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nerve tissue1ppt课件vCNS:consisting of the brain and the spinal cord;vPNS:consisting of nerves,ganglia(collection of nerve cell bodies)and specialized nerve endings.nervous system2ppt课件Composition of nerve tissuenervetissueneurons(nerve cells)supporting cellsIn the CNS:neuroglia cell (glia cell)In the PNS:Schwann cell satellite cell3ppt课件Function 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;metabolic exchange pathways between vascular system and neuron.4ppt课件neuron 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.Soma：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.5ppt课件neuron6ppt课件Nissl body in the soma：Basophilic granules.Each Nissl body is made up of a stack of RER and functions in producing proteins.7ppt课件2.Dendrite：numerous tapering branches form the dendritic trees,which increase the receptor surface area of a neuron.There are Nissl bodies in the dendrites.Function:receiving stimuli and conducting them to the cell body.8ppt课件neuron9ppt课件3.Axon:thin and long,similar in diameter.few branches.without Nissl bodies.Function as transmitting stimuli to other neurons or effector cells.Hillock:continuous 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 soma)Retrograde transport：(metabolic products and etc.)10ppt课件 neural structure11ppt课件Axon Hillock12ppt课件Axonal transport system13ppt课件 The classification of neurons 1.Based on the number of its processes multipolar neuron：one axon and two or more 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.14ppt课件three types of neurons15ppt课件2.Based on the function of the neuronsensory 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 (multipolar)network between sensory and motor neurons-intercalated neuron.16ppt课件 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-direction transmission independent of neurotransmitters consists of presynaptic element,synaptic cleft and postsynaptic element;one-direction transmission mediated by neurotransmitters;17ppt课件18ppt课件synaptic bag19ppt课件synapse20ppt课件the transmission of the nerve impulse Nerve impulse arrives at presynaptic cell membrane influx of the calcium ions through the presynaptic membrane Synaptic vesicles pour the neurotransmitters into the synaptic cleft Neurotransmitters reach and bind onto corresponding receptors The postsynaptic membrane becomes depolarized.21ppt课件22ppt课件synapse23ppt课件synapse24ppt课件several morphological kinds of synapsesvaxodendritic:occurring between axons and dendrites;vaxosomatic:occurring between axon and soma;vaxoaxonic:occurring between axon and axon;vdendrodentritic:occurring between dendrites and dendrites.25ppt课件kinds of synapses26ppt课件supporting cellssupporting 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 27ppt课件supporting cells in the PNS 1.Schwann cell 2.satellite cell28ppt课件 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.29ppt课件formation of myelin sheath myelin 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 concentric layers;vThe inner leaflets of the plasma membrane then fuse.30ppt课件formation of myelinated axon31ppt课件32ppt课件myelinated axon33ppt课件myelin sheath34ppt课件myelinated axon（SEM）35ppt课件longitudinal and cross sections of myelin sheath36ppt课件37ppt课件myelinated axon:surrounded by myelin sheath unmyelinated axon:without myelin sheath in the PNS38ppt课件 (1)myelinated axon in the PNS and its myelin sheath The myelin sheath is segmented because it is formed by 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 membrane 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 formed by one Schwann cell.39ppt课件40ppt课件 (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.41ppt课件 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.42ppt课件satellite cell43ppt课件satellite cell44ppt课件supporting cells in the CNS 1.neuron 2.oligodendrocyte 3.blood vessel 4.Axon 5.astrocyte 6.ependymal cell 7.microglia45ppt课件 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 endings 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 CNS46ppt课件end feet of astrocytes and BBBBBB:to restrict the material permeation between blood and brain.47ppt课件astrocyte48ppt课件astrocyte49ppt课件（1）fibrous astrocyte：more common in white matter.Fewer processes which are relative straight.50ppt课件（2）protoplasmic astrocyte：more prevalent in gray matter They have numerous,short,branching processes.51ppt课件 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.52ppt课件oligodendrocyte and the myelin sheath in the CNS53ppt课件(1)myelinated axon in the CNS 2.oligodendrocyte 4.Axon54ppt课件(1)myelinated axon in the CNSvIn the CNS,myelin sheath is formed by oligodendrocytes.veach process of the oligodendrocytes can surround some part of one axon:Processes of one neuron can surround the axons of several neurons.55ppt课件 (2)The unmyelinated axon in the CNS The axon is thinner.Usually there is no glia surrounding it.56ppt课件 3.microgliaprofile:the smallest glia cell.round or thin and long in shape.with fewer and shorter processes.nucleus:triangle in shape or looks like a pole.function:similar to that of macrophage.57ppt课件microglia58ppt课件4.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 barrier between the brain and cerebrospinal fluid.59ppt课件supporting cells in the CNS60ppt课件myelinated axon61ppt课件 axons in the PNS62ppt课件 nerve fiber and nervenerve fiber:It is composed of the axon with or without the myelin sheath.Based on the presence of myelin sheath,nerve fibers are divided into two categories:myelinated nerve fiber and unmyelinated nerve fiber.63ppt课件 nerve nerve:a bundle of nerve fibers held together by the connective tissue(C.T.).epineurium：CT surrounding a nerve.perineurium：CT surrounding each nerve fiber fascicle.endoneurium：CT surrounding each individual nerve fiber.64ppt课件 peripheral nerve epineuriumendoneurium perineurium65ppt课件5.nerve endingsensory nerve ending the terminal part of the peripheral arborization of the sensory neuron.It can form kinds of sensory receptors in the tissue or organ.1.free nerve ending 2.tactile corpuscle 3.lamellar corpuscle 4.muscle spindle66ppt课件 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 epithelium or in the C.T.of dermis and hair follicles,etc.Function:receptor of pain.67ppt课件 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.68ppt课件 3.lamellar corpuscle(Pacinian corpuscle)Distribution:mainly lying in deeper dermis and hypodermis,internal organs,etc.Function:deep pressure receptor for mechanic and vibratory pressure.69ppt课件Lamellar corpuscleLamellar corpuscle70ppt课件Lamellar corpuscleLamellar corpuscle71ppt课件 4.muscle spindleDistribution:lies in the skeletal muscle.Function:serve as a specialized stretch receptor within the skeletal muscle72ppt课件 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 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.73ppt课件motor end plate74ppt课件motor end plate75ppt课件76ppt课件Key point1.The 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.77ppt课件78ppt课件
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