神经组织--组织学和胚胎学课件

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1、nerve tissuenerve tissue1vCNS:consisting of the brain and the spinal cord;vPNS:consisting of nerves,ganglia(collection of nerve cell bodies)and specialized nerve endings.nervous systemCNS:consisting of the brain a2Composition of nerve tissuenervetissueneurons(nerve cells)supporting cellsIn the CNS:n

2、euroglia cell (glia cell)In the PNS:Schwann cell satellite cellComposition of nerve tissuener3Function of nerve tissuevNeuron:to receive stimuli and conduct electrical impulses.vSupporting cell:physical support(protection)for neuronal processes;electrical insulation for nerve cell body and processes

3、;metabolic exchange pathways between vascular system and neuron.Function of nerve tissueNeuron4neuron Neuron is the functional unit of the nerve system.It can receive stimuli and conduct electrical impulses.Structure of neuron Neuron is made up of cell body(soma or perikaryon),dendrite and axon.1.So

4、ma：where ribosomes,mitichondria,and other subcelluar parts do the metabolic work of cells Cell membrane:There are some ion-channels and receptors in it.Cytoplasm:Nissl bodies,neurofibrils,ribosomes,mitochondria,etc.Nucleus:central,large and round,lightly stained,with an obvious nucleolus.neuron Neur

5、on is the func5neuronneuron6Nissl body in the soma：Basophilic granules.Each Nissl body is made up of a stack of RER and functions in producing proteins.Nissl body in the soma：Basophi72.Dendrite：numerous tapering branches form the dendritic trees,which increase the receptor surface area of a neuron.T

6、here are Nissl bodies in the dendrites.Function:receiving stimuli and conducting them to the cell body.2.Dendrite：numerous tapering 8neuronneuron93.Axon:thin and long,similar in diameter.few branches.without Nissl bodies.Function as transmitting stimuli to other neurons or effector cells.Hillock:con

7、tinuous with the axon,the area of cell body where is free of large cytoplasmic organells:RER and so on.Axonal transport system：A mode of intercellular communication between cell body and the terminal of axon.Anterograde transport：from cell body to the terminal of axon（materials synthesized in the so

8、ma)Retrograde transport：(metabolic products and etc.)3.Axon:thin and long,simi10 neural structure neural structure11Axon HillockAxon Hillock12Axonal transport systemAxonal transport system13 The classification of neurons 1.Based on the number of its processes multipolar neuron：one axon and two or mo

9、re dendrites bipolar neurons：one axon and one dendrite.(limited to the retina and etc.)unipolar(pseudo-unipolar)neuron：one process,which divides close to the cell body into two long processes.The classification of14three types of neuronsthree types of neurons152.Based on the function of the neuronse

10、nsory neuron：convey impulses from receptors (unipolar)to CNS-afferent neuron.motor neuron：convey impulses from the CNS or (multipolar)ganglia to effector cells and control the activity of muscle and the secretion of the glands -efferent neuron.interneuron:form a communicating and integrating (multip

11、olar)network between sensory and motor neurons-intercalated neuron.2.Based on the function of the16 synapse synapse is some special cell junction between neurons or between neuron and its effector cell(muscle fiber or glandular cell).synapseelectrical synapsechemical synapsegap junction:two-directio

12、n transmission independent of neurotransmitters consists of presynaptic element,synaptic cleft and postsynaptic element;one-direction transmission mediated by neurotransmitters;synapse synapse is some spe17chemical synapse1.presynaptic element:bulb-like enlargements of the axon terminals which is ca

13、lled terminal button or synaptic bag.presynaptic membrane：presynaptic cell membrane with voltage sensitive calcium channels.synaptic vesicles：membrane bound vesicles which contain neurotransmitters.2.synaptic cleft：the space between the presynaptic and postsynaptic membranes.3.postsynaptic element：p

14、ostsynaptic cell membrane with chemical sensitive ion channels and receptors of the neurotransmitters.chemical synapse18synaptic bagsynaptic bag19synapsesynapse20the transmission of the nerve impulse Nerve impulse arrives at presynaptic cell membrane influx of the calcium ions through the presynapti

15、c membrane Synaptic vesicles pour the neurotransmitters into the synaptic cleft Neurotransmitters reach and bind onto corresponding receptors The postsynaptic membrane becomes depolarized.the transmission of the nerve 21神经组织-组织学和胚胎学课件22synapsesynapse23synapsesynapse24several morphological kinds of s

16、ynapsesvaxodendritic:occurring between axons and dendrites;vaxosomatic:occurring between axon and soma;vaxoaxonic:occurring between axon and axon;vdendrodentritic:occurring between dendrites and dendrites.several morphological kinds of25kinds of synapseskinds of synapses26supporting cellssupporting

17、cellsIn the PNS:Schwann cell satellite cellIn the CNS:neuroglia cell:astrocyte (glia cell)oligodendrocyte microglia ependymal cell nonconductive cells.function:insulate the neurons from each other,protect the neurons supporting cellssupporting cel27supporting cells in the PNS 1.Schwann cell 2.satell

18、ite cellsupporting cells in the PNS 28 1 Schwann cell and myelin sheath profile:flat sac in shape nucleus:flattened,stains darkly.function:surrounding the axon and constituting the neurilemma and myelin sheath.myelin sheath-forming cell in the PNS.1 Schwann cell and m29formation of myelin sheath mye

19、lin sheath:composed of multiple layers of Schwann cell membrane wrapped concentrically around the axon.vEach Schwann cell initially surrounds some part of an axon;vIt wraps a short segment of axon,forming multiple Schwann cell layers,and cytoplasm is squeezed out from between the membrane of the con

20、centric layers;vThe inner leaflets of the plasma membrane then fuse.formation of myelin sheath 30formation of myelinated axonformation of myelinated axon31神经组织-组织学和胚胎学课件32myelinated axonmyelinated axon33myelin sheathmyelin sheath34myelinated axon（SEM）myelinated axon（SEM）35longitudinal and cross sect

21、ions of myelin sheathlongitudinal and cross section36神经组织-组织学和胚胎学课件37myelinated axon:surrounded by myelin sheath unmyelinated axon:without myelin sheath in the PNSmyelinated axon:surrounded by38 (1)myelinated axon in the PNS and its myelin sheath The myelin sheath is segmented because it is formed b

22、y numerous Schwann cells arrayed sequentially along the axon.These breaks in myelination allow for saltatory conduction.neurilemma(the sheath of Schwann):It is part of Schwann cell which is external to,contiguous with,the myelin sheath.myelin sheath:composed of multiple layers of Schwann cell membra

23、ne wrapped concentrically around the axon.Ranvier node:The junction where two adjacent Scheann cells meet is devoid of myelin.This site is called Ranvier node.internode(internodal segment):the myelin between two sequential Ranvier nodes.It is composed of part of axon and its myelin sheath which is f

24、ormed by one Schwann cell.(1)myelinated axon in the39神经组织-组织学和胚胎学课件40 (2)Unmyelinated axon in the PNS The Schwann cells are elongated,and axons fit into the grooves in the surface of the cell.A single axon or a group of axons may be enclosed in the surface of one Schwann cell.(2)Unmyelinated axon41

25、2.satellite cell a layer of cuboidal or low columnar cells that surround the neuronal cell body of the ganglia.Function:providing electrical insulation and physical protection of the neuronal body.2.satel42satellite cellsatellite cell43satellite cellsatellite cell44supporting cells in the CNS 1.neur

26、on 2.oligodendrocyte 3.blood vessel 4.Axon 5.astrocyte 6.ependymal cell 7.microgliasupporting cells in the CNS 1.45 1.astrocyte(fibrous and protoplasmic)profile:largest,star-shaped glial cells of the CNS that have numerous processes.Many of these processes extend to blood vessels.The expanded ending

27、s of the astrocyte processes are known as end-feet.blood-brain-barrier:It is formed by tight junctions between endothelial cells,the end-feet function to induce and maintain the blood-brain barrier.supporting cells in the CNS 1.astrocyte(fibrous46end feet of astrocytes and BBBBBB:to restrict the mat

28、erial permeation between blood and brain.end feet of astrocytes and BBB47astrocyteastrocyte48astrocyteastrocyte49（1）fibrous astrocyte：more common in white matter.Fewer processes which are relative straight.（1）fibrous astrocyte：more comm50（2）protoplasmic astrocyte：more prevalent in gray matter They h

29、ave numerous,short,branching processes.（2）protoplasmic astrocyte：more51 2.oligodendrocyte Profile:smaller than astrocyte,processes are shorter and less than those of the astrocyte.Nucleus:smaller and stained darkly.Function:involved in the formation of the myelin sheath in the CNS.2.oligod52oligoden

30、drocyte and the myelin sheath in the CNSoligodendrocyte and the myel53(1)myelinated axon in the CNS 2.oligodendrocyte 4.Axon(1)myelinated axon in the CNS54(1)myelinated axon in the CNSvIn the CNS,myelin sheath is formed by oligodendrocytes.veach process of the oligodendrocytes can surround some part

31、 of one axon:Processes of one neuron can surround the axons of several neurons.(1)myelinated axon in the CNSI55 (2)The unmyelinated axon in the CNS The axon is thinner.Usually there is no glia surrounding it.(2)The unmyelinated a56 3.microgliaprofile:the smallest glia cell.round or thin and long in

32、shape.with fewer and shorter processes.nucleus:triangle in shape or looks like a pole.function:similar to that of macrophage.3.microgli57microgliamicroglia584.ependymal cell：column-shaped cells that line the ventricles of the brain and central canal of the spinal cord.it is an important part of the

33、barrier between the brain and cerebrospinal fluid.4.ependymal cell：column-shape59supporting cells in the CNSsupporting cells in the CNS60myelinated axonmyelinated axon61 axons in the PNS axons in the PNS62 nerve fiber and nervenerve fiber:It is composed of the axon with or without the myelin sheath.

34、Based on the presence of myelin sheath,nerve fibers are divided into two categories:myelinated nerve fiber and unmyelinated nerve fiber.nerve fiber and nervenerve f63 nerve nerve:a bundle of nerve fibers held together by the connective tissue(C.T.).epineurium：CT surrounding a nerve.perineurium：CT su

35、rrounding each nerve fiber fascicle.endoneurium：CT surrounding each individual nerve fiber.64 peripheral nerve epineuriumendoneurium perineurium peripheral 655.nerve endingsensory nerve ending the terminal part of the peripheral arborization of the sensory neuron.It can form kinds of sensory recepto

36、rs in the tissue or organ.1.free nerve ending 2.tactile corpuscle 3.lamellar corpuscle 4.muscle spindle5.nerve endingsensory nerve e66 1.Free nerve ending terminal branches of the myelinated sensory nerve fiber.It is devoid of myelin sheath.Distribution:between the cells of epidermis,corneal epithel

37、ium or in the C.T.of dermis and hair follicles,etc.Function:receptor of pain.67 2.tactile corpuscle(Meissners corpuscle)ellipse,free nerve endings with a capsule of C.T.Distribution:lie in the dermal papillae.Function:serving as touch receptors.2.tactile corpuscle(M68 3.lamellar corpuscle(Pacinian c

38、orpuscle)Distribution:mainly lying in deeper dermis and hypodermis,internal organs,etc.Function:deep pressure receptor for mechanic and vibratory pressure.3.lamellar 69Lamellar corpuscleLamellar corpuscleLamellar corpuscle70Lamellar corpuscleLamellar corpuscleLamellar corpuscle71 4.muscle spindleDis

39、tribution:lies in the skeletal muscle.Function:serve as a specialized stretch receptor within the skeletal muscle 4.mus72 motor nerve ending motor nerve ending:terminal branches of motor neuron distributing in muscle tissue and glands.one neuron can control many muscle fibers,while one muscle fiber

40、is controlled by only one neuron.motor unit：a neuron along with its specific muscle fibers that it innervates.motor end plate:the junction between motor nerve ending and skeletal muscle fibers.motor nerve 73motor end platemotor end plate74motor end platemotor end plate75神经组织-组织学和胚胎学课件76Key point1.Th

41、e composition of nerve tissue:neuron and supporting cells()2.basic structure of the neuron(soma,dendrite and axon)and the Nissl body3.Classification of the neuron4.Structure of the Chemical synapse5.Myelin sheath and myelin sheath-forming cells in the PNS and CNS;Myelinated axon and unmyelinated axon6.Nerve;the composition of sensory nerve endings and their function;motor unit;motor end plate.Key point1.The composition of77神经组织-组织学和胚胎学课件78