1、.,1,Central Nervous System Control of Movement,XING, GUOGANG(邢國(guó)剛), MD. Ph.D. 北京大學(xué) 神經(jīng)科學(xué)研究所 Neuroscience Research Institute, Peking University Email address: ggxing,.,2,Introduction,生命在于運(yùn)動(dòng) 運(yùn)動(dòng)是動(dòng)物維系個(gè)體生存和種族繁衍的基本功能之一,.,3,How does a coordinated movement achieved ?,.,4,The mental body image seems to be gene

2、rated by somatosensory, proprioceptive, and visual inputs to the posterior parietal cortex (area 5, area 7),A baseball pitcher planning a pitch,.,5,The highest level strategy Represented by the association areas of neocortex and basal ganglia of the forebrain Is concerned with strategy: The goal of

3、the movement and the movement strategy that best achieves the goal,The motor control hierarchy have three levels,.,6,The middle leveltactics Represented by the motor cortex and cerebellum Is concerned with tactics The sequences of muscle contractions Arranged in space and time Required to smoothly a

4、nd accurately achieve the strategic goal,The motor control hierarchy have three levels,.,7,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 neces

5、sary adjustments of posture,The motor control hierarchy have three levels,.,8,Overview,脊髓內(nèi)的“下運(yùn)動(dòng)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(dòng)區(qū)及腦干中許多“上運(yùn)動(dòng)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(dòng)神經(jīng)元提供某種感覺、認(rèn)知或感性的信息，使運(yùn)動(dòng)更加精確和協(xié)調(diào),.,9,.,10,These programs are accessed, executed, and modified by descending com

6、mands from the brain,The brains command and control of the motor programs in the spinal cord,The motor system consists of all our muscles and the neurons that command them,The spinal cord contains certain motor programs for the generation of coordinated movements,The motor control can be divided int

7、o two parts:,The spinal cords command and control of coordinated muscle contraction,.,11,Part 1 Spinal Control of Movement,.,12,Introduction,“running around like a chicken with its head cut off” The rhythmic movements could be elicited in the hind legs of cats and dogs long after their spinal cords

8、had been severed from the rest of the central nervous system Charles Sherington behavior A complete transectionof a cats spinal cord at the mid-thoracic level leaves the hind limbs capable of generating coordinated walking movements,When you walk, you alternately withdraw and extend your two legs Wh

9、at is the mechanism to coordinate the timing?,This could be descending commands from upper motor neurons?,No!,This control is exerted from within the spinal cord?,Yes!,.,42,.,43,Central pattern generators within the spinal cord,The circuit for the coordinated control of walking must reside within th

10、e spinal cord In general, circuits that give rise to rhythmic motor activity 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 (pacema

11、ker neurons),.,44,Rhythmic activity in a spinal interneuron (Pacemaker neuron),Some neurons respond to the activation of NMDA receptors with rhythmic depolarization,.,45,A possible circuit for rhythmic alternating activity (walking),Walking is initiated when a steady input excites two interneurons t

12、hat 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. Thus, a burst of

13、 activity in one interneuron strongly inhibits the other,(Pacemaker neuron),(Pacemaker neuron),.,46,Part 2 Brain Control of Movement,.,47,How does the brain communicate with the motor neurons of the spinal cord?,.,48,Overview,來自高級(jí)中樞的下行投射對(duì)腦干和脊髓環(huán)路的運(yùn)動(dòng)控制主要影響隨意運(yùn)動(dòng)和朝向目標(biāo)的運(yùn)動(dòng) 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(dòng)區(qū)域 腦干內(nèi)的

14、兩個(gè)主要結(jié)構(gòu)前庭核和網(wǎng)狀結(jié)構(gòu)對(duì)維持姿勢(shì)很重要 皮質(zhì)主要運(yùn)動(dòng)區(qū)和次要運(yùn)動(dòng)區(qū)(運(yùn)動(dòng)前區(qū))主要對(duì)運(yùn)動(dòng)進(jìn)行計(jì)劃并使運(yùn)動(dòng)高效率執(zhí)行，皮質(zhì)的這種作用是通過對(duì)腦干內(nèi)的某些高級(jí)中樞以及腦干、脊髓中運(yùn)動(dòng)神經(jīng)元和環(huán)路中間神經(jīng)元的控制來完成的,.,49,The descending spinal tracts control of movement,.,50,The descending spinal tracts,.,51,Control fine movements of the arms and fingers,The effects of lateral pathway lesions (in monkey

15、s) by Donald Lawrence & Hans Kuypers (in the late 1960s),The Lateral Pathways,X,.,52,The Ventromedial Pathways,Contain four descending tracts the vestibulospinal tract the tectospinal tract the pontine reticulospinal tract the medullary reticulospinal tract Oringinate in the brain stem Terminate amo

16、ng the spinal interneurons Controlling proximal and axial muscles Use sensory information about balance, body position, and the visual enviroment to reflexively maintain balance and body posture,.,53,The vestibulospinal and tectospinal tracts keep the head balance on the shoulders as the body moves

17、through space , and they turn the head in response to new sensory stimuli,(midbrain),Recive direct input from retina Recive projections from visual cortex, as well as afferents carring somatosensory and auditory information Construct a map of the word around us,The motion of the fluid in this labyri

18、nth, which accompanies movements of the head, activates hair cells that signal the vestibular nuclei via cranial nerve VIII,One: Projects bilaterally down the spinal cord and activates the cervical spinal circuits that control neck and back muscles and guid head movement,Another: Projects ipsilatera

19、lly as far down as the lumbar spinal cord It helps us maintain an upright and balanced posture by facilitating extensor motor neurons of the legs,Stimulation at one site in this map Lead to an orienting response that directs the head and eyes to move,.,54,The pontine reticulospinal tract enhance the

20、 antigravity reflexes of the spinal cord By facilitating the extensors of the lower limbs Helps maintain a standing posture by resisting the effects of gravity,The medullary reticulospinal tract has the opposite effect: it liberates the antigravity muscles from reflex control,Activity in both reticulospinal tracts is controlled by descending signals fro