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. But, and this is an important but even though the autonomic nervous system regulates the beat of the heart, it doesn't initiate that beat. So recall that cardiac muscle cells exhibit myogenic activity. And what myogenic activity means is our cardiac muscle cells are actually capable of generating their own electrical signal on their own accord without the input of our nervous system.