Glia, glial cells, or neuroglia are synonymous terms for a class of nonneuronal cells in the nervous system (CNS)--astrocytes, oligodendrocytes, ependyma, and microglia--and two types in the peripheral nervous system--Schwann and satellite cells.  THe astrocytes provide structural support to neurons and are the major cell type in glial scar tissue in the CNS.  The oligodendrocytes are the myelin-forming cells of the CNS and also may perform a nurturing role for neurons.  Both astrocytes and oligodendrocytes are involved in phagocytosis. of the spinal cord.  The surfaces of ependymal cells have a more direct and critical role in neuronal activity than is currently believed.