One function of an astrocyte is to support cells that make up the blood-brain barrier, which keeps many toxins out of the brain. Astrocytes also help regulate the balance of ions outside of the cells, help nourish nerve cells and help the central nervous system heal after injury.
Astrocytes also insulate parts of nerve cells that lack a protective myelin sheath and help oligodendrocytes create myelin sheaths. Oligodendrocytes are types of glial cells. One function of glial cells is to create myelin sheaths.
Astrocytes, which are star-shaped, specialized types of glial cells, help give the brain its structure. They also store and produce glycogen, a sugar necessary for the proper functioning of the brain. This storage and production is focused primarily with the astrocytes in the hippocampus and frontal cortex of the brain. Astrocytes also supply lactate to the nerve cells.
The uptake and release of neurotransmitters are also regulated by astrocytes. These neurotransmitters include adenosine triphosphate, or ATP, glutamate, alanine, aspartate, glutamine and gamma-Aminobutyric acid, or GABA. Astrocytes also clear the spaces between the neurons of excess potassium, which the neurons release when they're excited.
Some scientists also believe that astrocytes play a role in memory and learning in the hippocampus, as well as in the modulation of blood vessels and blood flow.