Nerve signals race through you at highway speeds
Wrap an axon in fatty insulation and its signals leap from a crawl to faster than a race car.
A nerve impulse is an electrical wave, and how fast it travels depends almost entirely on one thing: myelin, the fatty sheath that insulates many of your axons.
Unmyelinated fibres — the kind that carry dull, aching pain — creep along at around 0.5 to 2 metres per second, slower than a walking pace. Wrap that same fibre in myelin and the signal accelerates dramatically, with the fastest motor and sensory neurons reaching up to roughly 120 metres per second (about 430 km/h), and laboratory estimates running as high as 150 m/s.
The trick is saltatory conduction. Myelin leaves tiny bare gaps called nodes of Ranvier, and the impulse effectively jumps from node to node rather than oozing continuously down the membrane.
That speed boost is why you yank your hand off a hot stove before you consciously feel the burn — fast reflex fibres outrun the slow pain fibres.
Sources & references
2 referencesWell-established. Corroborated by 2 independent sources.
