The phrase "longest nerve" refers to the medical term for the largest nerve in the human body called the sciatic nerve. It runs all the way from the lower back, down through the buttocks, and into the legs. Full definition
Several hundred meters of silk are needed to bridge a 6 - cm - long nerve injury. (sciencedaily.com)
In an undamaged pathway, a type of brain cell called an oligodendrocyte produces myelin, an insulating substance that wraps around long nerve fibers called axons. (gladstone.org)
This differs from crustaceans where ganglia are further apart and connected by long nerves, like the rungs of a rope ladder. (sciencedaily.com)