Nerves enable rapid communication among multiple parts of the body. Signals are initiated in sensory organs (e.g., eyes, nose, skin) or from pain-detecting dendrites called nociceptors. 

Nerve signals begin at the dendrite as an electrical impulse that travels the length of the neuron. These signals, also known as action potentials, occur when particles (ions) with opposite charges switch between inside and outside of the cell. The signal can only move toward the axon and may be incredibly fast. Some signals travel at rates up to 330 feet per second (100 meters per second).

After the signal reaches the axon end of the cell, it must cross a synapse, or space, between the neuron and another cell, such as a muscle fiber, gland or another neuron. Signals may cross the synapse through chemical or electrical signals. Electrical signals cross the synapse rapidly. Chemical signals use the messengers called neurotransmitters to cross the synapse to the next cell. Neurotransmitters allow for more variety in the nerve signal and a stronger reaction from the responding tissue.

There are many types of neurotransmitters. Some are present throughout the body and may perform multiple functions. Some neurotransmitters include acetylcholine, dopamine, norepinephrine and serotonin. Deficiencies or excesses of neurotransmitters contribute to many neurological and mental health conditions.