Final answer:
The three basic characteristics of an action potential are depolarization, repolarization, and hyperpolarization, which occur after the neuron reaches the threshold potential.
Step-by-step explanation:
The three basic characteristics of all action potentials are depolarization, repolarization, and hyperpolarization. Initially, a stimulus causes the membrane to depolarize towards the threshold potential. If this threshold is reached, the neuron "fires" and causes a rapid influx of Na+ ions, leading to depolarization. This is followed by the opening of K+ channels and the exit of K+ ions, resulting in repolarization. Finally, the cell becomes hyperpolarized before the Na+/K+ pump helps to restore the resting potential.