北大神經(jīng)生物學(xué)神經(jīng)系統(tǒng)對運(yùn)動的調(diào)節(jié)實(shí)用教案

1、1Introductionv生命在于運(yùn)動生命在于運(yùn)動(yndng)v運(yùn)動運(yùn)動(yndng)是動物維系個是動物維系個體生存和種族繁衍的基本功能體生存和種族繁衍的基本功能之一之一第1頁/共112頁第一頁，共113頁。2How does a How does a coordinated movement coordinated movement achieved ?achieved ?第2頁/共112頁第二頁，共113頁。3The mental body image seems to be generated by somatosensory, proprioceptive, and visual

2、inputs to the posterior parietal cortex (area 5, area 7)第3頁/共112頁第三頁，共113頁。4 The highest level strategyRepresented by the association areas of neocortex and basal ganglia of the forebrainIs concerned with strategy: The goal of the movement and the movement strategy that best achieves the goalThe mot

3、or control hierarchy have three levels第4頁/共112頁第四頁，共113頁。5 The middle leveltacticsRepresented 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 goalThe motor control hie

4、rarchy have three levels第5頁/共112頁第五頁，共113頁。6 The lowest level execution Represented by the brain stem 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 postureThe motor control h

5、ierarchy have three levels第6頁/共112頁第六頁，共113頁。7Overview 脊髓內(nèi)的“下運(yùn)動神經(jīng)元(Lower neurons)”，除了受到脊髓內(nèi)局部環(huán)路的影響外，還受到大腦皮層運(yùn)動區(qū)及腦干中許多(xdu)“上運(yùn)動神經(jīng)元(Upper neurons)”的支配和協(xié)調(diào) 基底神經(jīng)節(jié)和小腦則向那些上運(yùn)動神經(jīng)元提供某種感覺、認(rèn)知或感性的信息，使運(yùn)動更加精確和協(xié)調(diào)第7頁/共112頁第七頁，共113頁。8第8頁/共112頁第八頁，共113頁。9SensorimotorcortexBasalgangliaCerebellumBrain stemSpinal cordInter

6、neuron - MotorneuronMotor unit(final common pathway)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

7、neurons that command themvThe spinal cord contains certain 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 contraction第9頁/共112頁第九頁，共113頁。10Part 1 Spinal Control of Movement第10頁/共112

8、頁第十頁，共113頁。11Introductionv“running around like a chicken with its head cut off” vThe rhythmic movements could be elicited in the hind legs of cats and dogs long after their spinal cords had been severed from the rest of the central nervous systemCharles Sherington & Graham Brown (English) The im

9、portance of circuitry within the spinal cord for the coordinated control of movements第11頁/共112頁第十一頁，共113頁。12Spinal circuitrySpinal circuitry control of control of movementmovement第12頁/共112頁第十二頁，共113頁。13Spinal motor neurons Alpha motor neurons Innervate skeletal muscle (extrafusal muscle) Function: d

10、irectly command muscle contract Gamma motor neurons Innervate muscle spindle (intrafusal muscle) Function: regulating the muscle spindle Interneurons Allows coordinated motor programs to be generated Final common pathway (directly command muscle contract) Compare: Upper motor neurons第13頁/共112頁第十三頁，共

11、113頁。14The Lower Motor Neurons Alpha motor neurons Alpha motor neurons are directly responsible for the generation of force by muscle Motor unit: one alpha motor neuron and all of the muscle fibers it innervates collectively make up motor unit, the elementary component of motor control Motor neuron

12、pool: The collection of alpha motor neurons that innervates a single muscle第14頁/共112頁第十四頁，共113頁。15The motor unit is an alpha motor neuron and all of the muscleThe motor neuron pool is all of the alpha motor neurons that innervate one muscle第15頁/共112頁第十五頁，共113頁。16Muscle innervation by lower motor neu

13、rons30 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 nerve第16頁/共112頁第十六頁，共113頁。17The cervical enlargement of the spinal cord contains the motor neuro

14、ns that innervate the arm musclesThe lumbar enlargement contains neurons that innervate the muscles of the leg支配上肢的神經(jīng)元集群位于頸膨大支配上肢的神經(jīng)元集群位于頸膨大(png d)處，支配下肢的則在腰膨大處，支配下肢的則在腰膨大(png d)處處The distribution of motor neurons in the spinal cordThe motor neurons that innervate distal and proximal musculature are

15、 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 ventral horn that innervate skeletal muscu

16、lature in legs第17頁/共112頁第十七頁，共113頁。18Motor neurons controlling flexors lie dorsal to those controlling extensors Motor neurons controlling axial muscles lie medial to those controlling distal muscles支配支配(zhpi)軀干部肌肉的神經(jīng)元位于軀干部肌肉的神經(jīng)元位于脊髓前角灰質(zhì)最內(nèi)側(cè)，由此向外排列的脊髓前角灰質(zhì)最內(nèi)側(cè)，由此向外排列的神經(jīng)元則支配神經(jīng)元則支配(zhpi)肢體由近及遠(yuǎn)分肢體由近及遠(yuǎn)分布的肌

17、肉布的肌肉The distribution of lower motor neurons in the ventral horn第18頁/共112頁第十八頁，共113頁。19 Muscle weakness and paralysis所支配的骨骼肌癱瘓、肌張力下降、腱反射消失(軟癱(run tn) 肌萎縮、纖維顫動或肌束顫動 見于如肌萎縮側(cè)索硬化癥(amyotrophic lateral sclerosis, ALS)：Selective damage to alpha motor neurons(degeneration)脊髓-運(yùn)動神經(jīng)元的進(jìn)行性潰變?yōu)橹飨逻\(yùn)動神經(jīng)元的損傷(snshng)表現(xiàn)

18、第19頁/共112頁第十九頁，共113頁。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 live for.Lou Gehr

19、ing, a star baseball player with New York Yankees, who died of ALS ( amyotrophic lateral sclerosis) in 1936第20頁/共112頁第二十頁，共113頁。21This 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 spi

20、nal motor programsThis input provides feedback about muscle length第21頁/共112頁第二十一頁，共113頁。22SPINAL CONTROL OF MOTOR UNITSHow the activity of the motor neuron is itself controlled ?第22頁/共112頁第二十二頁，共113頁。23ReceptorEffectorSpinal Motor Neuron(center)SkinMuscleJointMuscle contractionHigherCenterVoluntary

21、movementsNociceptive stimulusStretch musclesPosture maintenance第23頁/共112頁第二十三頁，共113頁。24vTwo types of myotatic reflex v Tendon reflex and muscle tonusvA.Tendon reflexv 快速牽拉肌腱而發(fā)生的牽張反射vClinic application：了解脊髓不同(b tn)節(jié)段的功能狀態(tài) s 只夠一次突觸傳遞時(shí)間(shjin)延擱第24頁/共112頁第二十四頁，共113頁。25第25頁/共112頁第二十五頁，共113頁。26B. Muscle

22、tonus 肌肉受到緩慢而持續(xù)的牽拉而發(fā)生的收縮 使骨骼肌能保持一定的肌肉張力 意義: 維持身體的姿勢(zsh)(posture)，而不表現(xiàn)明顯的動作 表現(xiàn)：extensor(伸肌)和flexor(屈肌)都發(fā)生肌緊張直立時(shí)，以伸肌緊張為主，因重力作用于關(guān)節(jié)，使關(guān)節(jié)趨向彎曲， 伸肌受到牽拉，引起肌緊張反射，肌緊張度增加以對抗關(guān)節(jié)屈曲 因重力持續(xù)作用于關(guān)節(jié)，肌緊張也就持續(xù)發(fā)生。使直立姿勢(zsh)得以維持多突觸反射(fnsh)潛伏期較長，經(jīng)過多個突觸傳遞第26頁/共112頁第二十六頁，共113頁。27 Muscle spindles:nConsists of specialized skeleta

23、l 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 thickest myelinated axons so t

24、hey 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 是一種可感受(gnshu)肌肉長度變化或感受(gnshu)牽拉刺激的 本體感受(gnshu)器v梭內(nèi)肌感受(gnshu)部裝置位于中間,收縮成分位

25、于兩端, 梭內(nèi)肌收縮時(shí)或牽拉梭外肌時(shí), 感受(gnshu)裝置對牽拉敏感性增高 第27頁/共112頁第二十七頁，共113頁。28+第28頁/共112頁第二十八頁，共113頁。29nExtrafusal 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 intr

26、afusal 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 active第29頁/共112頁第二十九頁，共113頁。30The function of gamma motor neuronsAc

27、tivation of alpha motor 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”第30頁/共112頁第三十頁，共113頁。31The Gamm

28、a loop Changing the activity of the gamma motor neurons changes the set point of the myotatic feedback loop The Gamma loop Gamma motor neuron intrafusal muscle fiber Ia afferent alpha motor neuron extrafusal muscle fibers Alpha and gamma motor neurons are simultaneously activated by descending comma

29、nds from the brain第31頁/共112頁第三十一頁，共113頁。32vGolgi tendon organnActs like a strain gauge, it 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 th

30、e muscle spindles第32頁/共112頁第三十二頁，共113頁。33Golgi tendon organs respond to increased tension on the muscle and transmit 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當(dāng)肌肉等長收縮時(shí),腱器官傳入沖動頻

31、率, 肌梭傳入沖動頻率不變;當(dāng)肌肉等張收縮時(shí),腱器官傳入沖動頻率不變, 肌梭傳入沖動頻率Golgi tendon organs lie in series between the muscle fibers and their points of attachmentMuscle spindles are arranged parallel to the extrafusal fibers第33頁/共112頁第三十三頁，共113頁。34The Ib afferents enter the spinal cord, branch repeatedly, and synapse on intern

32、eurons 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 parallel with the muscle fibers, Golgi tendon organs are situated in seriesIa activi

33、ty from the spindle encodes muscle length informationWhile Ib activity from the Golgi tendon organ encodes muscle tension information腱器官 是張力感受器, 其傳入沖動對同一肌肉運(yùn)動神經(jīng)元起抑制作用肌梭是長度感受器,其傳入沖動對同一肌肉運(yùn)動神經(jīng)元起興奮作用當(dāng)肌肉被動牽拉時(shí), 二者傳入沖動頻率均：首先興奮肌梭發(fā)動牽張反射, 肌肉收縮,牽拉力大到一定程度, 興奮腱器官而抑制牽張反射牽張反射的特點(diǎn)： 反射弧簡單，感受器和效應(yīng)器在同一塊肌肉第34頁/共112頁第三十四頁，

34、共113頁。35Significance of the reverse myotatic reflex In extreme circumstances, this reflex arc protects the muscle from overload The normal function is to regulate muscle tension within an optimal rangeAs muscle tension increases, the inhibition of the alpha motor neuron slows muscle contractionAs mu

35、scle tension falls, the inhibition of the alpha motor neuron is reduced, and muscle contraction increases This type of proprioceptive feedback is thought to be particularly important for the proper execution of fine motor acts, such as the manipulation of fragile objects with the hands, which requir

36、e a steady but not too powerful grip第35頁/共112頁第三十五頁，共113頁。36Spinal interneurons Most of the input to the alpha motor neurons comes from interneurons of the spinal cord Interneurons receive synaptic input from primary sensory axons, descending axons from the brain, and collaterals of lower motor neur

37、on axons The interneurons are themselves networked together in a way that allows coordinated motor programs to be generated in response to their many inputs第36頁/共112頁第三十六頁，共113頁。37Reciprocal inhibition of flexors and extensors of the same jointnInhibitory inputnContraction of one set of muscles acco

38、mpanied by the relaxation of the antagonist muscles is called reciprocal inhibitionnReciprocal inhibition is also used by descending pathways to overcome the powerful myotatic reflex第37頁/共112頁第三十七頁，共113頁。38(A& C fibers)nExcitatory inputnFlexor reflex: used to withdraw a limb from an aversive sti

39、mulus, 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 excite the alpha motor neurons that control all of the flexor muscles of the affected limb (and inhibi

40、tory interneurons are also recruited to inhibit the alphas that control the extensors)+第38頁/共112頁第三十八頁，共113頁。39Circuitry of the crossed-extensor reflexSpinalcordIpsilateralextensorsinhibitedContralateralextensorsactivated(contract)Ipsilateralflexorsactivated(contract)ContralateralflexorsinhibitedIps

41、ilateralknee jointcloses up to remove footfrom tackContralateralknee jointopens up to support greaterweight第39頁/共112頁第三十九頁，共113頁。40The generation of spinal motor programs for walking Headless chickens; behavior A complete transectionof a cats spinal cord at the mid-thoracic level leaves the hind lim

42、bs capable of generating coordinated walking movements第40頁/共112頁第四十頁，共113頁。41第41頁/共112頁第四十一頁，共113頁。42Central pattern generators within the spinal cord The circuit for the coordinated control of walking must reside within the spinal cord In general, circuits that give rise to rhythmic motor activity

43、are called central pattern generators How do neural circuits generate rhythmic patterns of activity? The simplest pattern generators, are single neurons whose membrane properties endow them with pacemaker properties (pacemaker neurons)第42頁/共112頁第四十二頁，共113頁。43Some neurons respond to the activation of

44、 NMDA receptors 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+

45、causes the Ca2+-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 oscil

46、lation第43頁/共112頁第四十三頁，共113頁。44A possible circuit for rhythmic alternating activity (walking)Walking 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 gener

47、ating 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 strongly inhibits the other(Pacemaker neuron)(Pacemaker neuron)第44頁/共112頁第四十四頁，共113頁。45Part 2 Brain Control of M

48、ovement第45頁/共112頁第四十五頁，共113頁。46How does the brain How does the brain communicate with the communicate with the motor neurons of the spinal motor neurons of the spinal cord?cord?第46頁/共112頁第四十六頁，共113頁。47Overview 來自高級中樞的下行投射對腦干和脊髓環(huán)路的運(yùn)動控制主要影響隨意運(yùn)動和朝向目標(biāo)的運(yùn)動 發(fā)出下行投射的中樞位于腦干某些部位以及大腦皮質(zhì)的運(yùn)動區(qū)域 腦干內(nèi)的兩個主要結(jié)構(gòu)前庭核和網(wǎng)狀結(jié)構(gòu)對維

49、持姿勢很重要 皮質(zhì)主要運(yùn)動區(qū)和次要運(yùn)動區(qū)(運(yùn)動前區(qū))主要對運(yùn)動進(jìn)行計(jì)劃并使運(yùn)動高效率執(zhí)行(zhxng)，皮質(zhì)的這種作用是通過對腦干內(nèi)的某些高級中樞以及腦干、脊髓中運(yùn)動神經(jīng)元和環(huán)路中間神經(jīng)元的控制來完成的第47頁/共112頁第四十七頁，共113頁。48The descending spinal The descending spinal tracts control of tracts control of movementmovement第48頁/共112頁第四十八頁，共113頁。49The descending spinal tractsControl posture and under b

50、rain stem controlContol voluntary movements of the distal musculature and under direct cortical control第49頁/共112頁第四十九頁，共113頁。50(Pyramidal 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)Joi

51、n 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 flexorsInput from frontal cortex第50頁/共112頁第五十頁，共113頁。51The Ventromedial

52、PathwaysContain four descending tracts the vestibulospinal tractthe tectospinal tractthe pontine reticulospinal tractthe medullary reticulospinal tract Oringinate in the brain stem Terminate among the spinal interneurons Controlling proximal and axial musclesUse sensory information about balance, bo

53、dy position, and the visual enviroment to reflexively maintain balance and body posture第51頁/共112頁第五十一頁，共113頁。52The 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

54、 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 this labyrinth, which accompanies movements of the head, activates hair cells that signal the vestibular

55、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 information from the vestibular labyrinth in the inner earAnother: Projects ipsilaterally as far down as the lu

56、mbar 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 directs the head and eyes to move第52頁/共112頁第五十二頁，共113頁。53The pontine reticulospinal tract enhance the antigrav

57、ity 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 liberates the antigravity muscles from reflex controlActivity in both reticulospinal trac

58、ts is controlled by descending signals from the cortexControl posture of the trunk and the antigravity muscles of the limbs第53頁/共112頁第五十三頁，共113頁。54第54頁/共112頁第五十四頁，共113頁。55our attentionour attention第55頁/共112頁第五十五頁，共113頁。56Motor Cortex(Primary motor cortex)(Premotor area) (lateral region)(Supplementar

59、y 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 anterior to the central sulcus on the precentral gyrusArea 6 lies just anterior to area 4第56頁/共112頁第五

60、十六頁，共113頁。57第57頁/共112頁第五十七頁，共113頁。58A somatotopic map of the human precentral gyrus運(yùn)動皮層對軀體運(yùn)動的調(diào)控特點(diǎn)：交叉性：但頭面部肌肉的支配是雙側(cè)性的有精細(xì)的功能定位：大體呈身體倒影:在4區(qū)內(nèi)側(cè)近中線部位是下肢代表區(qū)，向外側(cè)依次為軀干、前臂、手指，最外側(cè)靠近外側(cè)溝處為面部和舌代表區(qū)頭面代表區(qū)內(nèi)部(nib)為正立的運(yùn)動精細(xì)部位其代表區(qū)大：如手指和面部第58頁/共112頁第五十八頁，共113頁。59Prefrontal areas: in humans are thought to be important for abstract th