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

4. 2.       Neuron
The structural and functional cellular unit

5. 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

9. 2) structure of
neuron
①     cell 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

11. ---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

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

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

15. c.       other organelle
Golgi apparatus
mitochondria
pigment

16. ②     dendrite:
---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

19. ③    axon:
---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

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

22. 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

24. ---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

25. 3. synapse

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

27. ---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

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

30. -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

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

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

33. /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)

36. 4. Glial cell (neuroglia)

38. 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

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

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

42. /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)

43. 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)

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

45. 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

48. 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

49. 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

50. 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

53. EM: Schwann cell (neurilemmal cell) :
Schwann cell → 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

57. 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

59. 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

61. 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

62. 6. Nerve Ending

63. 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

64. 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

68. 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

69. 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

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

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