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. In this case, we have our action potential generated. And then somewhere in between, we have the initiation of the muscle contraction. So this is because before the muscle contraction actually takes place, we have to increase the concentration of our calcium ions inside the cytoplasm of that cell.