NEURON

also called nerve cell basic cell of the nervous system in vertebrates and most invertebrates from the level of the cnidarians upward. It transmits nerve impulses. A typical neuron has a cell body containing a nucleus and two or more long fibres. Impulses are carried along one or many of these fibres, the dendrites, to the cell body; in higher nervous systems, only one fibre, the axon, carries the impulse away from the cell body. Bundles of fibres from neurons are held together by connective tissue and form nerves. Some neurons of large vertebrates are several feet long. A sensory neuron is a nerve cell that transmits impulses from a receptor such as those in the eye or ear to a more central location in the nervous system. A motor neuron is a nerve cell that transmits impulses from a central area of the nervous system to an effector such as a muscle.