An action potential is defined as a abrupt spike of depolarization and re-polarization. This is a result of the opening/closing of ion channels that are found only in the axon. The cell is sitting at a resting potential of about -70 mV, when a stimulus occurs; this stimulus may be in the form of a electrical impulse, or a synapse with another neuron. Once the stimulus has occurred, the ion channels open, and the polarity of the cell changes; causing it to rise to a positive value of about 30 mV; this is depolarization. Once this occurs, the ion channels respond, and potassium is allowed into the cell, this causes the cellular polarity to drop, (re polarization) and finally, once it has past the resting potential, it will hyperpolarize to the resting potential. The action potential is what gives rise to synapses; and is the building block of learning and memory.
