Nerve signals are not particularly swift. Light travels at 300 million meters per second, while nerve signals move at a decidedly more stately 120 meters a second—about 2.5 million times slower. Still, 120 meters a second is nearly 270 miles an hour, quite fast enough over the space of a human frame to be effectively instantaneous in most circumstances. Even so, as an aid to responding quickly, we have reflexes, which means that the central nervous system can intercept a signal and act on it before passing it on to the brain. That’s why if you touch something very undesirable, your hand
...more
