The Speed of a Nerve Signal

Nerve conduction speed varies substantially among fibers. In the fastest large, myelinated human nerve fibers, it can reach about 120 m/s; thin or unmyelinated fibers conduct much more slowly. An electrical action potential propagates along the axon, and myelin speeds conduction. Between many neurons, signals cross a chemical synapse: one cell releases neurotransmitters that bind to receptors on the next cell. Electrical synapses also exist, so “usually chemical” applies to many, but not all, neural connections.