Axone

Axone is the French term for the nerve fiber that transmits electrical impulses away from a neuron's cell body. In English-language neuroscience, the term axon is used, but axone remains standard in French-language texts. The word derives from Greek axōn, meaning axis or axis-like projection.

Structure and location: An axon extends from the axon hillock and may be insulated by myelin sheaths formed by oligodendrocytes in the central nervous system or by Schwann cells in the peripheral nervous system. It terminates at axon terminals, where synapses connect with other neurons, muscle fibers, or glands. Along many axons are gaps called nodes of Ranvier, which facilitate rapid saltatory conduction of impulses. Axons vary widely in length and diameter, from fractions of a millimeter to more than a meter in some humans.

Function and transport: Axons carry action potentials from the neuron’s cell body to synapses. They rely on axonal transport to move proteins, organelles, and signaling molecules between the soma and distal terminals. This transport occurs in two main directions: anterograde (toward the synapse) and retrograde (toward the cell body), powered by motor proteins such as kinesin and dynein along microtubules.

Clinical and developmental context: Axon development and maintenance depend on cytoskeletal dynamics and proper myelination. Axonal injury or degeneration can cause sensory and motor deficits. Many neuropathies involve axonal dysfunction or loss, and conditions such as Wallerian degeneration describe the process after injury.

See also: Neuron, Axon hillock, Dendrite, Myelin, Nodes of Ranvier, Synapse, Neuronal transport.