What are some examples of action potentials?

The most famous example of action potentials are found as nerve impulses in nerve fibers to muscles.

Neurons, or nerve cells, are stimulated when the polarity across their plasma membrane changes. The polarity change, called an action potential, travels along the neuron until it reaches the end of the neuron.

If a depolarizing graded potential is sufficiently large, Na+ channels in the trigger zone open. In response, Na+ on the outside of the membrane becomes depolarized . If the stimulus is strong enough additional Na+ gates open, increasing the flow of Na+ even more, causing an action potential, or complete depolarization.

The retina sends information to the brain the same way. Taste receptors, hearing and balance, light touch, pain and temperature also send information to the brain.

Action potentials in the heart originate in specialized cardiac muscle cells called autorhythmic cells. These cells are self-excitable, able to generate an action potential without external stimulation by nerve cells. The autorhythmic cells serve as a pacemaker.