神经系统对运动的调节

1、会计学1神经系统对运动的调节神经系统对运动的调节23The mental body image seems to be generated by somatosensory, proprioceptive, and visual inputs to the posterior parietal cortex (area 5, area 7)4Represented by the association areas of neocortex and basal ganglia of the forebrainIs concerned with : The goal of the movement

2、 and the movement strategy that best achieves the goal5tacticsRepresented by the motor cortex and cerebellumIs concerned with tactics The sequences of muscle contractions Arranged in space and timeRequired to smoothly and accurately achieve the strategic goal6execution Represented by the brain stem

3、and spinal cord Is concerned with execution Action of the motor neuron and interneuron pools that generate the goal-directed movement and make any necessary adjustments of posture789SensorimotorcortexBasalgangliaCerebellumBrain stemSpinal cordInterneuron - MotorneuronMotor unit(final common pathway)

4、Receptorsmuscle, skin, joint12345vThese programs are accessed, executed, and modified by descending commands from the brainThe brains command and control of the motor programs in the spinal cordvThe motor system consists of all our muscles and the neurons that command themvThe spinal cord contains c

5、ertain motor programs for the generation of coordinated movements vThe motor control can be divided into two parts:The spinal cords command and control of coordinated muscle contraction1011 vThe rhythmic movements could be elicited in the hind legs of cats and dogs long after their spinal cords had

6、been severed from the rest of the central nervous systemCharles Sherington & Graham Brown (English) The importance of circuitry within the spinal cord for the coordinated control of movements1213nAlpha motor neurons Innervate skeletal muscle (extrafusal muscle) Function: directly command muscle

7、contractnGamma motor neurons Innervate muscle spindle (intrafusal muscle) Function: regulating the muscle spindlenInterneurons Allows coordinated motor programs to be generatedFinal common pathway (directly command muscle contract)1415The motor unit is an alpha motor neuron and all of the muscleThe

8、motor neuron pool is all of the alpha motor neurons that innervate one muscle1630 mixed spinal nervescervical 1-8thoracic 1-12lumbar 1-5sacral 1-5The ventral horn of the spinal cord contains motor neurons that innervate skeletal muscle fibersVentral roots + Dorsal root = Spinal nerve17The cervical e

9、nlargement of the spinal cord contains the motor neurons that innervate the arm musclesThe lumbar enlargement contains neurons that innervate the muscles of the leg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The distribution of motor neurons in the spinal cordThe motor neurons that inner

10、vate distal and proximal musculature are found mainly in the cervical and lumbar-sacral segments of the spinal cordWhereas those innervating axial musculature are found at all levelsSegments C3-T1 have a swollen ventral horn that innervate skeletal musculature in armsSegments L1-S3 have a swollen ve

11、ntral horn that innervate skeletal musculature in legs18Motor neurons controlling flexors lie dorsal to those controlling extensors Motor neurons controlling axial muscles lie medial to those controlling distal muscles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The distribution of lower motor neu

12、rons in the ventral horn19下运动神经元的损伤表现20Lou Gehrig Farewell Speech:Fans, for the past two weeks you have been reading about the bad break I got. Yet today I consider myself the luckiest man on the face of this earth. So I close in saying that I may have had a tough break, but I have an awful lot to l

13、ive for.Lou Gehring, a star baseball player with New York Yankees, who died of ALS ( amyotrophic lateral sclerosis) in 193621This input is important for the initiation and control of voluntary movementThis input may be excitatory or inhibitory and is part of the circuitry that generates the spinal m

14、otor programsThis input provides feedback about muscle length2223ReceptorEffectorSpinal Motor Neuron(center)SkinMuscleJointMuscle contractionHigherCenterVoluntary movementsNociceptive stimulusStretch musclesPosture maintenance24vTwo types of myotatic reflex Tendon reflex and muscle tonusA.Tendon ref

15、lex 快速牵拉肌腱而发生的牵张反射Clinic application：了解脊髓不同节段的功能状态 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2526B. Muscle tonus 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

16、，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 Muscle spindles:nConsists of specialized skeletal muscle fibersnIn this middle region, group Ia sensory axons wrap around the muscle fibers of the spindlenThe spindles and their associated Ia axons, specialized for the detection of c

17、hanges in muscle length (stretch): proprioceptors and propriceptionnIa axons are the thickest myelinated axons so they conduct action potentials very rapidlynIa axons enter the spinal cord via the dorsal roots, branch repeatedly, and form excitatory synapses upon both interneurons and alpha motor ne

18、urons of the ventral hornsvMuscle spindle 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v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 28+29nExtrafusal fibers are innervated by alpha motor neuronsnIntrafusal fibers receive their motor innervation by another type of lower motor neuron called a gamma motor neuronnGa

19、mma motor neurons innervate the intrafusal muscle fiber at the two ends of the muscle spindle nActivation of these fibers causes a contraction of the two poles of the muscle spindle, thereby pulling on the non-contractile equatorial region and keeping the Ia afferents active30Activation of alpha mot

20、or neurons shortens the extrafusal muscle fibers. If the muscle spindle becomes slack, it goes “off the air” and no longer reports the length of the muscleActivation of gamma motor neurons contracts the poles of the spindle, keeping it “on the air”3132vGolgi tendon organnActs like a strain gauge, it

21、 monitors muscle tension, or the force of contractionnLocated at the junction of the muscle and the tendon and are innervated by group Ib sensory axons that are slightly smaller than the Ia axons innervating the muscle spindles33Golgi tendon organs respond to increased tension on the muscle and tran

22、smit this information to the spinal cord via type Ib sensory afferents. Because the activated muscle does not change length, the Ia afferents remain silent in this example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Golgi tendon organs lie in series between the muscle fibers and thei

23、r points of attachmentMuscle spindles are arranged parallel to the extrafusal fibers34The Ib afferents enter the spinal cord, branch repeatedly, and synapse on interneurons in the ventral hornSome of these interneurons form inhibitory connections with the alpha motor neurons innervating the same mus

24、cle. This is the basis for the reverse myotatic reflex-Muscle spindle situated in parallel with the muscle fibers, Golgi tendon organs are situated in seriesIa activity from the spindle encodes muscle length informationWhile Ib activity from the Golgi tendon organ encodes muscle tension information腱

25、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353637nInhibitory inputnContraction of one set of muscles accompanied by the relaxation of the antagonist muscles is called reciprocal inhibitionnReci

26、procal inhibition is also used by descending pathways to overcome the powerful myotatic reflex38(A & C fibers)nExcitatory inputnFlexor reflex: used to withdraw a limb from an aversive stimulus, such as the withdrawal of your foot from the thumbtacknThe pain fibers entering the spinal cord branch

27、 profusedly and activate interneurons in several spinal segments. These cells eventually excite the alpha motor neurons that control all of the flexor muscles of the affected limb (and inhibitory interneurons are also recruited to inhibit the alphas that control the extensors)+39SpinalcordIpsilatera

28、lextensorsinhibitedContralateralextensorsactivated(contract)Ipsilateralflexorsactivated(contract)ContralateralflexorsinhibitedIpsilateralknee jointcloses up to remove footfrom tackContralateralknee jointopens up to support greaterweight40414243Some neurons respond to the activation of NMDA receptors

29、 with rhythmic depolarization(a) In the resting state, the NMDA receptor channels and the calcium-activated potassium channels are closed(b) Glutamate causes the NMDA receptors to open, the cell membrane to depolarize, and Ca2+ ions to enter the cell(c) The rise in intracellular Ca2+ causes the Ca2+

30、-activated potassium channels to open. K+ ions leave the neuron, hyperpolarizing the membrane. The hyperpolarization allows Mg2+ ions to enter and clog the NMDA channel, arresting the flow of Ca2+(d) As Ca2+ falls, the potassium channels close, resetting the membrane for another oscillation44Walking

31、 is initiated when a steady input excites two interneurons that connect to the motor neurons controlling the flexors and extensors, respectively. The interneurons respond to a continuous input by generating bursts of outputs. The activities of the two interneurons alternate because they inhibit each

32、 other via other (inhibitory) interneurons. Thus, a burst of activity in one interneuron strongly inhibits the other(Pacemaker neuron)(Pacemaker neuron)4546474849Control posture and under brain stem controlContol voluntary movements of the distal musculature and under direct cortical control50(Pyram

33、idal tract)Control fine movements of the arms and fingersThe effects of lateral pathway lesions(in monkeys)by Donald Lawrence & Hans Kuypers (in the late 1960s)Join in corticospinal tract in the lateral column of the spinal cordTerminate in the dorsolateral region of the ventral horns and interm

34、edial gray matterWhere motor neurons and interneurons control the distal muscles, particularly flexorsInput from frontal cortex51nContain four descending tracts the vestibulospinal tractthe tectospinal tractthe pontine reticulospinal tractthe medullary reticulospinal tractn Oringinate in the brain s

35、tem n Terminate among the spinal interneuronsn Controlling proximal and axial musclesnUse sensory information about balance, body position, and the visual enviroment to reflexively maintain balance and body posture52The vestibulospinal and tectospinal tracts keep the head balance on the shoulders as

36、 the body moves through space , and they turn the head in response to new sensory stimuli(midbrain)Recive direct input from retinaRecive projections from visual cortex, as well as afferents carring somatosensory and auditory informationConstruct a map of the word around usThe motion of the fluid in

37、this labyrinth, which accompanies movements of the head, activates hair cells that signal the vestibular nuclei via cranial nerve VIIIOne: Projects bilaterally down the spinal cord and activates the cervical spinal circuits that control neck and back muscles and guid head movementRely sensory inform

38、ation from the vestibular labyrinth in the inner earAnother: Projects ipsilaterally as far down as the lumbar spinal cordIt helps us maintain an upright and balanced posture by facilitating extensor motor neurons of the legsStimulation at one site in this map Lead to an orienting response that direc

39、ts the head and eyes to move53The pontine reticulospinal tract enhance the antigravity reflexes of the spinal cordBy facilitating the extensors of the lower limbsHelps maintain a standing posture by resisting the effects of gravityThe medullary reticulospinal tract has the opposite effect: it libera

40、tes the antigravity muscles from reflex controlActivity in both reticulospinal tracts is controlled by descending signals from the cortexControl posture of the trunk and the antigravity muscles of the limbs545556(Primary motor cortex)(Premotor area) (lateral region)(Supplementary motor area) (medial

41、 region)Areas of neocortex intimately involved in the planning and instruction of voluntary movementThe motor cortex is a circuscribed region of the frontal lobeArea 4 lies just anterior to the central sulcus on the precentral gyrusArea 6 lies just anterior to area 45758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

42、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59Prefrontal areas: in humans are thought to be important for abstract thought, decision making, and anticipating the consequences of actionnArea 6 and 4 together contribute most of the axons to the de

43、scending corticospinal tractnArea 6 lies at the junction where signals encoding what actions are desired are converted into signals that specify how the action will be carried outPrefrontal areas, along with the posterior parietal cortex , represent the highest levels of the motor control hierarchy,

44、 where decisions are made about what actions to take and their likely outcomenBoth the prefrontal and the parietal cortex send axons that converge on cortical area 6Area 5, receives inputs from primary somatosensory cortical area 3,1,2Area 7, receives inputs from higher-order visual cortical areas (

45、MT)The contributions of posterior parietal and prefrontal cortexFor abstract thought, decision making, and anticipating the consequences of action60Pyramidal cellIn cortical layer V(Motor cortex,M1,Area 4)Area 6(anterior)Area 3,1,2(posterior)Lower motor neurons of spinal cordThalamus(VLc)CerebellumB

46、rain stemBasal gangliaThalamus(VLo)Somatosensory inputs61nUsing PET (positron emission tomography) to monitor changes in the patterns of cortical activation that accompany voluntary movementsnWhen the subjects were asked to perform a series of finger movements from memory, the following regions of c

47、ortex showed increased blood flow: the somatosensory and posterior parietal areas, parts of the prefrontal cortex (area 8), area 6, and area 4nPlay a role in generating the intention to move and converting that intention into a plan of actionnWhen the subjects were asked only to rehearse the movemen

48、t mentally without actually moving the finger, area 6 remained active but area 4 did notPer Roland and his colleagues (Danish neurologist)62The discharge of a cell in the premotor area (PMA) before a movementArea 6 (SMA and PMA) plays an important role in the planning of movement, particularly compl

49、ex movement sequences of the distal musculature(a) Ready: A monkey sits before a panel of lights. The task is to wait for an instruction stimulus that will inform him o the movement required to receive a juice reward, then perform the movement when a trigger stimulus goes on. The activity of a neuro

50、n in PMA is recorded during the task(b) Set: the instruction stimulus occurs at the time indicated by the upward arrow, resulting in the discharge of the neuron in PMA(c) Go: shortly after the movement is initiated, the PMA cell ceases firing636465666768697071727374基底神经节(basal ganglia)是从端脑衍生的一些皮层下神经

51、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(input nuclei)，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(output nuclei)，后两者的结构和机能也很相似75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(supplementary motor area)和运动前皮层(premotor cortex)，而与脊髓没有直接的联系76n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1.皮层新

52、纹状体(尾、壳核)苍白球(内侧部)丘脑皮层2.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3.皮层新纹状体(尾、壳核)黑质丘脑皮层771. 皮层皮层 新纹状体新纹状体 苍白球苍白球( (内侧内侧) ) 丘脑丘脑 皮层回路皮层回路大脑皮层(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)78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79大脑皮层相当广泛的区域(包括运动

53、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n直接通路包括通路 1 和 3n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

54、的；再由丘脑返回到皮层的辅助运动区，则是兴奋性的。n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n间接通路包括通路2n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

55、助运动区，则是兴奋性的n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n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n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。n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

56、接通路或间接通路，最后对运动都起易化作用83+-84858687小脑表面存在的大量横向窄沟，将小脑表面分成许多平行、狭长的叶片(folia)。少数沟较深，成为裂，将小脑分成若干个小叶(lobule)两条最深的裂(原裂和后外侧裂)又将小脑横向地分成三个主要的叶(lobe)前叶、后叶和绒球小结叶Dorsal viewCross sectionMidsagittal view88小脑由外层的灰质(皮层)、内部的白质和位于白质中心的3对小脑深部核团(deep cerebellar nuclei)组成，分别是顶核(fastigial nucleus)、间位核(interposed nucleus)和齿状

57、核(dentate nucleus)。在人类，间位核分化成球状核和栓状核89n小脑的传入联系主要来自前庭、脊髓和大脑皮层等处，到达小脑的传入纤维分别与小脑深核和小脑皮层的神经元形成突触联系n小脑皮层的传出纤维，即浦肯野细胞浦肯野细胞(Purkinje cell)的轴突大多数投射到小脑深核，再由小脑深核神经元发出离核纤维(nucleofugal fiber)构成小脑的传出，投射到皮层运动区和脑干的四对运动核团(前庭核、网状结构、上丘、红核)n所有的小脑传入和传出纤维均经过三对小脑脚小脑下脚(绳状体)、小脑中脚(脑桥臂)和小脑上脚(结合臂)进出小脑90内侧区(蚓部)皮层的浦肯野细胞主要投射到顶核，

58、部分投射到前庭外侧核；中间区(蚓旁部)和外侧区的浦肯野细胞则分别投射到间位核和齿状核根据小脑皮层浦肯野细胞轴突投射到小脑深核，将小脑自内侧向外侧，纵向地划分成三个纵区内侧区、中间区和外侧区 91n内侧区经顶核与内侧下行系统相连接，控制躯体近端(体轴)肌肉装置的活动n中间区经间位核连接外侧下行系统，主要调节躯体远端(肢体)肌肉的活动n外侧区通过齿状核与大脑皮层运动区和运动前区相联系，参与随意运动的计划和编程92n从功能和进化的观点来看，可以将小脑划分成前庭小脑、脊髓小脑和皮层小脑三个主要的功能部分n它们分别主要接受前庭系统、脊髓和大脑皮层的传入，而且它们的传出也相应地主要作用于前庭核、脊髓和大脑

59、皮层n在脊椎动物的进化过程中，这三个功能部分分别随前庭系统、脊髓和大脑皮层的发展而先后出现，故又分别被称为古小脑、旧小脑、和新小脑93n构成：主要是绒球小结叶。靠近绒球小结叶的蚓垂也接受前庭系统的传入n传入纤维：初级传入纤维起自两侧半规管和耳石器，次级传入纤维则是起源于前庭核的间接投射。它们向小脑传递了头部位置变化和头部相对于重力作用方向的信息n传出纤维：通过前庭核，经前庭脊髓束影响脊髓中支配体轴肌肉的运动神经元的兴奋性活动，控制体轴肌肉的收缩活动，维持躯体平衡n前庭小脑也接受经桥核转接的外侧膝状体、上丘和纹状皮层等处的视觉传入，因而它还通过对眼外肌神经核的传出，控制眼球的运动和协调头部运动时

60、眼球为保持视像而进行的凝视运动前庭小脑维持躯体平衡和眼球的运动94n构成：脊髓小脑纵贯小脑体的前叶和后叶的正中部分，包括内侧区和中间区两个纵区n传入：主要来自脊髓的躯体感觉信息，经直接的和间接的脊髓小脑通路到达小脑脊髓小脑还接受经脑桥接转的大脑皮层感觉区和运动区的传入信息此外，脊髓小脑还接受视觉、听觉和前庭信息n传出：内侧区经顶核、中间区经间位核到达脑干和运动皮层n效应：控制脑干和皮层起源的内侧和外侧下行系统，对进行中的肢体运动起重要的适时调节作用脊髓小脑利用感觉反馈信息调节肌肉张力和适时地调节进行中的运动脊髓小脑调节肌紧张95n构成：皮层小脑即小脑的外侧区n输入纤维：来自于大脑皮层的感觉区、运动区、运动前区和感觉