When most people talk about brain cells, they're talking about neurons. There's another kind of cell in the brain, though, and they're known as glia (they're also called glial cells or neuroglia), and they're actually more numerous than neurons are. Glia aren't as sexy as neurons are--they don't seem to play major roles in the transmission of information--but they do play several vital roles. In the central nervous system, oligodendrocytes (spell THAT five times fast) create the myelin sheath that insulates axons. (In the peripheral nervous system, Schwann cells myelinate axons). Microglia help repair damage to the nervous system after a stroke or some similar event. Astrocytes make up the blood-brain barrier and also maintain homeostasis by helping to regulate the concentration of ions that play a role in the action potential. Radial glial cells help guide developing neurons into the proper locations. Thus, they're vital to brain function, even though you don't hear about them very much.
