How do nerves send signals through the body?

Nerve cells, or neurons, carry messages as electrical impulses called action potentials. These are created when charged particles, mainly sodium and potassium ions, rush in and out of the cell through its membrane, passing the impulse along the fibre like a wave. Many nerve fibres are wrapped in a fatty layer called myelin, which lets the signal jump along much faster. Signals travel at speeds from under 1 metre per second in thin, unmyelinated fibres to around 120 metres per second in the fastest ones. When an impulse reaches the end of a neuron, it triggers the release of neurotransmitters that cross a tiny gap, called a synapse, to activate the next cell.