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Myelinated and non-myelinated nerve fibres. Coloured transmission electron micrograph (TEM) of a section through some myelinated and non- myelinated nerve fibres. The myelinated nerve fibres consist of a nerve cell axon (green), the output process of a nerve cell, covered in an insulating fatty layer called a myelin sheath (brown). Myelin helps the nerve to transmit its signals more quickly. It is produced by Schwann cells wrapping themselves around the axons. Non- myelinated axons (green) do not have this sheath. Nerves in the body collect, interpret and relay information. Magnification unknown. (KEYSTONE/SCIENCE PHOTO LIBRARY/STEVE GSCHMEISSNER)