• largest and most numerous neuroglia
• secrete chemicals vital to the maintenence of the blood brain barrier
• create a structural framework for CNS neurons and perform repairs in damaged neural tissues

• The plasma membrane at the tip of each process forms a thin, expanded pad that wraps around an axon in the CNS
• When wrapped around an axon myelin, which serves as electrical insulation and increases the speed that action potentials travel across the axon, is formed
• each oligodendrocyte coats small portions of several axons so many are needed to coat an entire axon

• least numerous and smallest of the neuroglial cells
• derived from white blood cells that migrated into the CNS
• perform protective functions such as engulfing cellular waste and pathogens

• line the central canal of the spinal cord and the ventricles of the brain
• in some regions of the brain they produce CSF and in others they help circulate CSF

1- Satellite cells: surround and support neuron cell bodies in the PNS

2- Schwanns cells: cover every axon outside the CNS but can only cover one segment of a single axon