And that's exactly why the essay node is commonly referred to as the natural pacemaker of the heart. It generates an action potential in the right atrium, which then moves into the left atrium and eventually into our two ventricles. So it triggers a set of electrical events within the heart that causes the heart to actually contract and pump all that blood through the blood vessels of our body. Now, the rate at which the SA node actually contracts varies from about 60 to 100 beats every single minute. And this is actually pretty high. So what the parasympathetic nervous system does is it uses the vagus nerve to actually decrease the rate at which the heart actually contracts.