This section here contains a collection, a bundle of specialized cells that together are known as the sinoatrial note, or simply the SA node. And it's the ACA node. It's the cells within the essay node that are responsible for initiating an action potential by depolarizing. So, as the cells depolarize within the essay node, they generate an impulse, an action potential that moves within the atria of our heart. And as it moves within the two atrium of the heart, it causes those atria to actually contract. So the essay node basically initiates its own action potential without the input of our autonomic nervous system.