- Axon
- A long fiber of a nerve cell (a neuron) that acts somewhat like a fiber-optic cable carrying outgoing (efferent) messages. The neuron sends electrical impulses from its cell body through the axon to target cells. Each nerve cell has one axon. An axon can be over 20 cm (a foot) in length, which for the human body is remarkably long.
* * *The single process of a nerve cell that under normal conditions conducts nervous impulses away from the cell body and its remaining processes (dendrites). It is a relatively even filamentous process varying in thickness from about 0.25 to more than 10 μm. In contrast to dendrites, which rarely exceed 1.5 mm in length, Axons can extend great distances from the parent cell body (some axons of the pyramidal tract are 40–50 cm long). Axons 0.5 μm thick or over are generally enveloped by a segmented myelin sheath provided by oligodendroglia cells (in brain and spinal cord) or Schwann cells (in peripheral nerves). Like dendrites and nerve cell bodies, Axons contain a large number of neurofibrils. With some exceptions, nerve cells synaptically transmit impulses to other nerve cells or to effector cells (muscle cells, gland cells) exclusively by way of the synaptic terminals of their a.. [G. a., axis]
* * *
ax·on 'ak-.sän also ax·one -.sōn n a usu. long and single nerve-cell process that usu. conducts impulses away from the cell body* * *
n.a nerve fibre: a single process extending from the cell body of a neurone and carrying nerve impulses away from it. An axon may be over a metre in length in certain neurones. In large nerves the axon has a sheath (neurilemma) made of myelin; this is interrupted at intervals by gaps called nodes of Ranvier, at which branches of the axon leave. An axon ends by dividing into several branches called telodendria, which make contact with other nerves or with muscle or gland membranes.* * *
ax·on (akґson) [Gr. axōn axle, axis] 1. the process of a neuron by which impulses travel away from the cell body; at the terminal arborization of the axon, the impulses are transmitted to other nerve cells or to effector organs. The larger axons are surrounded by a myelin sheath (see under sheath). Called also axone. See also neurofibra. 2. columna vertebralis. axonal adj
Medical dictionary. 2011.
