Sx006-神经总论 脊髓课件.ppt

人体解剖学 Human Anatomy;第六篇 神经系统 Nervous system;Chapter 1 总论 Introduction;I.神经系统的区分 Divisions of Nervous System; ;and two types of processes: an ② 轴突 axon→ conducts impulse away from cell body, and one or more ③树突 dendrites → conduct impulses towards cell body. ;★ 神经元构造 Structure of neuron; ;★ 神经元分类 Classification of neuron;★ 神经元分类 Classification of neuron;3.神经纤维 Nerve fibers Longer processes of neuron enveloped by myelin sheath and neurilemma are termed nerve fibers. 有髓纤维 Myelinated fibers are surrounded by a myelin sheath and neurilemma. 无髓纤维 Unmyelinated fibers are not, however, ; 4.突触 Synapses Within nervous system impulses are conducted from one part to another along a chain of neurons. Terminal arborizations of axon of one neuron ramify in close contact with cell body or dendrites, less frequently with axonic terminals of many others. ; Presynaptic element contains numerous synaptic vesicles in which chemical substance neurotransmitter is present. When an impulse arrives at presynaptic element, neurotransmitter diffuses across synaptic cleft and binds to receptor molecules in postsynaptic membrane. As a result, postsynaptic neuron ; II)神经胶质 Neuroglia Neuroglial cells outnumber neurons in central nervous system 10:1. These cells appear to play a number of important roles, including myelin formation, guidance of developing neurons, maintenance of extracellular K+ levels, and reuptake of transmitters after synaptic activity. 1.星形胶质细胞 Astrocytes have many radiating processes, ; 2.寡突胶质细胞 Oligodendrocytes are smaller and have fewer branching processes; they tend to lay in rows between nerve fibers and are concerned with production and nourishment of myelin sheaths especially those surround axon in central nervous system. They are neuroectodermal in origin. 3.小胶质细胞 Microglia are diminutive cells, which;III. 反射与反射弧 Reflex and Reflex Arc Reflexes are automatic, subconscious responses to stimuli within or outside body. Reflex arc,