The trillion glia (ten times as many as there are neurons) in the brain, busy multitaskers, come in several forms:
- Radial glia: serve as ladders or scaffolding in the embryonic brain
- Microglia: serve as the brain's immune system
- Schwann cells and Oligodendroctes: form insulating sleeves around neurons to keep their electric signals from diffusing.
(Zimmer, Carl. The Dark Matter of the Human Brain. Discover Presents the Brain. p 62-63. NY: Fall 2010.)