Neuroglia (glia) are cells that support and protect neurons. The following four neuroglia are found in the CNS:

  • Astrocytes have numerous processes that give the cell a star‐shaped appearance. Astrocytes maintain the ion balance around neurons and control the exchange of materials between blood vessels and neurons.
  • Oligodendrocytes have fewer processes than astrocytes. They wrap these cytoplasmic processes around neurons to create an insulating barrier called a myelin sheath.
  • Microglia are phagocytic macrophages that provide a protective function by engulfing microorganisms and cellular debris.
  • Ependymal cells line the fluid‐filled cavities of the brain and spinal cord. Many are ciliated.

Two kinds of neuroglia are found in PNS:

  • Schwann cells (neurolemmocytes) wrap around axons to produce an insulating myelin sheath. Schwann cells provide the same function in the PNS as oligodendrocytes provide in the CNS.
  • Satellite cells are located in ganglia, where they surround the cell bodies of neurons.