A neuron typically has dendrites, a cell body, and an axon. Dendrites receive input, the cell body integrates signals, and the axon carries information to other cells. The axon may end in terminals that connect to a synapse.

Neurons can produce electrical signals because their membranes maintain differences in ion concentration. Ions are charged atoms or molecules, such as $Na^+$, $K^+$, $Ca^{2+}$, and $Cl^-$. These charge differences create a membrane potential, which is the electrical voltage across the cell membrane.

When a neuron receives enough input, it can fire an action potential, a brief electrical impulse that travels along the axon. This signal depends on the coordinated opening and closing of ion channels, which are proteins that let specific ions cross the membrane.