We have seen that neurons send signals from one neuron to the next by releasing neurotransmitters that diffuse across the synaptic cleft and bind to receptors. In Chapter 9, we discussed that this is a general mechanism of cell communication: A signaling cell releases a chemical signal that binds to a receptor on a receiving cell. However, once the receptor has bound the neurotransmitter and is activated, in neurons the signal is not propagated by a chemical signal diffusing through the cell, which would be much too slow. Instead, as we have seen, neurons send signals electrically from one end of the cell to the other.

All neurons are electrically excitable cells that transmit information in the form of electrical signals. Nerve signals travel at high speeds, up to 200 m/s (450 mph). Although the speed of nerve signals is fast by biological standards, it is slow by comparison with the speed of electrical signals transmitted by a wire. In this section, we discuss the electrical properties of neurons and how signals are propagated along neurons. We also describe special features of some neurons that enable even faster signal transmission and more rapid responses by animals to environmental cues.