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Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Nervous Tissue,ZHU YONG HONG(朱永红,Deparement of histology and embryology,1.Introduction,2.Neurons,(1).Classifications,(2).Structures,A.Cell Body,B.Processes:(Dendrites,Axon),3.Synapses,(1).Chemical synapses,(2).Electrical synapses,4.Glial Cells,5.Nerve Fiber Organization,(1).Nerve fibers:myelinated or unmyelinated fibers,(2).Nerves,6.Nerve Endings,(1).Sensory nerve endings,(2).Motor Endings(Myoneural junctions),Nervous Tissue,Cellular Elements,Neuron(Nerve Cell),Neuroglial Cells,central neurglia:,astrocyte,oligodendrocyte,microglia and ependymal cell,peripheral neuroglia:,Schwann cell in nerve and gaglion,satellite(capsular)cell,in ganglion,Intercellular Substance,:extremly sparse,2.Neuron,Two special properties:Irritability(the ability to respond to a stimulus).Propagation of impulses(the ability to conduct impulses).,Cell body/perikaryon(5-150,m dia),Axon(myelinated or unmyelinated)with terminals and synaptic junctions,Dendrites-receive input,Variety of neuron shapes:multipolar,bipolar,pseudounipolar,Morphology categories,Functional Categories,(1).Classifications,99%,of neurons are interneurons,Neurites:,Neurons can be classified by the number of neurites(axons and dendrites)that extend from the cell body.Cells can be,unipolar,bipolar,or,multipolar.,Dendrites:,Dendritic trees can vary widely between neurons.In the cerebral cortex,there are two types:,pyramidal cells,and,stellate cells,.Cells can also be classified by whether the dendrites have spines or not.Those that do are called,spiny,and those that dont are called,aspinous,.Pyramidal cells are spiny,while stellate cells can be spiny or aspinous,.,Connections:,Neurons can be classified based on their connections to different tissue types in the body.Neurons that have connections to sensory surfaces,such as the skin,are,primary sensory neurons,.Neurons that form synapses with muscles are,motorneurons,.However,most neurons form connections with other neurons-these are the,interneurons,.,Axon Length:,Neurons can be differentiated based on how long of an axon they have.Neurons with very,long,axons that extend from on area of the brain to another are the,Golgi Type I,while those with,short,local circuit axons are the,Golgi Type II,.,Neurotransmitter:,Aside from neuron morphology,neurons can also be classified based on their chemistry-the neurotransmitter(s)they release.For example,neurons that release acetylcholine are called,cholinergic,neuron.,Nucleus:large,euchromatic,prominent nucleolus,usually center of soma,Nissl,bodies:,clumps of RER,Golgi complex and mitochondria,Neurofilaments,and microtubules,Inclusions:melanin(rare),Cell membrane has specialized receptive areas,the,subsynaptic membranes,of synapses.,Perikaryon(Cell Body),In gray matter and ganglia,(2)Structures,Nissl bodies,:basophil,concentration of granular ER.In cell body and dendrites,Neurofilaments,:,a variety of intermediate filament-are bundle into neurofibrils visible after silver impregnations in the cytoplasm.,Skeleton and transportation,Dendrites,树突,May be highly branched and tapered,Contain mitochondria,microtubules,and granular ER.,Receptive surface for synaptic junctions,Tens of thousands of synapses on large dendrites,Dendritic spines树突棘 integrate the excitatory influences and modify their responses and morphology in learning,inputs from over 200,000 other cells,Purkinje cell of cerebellum,Axons,轴突,1,axon projects from cell body,long and thinner,Membrane is the axolemma轴膜,at its terminal/synapse which holds vesicles.,May or may not be myelinated around the axolemma,sometimes recurrent back to near the soma.,Has mitochondria,neurofilaments,microtubules,travelling vesicles,and,in some neurons,secretion droplets,in the axoplasm.,Can be meter long,Contains axoplasm flowing from the axon hillock轴丘.,The initial segments,the triggering of the action potential,retrograde transportation,anterograde transportation,Target,tissue,Axon transportation,3.Synapses(,Chemical,),突触,Synapses are specialized,axon terminal contacts to dendrites and cell bodies,and functionally polarized to transfer excitation one way.,In this image,used to quantify synapses,the proteins associated with synapses appear as blue and red dots.,Axodendritic synapse,Axosomatic synapse,Axoaxonic synapse,Structure of synapse,Types of synapse,LM:the axon terminal form bulbous swelling or terminal bouton.,cleft,receptors,1.,presynaptic element,presynaptic membranesynaptic vesicles,with neurotransmitter,e.g.,serotonin,acetylcholine,dopamine,etc.,dense projectionsynapsin Imitochondria,SER,microtubule,microfilament.,2.synaptic cleft 15-30nm,3.postsynaptic element,receptor,Action potentials travel down the axon of the neuron to its end,the axon terminal(synaptic knob),.,The synaptic knob opens Ca,2+,channels in the plasma membrane.,The influx of Ca,2+,triggers the exocytosis of some of the vesicles.,Their neurotransmit
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