The Action Potential

The animation to the left shows an idealized neuron. The red ovals represent Na+ ion channels and the green ovals represent K+ ion channels. You can start the movie and it will show an action potential (shown as a colored curve) move down the axon. When the sodium channels open during the depolarization (the red section of the action potential curve), the Na+ rushes in because both of the greater concentration of Na+ on the outside and the more positive voltage on the outside of the axon. When the Na+ channels close and the K+ channels open (the green section of the action potential curve), the K+ now leaves the axon due both to the greater concentration of K+ on the inside and the reversed voltage levels.

Thus, in many ways the action potential is not the movement of voltage or ions but the flow of these ion channels opening and closing moving down the axon. This movement of the ion channels explains why the action potential is slow relative to the normal flow of electricity. The normal flow electricity is the flow of electrons in an electrical field and electricity travels at the speed of light while these ion channels movment is considerably more slowly. These are mechanical movements and cannot move nearly at the speed of light.

Now proceed to a quiz to review this material.

Return to the beginning of the Neural tutorial quizes.
Return to Psychology contents.