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1、1,Central Nervous System Control of Movement,XING, GUOGANG(邢国刚), MD. Ph.D. 北京大学 神经科学研究所 Neuroscience Research Institute, Peking University Email address: ,2,Introduction,生命在于运动 运动是动物维系个体生存和种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 generated by somat
2、osensory, 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 the movement and
3、 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 tacticsThe sequences of muscle contractionsArranged in space and time Required to smoothly and accurately achiev
4、e the strategic goal,The motor control hierarchy have three levels,7,The lowest level executionRepresented by the brain stem and spinal cordIs concerned with executionAction of the motor neuron and interneuron pools that generate the goal-directed movement and make any necessary adjustments of postu
5、re,The motor control hierarchy have three levels,8,Overview,脊髓内的“下运动神经元(Lower neurons)”，除了受到脊髓内局部环路的影响外，还受到大脑皮层运动区及脑干中许多“上运动神经元(Upper neurons)”的支配和协调 基底神经节和小脑则向那些上运动神经元提供某种感觉、认知或感性的信息，使运动更加精确和协调,9,10,These programs are accessed, executed, and modified by descending commands from the brain,The brains
6、 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 into two parts:,The spinal cords c
7、ommand 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 had been severed from the rest of t
8、he central nervous system Charles Sherington & Graham Brown (English)The importance of circuitry within the spinal cord for the coordinated control of movements,13,Spinal circuitry control of movement,14,Spinal motor neurons,Alpha motor neurons Innervate skeletal muscle (extrafusal muscle) Function:
9、 directly command muscle contract Gamma motor neuronsInnervate muscle spindle (intrafusal muscle) Function: regulating the muscle spindle InterneuronsAllows coordinated motor programs to be generatedFinal common pathway(directly command muscle contract) Compare: Upper motor neurons,Lower motor neuro
10、ns,15,The 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 p
11、ool: The collection of alpha motor neurons that innervates a single muscle,16,The motor unit is an alpha motor neuron and all of the muscle,A motor unit and motor neuron pool,The motor neuron pool is all of the alpha motor neurons that innervate one muscle,17,Muscle innervation by lower motor neuron
12、s,30 mixed spinal nerves cervical 1-8 thoracic 1-12 lumbar 1-5 sacral 1-5,18,The cervical enlargement of the spinal cord contains the motor neurons that innervate the arm muscles The 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,The distributi
13、on of motor neurons in the spinal cord,The motor neurons that innervate distal and proximal musculature are found mainly in the cervical and lumbar-sacral segments of the spinal cord Whereas those innervating axial musculature are found at all levels,19,Motor neurons controlling flexors lie dorsal t
14、o 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 neurons in the ventral horn,20,Muscle weakness and paralysis所支配的骨骼肌瘫痪、肌张力下降、腱反射消失(软瘫) 肌萎缩、纤维颤动或肌束颤动 见于如
15、肌萎缩侧索硬化症(amyotrophic lateral sclerosis, ALS)：Selective damage to alpha motor neurons(degeneration)脊髓-运动神经元的进行性溃变为主,下运动神经元的损伤表现,21,Lou Gehring, a star baseball player with New York Yankees, who died of ALS ( amyotrophic lateral sclerosis) in 1936,22,Inputs to alpha motor neurons,23,SPINAL CONTROL OF
16、MOTOR UNITS,How the activity of the motor neuron is itself controlled ?,24,Reflex,25,The myotatic reflex (stretch reflex),Two types of myotatic reflex Tendon reflex and muscle tonus A.Tendon reflex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,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,26,+,27,B. 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,
