7神经系统对运动的调节ppt课件

1、The mental body image seems to be generated by somatosensory, proprioceptive, and visual inputs to the posterior parietal cortex (area 5, area 7)SensorimotorcortexBasalgangliaCerebellumBrain stemSpinal cordInterneuron - MotorneuronMotor unit(final common pathway)Receptorsmuscle, skin, joint12345vThe

2、se 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 certain motor programs for the generat

3、ion of coordinated movements vThe motor control can be divided into two parts:The spinal cords command and control of coordinated muscle contractionThe motor neuron pool is all of the alpha motor neurons that innervate one muscle30 mixed spinal nervescervical 1-8thoracic 1-12lumbar 1-5sacral 1-5The

4、ventral horn of the spinal cord contains motor neurons that innervate skeletal muscle fibersVentral roots + Dorsal root = Spinal nerveThe distribution of motor neurons in the spinal cordThe motor neurons that innervate distal and proximal musculature are found mainly in the cervical and lumbar-sacra

5、l 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 ventral horn that innervate skeletal musculature in legs下运动神经元的损伤表现Lou Gehrig Farewell S

6、peech: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 live for.Lou Gehring, a star baseball player with New York Ya

7、nkees, who died of ALS ( amyotrophic lateral sclerosis) in 1936This 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 motor programsThis input provides feedback about muscle lengthR

8、eceptorEffectorSpinal Motor Neuron(center)SkinMuscleJointMuscle contractionHigherCenterVoluntary movementsNociceptive stimulusStretch musclesPosture maintenancevTwo types of myotatic reflex v Tendon reflex and muscle tonusvA.Tendon reflexv 快速牵拉肌腱而发生的牵张反射vClinic application：了解脊髓不同节段的功能形状 单突触反射埋伏期很短，约

9、0.7s 只够一次突触传送时间延搁B. Muscle tonus 肌肉遭到缓慢而继续的牵拉而发生的收缩 使骨骼肌能坚持一定的肌肉张力 意义: 维持身体的姿态(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， 伸肌遭到牵拉，引起肌紧张反射，肌紧张度添加以对抗关节屈曲 因重力继续作用于关节，肌紧张也就继续发生。使直立姿态得以维持多突触反射埋伏期较长，经过多个突触传送 Muscle spindles:Consists of specialized skeletal muscle fiber

10、sIn this middle region, group Ia sensory axons wrap around the muscle fibers of the spindleThe spindles and their associated Ia axons, specialized for the detection of changes in muscle length (stretch): proprioceptors and propriceptionIa axons are the thickest myelinated axons so they conduct actio

11、n potentials very rapidlyIa axons enter the spinal cord via the dorsal roots, branch repeatedly, and form excitatory synapses upon both interneurons and alpha motor neurons of the ventral hornsvMuscle spindle 是一种可是一种可感受肌肉长度变化或感受牵拉感受肌肉长度变化或感受牵拉刺激的刺激的 本体感受器本体感受器v梭内肌感受部安装位于中间梭内肌感受部安装位于中间,收缩成分位于两端收缩成分位于

12、两端, 梭内肌收梭内肌收缩时或牵拉梭外肌时缩时或牵拉梭外肌时, 感受安感受安装对牵拉敏感性增高装对牵拉敏感性增高 +nExtrafusal fibers are innervated by alpha motor neuronsnIntrafusal fibers receive their motor innervation by another type of lower motor neuron called a gamma motor neuronnGamma motor neurons innervate the intrafusal muscle fiber at the two

13、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 activeActivation of alpha motor neurons shortens the extrafusal muscle fibers. If the muscle spind

14、le 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 airvGolgi tendon organvActs like a strain gauge, it monitors muscle tension, or the force of contractionvLocated at the juncti

15、on 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 spindlesGolgi tendon organs respond to increased tension on the muscle and transmit this information to the spinal cord via type Ib sensory afferents. Becau

16、se the activated muscle does not change length, the Ia afferents remain silent in this example当肌肉等长收缩时当肌肉等长收缩时,腱器官传入激动频率腱器官传入激动频率, 肌梭传入激动频率不变肌梭传入激动频率不变;当肌肉等张收当肌肉等张收缩时缩时,腱器官传入激动频率不变腱器官传入激动频率不变, 肌梭传入激动频率肌梭传入激动频率Golgi tendon organs lie in series between the muscle fibers and their points of attachmentM

17、uscle spindles are arranged parallel to the extrafusal fibersThe 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 muscle. This is the basis fo

18、r 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腱器官 是张力感受器, 其传入激动对同一肌肉运动神经

19、元起抑制造用肌梭是长度感受器,其传入激动对同一肌肉运动神经元起兴奋作用当肌肉被动牵拉时, 二者传入激动频率均：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nInhibitory inputnContraction of one set of muscles accompanied by the relaxation of the antagonist muscles is called reciprocal inhibitionnReciprocal inhibition is also used

20、by descending pathways to overcome the powerful myotatic reflex(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 profusedly and activate interneu

21、rons 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)+SpinalcordIpsilateralextensorsinhibitedContralateralext

22、ensorsactivated(contract)Ipsilateralflexorsactivated(contract)ContralateralflexorsinhibitedIpsilateralknee jointcloses up to remove footfrom tackContralateralknee jointopens up to support greaterweightSome neurons respond to the activation of NMDA receptors with rhythmic depolarization(a) In the res

23、ting 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+-activated potassium channels to open. K+ i

24、ons 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 oscillationWalking is initiated when a steady input excites two

25、 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 other via other (inhibitory) interneurons. T

26、hus, a burst of activity in one interneuron strongly inhibits the other(Pacemaker neuron)(Pacemaker neuron)Control posture and under brain stem controlContol voluntary movements of the distal musculature and under direct cortical control(Pyramidal tract)Control fine movements of the arms and fingers

27、The 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 intermedial gray matterWhere motor neurons and interneurons con

28、trol the distal muscles, particularly flexorsInput from frontal cortexThe vestibulospinal and tectospinal tracts keep the head balance on the shoulders as the body moves through space , and they turn the head in response to new sensory stimuli(midbrain)Recive direct input from retinaRecive projectio

29、ns from visual cortex, as well as afferents carring somatosensory and auditory informationConstruct a map of the word around usThe motion of the fluid in this labyrinth, which accompanies movements of the head, activates hair cells that signal the vestibular nuclei via cranial nerve VIIIOne: Project

30、s bilaterally down the spinal cord and activates the cervical spinal circuits that control neck and back muscles and guid head movementRely sensory information from the vestibular labyrinth in the inner earAnother: Projects ipsilaterally as far down as the lumbar spinal cordIt helps us maintain an u

31、pright and balanced posture by facilitating extensor motor neurons of the legsStimulation at one site in this map Lead to an orienting response that directs the head and eyes to moveThe pontine reticulospinal tract enhance the antigravity reflexes of the spinal cordBy facilitating the extensors of t

32、he lower limbsHelps maintain a standing posture by resisting the effects of gravityThe medullary reticulospinal tract has the opposite effect: it liberates the antigravity muscles from reflex controlActivity in both reticulospinal tracts is controlled by descending signals from the cortexControl pos

33、ture of the trunk and the antigravity muscles of the limbs(Primary motor cortex)(Premotor area) (lateral region)(Supplementary motor area) (medial region)Areas of neocortex intimately involved in the planning and instruction of voluntary movementThe motor cortex is a circuscribed region of the front

34、al lobeArea 4 lies just anterior to the central sulcus on the precentral gyrusArea 6 lies just anterior to area 4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，最外侧接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Prefrontal areas: in humans are thought to be important for

35、 abstract thought, decision making, and anticipating the consequences of actionnArea 6 and 4 together contribute most of the axons to the descending corticospinal tractnArea 6 lies at the junction where signals encoding what actions are desired are converted into signals that specify how the action

36、will be carried outPrefrontal areas, along with the posterior parietal cortex , represent the highest levels of the motor control hierarchy, 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 a

37、rea 6Area 5, receives inputs from primary somatosensory cortical area 3,1,2Area 7, receives inputs from higher-order visual cortical areas (MT)The contributions of posterior parietal and prefrontal cortexFor abstract thought, decision making, and anticipating the consequences of actionPyramidal cell

38、In cortical layer V(Motor cortex,M1,Area 4)Area 6(anterior)Area 3,1,2(posterior)Lower motor neurons of spinal cord Thalamus(VLc)CerebellumBrain stemBasal gangliaThalamus(VLo)Somatosensory inputsshowed increased blood flow: the somatosensory and posterior parietal areas, parts of the prefrontal corte

39、x (area 8), area 6, and area 4Play a role in generating the intention to move and converting that intention into a plan of actionWhen the subjects were asked only to rehearse the movement mentally without actually moving the finger, area 6 remained active but area 4 did notPer Roland and his colleag

40、ues (Danish neurologist)Area 6 (SMA and PMA) plays an important role in the planning of movement, particularly complex 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 re

41、quired to receive a juice reward, then perform the movement when a trigger stimulus goes on. The activity of a neuron 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 a

42、fter the movement is initiated, the PMA cell ceases firing基底神经节(basal ganglia)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(input nuclei)，惨白球的内侧部、脚内核和黑质网状部是基底神经节的主要输出核(output nuclei)，后两者的构造和机能也很类似纹状体的主要传入激动来自大脑皮层广泛的区域(运动区、体感区、结合区、边缘区甚至顶叶)传出激动经过丘脑前往皮层，主要是辅助运动区(supplem

43、entary motor area)和运动前皮层(premotor cortex)，而与脊髓没有直接的联络n基底神经节与大脑皮层的纤维联络，与运动有关的主要为三条回路n皮层新纹状体(尾、壳核)惨白球(内侧部)丘脑皮层n皮层新纹状体(尾、壳核) 惨白球(外)丘脑底核惨白球(内)丘脑皮层n皮层新纹状体(尾、壳核)黑质丘脑皮层纹状体纹状体( (尾壳核尾壳核) )黑质间存在具有部分黑质间存在具有部分定位特征的往返纤维联络定位特征的往返纤维联络从黑质的致密部有纤维投向新纹状体，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

44、，没有其有纤维至上丘和脚桥被盖核外，没有其他向下投射的纤维他向下投射的纤维所以，基底神经节的运动功能是经过大所以，基底神经节的运动功能是经过大脑皮层中与运动控制有关的区域而间接脑皮层中与运动控制有关的区域而间接实现的实现的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；重新纹状体到惨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；再由丘脑前往到皮层的辅助运动区，那么是兴奋性的。当皮层有兴奋激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)

45、了丘脑的神经元，再经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；从纹状体输入核到惨白球外侧部的递质是GABA和脑啡肽，是抑制性的；从惨白球外侧部到丘脑底核的递质是GABA，也是抑制性的；从丘脑底核到惨白球内侧部(输出核)的递质是谷氨酸，是兴奋性的；从惨白球内侧部到丘脑的递质是GABA，抑制性的；再由丘脑前往到皮层的辅助运动区，那么是兴奋性的当皮层与纹状体输入核兴奋而使惨白球外侧部抑制时，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

46、助运动区的兴奋性，产生抑制运动的效果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，也就是使新纹状体经过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与脑啡肽的抑制造用降低，因此兴奋了惨白球的外侧部，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，多巴胺能投射经过直接通路或间接通路，最后对运动都起易化作用+-小脑外表存在的大量横向窄沟，将小脑外表分成许多平行、狭长的叶片(folia)。少数沟较深，成为裂，将小脑分成假设干个小叶(

47、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 view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)和齿状核(dentate nucleus)。在人类，间位核分化成球状核和栓状核内侧区(蚓部)皮层的浦肯野细胞主要投射到顶核，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那么分别投射

48、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 n浦肯野细胞是皮层神经元环路的中心和传出途径n小脑皮层是三层构造，由表及里分别为分子层、浦肯野细胞层和颗粒层，其中含有苔藓纤维(mossy fiber)、攀缘纤维(climbing fiber)和平行纤维(parallel fiber)单胺(5HT和NA)能纤维四种传入纤维，以及浦肯野细胞、颗粒细胞、篮状细胞、星状细胞和高尔基细胞等五种神经元n浦肯野细胞是主要的神经元，也是独一的传出途径，投射到小脑深核和前庭核去；其他的四种神经元都是部分的中间神经元小脑皮层神经元环路的组成

49、Parallel fiber小脑皮层中的神经递质及其突触后作用Parallel fiber蓝班核Inferior olivary nucleusClimbing fiberMossy fiberPurkinje cellGolgi cellBasket cellStellate cellGranular cell中缝核小脑深核或前庭核细胞发出苔藓纤维的小脑前核神经元GLUn小脑的传入纤维和部分中间神经元以浦肯野细胞为中心构成了根本神经元环路，完成小脑皮层觉得运动的整合n攀缘纤维和苔藓纤维都是以兴奋性氨基酸为递质的兴奋性传入纤维，分别对浦肯野细胞和颗粒细胞发扬兴奋作用n浦肯野细胞是抑制性神经元，

50、经过轴突末梢释放的GABA，对其支配的小脑深核神经元和前庭核神经元发扬抑制造用n在四种部分中间神经元中，仅颗粒细胞的轴突末梢释放谷氨酸，是一个兴奋性神经元；而篮状细胞、星状细胞和高尔基细胞的轴突末梢均释放GABA，为抑制性神经元苔藓纤维和攀缘纤维构成了小脑皮层的两个构造和功能各不一样的传入系统Parallel fiber蓝班核Inferior olivary nucleusClimbing fiberMossy fiberPurkinje cellGolgi cellBasket cellStellate cellGranular cell中缝核小脑深核或前庭核细胞发出苔藓纤维的小脑前核神经元

51、n颗粒细胞是小脑皮层中独一的兴奋性神经元，它的轴突上行到分子层后分叉并沿小脑叶片的长轴方向向两侧伸展，构成平行纤维n平行纤维穿行于与其伸展方向成直角的一个个浦肯野细胞的扇状树突丛中，与浦肯野细胞树突远端的末梢分枝构成兴奋性突触n苔藓纤维来源于许多部位，如脊髓、前庭核和脑干中的一些中继核团(桥核、外侧网状核、三叉神经核等)，并以苔藓样末梢终止于颗粒层，与颗粒细胞构成兴奋性突触联络苔藓纤维和攀缘纤维构成了小脑皮层的两个构造和功能各不一样的传入系统Parallel fiber蓝班核Inferior olivary nucleusClimbing fiberMossy fiberPurkinje ce