Figure 2.

Illustration of glial cells and their function in the healthy nervous system. (A) The peripheral nervous system consists of Schwann cells (blue) that myelinate the axons of peripheral neurons (green). (B) The central nervous system consists of astrocytes (yellow) that regulate synaptic connections and comprise the blood–brain barrier, oligodendrocytes (blue) that myelinate axons of neurons, and microglia (purple), which act as resident innate immune cells.