How a Nerve Signal Travels

A neuron collects incoming signals through its branches, then fires one electrical pulse down its long fibre. The pulse leaps between gaps in the fatty sleeve and finally releases chemicals that carry the message to the next cell.

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In the picture

Dendrite — a branch of the cell body that receives signals from other neurons.
Cell body — adds up every incoming signal and fires only when the total crosses a threshold.
Myelin sheath — a fatty sleeve that insulates the axon so the charge stays inside it.
Node of Ranvier — the exposed gap where the pulse is rebuilt, so it leaps from gap to gap.
Axon terminal — the end bulb that releases neurotransmitters across the synapse to the next cell.

Examples

Touching a hot pan: the signal runs up your arm at over 100 metres per second, so your hand pulls back almost instantly.
The plastic coating on a charger cable does what myelin does — it keeps the current inside the wire.

Key takeaways

A signal always travels one way: dendrites → cell body → axon → terminals.
An action potential is all-or-nothing, and myelin makes it up to 100 times faster.