Another property of an excitable cell is its ability to conduct an action potential when adequately stimulated. An adequate stimulus is one that brings about a depolarization in a membrane that is sufficient to exceed the threshold potential of the membrane and thereby elicit an all-or-none action potential that travels in an unattenuated fashion at a constant velocity along the membrane of the excitable cellBecause of the steady resting potential, the cell membrane is said to be polarized.