Illustration showing the role of an oligodendrocyte in the myelination of nerve fibres (axons) in the central nervous system (CNS - the brain & spinal cord). Oligodendrocytes belong to a group of cells called neuroglia (nerve glue") which comprise all non-neural cells in the CNS. The dendritic processes from the cytoplasm of the oligodendrocyte give rise to the spiral-wrapped sandwich of cytoplasmic membrane that comprises the myelin sheath. A single oligodendrocyte may serve up to 50 nerve axons; 4 are visible here. Myelination effectively increases diameter of axon & hence velocity of impulse conduction."