Neuron : Supporting cells : CNS : neuroglia (glia) PNS : Schwann cells and satellite cells
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Transcript of Neuron : Supporting cells : CNS : neuroglia (glia) PNS : Schwann cells and satellite cells
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• Neuron :• Supporting cells :
– CNS : neuroglia (glia)– PNS : Schwann cells and satellite cells– Functions :
• physical support• electrical insulation• metabolic exchange• blood-brain barrier
Composition of Nervous Tissue
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Types and Functions of GliaName of Glial
CellFunction
Astrocyte (Astroglia)
Star-shaped cells that provide physical and nutritional support for neurons: 1) clean up brain"debris"; 2) transport nutrients to neurons; 3) hold neurons in place; 4) digest parts of dead neurons; 5) regulate content of extracellular space
Microglia Like astrocytes, microglia digest parts of dead neurons.
Oligo-dendroglia
Provide the insulation (myelin) to neurons in the central nervous system.
Satellite Cells Physical support to neurons in the peripheral nervous system.
Schwann Cells Provide the insulation (myelin) to neurons in the peripheral nervous system.
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Neuroglia in the CNS
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• Able to replicate!• Importance in nervous system function is
VASTLY underestimated!• Evidence is mounting:
1. Nurturing role2. Signaling role (Memory?)3. Inflammation4. Pain5. Many more to come!
Neuroglia: Distinguishing Feature
s
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1. Presence of tight junctions between the endothelial cells2. One of the notable features of endothelial cells in compa
rison to other cell is the lack of pinocytic vesicles3. Selective permeability to molecules based on their mole
cular weight and lipid solubility4. Presence of specific markers
• Rich in two enzymes: gamma glutamyl transpeptidase (GGTP) (for amino acid transport) and alkaline phosphatase (transport of phsopahte ions) used as marker for BBB.
• Others: glucose transporter (GLUT-1); endothelial barrier antigen (EBA; unknown function) and antigen recognized by the MRC OX-47 monoclonal antibody (important for cell-to-cell adhesion); transferrin receptor (transport of ferric ions).
Properties of Blood Brain Barriers
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BBB
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1. Neurons have TWO "processes" called axons and dendrites. Glial cells only have ONE.
2. Neurons CAN generate action potentials. Glial cells CANNOT, however, do have a resting potential.
3. Neurons HAVE synapses that use neurotransmitters. Glial cells do NOT have chemical synapses.
4. Neurons do NOT continue to divide. Glial cells DO continue to divide.
5. There are many MORE (10-50 times more) glial cells in the brain compared to the number of neurons.
Glia are different from neurons:
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Nerve Cells
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Neurons, Glia, Extracellular Space, and Bloo
d
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Bidirectional Communication Partners in the CNS
• Receiving signals from neighboring neurons and responding to them with release of neuroactive substances
• Express receptors for almost all neurotransmitters and neuromodulators
• Increase of intracellular calcium concentration• Membrane depolarization in astrocytes are common
responses to neural activity• Metabolically coupled to neural activity
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Metabolism of Astrocytes and their Metabolic Cooperation with Neurons
• Glucose• Amino acid metabolism• Enzymes:
• glutamine synthetase(glutamate-glutamine cycle);• glycogen phosphorylatase (glycogen mobilization); • pyruvate carboxylase (anaplerotic synthesis of oxal
oacetate); • cysteine sulfinate decarboxylase (synthesis of tauri
ne); • glycine cleavage system, glycine metabolism.
•
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Three Types of Metabolic Cooperation of Astrocytes and
Neurons1. Supply of the energy substrate lactate t
o neurons2. The recycling of neuronal glutamate b
y the glutamate-glutamine cycle3. The supply by astrocytes of precursors
for neuronal glutathione (GSH) synthesis