And this is important in our heart, because the heart must actually create a single, forceful and steady muscle contraction. So that means we need to have this extended period to actually depolarize the adjacent muscle cells inside our heart. So in cardiac muscle cells, the action potential also causes the release of calcium ions into the cytoplasm of the cardiac myoside, the cardiac muscle cell. And this ultimately causes the contraction of the sarcombers and the contraction of the muscle as a whole. Now, in both cases, the muscle contraction takes place sometime after the action potential has been initiated, has been generated on the cell membrane. In this case, the muscle contraction takes place after the action potential took place.