北大神经生物学7-1神经系统对运动的调节.ppt

1 CentralNervousSystemControlofMovement XING GUOGANG 邢国刚 MD Ph D NeuroscienceResearchInstitute PekingUniversityEmailaddress 2 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 3 Howdoesacoordinatedmovementachieved 4 Thementalbodyimageseemstobegeneratedbysomatosensory proprioceptive andvisualinputstotheposteriorparietalcortex area5 area7 Abaseballpitcherplanningapitch 5 Thehighestlevel strategyRepresentedbytheassociationareasofneocortexandbasalgangliaoftheforebrainIsconcernedwithstrategy Thegoalofthemovementandthemovementstrategythatbestachievesthegoal Themotorcontrolhierarchyhavethreelevels 6 Themiddlelevel tacticsRepresentedbythemotorcortexandcerebellumIsconcernedwithtacticsThesequencesofmusclecontractionsArrangedinspaceandtimeRequiredtosmoothlyandaccuratelyachievethestrategicgoal Themotorcontrolhierarchyhavethreelevels 7 Thelowestlevel executionRepresentedbythebrainstemandspinalcordIsconcernedwithexecutionActionofthemotorneuronandinterneuronpoolsthatgeneratethegoal directedmovementandmakeanynecessaryadjustmentsofposture Themotorcontrolhierarchyhavethreelevels 8 Overview 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 9 10 Theseprogramsareaccessed executed andmodifiedbydescendingcommandsfromthebrain Thebrain scommandandcontrolofthemotorprogramsinthespinalcord Themotorsystemconsistsofallourmusclesandtheneuronsthatcommandthem Thespinalcordcontainscertainmotorprogramsforthegenerationofcoordinatedmovements Themotorcontrolcanbedividedintotwoparts Thespinalcord scommandandcontrolofcoordinatedmusclecontraction 11 Part1SpinalControlofMovement 12 Introduction runningaroundlikeachickenwithitsheadcutoff Therhythmicmovementscouldbeelicitedinthehindlegsofcatsanddogslongaftertheirspinalcordshadbeenseveredfromtherestofthecentralnervoussystem CharlesSherington GrahamBrown English Theimportanceofcircuitrywithinthespinalcordforthecoordinatedcontrolofmovements 13 Spinalcircuitrycontrolofmovement 14 Spinalmotorneurons AlphamotorneuronsInnervateskeletalmuscle extrafusalmuscle Function directlycommandmusclecontractGammamotorneuronsInnervatemusclespindle intrafusalmuscle Function regulatingthemusclespindleInterneuronsAllowscoordinatedmotorprogramstobegeneratedFinalcommonpathway directlycommandmusclecontract Compare Uppermotorneurons Lowermotorneurons 15 TheLowerMotorNeurons Alphamotorneurons AlphamotorneuronsaredirectlyresponsibleforthegenerationofforcebymuscleMotorunit onealphamotorneuronandallofthemusclefibersitinnervatescollectivelymakeupmotorunit theelementarycomponentofmotorcontrolMotorneuronpool Thecollectionofalphamotorneuronsthatinnervatesasinglemuscle 16 Themotorunitisanalphamotorneuronandallofthemuscle Amotorunitandmotorneuronpool Themotorneuronpoolisallofthealphamotorneuronsthatinnervateonemuscle 17 Muscleinnervationbylowermotorneurons 30mixedspinalnervescervical1 8thoracic1 12lumbar1 5sacral1 5 18 ThecervicalenlargementofthespinalcordcontainsthemotorneuronsthatinnervatethearmmusclesThelumbarenlargementcontainsneuronsthatinnervatethemusclesoftheleg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 Thedistributionofmotorneuronsinthespinalcord Themotorneuronsthatinnervatedistalandproximalmusculaturearefoundmainlyinthecervicalandlumbar sacralsegmentsofthespinalcordWhereasthoseinnervatingaxialmusculaturearefoundatalllevels 19 MotorneuronscontrollingflexorsliedorsaltothosecontrollingextensorsMotorneuronscontrollingaxialmusclesliemedialtothosecontrollingdistalmuscles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 Thedistributionoflowermotorneuronsintheventralhorn 20 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 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 21 LouGehring astarbaseballplayerwithNewYorkYankees whodiedofALS amyotrophiclateralsclerosis in1936 22 Inputstoalphamotorneurons 23 SPINALCONTROLOFMOTORUNITS Howtheactivityofthemotorneuronisitselfcontrolled 24 Reflex 25 Themyotaticreflex 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 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 27 B 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 28 Musclespindles ConsistsofspecializedskeletalmusclefibersInthismiddleregion groupIasensoryaxonswraparoundthemusclefibersofthespindleThespindlesandtheirassociatedIaaxons specializedforthedetectionofchangesinmusclelength stretch proprioceptorsandpropriceptionIaaxonsarethethickestmyelinatedaxonssotheyconductactionpotentialsveryrapidlyIaaxonsenterthespinalcordviathedorsalroots branchrepeatedly andformexcitatorysynapsesuponbothinterneuronsandalphamotorneuronsoftheventralhorns Proprioceptionfrommusclespindles 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 30 Gammamotorneurons 31 Thefunctionofgammamotorneurons Activationofalphamotorneuronsshortenstheextrafusalmusclefibers Ifthemusclespindlebecomesslack itgoes offtheair andnolongerreportsthelengthofthemuscleActivationofgammamotorneuronscontractsthepolesofthespindle keepingit ontheair 32 TheGammaloop ChangingtheactivityofthegammamotorneuronschangesthesetpointofthemyotaticfeedbackloopTheGammaloopGammamotorneuron intrafusalmusclefiber Iaafferent alphamotorneuron extrafusalmusclefibersAlphaandgammamotorneuronsaresimultaneouslyactivatedbydescendingcommandsfromthebrain 33 ProprioceptionfromGolgitendonorgans GolgitendonorganActslikeastraingauge itmonitorsmuscletension ortheforceofcontractionLocatedatthejunctionofthemuscleandthetendonandareinnervatedbygroupIbsensoryaxonsthatareslightlysmallerthantheIaaxonsinnervatingthemusclespindles 34 35 TheIbafferentsenterthespinalcord branchrepeatedly andsynapseoninterneuronsintheventralhornSomeoftheseinterneuronsforminhibitoryconnectionswiththealphamotorneuronsinnervatingthesamemuscle Thisisthebasisforthereversemyotaticreflex Circuitryofthereversemyotaticreflex Musclespindlesituatedinparallelwiththemusclefibers Golgitendonorgansaresituatedinseries IaactivityfromthespindleencodesmusclelengthinformationWhileIbactivityfromtheGolgitendonorganencodesmuscletensioninformation 36 Significanceofthereversemyotaticreflex Inextremecircumstances thisreflexarcprotectsthemusclefromoverloadThenormalfunctionistoregulatemuscletensionwithinanoptimalrangeAsmuscletensionincreases theinhibitionofthealphamotorneuronslowsmusclecontractionAsmuscletensionfalls theinhibitionofthealphamotorneuronisreduced andmusclecontractionincreasesThistypeofproprioceptivefeedbackisthoughttobeparticularlyimportantfortheproperexecutionoffinemotoracts suchasthemanipulationoffragileobjectswiththehands whichrequireasteadybutnottoopowerfulgrip 37 Spinalinterneurons MostoftheinputtothealphamotorneuronscomesfrominterneuronsofthespinalcordInterneuronsreceivesynapticinputfromprimarysensoryaxons descendingaxonsfromthebrain andcollateralsoflowermotorneuronaxonsTheinterneuronsarethemselvesnetworkedtogetherinawaythatallowscoordinatedmotorprogramstobegeneratedinresponsetotheirmanyinputs 38 Reciprocalinhibitionofflexorsandextensorsofthesamejoint 39 A Cfibers Circuitryofthepolysynapticflexorreflex 40 Circuitryofthecrossed extensorreflex 41 Thegenerationofspinalmotorprogramsforwalking Headlesschickens behaviorAcompletetransectionofacat sspinalcordatthemid thoraciclevelleavesthehindlimbscapableofgeneratingcoordinatedwalkingmovements Whenyouwalk youalternatelywithdrawandextendyourtwolegsWhatisthemechanismtocoordinatethetiming Thiscouldbedescendingcommandsfromuppermotorneurons No Thiscontrolisexertedfromwithinthespinalcord Yes 42 43 Centralpatterngeneratorswithinthespinalcord ThecircuitforthecoordinatedcontrolofwalkingmustresidewithinthespinalcordIngeneral circuitsthatgiverisetorhythmicmotoractivityarecalledcentralpatterngeneratorsHowdoneuralcircuitsgeneraterhythmicpatternsofactivity Thesimplestpatterngenerators aresingleneuronswhosemembranepropertiesendowthemwithpacemakerproperties pacemakerneurons 44 Rhythmicactivityinaspinalinterneuron Pacemakerneuron SomeneuronsrespondtotheactivationofNMDAreceptorswithrhythmicdepolarization 45 Apossiblecircuitforrhythmicalternatingactivity walking Walkingisinitiatedwhenasteadyinputexcitestwointerneuronsthatconnecttothemotorneuronscontrollingtheflexorsandextensors respectively Theinterneuronsrespondtoacontinuousinputbygeneratingburstsofoutputs Theactivitiesofthetwointerneuronsalternatebecausetheyinhibiteachotherviaother inhibitory interneurons Thus aburstofactivityinoneinterneuronstronglyinhibitstheother Pacemakerneuron Pacemakerneuron 46 Part2BrainControlofMovement 47 Howdoesthebraincommunicatewiththemotorneuronsofthespinalcord 48 Overview 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 49 Thedescendingspinaltractscontrolofmovement 50 Thedescendingspinaltracts 51 Controlfinemovementsofthearmsandfingers Theeffectsoflateralpathwaylesions inmonkeys byDonaldLawrence HansKuypers inthelate1960s TheLateralPathways X 52 TheVentromedialPathways ContainfourdescendingtractsthevestibulospinaltractthetectospinaltractthepontinereticulospinaltractthemedullaryreticulospinaltractOringinateinthebrainstemTerminateamongthespinalinterneuronsControllingproximalandaxialmusclesUsesensoryinformationaboutbalance bodyposition andthevisualenviromenttoreflexivelymaintainbalanceandbodyposture 53 Thevestibulospinalandtectospinaltractskeeptheheadbalanceontheshouldersasthebodymovesthroughspace andtheyturntheheadinresponsetonewsensorystimuli midbrain RecivedirectinputfromretinaReciveprojectionsfromvisualcortex aswellasafferentscarringsomatosensoryandauditoryinformationConstructamapofthewordaroundus Themotionofthefluidinthislabyrinth whichaccompaniesmovementsofthehead activateshaircellsthatsignalthevestibularnucleiviacranialnerveVIII One Projectsbilaterallydownthespinalcordandactivatesthecervicalspinalcircuitsthatcontrolneckandbackmusclesandguidheadmovement Another Projectsipsilate