astrocyte

An astrocyte is a star-shaped support cell in the brain and spinal cord, named for the many thin arms that branch out from its body in every direction, like a child's drawing of a star. It is not a neuron (the cell that fires electrical signals), but one of the helper cells called glia, which means glue in Greek. The old idea was that these cells were just packing material holding neurons in place, but we now know astrocytes are busy caretakers, and they are so plentiful that they make up a large share of all the cells in your brain.

Their job is to keep the neighborhood around each neuron in good working order. With their many arms, astrocytes mop up spare potassium and other charged particles, called ions, that build up in the fluid around neurons after the neurons fire, so the next signal can travel cleanly. They also soak up leftover chemical messengers, called neurotransmitters, from the gaps between neurons once a message has been sent, then recycle them and hand the raw materials back. On top of this housekeeping, astrocytes feed neurons: they reach out to nearby blood vessels, take in sugar and other fuel from the blood, and pass energy along to the hard-working neurons next door.