neuron, neurone


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neuron, neurone

The functional unit of the nervous system. A neurone is a single cell having a very long, fibre-like extension, called an axon, and one or many short extensions called dendrites. The axon may be 100,000 times as long as the diameter of the cell body-some are as long as 1 m. Nerve impulses are moving zones of electrical depolarization and these travel outwards along the axon from the cell body. Incoming impulses travel to the cell body along the dendrites. Neurones interconnect with each other at specialized junctions called SYNAPSES, situated mainly between the end of an axon of one neurone and the cell body or the dendrites of another. Many neurones receive as many as 15,000 synapses, some more. Most synapses are interneurones connecting with other nerve cells, rather than with muscles or glands.
Neuronclick for a larger image
Fig. 228 Neuron . A vertebrate motor nerve cell.

neuron, neurone

or

nerve cell

the structural unit of the nervous system, usually consisting of the cell body and cytoplasmic extensions. Long single extensions are known as AXONS and these carry impulses from the cell body to other nerve cells or effectors. Short multiple extensions known as DENDRITES receive impulses. Axons may be myelinated (with MYELIN SHEATHS) or nonmyelinated, but in the former the transmission of impulses is quicker as action potentials jump from one node of Ranvier to another.
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