Transcript NeuralCell-Glia.stud

Composition of Nervous Tissue
• Neuron :
• Supporting cells :
– CNS : neuroglia (glia)
– PNS : Schwann cells and satellite cells
– Functions :
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physical support
electrical insulation
metabolic exchange
blood-brain barrier
Types and Functions of Glia
Name of Glial
Cell
Astrocyte
(Astroglia)
Function
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.
Oligodendroglia
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.
Neuroglia
in the CNS
Neuroglia:
Distinguishing Features
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Able to replicate!
Importance in nervous system function is
VASTLY underestimated!
• Evidence is mounting:
1.
2.
3.
4.
5.
Nurturing role
Signaling role (Memory?)
Inflammation
Pain
Many more to come!
Properties of Blood Brain Barriers
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
3. Selective permeability to molecules based on their
molecular weight and lipid solubility
4. Presence of specific markers
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Rich in two enzymes: gamma glutamyl transpeptidase (GGTP)
(for amino acid transport) and alkaline phosphatase (transport of
phsopahte ions) used as marker for BBB.
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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).
BBB
Glia are different from neurons:
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.
Nerve Cells
Neurons, Glia,
Extracellular Space,
and Blood
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
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
oxaloacetate);
• cysteine sulfinate decarboxylase (synthesis of
taurine);
• glycine cleavage system, glycine metabolism.
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Three Types of Metabolic
Cooperation of Astrocytes and
Neurons
1. Supply of the energy substrate lactate
to neurons
2. The recycling of neuronal glutamate by
the glutamate-glutamine cycle
3. The supply by astrocytes of precursors
for neuronal glutathione (GSH)
synthesis