Neurons

The signaling cells of the nervous system — the cells that carry information as electrical impulses. The body has tens of billions of them.

Structure

• Dendrites — branched receivers that collect incoming signals.
• Cell body — contains the nucleus; integrates the incoming signals.
• Axon — a long fiber that carries the outgoing impulse, sometimes over a meter.
• Synapses — the junctions where one neuron passes its signal to the next, usually via chemical messengers (neurotransmitters).

What it does

Receives, integrates, and transmits information; networks of neurons underlie sensation, movement, thought, and memory.

Key idea

A neuron signals in two ways at once — electrically along its own length, and chemically across the synapse to the next cell.