

:2Introduction❖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一3Howdoesacoordinatedmovementachieved?4Thementalbodyimageseemstobegeneratedbysomatosensory,propri

oceptive,andvisualinputstotheposteriorparietalcortex(area5,area7)Abaseballpitcherplanningapitch…5◼Thehighestlevel－strate

gy➢Representedbytheassociationareasofneocortexandbasalgangliaoftheforebrain➢Isconcernedwithstrategy:—Thegoalofthemovementandthemovementstrategyth

atbestachievesthegoalThemotorcontrolhierarchyhavethreelevels6◼Themiddlelevel－tactics➢Representedbythemotorcortexandcerebellum➢Is

concernedwithtactics—Thesequencesofmusclecontractions•Arrangedinspaceandtime•RequiredtosmoothlyandaccuratelyachievethestrategicgoalThemot

orcontrolhierarchyhavethreelevels7◼Thelowestlevel－execution➢Representedbythebrainstemandspinalcord➢Isconcernedwithexecution—Actio

nofthemotorneuronandinterneuronpoolsthatgeneratethegoal-directedmovementandmakeanynecessaryadjustmentsofpostureThemotorcontrolhierarchyhavethree

levels8Overview◼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910SensorimotorcortexBasalgangliaCerebellumBrainstemSpinalcordInterneuron-MotorneuronM

otorunit(finalcommonpathway)Receptorsmuscle,skin,joint12345❖Theseprogramsareaccessed,executed,andmodifiedbydescendingcomman

dsfromthebrain➢Thebrain’scommandandcontrolofthemotorprogramsinthespinalcord❖Themotorsystemconsistsofallourmuscl

esandtheneuronsthatcommandthem❖Thespinalcordcontainscertainmotorprogramsforthegenerationofcoordinatedmovements❖Themotorcontrolcanb

edividedintotwoparts:➢Thespinalcord’scommandandcontrolofcoordinatedmusclecontraction11Part1SpinalControlofMove

ment12Introduction❖“runningaroundlikeachickenwithitsheadcutoff”❖Therhythmicmovementscouldbeelicitedinthehindlegsofcatsanddogslongaftertheirspinalcord

shadbeenseveredfromtherestofthecentralnervoussystem–CharlesSherington&GrahamBrown(English)—Theimportanceofcircuitrywithinthespinalcordforthecoordi

natedcontrolofmovements13Spinalcircuitrycontrolofmovement14Spinalmotorneurons◼AlphamotorneuronsInnervateskeletalmu

scle(extrafusalmuscle)Function:directlycommandmusclecontract◼GammamotorneuronsInnervatemusclespindle(intrafusa

lmuscle)Function:regulatingthemusclespindle◼InterneuronsAllowscoordinatedmotorprogramstobegenerated▪Finalcommonpathway(directlycommandmuscleco

ntract)•Compare:UppermotorneuronsLowermotorneurons15TheLowerMotorNeurons－Alphamotorneurons◼Alphamotor

neuronsaredirectlyresponsibleforthegenerationofforcebymuscle◼Motorunit:onealphamotorneuronandallofthemusclefibe

rsitinnervatescollectivelymakeupmotorunit,theelementarycomponentofmotorcontrol◼Motorneuronpool:Thecollectionofalphamoto

rneuronsthatinnervatesasinglemuscle16ThemotorunitisanalphamotorneuronandallofthemuscleAmotorunitandmotorne

uronpoolThemotorneuronpoolisallofthealphamotorneuronsthatinnervateonemuscle17Muscleinnervationbylowermotorneurons30mixedspi

nalnervescervical1-8thoracic1-12lumbar1-5sacral1-5TheventralhornofthespinalcordcontainsmotorneuronsthatinnervateskeletalmusclefibersV

entralroots+Dorsalroot=Spinalnerve18ThecervicalenlargementofthespinalcordcontainsthemotorneuronsthatinnervatethearmmusclesThelumbarenlargemen

tcontainsneuronsthatinnervatethemusclesoftheleg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ThedistributionofmotorneuronsinthespinalcordThemotorneuronsthatinnervat

edistalandproximalmusculaturearefoundmainlyinthecervicalandlumbar-sacralsegmentsofthespinalcordWhereasthoseinnervatingaxialmusculaturearefounda

talllevelsSegmentsC3-T1haveaswollenventralhornthatinnervateskeletalmusculatureinarmsSegmentsL1-S3haveaswollenventralhor

nthatinnervateskeletalmusculatureinlegs19MotorneuronscontrollingflexorsliedorsaltothosecontrollingextensorsMotor

neuronscontrollingaxialmusclesliemedialtothosecontrollingdistalmuscles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Thedistributionoflowermotorneur

onsintheventralhorn20◼Muscleweaknessandparalysis－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,AL

S)：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21LouGehrigFarewellSpeec

h:"Fans,forthepasttwoweeksyouhavebeenreadingaboutthebadbreakIgot.YettodayIconsidermyselftheluckiestmanonthefaceofthisearth.……SoIcloseinsa

yingthatImayhavehadatoughbreak,butIhaveanawfullottolivefor."LouGehring,astarbaseballplayerwithNewYorkYankees,whodiedofALS(amyotrophiclateral

sclerosis)in193622InputstoalphamotorneuronsThisinputisimportantfortheinitiationandcontrolofvoluntarymovementTh

isinputmaybeexcitatoryorinhibitoryandispartofthecircuitrythatgeneratesthespinalmotorprogramsThisinputprovidesfeedbackabout

musclelength23SPINALCONTROLOFMOTORUNITSHowtheactivityofthemotorneuronisitselfcontrolled?24ReflexRece

ptorEffectorSpinalMotorNeuron(center)SkinMuscleJointMusclecontractionHigherCenter•Voluntarymovements•Nociceptivestimulus•Stretchmus

cles•Posturemaintenance25Themyotaticreflex(stretchreflex)❖Twotypesofmyotaticreflex－TendonreflexandmuscletonusA.Tendonrefle

x—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26+27B.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：extenso

r(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28Musclespindles:◼Consistsofspecializedskeletalmusclefibers◼Inthismiddleregion,groupIasensoryaxonswraparoundthem

usclefibersofthespindle◼ThespindlesandtheirassociatedIaaxons,specializedforthedetectionofchangesinmusclelength(stretch):proprioceptorsandpropr

iception◼Iaaxonsarethethickestmyelinatedaxonssotheyconductactionpotentialsveryrapidly◼Iaaxonsenterthespinalcordviathedorsalroots,

branchrepeatedly,andformexcitatorysynapsesuponbothinterneuronsandalphamotorneuronsoftheventralhornsProprioceptionfrommusclespin

dles❖Musclespindle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29+30Gammamo

torneurons◼Extrafusalfibersareinnervatedbyalphamotorneurons◼Intrafusalfibersreceivetheirmotorinnervationbyanothertypeof

lowermotorneuroncalledagammamotorneuron◼Gammamotorneuronsinnervatetheintrafusalmusclefiberatthetwoendsofthemusclespindle◼Activationofthesefib

erscausesacontractionofthetwopolesofthemusclespindle,therebypullingonthenon-contractileequatorialregionandkeepingtheIaafferentsactive31Thefunctionofg

ammamotorneurons•Activationofalphamotorneuronsshortenstheextrafusalmusclefibers.Ifthemusclespindlebecomesslack,it

goes“offtheair”andnolongerreportsthelengthofthemuscle•Activationofgammamotorneuronscontractsthepolesofthe

spindle,keepingit“ontheair”32TheGammaloop◼Changingtheactivityofthegammamotorneuronschangesthesetpointofthemyotaticfee

dbackloop◼TheGammaloop◼Gammamotorneuron→intrafusalmusclefiber→Iaafferent→alphamotorneuron→extrafusalmusclefibers◼Alphaandgammamotorneuro

nsaresimultaneouslyactivatedbydescendingcommandsfromthebrain33ProprioceptionfromGolgitendonorgans❖Golgitendonorgan◼Actsl

ikeastraingauge,itmonitorsmuscletension,ortheforceofcontraction◼LocatedatthejunctionofthemuscleandthetendonandareinnervatedbygroupIbsensoryaxon

sthatareslightlysmallerthantheIaaxonsinnervatingthemusclespindles34Golgitendonorgansrespondtoincreasedtensiononthemuscleandtransmitthisinformationto

thespinalcordviatypeIbsensoryafferents.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Golgitendonorganslieinseriesbetweenthemusclefibersandtheirpo

intsofattachmentMusclespindlesarearrangedparalleltotheextrafusalfibers35TheIbafferentsenterthespinalcord,

branchrepeatedly,andsynapseoninterneuronsintheventralhornSomeoftheseinterneuronsforminhibitoryconnectionswiththealphamotorneuronsinne

rvatingthesamemuscle.ThisisthebasisforthereversemyotaticreflexCircuitryofthereversemyotaticreflex＋-Musclespindlesituatedinparallelwit

hthemusclefibers,GolgitendonorgansaresituatedinseriesIaactivityfromthespindleencodesmusclelengthinfor

mationWhileIbactivityfromtheGolgitendonorganencodesmuscletensioninformation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36Significa

nceofthereversemyotaticreflex◼Inextremecircumstances,thisreflexarcprotectsthemusclefromoverload◼Thenor

malfunctionistoregulatemuscletensionwithinanoptimalrange➢Asmuscletensionincreases,theinhibitionofthealphamotorneuro

nslowsmusclecontraction➢Asmuscletensionfalls,theinhibitionofthealphamotorneuronisreduced,andmusclecontractionincreases◼Thistypeofproprioceptivefeed

backisthoughttobeparticularlyimportantfortheproperexecutionoffinemotoracts,suchasthemanipulationoffragileobjectswiththehand

s,whichrequireasteadybutnottoopowerfulgrip37Spinalinterneurons◼Mostoftheinputtothealphamotorneuronsc

omesfrominterneuronsofthespinalcord◼Interneuronsreceivesynapticinputfromprimarysensoryaxons,descending

axonsfromthebrain,andcollateralsoflowermotorneuronaxons◼Theinterneuronsarethemselvesnetworkedtogetherinawaythatallow

scoordinatedmotorprogramstobegeneratedinresponsetotheirmanyinputs38Reciprocalinhibitionofflexorsandextensorsofthesamejoint+++-◼Inhibitoryinpu

t◼Contractionofonesetofmusclesaccompaniedbytherelaxationoftheantagonistmusclesiscalledreciprocalinhibition◼Reciprocalinhibitionisalsousedbydescending

pathwaystoovercomethepowerfulmyotaticreflex39(A&Cfibers)◼Excitatoryinput◼Flexorreflex:usedtowithdrawalimbfromana

versivestimulus,suchasthewithdrawalofyourfootfromthethumbtack◼Thepainfibersenteringthespinalcordbranchprofusedlyandactivat

einterneuronsinseveralspinalsegments.Thesecellseventuallyexcitethealphamotorneuronsthatcontrolallofthef

lexormusclesoftheaffectedlimb(andinhibitoryinterneuronsarealsorecruitedtoinhibitthealphasthatcontroltheextensors)++++Circuitryofthepolysynapt

icflexorreflex40Circuitryofthecrossed-extensorreflexSpinalcordIpsilateralextensorsinhibitedContralateralextensorsactivated(contract)Ipsilateralf

lexorsactivated(contract)ContralateralflexorsinhibitedIpsilateralkneejointclosesuptoremovefootfromtackContrala

teralkneejointopensuptosupportgreaterweight41Thegenerationofspinalmotorprogramsforwalking◼Headlesschickens;behavi

or◼Acompletetransectionofacat’sspinalcordatthemid-thoraciclevelleavesthehindlimbscapableofgeneratingcoordinatedwalkingmovements◼Whenyo

uwalk,youalternatelywithdrawandextendyourtwolegs◼Whatisthemechanismtocoordinatethetiming?◼Thiscouldbedesce

ndingcommandsfromuppermotorneurons?No!◼Thiscontrolisexertedfromwithinthespinalcord?Yes!4243Centralpatterngeneratorswithinthespinalcord

◼Thecircuitforthecoordinatedcontrolofwalkingmustresidewithinthespinalcord◼Ingeneral,circuitsthatgiverisetorhythmicmotoractivityarecalled

centralpatterngenerators◼Howdoneuralcircuitsgeneraterhythmicpatternsofactivity?–Thesimplestpatterngenerators,are

singleneuronswhosemembranepropertiesendowthemwithpacemakerproperties(pacemakerneurons)44Rhythmicactivityinaspinalinterneuron(Pacemakerneuron)Somen

euronsrespondtotheactivationofNMDAreceptorswithrhythmicdepolarization(a)Intherestingstate,theNMDArecepto

rchannelsandthecalcium-activatedpotassiumchannelsareclosed(b)GlutamatecausestheNMDAreceptorstoopen,t

hecellmembranetodepolarize,andCa2+ionstoenterthecell(c)Theriseinintracellular[Ca2+]causestheCa2+-activatedpotassiumchannelstoopen.K+io

nsleavetheneuron,hyperpolarizingthemembrane.ThehyperpolarizationallowsMg2+ionstoenterandclogtheNMDAchannel,arrestingtheflowofCa2+(d)As[Ca2+]falls

,thepotassiumchannelsclose,resettingthemembraneforanotheroscillation45Apossiblecircuitforrhythmicalternatingactivity(walking)Walkingisinitiatedwhena

steadyinputexcitestwointerneuronsthatconnecttothemotorneuronscontrollingtheflexorsandextensors,respectively.Theinterneurons

respondtoacontinuousinputbygeneratingburstsofoutputs.Theactivitiesofthetwointerneuronsalternatebecausetheyinhibiteachotherviaot

her(inhibitory)interneurons.Thus,aburstofactivityinoneinterneuronstronglyinhibitstheother(Pacemakerneuron)(Pacem

akerneuron)46Part2BrainControlofMovement47Howdoesthebraincommunicatewiththemotorneuronsofthespinalcord?48Ov

erview◼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49Thedescendingspinaltractscontrolofmovement50Th

edescendingspinaltractsControlpostureandunderbrainstemcontrolContolvoluntarymovementsofthedistalmusculatureandunderdirectcorticalcontrol51(Pyr

amidaltract)ControlfinemovementsofthearmsandfingersTheeffectsoflateralpathwaylesions(inmonkeys)－byDonald

Lawrence&HansKuypers(inthelate1960s)TheLateralPathwaysXJoinincorticospinaltractinthelateralcolumnofthespinalcordT

erminateinthedorsolateralregionoftheventralhornsandintermedialgraymatterWheremotorneuronsandinterneuronscont

rolthedistalmuscles,particularlyflexorsInputfromfrontalcortexX52TheVentromedialPathways◼Containfourd

escendingtracts—thevestibulospinaltract—thetectospinaltract—thepontinereticulospinaltract—themedullaryr

eticulospinaltract◼Oringinateinthebrainstem◼Terminateamongthespinalinterneurons◼Controllingproximalandaxialmuscles◼Usesensory

informationaboutbalance,bodyposition,andthevisualenviromenttoreflexivelymaintainbalanceandbodyposture53Thevestibulospinalandtectospinaltracts

keeptheheadbalanceontheshouldersasthebodymovesthroughspace,andtheyturntheheadinresponsetonewsensorystimuli(midbrai

n)RecivedirectinputfromretinaReciveprojectionsfromvisualcortex,aswellasafferentscarringsomatosensoryandauditoryinformationConstructamapof

thewordaroundusThemotionofthefluidinthislabyrinth,whichaccompaniesmovementsofthehead,activateshaircellsthatsignalthevestibularnucleiviacra

nialnerveVIIIOne:Projectsbilaterallydownthespinalcordandactivatesthecervicalspinalcircuitsthatcontrolneckandbackmuscle

sandguidheadmovementRelysensoryinformationfromthevestibularlabyrinthintheinnerearAnother:ProjectsipsilaterallyasfardownasthelumbarspinalcordIth

elpsusmaintainanuprightandbalancedposturebyfacilitatingextensormotorneuronsofthelegsStimulationatonesiteinthismapLeadtoanorientingresponsethatdirects

theheadandeyestomove…54ThepontinereticulospinaltractenhancetheantigravityreflexesofthespinalcordByfacilitatingtheex

tensorsofthelowerlimbsHelpsmaintainastandingposturebyresistingtheeffectsofgravityThemedullaryreticulospinaltracthastheoppositeeffect:itliber

atestheantigravitymusclesfromreflexcontrolActivityinbothreticulospinaltractsiscontrolledbydescendingsignalsfromthecortexControlpostureofthetrunk

andtheantigravitymusclesofthelimbs55AsummaryofthemajordescendingspinaltractsandtheirpointsoforiginMotorcortexdi

rectlyactivatesspinalmotorneuronsandliberatesthemfromreflexcontrolbycommunicatingwiththenucleioftheventromedialpathwaysSo,thecortexiskey

forvoluntarymovementandbehaviorTheventromedialpathwaysoriginatefromseveralregionsofthebrainstemandparticipatemainlyinthemai

ntenanceofpostureandcertainreflexmovementsInitiationofavoluntarymovements,requiresinstructionsthatdescendfromthemotorcortexalongthelateralpath

ways56ourattention