Now, what we're going to emphasize is in this lecture is the fact that an action potential is not the same thing as a muscle contraction. So oftentimes when students are learning about these two concepts, they forget that these two concepts are different, but they are connected. So an action potential is an electrical signal that is usually generated in the nervous system of our body. And that electrical signal travels to a particular muscle cell and it causes that particular muscle cell to basically contract. So although these two concepts are related, they are not the same thing. So let's begin by discussing the action potential and the muscle contraction of skeletal muscles.