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1、nerve tissue,CNS:consisting of the brain and the spinal cord;PNS:consisting of nerves,ganglia(collection of nerve cell bodies)and specialized nerve endings.,nervous system,Composition of nerve tissue,nervetissue,neurons(nerve cells)supporting cells,In the CNS:neuroglia cell(glia cell)In the PNS:Schw
2、ann cell satellite cell,Function of nerve tissue,Neuron:to receive stimuli and conduct electrical impulses.Supporting cell:physical support(protection)for neuronal processes;electrical insulation for nerve cell body and processes;metabolic exchange pathways between vascular system and neuron.,neuron
3、,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 membra
4、ne: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,Nissl body in the soma：Basophilic granules.Each Nissl body is made up of a stack of RER and functions in
5、 producing proteins.,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.,neuron,3.Axon:thin and long,similar in diameter.few branch
6、es.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 termin
7、al of axon.Anterograde transport：from cell body to the terminal of axon（materials synthesized in the soma)Retrograde transport：(metabolic products and etc.),neural structure,Axon Hillock,Axonal transport system,The classification of neurons 1.Based on the number of its processes multipolar neuron：on
8、e 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.,three types of neurons,2.Based on the function of the neuronsensory neuron：convey impul
9、ses 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
10、and motor neurons-intercalated neuron.,synapse,synapse is some special cell junction between neurons or between neuron and its effector cell(muscle fiber or glandular cell).,synapse,electrical synapsechemical synapse,gap junction:two-direction transmission independent of neurotransmitters consists o
11、f presynaptic element,synaptic cleft and postsynaptic element;one-direction transmission mediated by neurotransmitters;,chemical synapse1.presynaptic element:bulb-like enlargements of the axon terminals which is called terminal button or synaptic bag.presynaptic membrane：presynaptic cell membrane wi
12、th 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：postsynaptic cell membrane with chemical sensitive ion channels and receptors of the ne
13、urotransmitters.,synaptic bag,synapse,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 corres
14、ponding receptors The postsynaptic membrane becomes depolarized.,synapse,synapse,several morphological kinds of synapses,axodendritic:occurring between axons and dendrites;axosomatic:occurring between axon and soma;axoaxonic:occurring between axon and axon;dendrodentritic:occurring between dendrites
15、 and dendrites.,kinds of synapses,supporting cells,supporting cells,In 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 cells in t
16、he PNS,1.Schwann cell 2.satellite cell,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.,formation of myelin sheath,myelin sheath:composed o
17、f multiple layers of Schwann cell membrane wrapped concentrically around the axon.Each Schwann cell initially surrounds some part of an axon;It wraps a short segment of axon,forming multiple Schwann cell layers,and cytoplasm is squeezed out from between the membrane of the concentric layers;The inne
18、r leaflets of the plasma membrane then fuse.,formation of myelinated axon,myelinated axon,myelin sheath,myelinated axon（SEM）,longitudinal and cross sections of myelin sheath,myelinated axon:surrounded by myelin sheath unmyelinated axon:without myelin sheath,in the PNS,(1)myelinated axon in the PNS a
19、nd 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 myel
20、in 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 Ran
21、vier nodes.It is composed of part of axon and its myelin sheath which is formed by one Schwann cell.,(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 Schwa
22、nn cell.,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.,satellite cell,satellite cell,supporting cells in the CNS,1.neuron 2.oligodendrocyte 3.blood
23、vessel 4.Axon 5.astrocyte 6.ependymal cell 7.microglia,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-brai
24、n-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,end feet of astrocytes and BBB,BBB:to restrict the material permeation between blood and brain.,astrocyte,astrocyte,（1）fibrous astrocy
25、te：more common in white matter.Fewer processes which are relative straight.,（2）protoplasmic astrocyte：more prevalent in gray matter They have numerous,short,branching processes.,2.oligodendrocyte Profile:smaller than astrocyte,processes are shorter and less than those of the astrocyte.Nucleus:smalle
26、r and stained darkly.Function:involved in the formation of the myelin sheath in the CNS.,oligodendrocyte and the myelin sheath in the CNS,(1)myelinated axon in the CNS,2.oligodendrocyte 4.Axon,(1)myelinated axon in the CNS,In the CNS,myelin sheath is formed by oligodendrocytes.each process of the ol
27、igodendrocytes can surround some part of one axon:Processes of one neuron can surround the axons of several neurons.,(2)The unmyelinated axon in the CNS The axon is thinner.Usually there is no glia surrounding it.,3.microgliaprofile:the smallest glia cell.round or thin and long in shape.with fewer a
28、nd shorter processes.nucleus:triangle in shape or looks like a pole.function:similar to that of macrophage.,microglia,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 cerebrosp
29、inal fluid.,supporting cells in the CNS,myelinated axon,axons in the PNS,nerve fiber and nerve,nerve 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 fi
30、ber.,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.,peripheral nerve,epineurium,endoneurium,perineurium,5.nerve ending,sen
31、sory 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 spindle,1.Free nerve ending terminal branches of the myelinated sensory nerve f
32、iber.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.,2.tactile corpuscle(Meissners corpuscle)ellipse,free nerve endings with a capsule of C.T.Distribution:lie in the dermal papillae
33、.Function:serving as touch receptors.,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.,Lamellar corpuscle,Lamellar corpuscle,4.muscle spindleDistribution:lies in
34、the skeletal muscle.Function:serve as a specialized stretch receptor within the skeletal muscle,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
35、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 end plate,motor end plate,Key point,1.The composition of nerve tissue:neuron and supporting cells()2.basic structure of the ne
36、uron(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.,
