Nervous tissue 神经组织 Jun Zhou( 周俊 ) School of Medicine, Zhejiang University

Overview ---Components:  nerve cell: neuron  Glial cell: neuroglia ---Function:  Neurons : receive the stimulation, conduct the nerve impulse  Glial cell: support, protect and insulate, nourish neurons

neuron Synapse Nerve fiber ending neuroglial neuron

Neuron The structural and functional cellular unit

LM: ---cell body: spherical, pyramidal fusiform or stellate in shape, 5um- 150um ---dendrite （树突） ---axon （轴突）

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 pale stained, with a clear nucleolus

---cytoplasm: perikaryon a. Nissl body ( 尼氏体 ): LM: basophilic granule-liked structure EM: parallelly-arranged RER and free ribosome Function: synthesis proteins  structural protein  enzymes of neurotransmitters

b. Neurofibril ( 神经原纤维 ): silver impregnation methods (silver preparation) thread-liked dark brown color structure to form a network.

EM:  neurofilament: 10 nm in diameter  microtubule: 25 nm in diameter Function:  supporting  involving in intracellular transportation

c. other organelle  Golgi apparatus  mitochondria  pigment

② dendrite( 树突 ): many, short and more branches structure similar to cell body dendritic spine (synapse) and spine apparatus (structure formed by 2-3 layers SER) Function: receive the information

③ axon( 轴突 ): thin, less branch axon hillock( 轴丘 ): the beginning without Nissl body axolemma axoplasm ---Function: initiate an impulse and conduct the impulse

* 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 neurotropic factors ( mm/d)

3) classification: ---According to the 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

---According to function  sensory neuron  motor neuron  interneuron

--- According to the neurotransmitter or neuromodulator cholinergic neuron aminergic neuron peptidergic neuron aminoacidergic neuron

Synapse ( 突触 )

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

---structure of chemical synapse: LM in silver preparation on the surface of dendrites and cell body button-liked structures (synaptic button)

EM 1)presynaptic element: axonal terminal  presynaptic membrane  synapse vesicle: -round or flattened, 40-60nm -clear or with electron dense core 2)synaptic space: 15-30nm 3)postsynaptic element:  postsynaptic membrane  receptors

Glial cell (neuroglia) 神经胶质细胞

Glial cell in CNS Astrocyte ( 星形胶质细胞 )  fibrous astrocyte  protoplasmic astrocyte Oligodendrocyte ( 少突胶质细胞 ) Microglia ( 小胶质细胞 ) Ependymal cell ( 室管膜细胞 )

fibrous astrocytes -white matter, have long, thin and smooth processes -more glial filament- glial fibrillary acidic protein, GFAP protoplasmic astrocytes -gray matter, short, thick processes with more branch -less glial filament

Oligodendrocyte( 少突胶质细胞 ): smaller, fewer process form myelin-sheath of NF in CNS

Microglia( 小胶质细胞 ): smallest, elongate shape or ovoid, with a small dark irregular N phagocytosis- mononuclear phagocyte system ？

Ependymal cell ( 室管膜细胞 ):  simple cuboidal or columnar epi  apical: microvilli and cilia  basal: long processes ---Distribution: ventricle of brain and central canal of spinal cord

Glial cell in PNS a. Schwann cell: form myelin-sheath in PNS b. Satellite cell (capsular cell): surrounding the Neuron in ganglion

Nerve fiber and Nerve formed by axon and glial cell classification  myelinated nerve fiber ( 有髓神经纤维 )  unmyelinated nerve fiber ( 无髓神经纤维 )

LM:  Axon  myelin-sheath:  net-liked  OsO 4 (osmium tetroxide) fixation and stain  Schmidt-Lantermann incisure  neurilemma: cell membrane +basement membrane  Schwann cells (PNS)  Oligodendrocyte (CNS) Myelinated nerve fiber

Ranvier node ( 郎飞结 ): narrow part, no myelin- sheath- saltatory conduction Internode segment ( 结间体 ): the segment of NF between two Ranvier nodes

MNF in CNS  similar to that of PNS  oligodendrocyte  one oligodendrocyte can envelop many axons  no incisure and basement membrane

Unmyelinated nerve fiber thin axon and Schwann cell connect end to end no myelin-sheath and Ranvier node one Schwann cell envelops more axons naked axon (CNS)

Nerve ---Nerve fiber gets together Epineurium perineurium endoneurium

Blood brain barrier ( 血脑屏障 )  Endothelial cell of continuous Cap.  basement membrane  Foot processes of astrocytes

Nerve Ending

1.Free nerve ending ---function: feel cold, hot, pain and slight touch 2.Encapsulated N ending ---have CT capsule Meissner’s corpuscle (tactile) 触觉小体 : touch receptor Pacinian corpuscle(lamellar) 环层小体 : pressure receptor Muscle spindle ( 肌梭 ) : tension receptor Sensory nerve ending

tactile corpuscle Muscular spindles lamellar corpuscle

Somatic MNE: motor end plate ( neuromuscular junction) Visceral MNE Motor nerve ending

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