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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,nerve tissue,neurons (nerve cells) supporting cells,In the CNS: neuroglia cell (glia cell) In th
2、e PNS: Schwann 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
3、and neuron.,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 w
4、ork 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,Nissl body in the soma：Basophilic granules. Each Nissl body is made
5、up of a stack of RER and functions in 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: th
6、in 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 intercell
7、ular 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.),neural structure,Axon Hillock,Axonal transport system,The classification of neurons 1.Ba
8、sed 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.,three types of neurons,2.Ba
9、sed on the function of the neuron sensory 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 : f
10、orm a communicating and integrating (multipolar) network between sensory 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 synapse chemical synapse,gap ju
11、nction: two-direction transmission independent of neurotransmitters consists of presynaptic element, synaptic cleft and postsynaptic element; one-direction transmission mediated by neurotransmitters;,chemical synapse 1.presynaptic element: bulb-like enlargements of the axon terminals which is called
12、 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：
13、 postsynaptic cell membrane with chemical sensitive ion channels and receptors of the neurotransmitters.,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 th
14、e neurotransmitters into the synaptic cleft Neurotransmitters reach and bind onto corresponding receptors The postsynaptic membrane becomes depolarized.,synapse,synapse,several morphological kinds of synapses,axodendritic: occurring between axons and dendrites; axosomatic: occurring between axon and
15、 soma; axoaxonic: occurring between axon and axon; dendrodentritic: occurring between dendrites and dendrites.,kinds of synapses,supporting cells,supporting cells,In the PNS: Schwann cell satellite cell In the CNS: neuroglia cell: astrocyte (glia cell) oligodendrocyte microglia ependymal cell,noncon
16、ductive cells. function: insulate the neurons from each other, protect the neurons,supporting cells in the 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
