Nervous tissue神经组织

Jun Zhou( 周俊 )

School of Medicine, Zhejiang University

20140325

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 (0.1-0.4 mm/d)

fast anterograde synaptic vesicles, enzymes and

proteins( 100-400 mm/d) fast retrograde products of metabolism, intaking

materials including protein or neurotropic factors (100-300 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, GFAPprotoplasmic 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 OsO4(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 conductionInternode 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 endno myelin-sheath and Ranvier nodeone Schwann cell envelops more axonsnaked 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 touch2.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 corpuscleMuscular spindles lamellar corpuscle

Somatic MNE: motor end plate ( neuromuscular junction)Visceral MNE

Motor nerve ending

THE END