The beating heart

Maybe I'm just being obtuse. I know I'm being a pest, but I plead your indulgence. It is because my own heart's continued beating is not a foregone conclusion with the results a few weeks ago of a Holter Monitor test that I am so curious. I've been posing this question to doctors, Wikipedia, and anyone who did better in high school science than I did: "What makes the heart keep beating?" I figure everything is caused by something, right?

They respond in blasé fashion that the heart is an involuntary muscle. (It will keep beating if you take it out and put it in a bucket.) "The heart is made of specialized muscle capable of sustaining continuous beating." That sure looks like tautology to me: The heart pumps on its own because it pumps on its own.

More sophisticated responders tell me it's the sinoatrial (SA) node. Is it me, or does that explanation just push my query back one step? Now I have to ask, what makes the SA node work?

One children's text reads, "How does the heart beat? Before each beat your heart fills with blood. Then its muscle contracts to squirt the blood along. Your heart does this all day and all night. The heart is one hard worker!" Thanks a lot. You just tried to sneak past a description as an explanation.

I get it now. Nobody knows what keeps the heart beating 70 beats per minute uninterruptedly over 2.5 billion times a lifetime. But what is most curious is that they all seem satisfied that they have solved the mystery. I shall have to conclude that God is the one who keeps the heart beating.

Next question: What keeps the body temperature at 98 degrees? And don't tell me it's the internal thermostat.