Myelination. Coloured Scanning Electron Micrograph (SEM) of an oligodendrocyte cell (centre, orange) attaching to an axon nerve fibre (light green). This is the start of myelination in the central nervous system (CNS). Dendritic processes from the cytoplasm of oligodendrocyte cells give rise to spiral-wrapped layers of cytoplasmic membrane, which form myelin sheaths around nerve axons. A single oligodendrocyte may serve up to 50 axons. Myelination provides axons with support and insulation, allowing rapid impulse conduction. Oligodendrocytes belong to a group of cells called neuroglia, all the non-neural cells in the CNS. Magnification: x1,050 at 5x7cm size.