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1、Nervous systemNervous system11Department of AnatomyDepartment of AnatomyLuzhouLuzhou Medical College 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 b
2、y 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 po
3、ssesses(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 c
4、oncerned 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 en
5、vironment 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 comp
6、lex 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 Introductionn nThe elements of the
7、 nervous systemn nThe nervous system composed of nervous tissue The nervous system composed of nervous tissue that consists of billions of that consists of billions of nerve cellsnerve cells (neurons) (neurons) and supported by a special variety of connective and supported by a special variety of co
8、nnective tissue known as tissue known as neuroglianeuroglia. .（神经胶质）（神经胶质）n nThe neuron（神经元）（神经元）n nThe neuron are independent structural unit of The neuron are independent structural unit of the nervous system and are functional the nervous system and are functional specialized for reception, integ
9、rationspecialized for reception, integration（整合）, and , and transmission of coded informationtransmission of coded information（编码）（编码）. .Nervous system IntroductionRough granularEndoplasmicreticulum Smooth granularEndoplasmic reticulumMicrotubuleSchwanns cellMyelin sheathLysosomesLysosomesLipofuscin
10、Lipofuscin脂褐质脂褐质脂褐质脂褐质dendriten nEach neuron possesses a nucleated cell body Each neuron possesses a nucleated cell body and two types of processes(and two types of processes(突起突起), an neuron, ), an neuron, which conducts impulse away from the cell which conducts impulse away from the cell body, and
11、 one or more dendritesbody, and one or more dendrites（树突）（树突） that that conducts impulses towards the cell body. Both conducts impulses towards the cell body. Both of these processes show marked of these processes show marked morphologicalmorphological（形态学的）（形态学的） difference. The cell difference. Th
12、e cell body serves as metabolic body serves as metabolic （代谢的）（代谢的）center of center of the entire unit and consists of a large, pale the entire unit and consists of a large, pale （灰白的）（灰白的）nucleusnucleus（胞核）（胞核） and cytoplasmand cytoplasm（细（细胞浆）胞浆） ( ( perikaryonperikaryon). ). Nervous system Introd
13、uctionThe structures of The structures of the neuron the neuronn nThe nuclear envelope is double-layered membrane with The nuclear envelope is double-layered membrane with numerous poresnumerous pores（小孔）（小孔）. The chr. The chro omatinmatin（染色质）（染色质） consists consists mostly of large molecules of deo
14、xyribonucleic acid mostly of large molecules of deoxyribonucleic acid (DNA). The nucl(DNA). The nucle eolusolus（核仁）（核仁） occupies a prominent occupies a prominent position in the nucleus, which is rich in ribonucleic acid position in the nucleus, which is rich in ribonucleic acid (RNA). As in all cel
15、ls, the nucleus engages in marked (RNA). As in all cells, the nucleus engages in marked degree of degree of protein synthesisprotein synthesis（蛋白质合成）（蛋白质合成）. The . The organellesorganelles（细胞器）（细胞器） contained within the cytoplasmcontained within the cytoplasm（细胞（细胞质质 你）你） are common to other cells i
16、n the body, but are common to other cells in the body, but there is abundant granular endoplasmic reticulum that there is abundant granular endoplasmic reticulum that constitutes the constitutes the NisslNissl body, a protein synthesis body, a protein synthesis apparatus. apparatus. Nervous system I
17、ntroductionengage in engage in 从事于从事于从事于从事于The structures of The structures of the neuron the neuronn nThe microtubules and The microtubules and neurofilamentsneurofilaments in the cytoplasm in the cytoplasm extend throughout the cell body and processes and extend throughout the cell body and proces
18、ses and constitute the cytoskeleton of the neuron, which are constitute the cytoskeleton of the neuron, which are involved in the maintenance of the shape of neuron and involved in the maintenance of the shape of neuron and facilitatefacilitate（易于）（易于） transfer of substance between the cells body tr
19、ansfer of substance between the cells body and cell processes. The neuron also contains abundant and cell processes. The neuron also contains abundant lysosomeslysosomes（溶酶体溶酶体溶酶体溶酶体）, and mitochondria, and mitochondria（线粒体）（线粒体） for energy for energy metabolism. There are metabolism. There are lipo
20、flipofu uscinscin（脂褐质脂褐质脂褐质脂褐质n n） granules ( prominently in some large adult neuron) which granules ( prominently in some large adult neuron) which are byproducts of are byproducts of metablismmetablism, and the , and the neuromneurome elaninlanin（神经黑色素）神经黑色素）神经黑色素）神经黑色素）granules in the granules in
21、 the substantiasubstantia nigranigra and locus and locus ceruleusceruleus which which are the waste product of catechare the waste product of catecho olaminelamine（儿茶酚胺）（儿茶酚胺） synthesis synthesis probably.probably.Nervous system IntroductionThe structures of The structures of the neuron the neuronn
22、nThe axon is a slender process. It may arise from the conical region 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 of the cell body called axon hillock, or from the base of one of the main dendrites. The axon
23、gives rise to several side branches or main dendrites. The axon gives rise to several side branches or collaterals, usually oriented perpendicularcollaterals, usually oriented perpendicular（垂直的）（垂直的） to the main axon to the main axon process. Distally, the axon breaks up into fine branches that end
24、in process. Distally, the axon breaks up into fine branches that end in swollen button called button terminal or axon terminal. The latter swollen button called button terminal or axon terminal. The latter comes into contact with other neurons to form synapse, or with comes into contact with other n
25、eurons to form synapse, or with muscle to cause muscle contraction, or with the gland to cause muscle to cause muscle contraction, or with the gland to cause secretion. The secretion. The plasmicplasmic membrane of the axon is known as membrane of the axon is known as axolemmaaxolemma（轴膜）（轴膜） and th
26、e interior of axon called and the interior of axon called axoplasmaxoplasm（轴索原浆）（轴索原浆）. . The The axoplasmaxoplasm differs from the cytoplasm of the dendrites by differs from the cytoplasm of the dendrites by complete absence of the complete absence of the NisslNissl body. Components of the body. Co
27、mponents of the axoplasmaxoplasm consist of consist of agranularagranular endoplasmic reticulum, mitochondria, endoplasmic reticulum, mitochondria, microtubules and microtubules and neurofilmentsneurofilments. The terminal segments of axon . The terminal segments of axon comprises numerous synaptic
28、vesicles that contain neurotransmitter comprises numerous synaptic vesicles that contain neurotransmitter substances.substances.Nervous system IntroductionThe structures of The structures of the neuron the neuron Because the Because the axoplasmaxoplasm does not contain RNA, proteins synthesis does
29、not contain RNA, proteins synthesis cannot take place in the axon. All axonal proteins, therefore, must cannot take place in the axon. All axonal proteins, therefore, must come from the cell body, and products are transported by a come from the cell body, and products are transported by a perpetualp
30、erpetual（永久的）（永久的） axoplasmicaxoplasmic motion, some organelles, structural motion, some organelles, structural protein and neurotransmitters contained within cytoplasm are protein and neurotransmitters contained within cytoplasm are carried by carried by axoplasmicaxoplasmic flow which moves in bot
31、h directions and with flow which moves in both directions and with varying velocity. The varying velocity. The anterogradeanterograde transport, moving from the cell transport, moving from the cell body to the nerve terminals, has two types of rate: one is the slow body to the nerve terminals, has t
32、wo types of rate: one is the slow transport, which is bulk flowtransport, which is bulk flow（总体流动）（总体流动） of of axoplasmaxoplasm carrying carrying mitochondria, mitochondria, lysosomeslysosomes（溶酶体）（溶酶体） and vesicles; the other is a rapid and vesicles; the other is a rapid transport which moves the m
33、embrane-bound vesicles, and other transport which moves the membrane-bound vesicles, and other material.material.Nervous system IntroductionAxoplasmic transportn nThe retrograde transports, moving from the synaptic The retrograde transports, moving from the synaptic terminal to the cell body, provid
34、e a feedback passage. terminal to the cell body, provide a feedback passage. Some Some pinocytoticpinocytotic（胞饮的）（胞饮的） material material uptakenuptaken by an axonal by an axonal terminals or distal dendrites are carried to the cell body terminals or distal dendrites are carried to the cell body for
35、 utilization or for utilization or lysosomallysosomal degradation. The degradation. The axoplasmicaxoplasmic transport can be used experimentally to determine transport can be used experimentally to determine neuronal connectivityneuronal connectivity（连通性）（连通性） by an axon-tracing technique by an axo
36、n-tracing technique and gas a clinic implication as centripetaland gas a clinic implication as centripetal（向心力）（向心力） transport transport of of neurotoxicneurotoxic（神经毒素）（神经毒素） and infective agents, which may be and infective agents, which may be responsible for some disease.responsible for some dise
37、ase.Nervous system IntroductionAxoplasmic transportn nThe dendrites constitute protoplasmicThe dendrites constitute protoplasmic( (原浆原浆) ) extensions of extensions of the cell body. The main or primary dendrites arises from the cell body. The main or primary dendrites arises from the cell body and t
38、hen branch repeatedly in a tree-like the cell body and then branch repeatedly in a tree-like manner to form a complex dendrites tree. Further, the manner to form a complex dendrites tree. Further, the dendrites are studdeddendrites are studded（颗粒状的）（颗粒状的） with a large members of with a large members
39、 of thornthorn（棘）（棘） like process, dendrite spines or like process, dendrite spines or gemmulusgemmulus（芽）（芽）, , which are structures specialized for synoptic contact. In which are structures specialized for synoptic contact. In this manner the dendrites greatly increase the receptive this manner th
40、e dendrites greatly increase the receptive surface areasurface area（接收面积）（接收面积） of the whole neuron and thus of the whole neuron and thus enhanceenhance（增加）（增加） the scopethe scope（机会（机会） for its being influenced by for its being influenced by other neurons. To a large extend, the diversityother neur
41、ons. To a large extend, the diversity（多样性）（多样性） among neurons depends on the complexity, configurations among neurons depends on the complexity, configurations and position of the dendrites.and position of the dendrites.Nervous system IntroductionAxoplasmic transportNervous system IntroductionClassi
42、fication of the neuronneuronBipolar neuron pseudounipolar neuronMultipolar neuronAccording to the numberOf their processesneuronSensory neuronMotor neuron Association neuronAfferent neuronEfferent neuronIntermediate neuronfunctionallyneuronSmall Medium Large From 10200umBipolar neuronpseudounipolar
43、neuronMultipolar neurondendritenucleusaxonNissl bodyAxon hillockNervous system Introduction nervous fibersThe 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 unmyelina
44、ted fibers are not, however, insulated（绝缘的） by a myelin sheath. Oligodendrocytes form myelin in the central nervoussystem while Schwann cells form myelin in peripheral nerves.Nervous system IntroductionSynapses concept of the synapseWithin the nervous system impulses are conducted fromOne part to an
45、other along a chain of neurons. The terminal arborizations of the axon of one neuron ramify in closecontact with the cell body or dentrites, less frequently with axonic terminals of many others.Concept Of the synapsesStructures of the synapsesEach synapse involves the close apposition of a presynapt
46、ic element with a postSynaptic element from which it is separated by a synaptic cleft. The presynaptic element contains numerous synaptic vesicles in which the chemical substance neurotransmitter is present. ()Presynaptic membranePostsynapse membraneSynaptic cleftSynaptic vesicleMitochondria Nervous
47、 system IntroductionSynapses ()When an impulse arrives at the presynaptic 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 o
48、thers. The “chemical synapse” involving the release the transmitter substance 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 neurom
49、uscular junctions or motor end plates. The fibersInnervating the voluntary muscles 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 fr
50、om the terminal axonal ramifications of Up to 1000 other nerve cells. Nervous 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, main
51、tenace of extracellular K+levels, and reuptake of transmitters after synaptic activity.1.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 Pr
52、oducts between the neurons and the blood. Nervous system Introduction2. The oligodendrocytesOligodendrocytes 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
53、 axons in the central nervous system. They are neuroectodermal in origin.3. The microgliaMicroglia 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
54、 Introduction. The reflex and reflex arcReflexes are subconscious stimulus-esponse mechanism. 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 recepto
55、r whose stimulation initiates an impulse; the afferent neuron, which transmits the impulse through a peripheral nerve to the central nervous systemwhere 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
56、efferent neuron which passes outward in the nerve and delivers the impulse to the effectorand an effector. The interruption of this reflex arc at any point abolishes the response.Nervous system Introduction Terminology Gray matterIn the CNS, the part of aggregations of nerve cell bodiesEmbedded in a
57、 network of delicate nerve processes is Known as gray matter, it has a gray color during the Fresh 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 layer
58、s.Nucleus Nerve cells with common shape, function and connectionswithin the CNS are grouped together 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 matterIn the CNS,
59、 the part that contains mainly bundles of nerve fibers is white matter and the white color is dueTo a rich content of fatty myelin sheath.Medullary substanceThe medullary substance is a central core of whitematter beneath the cortex of the cerebrum and cerebellum. Funiculus(fasciculus)In the CNS, a
60、distinct collection of nerve with commonorigins, destinations and functions is referred to fasciculus, or tract. A funiculus is a collection of tractshaving different origins, destinations and functionsNerve In the peripheral nervous system, the nerve fibers are grouped into bundles to form the nerv
61、e trunk called nerve. Most of nerves have a whitish appearance because of their myelin content.n n 专业单词复习专业单词复习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 Integration 整合 Coded information Coded information 编码信息编码信息ChrChro omatin mat
62、in 染色质染色质 NuclNucle eolus olus 核仁核仁 Organelles Organelles 细胞器细胞器 LysosomesLysosomes 溶酶体溶酶体溶酶体溶酶体 Mitochondria Mitochondria 线粒体线粒体 LipofLipofu uscinscin 脂褐质脂褐质脂褐质脂褐质n nNeuromNeurome elaninlanin （神经黑色素）神经黑色素）神经黑色素）神经黑色素） n nCatechCatecho olamine lamine （儿茶酚胺）（儿茶酚胺） n nAxoplasmAxoplasm （轴索原浆（轴索原浆n nAxolemmaAxolemma （轴膜）（轴膜） n nLysosomesLysosomes （溶酶体）（溶酶体） n nPinocytoticPinocytotic （胞饮的）（胞饮的） n nNeurotoxicNeurotoxic （神经毒素）（神经毒素） n nProtoplasmic (Protoplasmic (原浆原浆) ) nMicrotubulenRough granular endoplasmic reticulumnSmooth granular endoplasmic reticulumnMyelin sheath
