So we have depolarization, then we have repolarization and we have hyperpolarization. And only then does our muscle contraction actually begin to take place. So with respect to our red curve, with respect to the muscle contraction, this section is known as the late 10th period because this is when our action potential is actually taking place. When the action potential is taking place, that basically leads to the sarcoplasm reticulum of the skeleton muscle cell to open up, open its calcium channels, and release the calcium ions into the cytoplasm of that cell. And that takes time. So, as the action potential is taking place, during this latent period of the muscle contraction, we basically have the increase in concentration of the calcium inside the cytoplasm.