Astrocyte

function

metabolic support

Blood–brain barrier

Regulation of ion concentration in the extracellular space

types

Fibrous astrocytes (white matter)

radial glia (bipolar)

semi-radial glia (Bergmann glia)

Velate astrocytes

cerebellum

form a sheath surrounding granule neurones

each velate astrocyte enwraps a single granule neurone

Interlaminar astrocytes

Perivascular and marginal astrocytes

stem cells

control extracellular K+ homeostasis
(resting level of about 3 mM to a maximum of 10 - 12 mM )

remove excess glutamate (by excitatory amino acid transporters (EAAT))

Five types of EAATs are present in the human brain; the EAAT1 and EAAT2 are expressed almost exclusively in astrocytes (the rodent analogues are known as glutamate/aspartate transporter, GLAST, and glutamate transporter-1, GLT-1).

supply glutamine to maintain glutamatergic neurotransmission