Now, the question is, what exactly causes the muscle, the heart, to actually contract in the first place? This is what we're going to focus on in this lecture. So it turns out that the heart itself is actually capable of generating an electrical signal. And as this electrical signal moves within the chambers of the heart, it causes those chambers to actually contract. So it's the electrical signal that moves to the heart that causes the heart to contract as a whole and pump all that blood through the blood vessels of our body. Now, recall that the autonomic nervous system is capable of regulating the rate at which the heart contracts.