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1、第六篇 神经系统 Nervous system,Chapter 1 总论 Introduction,Human nervous system is most complex anatomical and physical system in body;it regulates and integrates activities of all bodily systems for benefit of organism as a whole;and makes balance of external and internal environments in body.基本要求 掌握神经系统的区分
2、和常用术语。了解神经系统的组成。,I.神经系统的区分 Divisions of Nervous System,中枢神经系统central nervous system(CNS),周围神经系统Peripheral nervous system(PNS),按相连部位,按分布区分,按功能区分,内脏神经的传出部分又称为自主神经系统或植物神经系统Autonomic nervous system(交感神经 Sympathetic n.&副交感神经Parasympathetic n.),感觉(传入)神经 Sensory(afferent)n.运动(传出)神经 Motor(efferent)n.,脑 Brai
3、n脊髓 Spinal cord,脑神经 Cranial n.(12 pairs)脊神经 Spinal n.(31 pairs),躯体神经 Somatic n.内脏神经 Visceral n.,Visceral sensory n.Visceral motor n.,II.神经系统的组成 Organization of Nervous Sys.Nervous system is composed of nervous tissue that consists of billions of nerve cells(neurons)and supported by a special variety
4、 of connective tissue known as neuroglia.I)神经元 Neuron are independent structural unit of nervous,system and are functional specialized for reception,integration,and transmission of coded information.1.Structure of neuron Each neuron possesses a nucleated 胞体 cell body,and two types of processes:an 轴突
5、 axon conducts impulse away from cell body,and one or more 树突 dendrites conduct impulses towards cell body.,Cell body serves as metabolic center of entire unit and consists of a large,pale nucleus and cytoplasm.Nucleolus occupies a prominent position in nucleus,which is rich in ribonucleic acid(RNA)
6、.,Organelles contained within cytoplasm are common to other cells in body,but there is abundant granular endoplasmic reticulum that constitutes Nissl body(Franz Nissl,German nuerologist,18601919),a protein synthesis apparatus.,神经元构造 Structure of neuron,2.Classification of neuron Neurons are classifi
7、ed according to their size,shape,function or by various other criteria.Structural classification depending on type and number of their processes:双极神经元 Bipolar neuron 假单极神经元 Pseudounipolar neuron(They has a central branch and a peripheral branch);多极神经,元 Multipolar neuron has an axon and two or more d
8、endrites.Functional classification:感觉神经元 Sensory(afferent)neuron 运动神经元 Motor(efferent)neuron 联络神经元Association 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 My
9、elinated fibers are surrounded by a myelin sheath and neurilemma.无髓纤维 Unmyelinated fibers are not,however,insulated by a myelin sheath.Oligodendrocytes form myelin in central nervous system while Schwann cells form myelin in peripheral nerves.,4.突触 Synapses Within nervous system impulses are conduct
10、ed 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.,These structural and functional areas of contact are termed synapses.Each synapse involves close
11、 apposition of a presynaptic element with a postsynaptic element from which it is separated by a synaptic cleft.,Presynaptic element contains numerous synaptic vesicles in which chemical substance neurotransmitter is present.When an impulse arrives at presynaptic element,neurotransmitter diffuses ac
12、ross synaptic cleft and binds to receptor molecules in postsynaptic membrane.As a result,postsynaptic neuron,is activated and impulse is conducted from one neuron to others.The“chemical synapse”involving release of transmitter substance is most common type in mammalian nervous sys.,II)神经胶质 Neuroglia
13、 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
14、 radiating processes,some of which end at nerve cells and others at capillaries.They are neuroectodermal in origin and may assist in transfer of nutrients and metabolic products between neurons and blood.,2.寡突胶质细胞 Oligodendrocytes are smaller and have fewer branching processes;they tend to lay in ro
15、ws 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,permeate entire central nervous system.They are modified macrophages an
16、d form part of reticulo-endothelial system and are probably mesodermal in origin.,III.反射与反射弧 Reflex and Reflex Arc Reflexes are automatic,subconscious responses to stimuli within or outside body.Reflex arc,a linkage of afferent and efferent neurons,is defined as entire neural pathway that is involve
17、d in a reflex.Reflex arc has 5 basic components:Receptor Sensory neurons CNS Moter neurons Effector,Interruption of this reflex arc at any point abolishes response.,Receptor,Effector,Centre,Efferent,Afferent,Reflex Arc,Int,Ext Environment,Higher Centre,Responses,IV.神经系统的常用术语 Basic terminology in ner
18、vous sys.In the CNS,灰质 Gray matter collection of nerve cell bodies and their dendrites,gray color during fresh condition.皮质 Cortex matter outermost layer of gray matter in cerebrum and cerebellum.白质 White matter collection of nerve fibers,white color during fresh condition.髓质 Medulla matter a centra
19、l core of white matter beneath cortex of cerebrum and cerebellum.,Neuroanatomical terms in common usage,神经核 Nucleus a collection(group)of cell bodies which have same shape and function.纤维束 Fasciculus(tract)a bundle of nerve fibers which have the same origin,termination,pathway and function.网状结构 Reti
20、cular formation an admixture of cross-crossing fibers with larger or smaller groups of nerve cells occupying the meshes.,In the PNS 神经节 Ganglion a collection of neuronal cell bodies outside the CNS.神经 Nerve a bundle of nerve fibers held together by connective tissue sheath.,Chapter 2 中枢神经系统 Central
21、Nervous Sys.Section 1 脊髓 Spinal Cord,基本要求 掌握脊髓的外形；脊髓灰质的分部、主要核团的名称、位置和功能；脊髓白质的分部，后索和外侧索通过纤维束的名称和功能。熟悉脊髓的位置；脊髓节与椎骨的对应关系；脊髓灰质的分层；前索通过的纤维束；脊髓的前角、后角、白质前连和半离断时出现的症状或体征。了解脊髓网状结构的位置；脊髓的功能。,Spinal cord is about 18 inches(40 45 cm)long,1/2 inch(14 mm)wide Lies in vertebral canal Continuous above with medulla
22、oblongata at level,of foramen magnum Ends below at lower border of L1 in adult;at birth at level of L3.It consists of centrally located gray matter,involved in reflexes,and peripherally located ascending and descending tracts of white matter that conduct impulses to and from brain.,I.脊髓的外形 External
23、features A long cylindrical structure and slightly flattened anteroposteriorly Two prominent enlargements can be seen,in a posterior view:颈膨大 Cervical enlargement is located between C3 and T2 vertebrae Nerves emerging from this region serve upper extremities;腰骶膨大 Lumbar enlargement lies between T9 a
24、nd T12 vertebrae Nerves from lumbar enlargement supply lower extremities.,Caudal to lumbosacral enlargement,spinal cord tapers gradually and becomes conical termination known as 脊髓圆锥 conus medullaris.A condensation of pia mater forms 终丝filum terminale that descends from conus medullaris to level of,
25、S2 vertebra;from here it is enveloped by dura mater and continues to posterior surface of coccyx.Some spinal roots surround film terminale and extends inferiorly referred to as 马尾 cauda equina,because they resemble a horses tail.,A longitudinal fissure and some sulci are shown on surface of naked sp
26、inal cord:前正中裂 Anterior median fissure on median line of anterior surface,where anterior spinal artery and companion vein are lodged.后正中沟 Posterior median sulcus On posterior surface.前外侧沟 Anterolateral sulcus anterior(motor)roots emerge serially.后外侧沟 Posterolateral sulcus posterior(sensory)roots,ent
27、er spinal cord,each bear a spinal ganglion which constitutes first cell-station of sensory nerves.,External features of spinal cord,脊髓节段与椎骨的对应关系 Relationship of segments of spinal cord to vertebrae A portion of the cord that gives rise to a pair of spinal nerve constitutes a segment.There are 31 seg
28、ments:8 cervical,12 thoracic,5 lumbar,5 sacral,and 1 coccygeal.Embryonic spinal cord develops more slowly than associated vertebral column;thus in adult,cord does not extend beyond L1.Spinal cord is markedly shorter than vertebral column,each spinal cord segment at lower levels is located above simi
29、larly numbered vertebral body.,Relationship of spinal cord with vertebral body in adults,II.脊髓的内部结构 Internal structures In cross-section spinal cord appears as a white oval with a gray,butterfly-shaped area in centre.White matter surrounds grey matter,and is composed of myelinated(sheathed)fibres,or
30、 axons;Gray matter consists of cell columns or horns and contains cell bodies,unsheathed motor-neuron fibres,and interneurons connecting either two sides of the cord or dorsal and ventral ganglia.,I)灰质 Gray matter Projections of gray matter within spinal cord are called horns or column,and named acc
31、ording to direction in which they project.前角(柱)Anterior horn(column)project anteriorly;后角(柱)Posterior horn(column)project,posteriorly;中间带 Intermediate zone lies between posterior and anterior horns,侧角(柱)Lateral horn(column)is a spike-like grey extension of intermediate zone,from T1 to L3 segments.,灰
32、质连合 Gray commissure transverse bar of gray matter that connects horns across center of spinal cord.中央管 Central canal,a longitudinal canal,traverses center of grey commissure.It continues superiorly with central canal of medulla oblongata.,Grey matter of spinal cord contains an enormous number of neu
33、rons of varying size and shape.Main nuclei of spinal cord are as follows:,1.后角 Posterior horn(column):1)后角边缘核 Nucleus posteromarginalis forms a thin layer of cells covering tip of posterior horn.These cells are found throughout cord and their axons pass into lateral funiculus,probably forming inters
34、egmental pathways.2)胶状质 Substantia gelatinosa forms outer cap-like portion,of head of posterior horn.They are presented at all spinal levels and may be excited by primary afferent fibers related to nociceptive stimuli.,3)后角固有核 Nucleus proprius is located deeply in substantia gelatinosa.Dendrites of
35、cells radiate into substantia gelatinosa where they make synaptic contact with primary afferent fibers.Axons of nucleus cross in anterior white commissure and contribute to spinothalamic tracts.4)胸核 Nucleus thoracicus is situated in medial portion of,base of posterior horn.It begins to be well defin
36、ed in C8L3 segments and receives collateral branches of primary afferent fibers.Axons contribute fibers to posterior spinocerebellar tracts.,2.中间带 Intermediate zone 1)中间内侧核 Intermediomedial nucleus receives collateral branches of posterior root fibers and gives rise to fibers that constitute spinoce
37、rebellar tract of both sides of spinal cord,regard sensation of viscera.2)中间外侧核 Intermediaolateral n.(lateral horn)lies in segments T1L3,containing sympathetic preganglionic neurons.,3)骶副交感核 Sacral parasympathetic nucleus lies in segments S2S4,containing parasympathetic preganglionic neurons.,3.前角An
38、terior horn(column)containing:1)Three kinds of neuron-motor neuron:larger multipolar neuron,innervates extrafusal fibers of skeletal m.,producing contraction of m.;-motor neuron:smaller neuron,innervates intrafusal fibers regulating muscular tonus;Renshaws cell:negative feedback mechanism.2)Two grou
39、ps of nuclei 内侧群 Medial nuclear group:,present in most segments of spinal cord,innervating axial m.外侧群Lateral nuclear group:present only in cervical and lumbosacral enlargements,innervating limb muscles.,4.板层 Rexeds lamina In cross section of spinal cord,based on neuronal size,shape,cytological feat
40、ures and density in different regions,ten laminae has been distinguished,which are arrayed more or less parallel with dorsal and ventral limits of grey matter and extend throughout most of length of spinal cord.Briefly,structure of laminae is as follows:Posterior horn is formed by lamina I to VI;Int
41、ermediate,zone corresponding to lamina VII;Anterior horn is composed laminae VIII and IX;Lamina X is gray matter surrounding central canal.,Important Subdivision of Spinal Cord Gray Matter,Important Subdivision of Spinal Cord Gray Matter,II)白质 White matter It surrounds grey matter,and is composed of
42、 myelinated and unmyelinated nerve fibers.It is usually divided into three pairs of funiculi.Each funiculus is composed of many tracts.前索anterior funiculus lies between the anterior median,fissure and anterolateral sulcus;外侧索 lateral funiculus lies between posterolateral sulcus and anterolateral sul
43、cus;,后索 posterior funiculus lies between posterolateral sulcus and posterior median septum.白质前连合Anterior white commisure is a bundle of transverse fibers,anterior to grey commissure.It is composed of crossing fibers arising from nerve cells or extending from nerve fibers of opposite side.,White matt
44、er contains three kinds of fibers:ascending,descending,and proprius tracts.1.上行纤维束 Ascending tracts carry sensory impulses from spinal cord to brain or suprasegmental structures.(1)薄束和楔束 fasciculus gracilis and cuneatus are large proportion of myelinated fibers of posterior root enter,ipsilateral po
45、sterior funiculus.Fibers arising from sacral,lumbar and lower eight thoracic segments make up fasciculus gracilis,while fibers arising from upper four thoracic and cervical segments make up fasciculus cuneatus.After reaching medulla oblongata,fasciculi gracilis and cuneatus,terminate upon nuclei gra
46、cilis and cuneatus respectively.These two tracts conduct discriminating tactile(ability to,recognize size,shape and texture of an object)and kinesthetic senses(sense of position and movement).,Lesion of posterior funiculus naturally abolishes or diminishes discriminating tactile and kinesthetic sens
47、es(sensory ataxia),and symptoms appear on same side as lesion.Tactile localization is poor,and two-point discrimination and vibratory sense are lost or diminished.,(2)脊髓小脑后束 posterior spinocerehellar tract is situated along posterolateral periphery of spinal cord.It arises from ipsilateral dorsal nu
48、cleus and ascends through spinal cord to medulla oblongata in which it becomes incorporated in inferior cerebellar peduncle.It conveys subconscious proprioceptive impulses to cerebellum.(3)脊髓小脑前束 anterior spinocerebellar tract is anterior to posterior one.Its fibers arise from intermediomedial nucle
49、us,cross spinal cord and ascend through medulla oblongata and pons,then enter cerebellum by coursing along sup.cerebellar peduncle.Its function is same as that of the posterior one.,(4)脊髓丘脑束spinothalamic tract includes lateral and anterior spinothalamic tracts.脊髓丘脑侧束 lateral spinothalamic tract Nucl
50、eus proprius receives fibers from dorsolateral fasciculus and gives rise to most of axons that cross in anterior white commissure and ascend in opposite lateral funiculus Ends directly in thalamus.,Unilateral lesion of this tract produces a complete loss of pain and thermal sense on opposite side of
