Chapter 7 Nervous tissue

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

6. 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

7. ---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

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

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

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

11. 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

12. 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

13. * 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)

15. 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

16. ---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

17. 3. synapse

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

19. ---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

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

21. -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

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

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

24. /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)

25. 4. Glial cell(neuroglia)

27. 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

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

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

30. /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-drived neurotrophic factor, GDNF

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

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

33. 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

34. 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, 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

35. 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

36. 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

37. EM: Schwann cell (neurilemmal cell) : Schwann cell →invagination and envelop the axon →form mesaxon → mesaxon become longer and longer →spiral around the fiber →to force the N and cytoplasm go to two side, inner and out edges connecting with incisure

39. ②MNF in CNS ---structure: • similar to in PNS • myelin-sheath formed by flattened ending of oligodendrocyte’s processes • one oligodendrocyte can envelop many axons • no incisure and basement membrane

40. 2) N-MNF ①N-MNF in PNS ---structure: • thin axon and Schwann cell connect end to end • no myelin-sheath and Ranvier node • one Schwann cell envelops more axons ②N-MNF in CNS * nothing to envelop the axon-naked axon

41. 3) Nerve ---Nerve fiber gets together to form nerve • efferent N • afferent N • mixed N ---structure: • epineurium: DCT • perineurium: -two layers: /outer layer- CT /inner layer-several layers of SSE- perineural epithelium(tight junction and basement membrane) • endoneurium: thin layer of LCT

42. 6. Nerve Ending

43. 1) Sensory nerve ending ---peripheral processes of pseudounipolar neuron + other structure to form sensory receptor ①free nerve ending ---structure: NF→lose myelin-sheath → branch → distribute in epidermis, cornea, hair follicle epithelial cell and CT ---function: feel cold, hot, pain and slight touch

44. ② Encapsulated N ending ---have CT capsule a. tactile corpuscle ---structure: • oval • CT capsule • flattened cell-transverse arranged • NF→lost myelin-sheath→spiral flattened cells ---distribution: dermal papillae, especially in tip of finger or toe, palms, soles and lips ---function: touch receptors

46. b. lamellar corpuscle ---structure: • large , oval or spherical • capsule: several layers of flattened cell concentrically-arranged • bulb- cylindrical • NF →lost MS→enter the bulb ---distribution: subcutaneous T, mesentery, ligament ---function: feel deep or heavy pressure

47. c.Muscular spindles ---structure: • fusiform • CT capsule • a few small muscle fibers- intrafusal muscle fiber • NF: roll up the muscle F ---distribution: skeletal muscle ---function: detect muscle length and change in muscle length

48. 2)Motor nerve ending: muscular T and gland ①Somatic MNE: motor end plate, neuromuscular junction

49. ---structure: EM • muscle F: rich in cytoplasm, nuclei and mito • presynaptic membrane: - synaptic vesicles- achtylcholine • synaptic cleft: • postsynaptic membrane: -synaptic gatter -junctional folds -type N receptor * motor unit: axon of one neuron and all skeletal muscle fiber controlled by it