Expansion
Astrocytes, oligodendrocytes, microglia and ependyma centrally; Schwann cells peripherally
Expansion
Central nervous system
- Astrocytes: the most numerous. Structural support, blood-brain barrier induction via foot processes, potassium and neurotransmitter buffering, and gliosis (scarring) after injury. Marker: GFAP
- Oligodendrocytes: myelinate up to 50 axons each. Targeted in multiple sclerosis
- Microglia: the resident macrophages, of monocyte origin
- Ependymal cells: line the ventricles; specialised as choroid plexus to make cerebrospinal fluid
Peripheral nervous system
- Schwann cells: one cell per internode of a single axon. Targeted in Guillain-Barre syndrome. Also ensheath unmyelinated axons in Remak bundles
- Satellite cells: surround ganglion cell bodies
The one-to-many versus one-to-one difference explains a great deal: a single oligodendrocyte lesion affects many axons, and CNS myelin does not regenerate well, whereas peripheral nerve can regenerate along Schwann cell tubes at about 1 mm a day.
Gliosis replaces damaged CNS tissue, since there are no fibroblasts to form a collagenous scar, which is why CNS injury leaves a glial scar and a cystic cavity.