 that isn't regulated by the brain. As you know, you can't control your heartbeat. You can control it to some extent by slowing it down, or if you're nervous, it speeds up, but you can't make it stop. You can't make your own heart stop. So it's not under your voluntary control. And all the cells in your heart beat in perfect synchrony thanks to these special ion channels called gap junctions, which are electrical synapses that don't have chemistry in them. It's just electricity, and that's what keeps your heart beating for your whole life.