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1、Nervous system1,Department of AnatomyLuzhou Medical College,Edited by professor Xiao,Nervous system Introduction The 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 th
2、e spinal and cranial nerves.The autonomic nervous system,often considered as a separate functional entity,is a part central and a part peripheral.,Brain,Spinal cord,Cranial nerves,Spinal nerves,Nervous system as a whole,The nervous system possesses(拥有)particular importance in all organs and systems
3、of human body.It modulates（调整）the different cells,tissues and organs,to complete certain activities or response（反射）exterior stimulus（外界刺激）for the benefit of organism（机体）as a whole.The brain is commonly regarded as the organ solely concerned with thought,memory and consciousness.All information we ha
4、ve concerningthe world about us is conveyed centrally to the brain by an elaborate（精心的详尽的）sensory system.,Nervous system Introduction,Receptor 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 t
5、o.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 espec
6、ially 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 Introduction,The elements of the nervous systemThe nervous system composed of nervous tissue that consists of billions
7、 of nerve cells(neurons)and supported by a special variety of connective tissue known as neuroglia.（神经胶质）The neuron（神经元）The 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 sys
8、tem Introduction,Rough granularEndoplasmicreticulum,Smooth granularEndoplasmic reticulum,Microtubule,Schwanns cell,Myelin sheath,Lysosomes,Lipofuscin脂褐质,dendrite,Each neuron possesses a nucleated cell body and two types of processes(突起),an neuron,which conducts impulse away from the cell body,and on
9、e 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 Introductio
10、n,The structures of the neuron,The 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 cel
11、ls,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 Introdu
12、ction,engage in 从事于,The structures of the neuron,The 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 betwe
13、en 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）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
14、locus ceruleus which are the waste product of catecholamine（儿茶酚胺）synthesis probably.,Nervous system Introduction,The structures of the neuron,The 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
15、 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 m
16、uscle 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 of axon called axoplasm（轴索原浆）.The axoplasm differs from the cytoplasm of the dendrites by complete absence of the Nissl body.Components of the axoplasm con
17、sist of agranular endoplasmic reticulum,mitochondria,microtubules and neurofilments.The terminal segments of axon comprises numerous synaptic vesicles that contain neurotransmitter substances.,Nervous system Introduction,The structures of the neuron,Because the axoplasm does not contain RNA,proteins
18、 synthesis cannot take place in the axon.All axonal proteins,therefore,must come from the cell body,and products are transported by a perpetual（永久的）axoplasmic motion,some organelles,structural protein and neurotransmitters contained within cytoplasm are carried by axoplasmic flow which moves in both
19、 directions and with varying velocity.The anterograde transport,moving from the cell body to the nerve terminals,has two types of rate:one is the slow transport,which is bulk flow（总体流动）of axoplasm carrying mitochondria,lysosomes（溶酶体）and vesicles;the other is a rapid transport which moves the membran
20、e-bound vesicles,and other material.,Nervous system Introduction,Axoplasmic transport,The retrograde transports,moving from the synaptic terminal to the cell body,provide a feedback passage.Some pinocytotic（胞饮的）material uptaken by an axonal terminals or distal dendrites are carried to the cell body
21、for utilization or lysosomal degradation.The axoplasmic transport can be used experimentally to determine neuronal connectivity（连通性）by an axon-tracing technique and gas a clinic implication as centripetal（向心力）transport of neurotoxic（神经毒素）and infective agents,which may be responsible for some disease
22、.,Nervous system Introduction,Axoplasmic transport,The dendrites constitute protoplasmic(原浆)extensions of the cell body.The main or primary dendrites arises from the cell body and then branch repeatedly in a tree-like manner to form a complex dendrites tree.Further,the dendrites are studded（颗粒状的）wit
23、h a large members of thorn（棘）like process,dendrite spines or gemmulus（芽）,which are structures specialized for synoptic contact.In this manner the dendrites greatly increase the receptive surface area（接收面积）of the whole neuron and thus enhance（增加）the scope（机会）for its being influenced by other neurons.
24、To a large extend,the diversity（多样性）among neurons depends on the complexity,configurations and position of the dendrites.,Nervous system Introduction,Axoplasmic transport,Nervous system Introduction,Classification of the neuron,neuron,Bipolar neuron,pseudounipolar neuron,Multipolar neuron,According
25、to the numberOf their processes,neuron,Sensory neuron,Motor neuron,Association neuron,Afferent neuron,Efferent neuron,Intermediate neuron,functionally,neuron,Small,Medium,Large,From 10200um,Bipolar neuron,pseudounipolar neuron,Multipolar neuron,dendrite,nucleus,axon,Nissl body,Axon hillock,Nervous s
26、ystem Introduction,nervous fibers,The longer processes of the neuron enveloped by themyelin sheath and the neurilemma are termed nerve fibers.The myelinated fibers are surrounded by a myelin sheath and neurilemma.The unmyelinated fibers are not,however,insulated（绝缘的）by a myelin sheath.Oligodendrocyt
27、es form myelin in the central nervoussystem while Schwann cells form myelin in peripheral nerves.,Nervous system Introduction,Synapses,concept of the synapse,Within the nervous system impulses are conducted fromOne part to another along a chain of neurons.The terminal arborizations of the axon of on
28、e neuron ramify in closecontact with the cell body or dentrites,less frequently with axonic terminals of many others.,Concept Of the synapses,Structures of the synapses,Each synapse involves the close apposition of a presynaptic element with a postSynaptic element from which it is separated by a syn
29、aptic cleft.The presynaptic element contains numerous synaptic vesicles in which the chemical substance neurotransmitter is present.,(),Presynaptic membrane,Postsynapse membrane,Synaptic cleft,Synaptic vesicle,Mitochondria,Nervous system Introduction,Synapses,(),When an impulse arrives at the presyn
30、aptic element,the neurotransmitter Diffuses across the synaptic cleft and binds to receptor molecules in the postsynaptic membrane.As a result,the postsynaptic neuron is activated and impulse is conducted from one neuron to the others.The“chemical synapse”involving the release the transmitter substa
31、nce is the most common type in the mammalian nervous system.The axon of lower motor neuron project through peripheral nerves to Muscle cells and terminate at a specialized portion of the muscle membraneWhich are called neuromuscular junctions or motor end plates.The fibersInnervating the voluntary m
32、uscles of the body and limbs are the axon of large multipolar nerve cells located in anterior horn of the gray matter of The spinal cord.It has been estimated that each of these motor neuronsReceives synaptic connections from the terminal axonal ramifications of Up to 1000 other nerve cells.,Nervous
33、 system Introduction,.The neurogliaNeuroglia cells outnumber neurons in the central nervous system10:1.These cells appear to play a number of important roles,including myelin formation,guidance of developing neurons,maintenace of extracellular K+levels,and reuptake of transmitters after synaptic act
34、ivity.The astrocytes Astrocytes have many radiating processes,some of which end at Nerve cells and others at capillaries.They are neuroectodermal inOrigin and may assist in the transfer of nutrients and metabolic Products between the neurons and the blood.,Nervous system Introduction,2.The oligodend
35、rocytesOligodendrocytes are smaller and have fewer branching processes;they tend to lay in rows between nerve fibers and are concerned with the production and nourishment of myelin sheaths especially those surround axons in the central nervous system.They are neuroectodermal in origin.3.The microgli
36、aMicroglia are diminutive cells,which permeate the entire central nervous system.They are modified macrophages and form partOf the reticulo-endothelial system and are probably mesodermalIn origin.,Nervous system Introduction,.The reflex and reflex arcReflexes are subconscious stimulus-esponse mechan
37、ism.The reflex arc,a linkage of afferent and efferent neurons,is defined as the entire neural pathway that is involved in a reflex.Several structures are involved in the reflex arc.These include the receptor whose stimulation initiates an impulse;the afferent neuron,which transmits the impulse throu
38、gh a peripheral nerve to the central nervous system,where the nerve synapses with a lower motor neuron or an interneuron up to one or more interneurons which relay the impulse to the efferent neurons;the efferent neuron which passes outward in the nerve and delivers the impulse to the effectorand an
39、 effector.The interruption of this reflex arc at any point abolishes the response.,Nervous system Introduction,Terminology,Gray matter,In the CNS,the part of aggregations of nerve cell bodiesEmbedded in a network of delicate nerve processes is Known as gray matter,it has a gray color during the Fres
40、h condition.,Cortex,The cortex is the outmost layer of gray matter in the Cerebral hemispheres or in the cerebellum.The cellBodies in the cortex are arranged in more or less well-Defined laminae or layers.,Nucleus,Nerve cells with common shape,function and connectionswithin the CNS are grouped toget
41、her into nucleus.,Ganglion,Nerve cells with the same shape,function and connectionsOutside the CNS often are grouped together into ganglion.,Nervous system Introduction,Terminology,White matter,In the CNS,the part that contains mainly bundles of nerve fibers is white matter and the white color is du
42、eTo a rich content of fatty myelin sheath.,Medullary substance,The medullary substance is a central core of whitematter beneath the cortex of the cerebrum and cerebellum.,Funiculus(fasciculus),In the CNS,a distinct collection of nerve with commonorigins,destinations and functions is referred to fasc
43、iculus,or tract.A funiculus is a collection of tractshaving different origins,destinations and functions,Nerve,In the peripheral nervous system,the nerve fibers are grouped into bundles to form the nerve trunk called nerve.Most of nerves have a whitish appearance because of their myelin content.,专业单
44、词复习Imagination 想像力Versatility 多功能性Potential capabilities 濽能Efficiency 效率 Self-programming nature 自我谋略天性Integration 整合 Coded information 编码信息Chromatin 染色质 Nucleolus 核仁 Organelles 细胞器 Lysosomes 溶酶体 Mitochondria 线粒体 Lipofuscin 脂褐质,Neuromelanin（神经黑色素）Catecholamine（儿茶酚胺）Axoplasm（轴索原浆Axolemma（轴膜）Lysosomes（溶酶体）Pinocytotic（胞饮的）Neurotoxic（神经毒素）Protoplasmic(原浆)MicrotubuleRough granular endoplasmic reticulumSmooth granular endoplasmic reticulumMyelin sheath,
