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Neuron Neuron Neuroglia (glia)Neuroglia (glia)
PNS :PNS : Schwann cells Schwann cells
Satellite cellsSatellite cells
CNS :CNS :AstrocytesAstrocytes
OligodendrocytesOligodendrocytes
Microglial cells Microglial cells
Ependymal cells Ependymal cells
Composition of Nervous TissueComposition of Nervous Tissue
1. Neurons have1. Neurons have TWOTWO kinds of “processes” called axons kinds of “processes” called axons
and dendritesand dendrites ,, but Glial cells only havebut Glial cells only have ONEONE. .
CANNOTCANNOT. however, Glia do have a resting potential.. however, Glia do have a resting potential.
3. Neurons3. Neurons HAVEHAVE synapses that use neurotransmitters. synapses that use neurotransmitters.
Glial cells Glial cells DO NOTDO NOT have chemical synapses.have chemical synapses.
4. Neurons 4. Neurons DODO NOTNOT continue to divide. Glial cellscontinue to divide. Glial cells DODO
continue to divide. continue to divide.
Glia are different from neurons:Glia are different from neurons:
Importance of glial cells in nervous system Importance of glial cells in nervous system function is VASTLY underestimated!function is VASTLY underestimated!
Evidence is mounting: Evidence is mounting: 1.1. Nurturing roleNurturing role
2.2. Signaling role (Memory?)Signaling role (Memory?)
3.3. InflammationInflammation
4.4. PainPain
5.5. Many more to come!Many more to come!
There are two main kinds in PNS
Schwann cellsSchwann cells (雪旺细胞)(雪旺细胞)
Satellite cellsSatellite cells (卫星细胞)(卫星细胞)
Schwann cell
The Schwann cell making the myelin sheath (M) around the axon (A) was cut at the level of the nucleus (N). E - endoneurium. Scale = 300 nm. (Rat, trigeminal nerve.)
Most numerous cell type in brainMost numerous cell type in brainConstitute ~30-50% of brain volumeConstitute ~30-50% of brain volume
Some astrocytes develop processes with Some astrocytes develop processes with expanded expanded end-feetend-feet (终足)(终足) that are linked to that are linked to endothelial cells, or to ependymal cellsendothelial cells, or to ependymal cells ,, et al.et al.
Express GFAP-an intermediate filament protein Express GFAP-an intermediate filament protein
end-feet that are linked to endothelial cellsend-feet that are linked to endothelial cells
内皮细胞内皮细胞 基膜基膜 星形胶质细胞星形胶质细胞
BBBBBB
1. Presence of tight junctions between the
endothelial cells
2. One of the notable features of endothelial cells
in comparison to other cell is the lack of
pinocytic vesicles( 胞饮小泡 )
3. Selective permeability to molecules based on
their molecular weight and lipid solubility
Properties of Blood Brain BarriersProperties of Blood Brain Barriers
end-feet end-feet that are that are linked to linked to endothelial endothelial cells, or to cells, or to ependymal ependymal cells, or to cells, or to the pia the pia mattermatter
Astrocytes can absorb local excess of Astrocytes can absorb local excess of neurotransmitters, and release metabolic neurotransmitters, and release metabolic and neuroactive molecules. and neuroactive molecules.
Astrocytes can influence neuronal survival Astrocytes can influence neuronal survival and activity through their ability to and activity through their ability to regulate constituents of the extracellular regulate constituents of the extracellular environmentenvironment 。。
ASAS 参与维持中枢神经系统内环境稳参与维持中枢神经系统内环境稳定定
葡萄糖葡萄糖乳糖
酵解
normal disease
储存糖原
1. 参与葡萄糖代谢参与葡萄糖代谢
2. 参与脑内谷氨酸的代谢
Nature 411, 261 - 268 (2001)
AChBP as anAChR decoy
星形胶质细胞对突触的调节作用
Astrocytes
Astrocytes contact virtually every cell Astrocytes contact virtually every cell component in braincomponent in brain
Who are the stem cells of the adult brain?astrocytes vs. ependymal cells
astrocytes
Ependymal cells
Johansson et al., "Identification of a neural stem cell in the adult mammalian central nervous system," Cell, 96:25-34, 1999. Doetsch et al., "Subventricular zone astrocytes are neural stem cells in the adult mammalian brain," Cell, 97:703-16, 1999.
The subventricular zone
Dr Jonas Frisen contends that neural stem cells are cells that line ventricles
Dr Arturo Alvarez-Buylla contends neural stem are astrocytes that lie one layer in from ventricle lining;
Microglial cells ( 小胶质细胞)
microglia
Typical features of neuronophagia, a cluster of microglia around a necrotic neuron, are shown (HE, high power).
On the left side of the diagram, cells labeled "B1", "B2", and "B3" represent chronically activated microglial cells. "B3" is a markedly elongated cell, the nucleus in particular having a long, rod-shaped form. This rod cell is classically seen in general paresis (paretic neurosyphilis) but may also be seen in other chronic disease states of the brain.
Microglial activation
"Al" is a normal resting microglial cell. Under the stimulus of tissue necrosis, the resting microglial cell undergoes hypertrophy and hyperplasia, entering an intermediate phase often referred to as the "pleomorphic microglial response". Transitional forms in this pleomorphic microglial stage would include "A2a" and "A2b". It is important to remember that as soon as the resting microglial cell is activated it becomes an active mobile scavenger cell. If the necrosis is subtotal, the microglial cells may not be stimulated to evolve beyond this "pleomorphic" stage of response. If necrosis is complete, microglia proceed through further transitional forms, as shown on the diagram, to become rounded macrophages, "A6". The latter are also referred to as "compound granular corpuscles" or "gitter cells".