Astrocytes

The Astrocytes are irregularly shaped cells and many have long procedure that superficially resembles the dendrites of neurons. Astrocytes can be differentiating from neurons by their lack of Nissl bodies and by the existence of particular astrocyte marker molecules. The Astrocytes invest neurons and synapses leaving a gap of merely 20 nm across. They extend procedure, forming endfeet that butt onto capillaries or onto the pia mater to generate a layer covering the surface of peripheral nerves and CNS known as the glial membrane. The Astrocytes are coupled to each other via electrical synapses.

The Astrocytes have a large variety of functions:

1. controlling the local potassium concentration by eliminating K⁺ which accumulates in the extracellular space as a result of neural activity and dumping it, using their endfeet, into the capillaries.
2. Uptake or synthesis of the precursors for neurotransmitters glutamate and γ-aminobutyrate.
3. Terminating the actions of small transmitter molecules by eliminating them from the synaptic cleft.
4. Providing the neurons with metabolic energy. The Astrocytes take up glucose from blood and either store it as glycogen or convert it into lactate that is exported to neurons.
5. The Detoxification of ammonia (using the ornithine-arginine cycle), and of free radicals.
6. Regulating the blood-brain barrier.
7. Regulation of synapse arrangement in the developing brain and the production of new neurons in the adult brain.
8. Since radial glial cells they guide neurons to their appropriate destinations in the developing brain.
9. Gliotransmission: The astrocytes release transmitters under some conditions (example glutamate, adenosine) and may have a role in information processing, but are not excitable.