Why a nerve spike is always the same size: the all-or-nothing action potential
30seconds
Every nerve signal in your body is the same size. A feather touch and a hammer blow send identical electrical spikes, so how does the brain tell them apart?
Drive a live Hodgkin–Huxley neuron: zap it weakly and nothing is passed on, zap it past the threshold and it fires a full spike. Push harder and the spikes come faster, not taller. Then switch off the sodium channels, as pufferfish toxin does.
Deep dive · 4 min
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