Generating Nerve Signals

One of the big breakthroughs came from Charles Scott Sherrington, the man who in 1897gave the synapse its name. Sherrington revealed how the nerve system coordinates movement. Scientists were already familiar with simple reflexes, such as the knee jerk, in which a tap on the knee makes the leg jerk up automatically and uncontrollably long before the brain knows what's going on. Sherrington's genius was to realize that nerve impulses are coordinated to create muscle movements in such reflexes, and that this is part of the integrated way that nerves control the body.

Sherrington got the idea from watching a cat amble along a wall, then leap neatly over a gap to resume its stroll. How did it manage the amazing coordination to gauge the jump and land so effortlessly? Sherrington realized it works by playing off a mass of signals from two types of neuron, one which sends a signal that excites a reaction and the other a signal that inhibits it. Motor neurons, Sherrington realized, receive numerous excitors and inhibitors as data buzzes in from sense receptors - but only flash out a signal for a muscle to contract when excitement overpowers inhibition. The continual cross-feeding of excitors and inhibitors firing through nerves across the body ensures a wonderfully co-ordinated response without you even having to think about it - what Sherrington dubbed the 'integrative action of the nervous system.'

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