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. So let's begin by taking a look at a cross section of the heart, as shown in this diagram. So we have the right side of the heart. We have the left side of the heart.