Pumping

They say that cells from the same heart beat independently of each other. And they beat in unison. Say you were to take a cardiac cell that is beating fast and place it in space, outside the heart. Then you take a cardiac cell from the same heart that beats a little slower and place it next to the first one. They will eventually sync up... usually taking up the faster beat. See.

What are your heart cells doing? Because my heart is beating really fast right now. (Must be the coffee.)