The astrocytes are a type of glial cell that:
(a) are widely branched and ubiquitous in the brain and spinal cord;
(b) has a mechanically stabilising and protective function;
c) form the surface layer of the brain and spinal cord: membrana glia limitans external.
(d) ensures that the extracellular space has the correct composition of certain ions;
(e) dispose of released neurotransmitters;
f) reacts violently to damage to nerve tissue and forms protective scars that unfortunately complicate the growth/regeneration of damaged nerve fibers in the spinal cord and brain,
(g) together with the cerebral capillaries, astrocytes form the so-called blood-brain barrier, which prevents a number of blood-borne substances from entering the CNS tissue (e.g. penicillin, dopamine);
h) sends protrusions to the Ranvier nodes in white matter.
i) Recent research suggests that astrocytes may be directly involved in the brain's information processing and memory management.