Spinal nerve. Coloured scanning electron micrograph (SEM) of a spinal nerve, which has been freezefractured to reveal the bundle of nerve fibres (axons, green and blue) inside. The axons are sheathed in myelin, a fatty insulating substance that increases the speed that nerve impulses are conducted. In the centre of the nerve is a blood vessel (purple) containing biconcave red blood cells. Magnification: 100x at 10cm across.
