北大神经生物学课件7神经系统对运动的调节PPT.ppt

1、1234The mental body image seems to be generated by somatosensory, proprioceptive, and visual inputs to the posterior parietal cortex (area 5, area 7)578910SensorimotorcortexBasalgangliaCerebellumBrain stemSpinal cordInterneuron - MotorneuronMotor unit(final common pathway)Receptorsmuscle, skin, join

2、t12345vThese 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 t

3、he generation of coordinated movements vThe motor control can be divided into two parts:The spinal cords command and control of coordinated muscle contraction111213141516The motor neuron pool is all of the alpha motor neurons that innervate one muscle1730 mixed spinal nervescervical 1-8thoracic 1-12

4、lumbar 1-5sacral 1-5The ventral horn of the spinal cord contains motor neurons that innervate skeletal muscle fibersVentral roots + Dorsal root = Spinal nerve18The distribution of motor neurons in the spinal cordThe motor neurons that innervate distal and proximal musculature are found mainly in the

5、 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 ventral horn that innervate skeletal musculature in legs1920下运

6、动神经元的损伤表现21Lou 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 live for.Lou Gehring, a star

7、baseball player with New York Yankees, who died of ALS ( amyotrophic lateral sclerosis) in 193622This 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 prov

8、ides feedback about muscle length2324ReceptorEffectorSpinal Motor Neuron(center)SkinMuscleJointMuscle contractionHigherCenterVoluntary movementsNociceptive stimulusStretch musclesPosture maintenance25vTwo types of myotatic reflex Tendon reflex and muscle tonusA.Tendon reflex 快速牵拉肌腱而发生的牵张反射Clinic app

9、lication：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2627B. 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，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 Muscle spindles:nCon

10、sists 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 changes in muscle length (stretch): proprioceptors and propriceptionnIa axons are the th

11、ickest 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 neurons 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

12、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+30nExtrafusal 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 ends of the muscle s

13、pindle 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 active31Activation of alpha motor neurons shortens the extrafusal muscle fibers. If the muscle spindle becomes slack,

14、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”3233vGolgi tendon organnActs like a strain gauge, it monitors muscle tension, or the force of contractionnLocated at the junction of the mu

15、scle and the tendon and are innervated by group Ib sensory axons that are slightly smaller than the Ia axons innervating the muscle spindles34Golgi tendon organs respond to increased tension on the muscle and transmit this information to the spinal cord via type Ib sensory afferents. Because the act

16、ivated 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 their points of attachmentMuscle spindles are arranged parallel to the extrafusal fibers35T

17、he 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 for the reverse myotatic reflex-Muscle spindle situated in paral

18、lel 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

19、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363738nInhibitory inputnContraction of one set of muscles accompanied by the relaxation of the antagonist muscles is called reciprocal inhibitionnReciprocal inhibition is also used by descending pathways to overcome the powerful myotatic

20、 reflex39(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 interneurons in several spinal segments. These cells eventually ex

21、cite 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)+40SpinalcordIpsilateralextensorsinhibitedContralateralextensorsactivated(contract)Ipsilateralflexorsactivated(con

22、tract)ContralateralflexorsinhibitedIpsilateralknee jointcloses up to remove footfrom tackContralateralknee jointopens up to support greaterweight41424344Some neurons respond to the activation of NMDA receptors with rhythmic depolarization(a) In the resting state, the NMDA receptor channels and the c

23、alcium-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+ ions leave the neuron, hyperpolarizing the membra

24、ne. 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 oscillation45Walking is initiated when a steady input excites two interneurons that connect to the motor neuron

25、s 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. Thus, a burst of activity in one interneuron st

26、rongly inhibits the other(Pacemaker neuron)(Pacemaker neuron)4647484950Control posture and under brain stem controlContol voluntary movements of the distal musculature and under direct cortical control51(Pyramidal tract)Control fine movements of the arms and fingersThe effects of lateral pathway les

27、ions(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 control the distal muscles, particularly

28、flexorsInput from frontal cortex5253The 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 projections from visual cortex, as well as

29、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: Projects bilaterally down the spinal cord

30、 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 upright and balanced posture by fac

31、ilitating extensor motor neurons of the legsStimulation at one site in this map Lead to an orienting response that directs the head and eyes to move54The pontine reticulospinal tract enhance the antigravity reflexes of the spinal cordBy facilitating the extensors of the lower limbsHelps maintain a s

32、tanding 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 posture of the trunk and the antigr

33、avity muscles of the limbs555657(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 frontal lobeArea 4 lies just an

34、terior to the central sulcus on the precentral gyrusArea 6 lies just anterior to area 45859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60Prefrontal areas: in humans are thought to be important for abstract thought, d

35、ecision 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 will be carried outP

36、refrontal 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 area 6Area 5, receive

37、s 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 action61Pyramidal cellIn cortical layer

38、V(Motor cortex,M1,Area 4)Area 6(anterior)Area 3,1,2(posterior)Lower motor neurons of spinal cordThalamus(VLc)CerebellumBrain stemBasal gangliaThalamus(VLo)Somatosensory inputs6263Area 6 (SMA and PMA) plays an important role in the planning of movement, particularly complex movement sequences of the

39、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 neuron in PMA is recorded during t

40、he 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 firing646566676869707172737475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

41、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76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77n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皮层新纹状体(尾、壳核)苍白球(内侧部)丘脑皮层皮层新纹状体(尾、壳

42、核) 苍白球(外)丘脑底核苍白球(内)丘脑皮层皮层新纹状体(尾、壳核)黑质丘脑皮层787980纹状体纹状体( (尾壳核尾壳核) ) 黑质间存在具有局部黑质间存在具有局部定位特征的往返纤维联系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81直接通路易化运动n直接通路包括通路 1 1 和 3 3n从皮层到新纹状体(输入核)的递质是谷氨酸，是兴奋性兴奋性的；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

43、制性抑制性的；从这些输出核到丘脑的递质也是GABA，也是抑制性抑制性的；再由丘脑返回到皮层的辅助运动区，则是兴奋性兴奋性的。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82间接通路抑制运动n间接通路包括通路2 2n从皮层到新纹状体(输入核)的递质是谷氨酸，是兴奋性兴奋性的；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，也是抑制性抑制性的；从丘脑底核到苍白球内侧部(输出

44、核)的递质是谷氨酸，是兴奋性兴奋性的；从苍白球内侧部到丘脑的递质是GABA，抑制性抑制性的；再由丘脑返回到皮层的辅助运动区，则是兴奋性兴奋性的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83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

45、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接通路或间接通路，最后对运动都起易化作用84+-85868788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 view89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 cerebella

46、r 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9091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 929394959697n浦肯野细胞是皮层神经元环路的核心和传出途径n小脑皮层是三层结构，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(mos

47、sy 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，也是唯一的传出路径，投射到小脑深核和前庭核去；其余的四种神经元都是局部的中间神经元小脑皮层神经元环路的组成Parallel fiber98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

48、 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小脑的传入纤维和局部中间神经元以浦肯野细胞为核心构成了基本神经元环路，完成小脑皮层感觉运动的整合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挥兴奋作用n浦肯野细胞是抑制性神经元，通过轴突末梢释放的GABA，对其支配的小脑深核神经元和前庭核神经元发挥抑制作用n在四种局部中间神经元中，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99苔藓纤维和攀缘纤维构

49、成了小脑皮层的两个结构和功能各不相同的传入系统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n颗粒细胞是小脑皮层中唯一的兴奋性神经元，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，形成平行纤维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形成兴奋性突触n苔藓纤维起源于许多部

50、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，与颗粒细胞形成兴奋性突触联系100苔藓纤维和攀缘纤维构成了小脑皮层的两个结构和功能各不相同的传入系统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101浦肯野细胞对苔藓纤维和攀缘纤维传的放电反应不同n复杂锋电位的发生机制：攀缘纤维的传入