Axon or Nerve Fiber:

Axon or nerve fiber is a long slender nerve fiber (several times thinner than a human hair) that conducts electrical signals (triggered action potentials) to the nerve synapse (gap between neurons). The axon snakes away from the main part of the neuron cell body (soma) toward other neurons or other types of cells to affect them directly. Each axon typically has multiple branches coming off its main branch (axon collaterals), which then split into terminal branches. Depending on neuron type, axons vary greatly in length — from a millimeter to more than a meter (longest axons go from brain down spinal cord). They can make up 95% of a neuron’s total volume. A single axon can generate thousands of synaptic terminals and target many brain parts. Some are encased in fatty substance (myelin), acting as insulation and making brain white matter white.