How does the nervous system work?

A brain, a finger-thick cable down your back and nerves that reach your toes carry messages at up to 120 metres a second. The brain and spinal cord are the central nervous system. From them run 31 pairs of spinal nerves and 12 pairs of cranial nerves, joining into big nerves like the sciatic and the vagus.

Read how it works: How does the nervous system work? · The history of the nervous system · More boxes on Glassbox

Chapters in this interactive model

1. The wiring in every part of you: A brain, a cable down your back, and nerves that reach from your scalp to your toes.
2. A spark that runs down a wire: Salt, a battery in every cell, and a pulse that jumps from gap to gap.
3. Crossing the gap: Where one neuron talks to the next, or to a muscle, with a puff of chemicals.
4. Faster than thinking: A short cut through the spinal cord moves you before your brain knows why.
5. Fight or flight, rest and digest: Two sets of wires run your organs without asking you.
6. Protecting the wiring: Strokes, seizures, injuries, the diseases people fear, and the everyday things that help.