AP PSYCHOLOGY

Detailed explanation-1: -The action potential is an explosion of electrical activity that is created by a depolarizing current. This means that some event (a stimulus) causes the resting potential to move toward 0 mV. When the depolarization reaches about-55 mV a neuron will fire an action potential. This is the threshold.

Detailed explanation-2: -When the intensity of the stimulus is increased, the size of the action potential does not become larger. Rather, the frequency or the number of action potentials increases.

Detailed explanation-3: -However, if the voltage increases past a critical threshold, typically 15 mV higher than the resting value, the sodium current dominates. This results in a runaway condition whereby the positive feedback from the sodium current activates even more sodium channels. Thus, the cell fires, producing an action potential.

Detailed explanation-4: -When a nerve impulse (which is how neurons communicate with one another) is sent out from a cell body, the sodium channels in the cell membrane open and the positive sodium cells surge into the cell. Once the cell reaches a certain threshold, an action potential will fire, sending the electrical signal down the axon.