1、nerve tissuevCNS: consisting of the brain and the spinal cord;vPNS: consisting of nerves,ganglia(collection of nerve cell bodies) and specialized nerve endings.nervous systemComposition of nerve tissuenervetissueneurons (nerve cells)supporting cellsIn the CNS: neuroglia cell (glia cell) In the PNS:
2、Schwann cell satellite cellFunction 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 neur
3、on. 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 c
4、ells 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.neuronNissl body in the soma：Basophilic granules. Each Nissl body is made up of a st
5、ack 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.neuron3. Axon: thin and long,
6、 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 communi
7、cation 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 structureAxon HillockAxonal transport system The classification of neurons 1.Based on the num
8、ber 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 neurons2.Based on the funct
9、ion 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 communicati
10、ng 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) .synapseelectrical synapsechemical synapsegap junction: two-direction
11、 transmission independent of neurotransmitters consists of 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 syn
12、aptic 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： postsynaptic cell membra
13、ne with chemical sensitive ion channels and receptors of the neurotransmitters.synaptic bagsynapsethe 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
14、 synaptic cleft Neurotransmitters reach and bind onto corresponding receptors The postsynaptic membrane becomes depolarized.synapsesynapseseveral morphological kinds of synapsesvaxodendritic: occurring between axons and dendrites;vaxosomatic: occurring between axon and soma;vaxoaxonic: occurring bet
15、ween axon and axon;vdendrodentritic: occurring between dendrites and dendrites. kinds of synapsessupporting cellssupporting cellsIn the PNS: Schwann cell satellite cellIn the CNS: neuroglia cell: astrocyte (glia cell) oligodendrocyte microglia ependymal cell nonconductive cells.function: insulate th
16、e 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-for
17、ming cell in the PNS.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
18、is squeezed out from between the membrane of the concentric layers;vThe inner leaflets of the plasma membrane then fuse.formation of myelinated axonmyelinated axonmyelin sheathmyelinated axon（SEM）longitudinal and cross sections of myelin sheathmyelinated axon: surrounded by myelin sheath unmyelinate
19、d axon: without myelin sheath in the PNS ( 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 Schwa
20、nn): 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
21、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. (2) Unmyelinated axon in the PNS The Schwann cells are elongated,and axons fit into the grooves in the surface of the
22、cell. A single axon or a group of axons may be enclosed in the surface of one Schwann 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. satellit
23、e cellsatellite cellsupporting cells in the CNS 1. neuron 2. oligodendrocyte 3. blood 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 bl
24、ood 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 CNSend feet of astrocytes and BBBBBB: to
25、 restrict the material permeation between blood and brain.astrocyteastrocyte（1）fibrous astrocyte：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:
26、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.oligodendrocyte and the myelin sheath in the CNS(1) myelinated axon in the CNS 2. oligodendrocyte 4. Axon(1)myeli
27、nated 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. (2)The unmyelinated axon in the CNS The axon is thinner. Usually there is no glia
28、surrounding it. 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.microglia4. ependymal cell：column-shaped cells that line the ventricles of the brain
29、and central canal of the spinal cord.it is an important part of the barrier between the brain and cerebrospinal fluid.supporting cells in the CNSmyelinated axon axons in the PNS nerve fiber and nervenerve fiber: It is composed of the axon with or without the myelin sheath. Based on the presence of m
30、yelin sheath, nerve fibers are divided into two categories: myelinated nerve fiber and unmyelinated nerve fiber. 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
31、 surrounding each individual nerve fiber. peripheral nerve epineuriumendoneurium perineurium5. 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 corpuscl
32、e 3.lamellar corpuscle 4.muscle spindle 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. 2.tactile cor
33、puscle(Meissners corpuscle) ellipse, free nerve endings with a capsule of C.T.Distribution: lie in the dermal papillae.Function: serving as touch receptors. 3. lamellar corpuscle (Pacinian corpuscle)Distribution: mainly lying in deeper dermis and hypodermis,internal organs,etc.Function: deep pressur
34、e receptor for mechanic and vibratory pressure.Lamellar corpuscleLamellar corpuscle 4. muscle spindleDistribution: lies in 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 distri
35、buting 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.
36、motor end platemotor end plateKey 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.
