Glial cells outnumber neurons by a factor of ten (one neuron for every ten glial cells).

They were once thought to be inactive, or to serve as insulation. Modern science has revealed a variety of glial types and roles. We still know more about neural than glial function, but our understanding is improving.

Glia of the peripheral nervous system (PNS):

  1. Satellite cells aren’t well-understood; they surround cell bodies (somas) of neurons to create a healthy environment
  2. Shwann cells have two main functions
    1. Assistance in the disposal of cell waste
    2. Applying myelin to axons, increasing the speed of communication


Glia of the central nervous system (CNS)

  1. Ependyma
    1. Line the four ventricles in the brain, which are filled with cerebrospinal fluid
    2. Also participate in neuronal maintenance
  2. Ogliodendricytes are the CNS version of shwann cells, in that they myelinate axons
    1. But one ogliodendricyte can simultaneously work on many different neurons
  3. Microglia are the white blood cells of the brain
    1. Dispose of bacteria, pathogens, loose material, and waste
    2. Detect and direct the repair of damaged neurons
  4. Astrocytes play a large variety of roles.
    1. Facilitate healthy neurotransmission by wrapping around two neurons and increase efficiency, creating what’s called a tripartite synapse
    2. Provide glucose and other nutrients to neurons
    3. Bar harmful substances from the brain
    4. Remove waste
    5. Secrete chemical messengers
    6. Aid in the metabolism and construction of glutamate: the main excitatory neurotransmitter



Sources: Dr. Kevin Davis, Biopsychology,