The other cells of the nervous system, Glial cells , can be divided into macroglia and microglia . Microglia arise from macrophages and remove debris after cell injury or death. Macroglia can be divided into schwann cells , oligodendrocytes and astrocytes . Schwann cells create the myelin sheath around axons in the peripheral nervous system. Oligodendrocytes produce the myelin in the central nervous system.
Astrocytes contain many intermediate filaments suggesting they provide structural support .
Both schwann cells and oligodendrocytes can enclose many unmyelinated axons. However, Schwann cells differ from oligodendrocytes because schwann cells produce myelin for only one axon while oligodendrocytes can myelinate several axons. Astrocytes not only provide structural support but seem to buffer the synaptic cleft. Astrocytes have a high permeability for potassium ions and uptake mechanisms for certain neurotransmitters. The nodes of Ranvier are regions of the axons that are not covered by myelin and are responsible for the saltatory conduction.