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Role of Astrocytes
Astrocytes (astroglia) are specialized glial cells. Their name comes from the greek words astron
(meaning star) and cyte (meaning cell), which is fitting as they have a unique, star-like shape. They
have two main types:
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the white matter of CNS is rich in “fibrous” astrocytes, while
the gray matter of CNS contains protoplasmic astrocytes
The cytoplasm of astrocytes contain special organelles, called gliofilaments, made glial fibrillary acidic
protein (GFAP).
Astrocytes are linked by gap junctions, and as a result, they are capable of generating a “Calcium wave”
as they use Ca2+ ions to communicate with/signal to each other.
Functions:
1) Like other neuroglia cells, astrocytes also provide structural support for neurons, usually by
filling the gaps that would exist between neurons. The GFAP also adds a bit more rigidity to
the cells, which makes astrocytes able to support other cells physically as well.
2) They provide metabolic support for neurons.
3) They, with their potassium pumps and channels, quickly regulate the amount of extracellular
potassium. The astrocytes absorb the unnecessary K+ ions to stop the information from going
through too many neurons. If, for example some genetic mutation makes the astrocytes
unable to do so, it often causes seizures.
4) Potassium is not the only thing astrocytes regulate, they also control the pH and Calcium
homeostasis of the extracellular space.
5) Astrocytes contain glycogen and they can also create it, then send it to the nearby neurons
when those have spent their own, as some kind of fuel tanks.
6) They also coordinate/promote the oligodendrocytes (an other type of neuroglia) when they
form the myelin sheath for the axons.
7) When the CNS tissue gets injured, astrocytes are the cells that with a process called astrogliosis
form the glial scars, repairing the damaged tissue as much as possible.
8) They interact with blood vessels and regulate the CNS blood flow.
9) They produce some neurosteroids (estradiol, progesterone) that can have synaptic effects, for
example on GABA receptors.
10) They supply glutamine to maintain glutamatergic neurotransmission.
11) The astrocytes’ end feet tightly surround the blood-brain barrier (BBB) and provide support in
the form of supplying sodium, glucose and amino acids to the endothelial cells.
Astrocytes are extremely important neuroglial cells that have a lot of functions and without them, the
neurons in our brain and spinal cord would not be able to operate properly. If there’s a problem with
the cells (like losing functions), serious illnesses appear, for example Epilepsy, schizophrenia or chronic
pain syndrome.
Sources:
Dr. Liposits Zsolt’s notes
Astrocytes: biology and pathology (Michael V. Sofroniew, Harry V. Vinters)
Essential protective roles of reactive astrocytes in traumatic brain injury (Dimitri M. Kullmann)
Role of Astrocytes in Epilepsy (Douglas A. Coulter, Christian Steinhauser)
Network Glia
Cells of the Central Nervous System
Blood-Brain Barrier