Neurons consist of three elements: the cell body, axons, and dendrites. A signal is transmitted from neuron to neuron by an electrical force known as the action potential. The size of the signal is always the same; what varies is whether it's switched "on" or "off." When a cell body receives enough stimulation--for example, when you touch a very hot teapot--voltage-gated ion channels open on its surface to let charged particles (ions) into, and then out of, the cell. The flow of these particles causes the cell to generate an electrical discharge that is transmitted down the length of the axon to its end, or terminal.