What powers a heartbeat?

Now, this is a really good one because basically it's the same energy that we use for all our metabolism. That's the energy created by eating fuel, metabolizing the food that we eat, turning into energy in the form of ATP within ourselves, it generates energy. But actually, the stuff that makes the heart beat is electrical impulses from our nerves and then the electrical impulses in the muscles and interestingly, you can take muscle cells out of the heart. You can grow them in the lab and they'll still beat within the lab because basically, you have this kind of feedback loop that just keeps on beating, but they get all out of rhythm and you need the nervous energy, the nerve impulses to get them all beating together.