Your nerves carry messages as tiny electrical spikes. A gentle poke does nothing — but past a certain strength, called the threshold, the nerve fires a full-size spike that zips all the way down. When it reaches the end, it jumps a small gap to the next nerve by squirting out chemicals. Turn up the dial in the simulator and fire one off.
Most people think a nerve signal is electricity flowing through a wire at light speed. In fact it is a wave of tiny gates flipping open and shut down the cell, each nudging the next, which is why it tops out around 120 metres per second yet never fades.
What's actually happening
People imagine nerve signals as electricity flowing through a copper wire, but that picture is wrong in a useful way. Real wire carries electricity at nearly the speed of light. Nerves are a million times slower, topping out around 120 metres per second in the best-insulated fibres. That is because a nerve signal is not current rushing along a cable; it is a wave of tiny gates flipping open and shut down the length of the cell, each one nudging the next. The signal rebuilds itself at every step, which is why it never fades out — it arrives at your fingertip exactly as strong as it left your spine.
The spike obeys a strict rule: all-or-nothing. A weak stimulus does nothing at all. But the moment it crosses a line called the threshold, the nerve fires a full-size spike, the same size every time, no matter how hard you pushed past the line. It is like a flush toilet, not a dimmer switch — either it goes, completely, or it does not. That is the trick the simulator above shows: dial the stimulus below threshold and you get a fizzle; nudge it over, and a clean wave races the whole length.
Then comes the hand-off. Neurons do not actually touch; there is a microscopic gap between them called the synapse. When the spike reaches the end, it cannot jump the gap electrically, so it switches to chemistry: it releases little packets of messenger molecules that drift across and land on the next cell, restarting the spike on the far side. Your fastest reflexes lean on this whole relay. A hand leaving a hot stove fires through a shortcut loop in your spinal cord, pulling back before the pain report has even reached your brain — the signal acts first and tells you about it later.
A nerve spike is all-or-nothing and rebuilds itself at every step, so it arrives at your fingertip exactly as strong as it left.
- 1Have a row of friends hold hands and close their eyes. The person at one end squeezes the next hand the instant they feel theirs squeezed.
- 2Start a stopwatch as you squeeze the first hand, and stop it when the last person calls out.
- 3Divide the time by the number of people: you have just measured the delay of human nerves plus brains, hand to hand, one spike at a time.
Common questions
No. Real wire carries current at nearly light speed, but a nerve signal tops out around 120 metres per second because it is a wave of gates opening down the cell rather than current rushing along a cable.
A weak poke does nothing at all, but the moment the stimulus crosses the threshold the nerve fires a full-size spike, the same size every time. It works like a flush toilet, not a dimmer switch.
Neurons do not touch; a tiny gap called the synapse separates them. The spike cannot jump it electrically, so it releases packets of messenger chemicals that drift across and restart the spike on the next cell.