Nervous system1Department of AnatomyDepartment of Anatomy LuzhouLuzhou Medical College Medical College Edited by professor XiaoNervous system IntroductionThe nervous system is composed of two parts, the central nervous system and peripheral nervous system. The former is represented by the brain and spinal cord; while the latter consists of the spinal and cranial nerves. The autonomic nervous system, often considered as a separate functional entity, is a part central and a part peripheral. BrainSpinal cordCranial nervesSpinal nervesNervous system as a wholenThe nervous system possesses(拥有) particular importance in all organs and systems of human body. It modulates（调整）the different cells, tissues and organs, to complete certain activities or response（反射）nexterior stimulus（外界刺激） for the benefit of organism （机体）as a whole. nThe brain is commonly regarded as the organ solely concerned with thought, memory and consciousness. All information we have concerningnthe world about us is conveyed centrally to the brain by an elaborate（精心的详尽的） sensory system. Nervous system IntroductionnReceptor of many kinds act as transducers which change physical and chemical stimuli in our environment into nerve impulse which the brain can read and give meaning to. Attention, consciousness, emotional experience and sleep are all central neural functions. Such higher functions as memory, imagination(想像力), thought and creative ability are poorly understood（难懂的） but must be related to complex neuronal activity. While the gross features of the human brain are not especially impressive（印象）, its versatility（多功能性）, potential capabilities（濽能）, efficiency（效率）and self- programming nature（自我谋略天性） put it in a class beyond any “electronic brain”.Nervous system IntroductionnThe elements of the nervous systemnThe nervous system composed of nervous tissue that consists of billions of nerve cells (neurons) and supported by a special variety of connective tissue known as neuroglia.（神经胶质）nThe neuron（神经元）nThe neuron are independent structural unit of the nervous system and are functional specialized for reception, integration（整合）, and transmission of coded information（编码）.Nervous system IntroductionRough granular Endoplasmic reticulumSmooth granular Endoplasmic reticulumMicrotubuleSchwanns cellMyelin sheathLysosomesLysosomesLipofuscinLipofuscin脂褐质脂褐质dendritenEach neuron possesses a nucleated cell body and two types of processes(突起), an neuron, which conducts impulse away from the cell body, and one or more dendrites（树突） that conducts impulses towards the cell body. Both of these processes show marked morphological （形态学的） difference. The cell body serves as metabolic （代谢的）center of the entire unit and consists of a large, pale （灰白的） nucleus（胞核） and cytoplasm（细胞浆） ( perikaryon). Nervous system IntroductionThe structures of The structures of the neuron the neuronnThe nuclear envelope is double-layered membrane with numerous pores（小孔）. The chromatin（染色质） consists mostly of large molecules of deoxyribonucleic acid (DNA). The nucleolus（核仁） occupies a prominent position in the nucleus, which is rich in ribonucleic acid (RNA). As in all cells, the nucleus engages in marked degree of protein synthesis（蛋白质合成）. The organelles（细胞器） contained within the cytoplasm（细胞 质 你） are common to other cells in the body, but there is abundant granular endoplasmic reticulum that constitutes the Nissl body, a protein synthesis apparatus. Nervous system Introductionengage in engage in 从事于从事于The structures of The structures of the neuron the neuronnThe microtubules and neurofilaments in the cytoplasm extend throughout the cell body and processes and constitute the cytoskeleton of the neuron, which are involved in the maintenance of the shape of neuron and facilitate（易于） transfer of substance between the cells body and cell processes. The neuron also contains abundant lysosomes（溶酶体）, and mitochondria（线粒体） for energy metabolism. There are lipofuscin（脂褐质n） granules ( prominently in some large adult neuron) which are byproducts of metablism, and the neuromelanin（神经黑色素）granules in the substantia nigra and locus ceruleus which are the waste product of catecholamine（儿茶酚胺） synthesis probably.Nervous system IntroductionThe structures of The structures of the neuron the neuronnThe axon is a slender process. It may arise from the conical region of the cell body called axon hillock, or from the base of one of the main dendrites. The axon gives rise to several side branches or collaterals, usually oriented perpendicular（垂直的） to the main axon process. Distally, the axon breaks up into fine branches that end in swollen button called button terminal or axon terminal. The latter comes into contact with other neurons to form synapse, or with muscle to cause muscle contraction, or with the gland to cause secretion. The plasmic membrane of the axon is known as axolemma（轴膜） and the interior