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Chapter 7 Nervous tissue

Chapter 7 Nervous tissue. 1. General description: ---Components: nerve cell: neuron Glial cell: neuroglial ---Function: Neurons : receive the stimulation, conduct the nerve impulse Glial cell: support, protect and insulate, nourish neurons. 2. Neuron.

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Chapter 7 Nervous tissue

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  1. Chapter 7 Nervous tissue

  2. 1.General description: ---Components: • nerve cell: neuron • Glial cell: neuroglial ---Function: • Neurons : receive the stimulation, conduct the nerve impulse • Glial cell: support, protect and insulate, nourish neurons

  3. 2.Neuron The structural and functional cellular unit

  4. shape of neuron: consists of cell body, dendrite and axon ---cell body: spherical, pyramidal, fusiform or stellate in shape, 5um-150um ---dendrite: like branches of tree ---axon: long thin cord-liked

  5. 2) structure of neuron ①cell body: ---cell membrane: • unit membrane-irritability, receive stimuli, initiate and conduct nerve impulse • membrane proteins-ions channel and receptor ---cell nucleus: large and round, centrally- located, less heterochromatin, so pale stained, with a large, clear nucleolus

  6. ---cytoplasm: perikaryon a.Nissl body: LM: basophilic spot-liked or granule-liked structure EM: parallelly-arranged RER and free ribosome function: synthesis of proteins • structural protein • enzymes related to the production of neurotransmitters

  7. b.Neurofibril: LM: in silver impregnation methods(silver preparation), there are many thread-liked dark brown color structure to form a network.

  8. EM: • neurofilament: 10 nm in diameter • microtubule: 25 nm in diameter function: • supporting • involving in intracellular transportation

  9. c.other organelle • Golgi apparatus • mitochondria • pigment

  10. ②dendrite: ---many, short and more branches ---structure: similar to cell body ---dendritic spine ( places for formation of synapse) and spine apparatus (structure formed by 2-3 layers SER) ---function: receive the information

  11. ③axon: ---thin, less branch ---structure: no Nissl body, but have microtubule, neurofilament, microfilament, mitochondria, SER and vesicle • axon hillock: the beginning part of axon • axolemma • axoplasm ---function: initiate an impulse and conduct the impulse

  12. * axonal transports: • slow anterograde: cytoskeletal protein: microtubule, microfilament and neurofilament (0.1-0.4mm/d) • fast anterograde: synaptic vesicles, enzymes and proteins( 100-400mm/d) • fast retrograde: products of metabolism, intaking materials including protein or neurotrophic factors(100-400/d)

  13. 3) classification: ---According to number of processes • multipolar neuron • bipolar neuron • pseudounipolar neuron ---According to length of axon • Golgi type I neuron: long axon and large • Golgi type II neuron: short axon

  14. ---According to function • sensory neuron • motor neuron • interneuron ---According to the neurotransmitter or neuromodulator release by the neuron • cholinergic neuron • aminergic neuron • peptidergic neuron • aminoacidergic neuron

  15. 3. synapse

  16. ---definition: is the junctions between neurons or neuron and non-nerve cells ---classification: • chemical synapse: taking neurotransmitter as communicating medium • electrical synapse: gap junction

  17. ---structure of chemical synapse: LM: in silver preparation, there are many button-liked structures on the surface of dendrites and cell body, called synaptic button

  18. EM: /presynaptic element: axonal terminal • presynaptic membrane • synapse vesicle: -round or flattened, 40-60nm -clear or with electron dense core

  19. -contain neurotransmitters: acetylcholine, Ach norepinephrine, NE dopamine, DA -neuromodulator: peptides- change the reaction of neuron to neurotransmitter, modulate neurotransmitter substance P enkephalin vasoactive intestinal polypeptide, VIP

  20. there are synapsin I • mito, SER, microtubule and microfilament /synaptic cleft: 15-30nm /postsynaptic element: • --postsynaptic membrane • --receptors

  21. Classification of chemical synapse: /According to function: • excitatory synapse • inhibitory synapse

  22. /According to structure: • type I: postsynaptic membrane is thicker than presynaptic membrane, with wide synaptic cleft (excitatory synapse) • type II: there are less electron dense material attached on synaptic membrane, the thickness of postsynaptic membrane is same to presynaptic membrane (symmetrical synapse)

  23. 4. Glial cell (neuroglia)

  24. 1)Glial cell in CNS (central nervous system) a. Astrocyte: /large stellate /round or ovoid nucleus, large and pale (euchromatin) /gliafilament: intermediate filament /end feet: to form glia limitans or vascular feet-constitute blood brain barrier

  25. /classification fibrous astrocytes: • -white matter, have long, thin and smooth processes • -more glial filament- glial fibrillary acidic protein, GFAP

  26. protoplasmic astrocyte: • -gray matter, short, thick processes with more branch • -less glial filament

  27. /function: • ⅰ.supporting, insulating and repairing • ii. regulate the environment and movement of neuron • iii. secret neurotrophic factor: nerve growth factor (NGF), ciliary neurotrophic factor (CNTP) and glial cell line-derived neurotrophic factor (GDNF)

  28. b. Oligodendrocyte: ---structure: smaller, fewer process with a small round and dark stained Nucleus ---function: i. their processes form myelin-sheath of NF in CNS • ii. inhibit growth of processes of neuron (secrete inhibiting factor- NI-35,NI-250 myelin-associated glycoprotein)

  29. c. Microglia: ---structure: smallest, elongate shape or ovoid, with a small dark irregular nucleus ---function: phagocytosis-mononuclear phagocyte system

  30. d. Ependymal cell: ---structure: • simple cuboidal or columnar epi • apical: microvilli and cilia • basal: long processes-tanycyte ---function: • produce cerebrospinal fluid • nerve stem cell in or under ependyma ---distribution: ventricle of brain and central canal of spinal cord

  31. 2) glial cell in PNS ( peripheral nervous system) a. Schwann cell: /envelop the axon end to end to form myelin-sheath in PNS and /produce NGF, ciliary neurotrophic factor (CNTF) and BDNF (brain derived neurotrophic factor) b. Satellite cell (capsular cell): /one layer of flattened or cuboidal cell, with round, ovoid and dark N /surrounding the Neuron in ganglion

  32. 5. Nerve fiber and Nerve ---definition: a structure formed by axon and glial cell can conduct the impulse to certain direction ---classification: according to myelin-sheath • myelinated nerve fiber • unmyelinated nerve fiber

  33. 1) MNF ① MNF in PNS LM: • Axon • myelin-sheath: HE: net-liked; OsO4(osmium tetroside) fixation and stain: black with Schmidt-Lantermann incisure • neurilemma: cell membrane of Schwann and basement membrane * Ranvier node: narrow part, no myelin-sheath-saltatory conduction * internode: the segment of NF between two Ranvier nodes

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