Dr. Andy Galpin

But those are really backup systems.

So in case the SA node fails, it'll go to the next one, go to the next one, and all the way down there.

So we've got various fail-safes that give us the ability to say, all right, if we have a problem, we're still going to get contraction.

Because remember...

All we've got to do is get one chunk to fire and it'll spread through those gap junctions and get everything else to contract in the appropriate fashion.

And so we want to have that in position.

This is also why if you have something like a heart attack and several of your tissue in your heart die, you can still survive because you can get contraction of everything else.

But it complicates the process, right, because we start to lose electrical impulse through the parts of the tissue that are dead.

Now, the SA node itself is actually a bit of a marvel.

You could sort of think about this and actually remember in school being told that we have no idea.

It's one of the modern mysteries of the world of how the essay note intrinsically develops its pace.

Well, that's not exactly true.

I think my teacher, they didn't know the answer or was just trying to hype me up a little bit.

We know a lot more about what controls.

In fact, there's a number of things that go into that.

It does have a little bit of wonder.

I don't want to steal that.

We don't know exactly how or why this thing beats the way it does, why it's similar between almost every human, and how it can just spontaneously create these action potentials.

It is regulated by a number of things, including various endocrine or paracrine hormones that are circulating in your system, blood pressure,

the strength of your contraction, the amount of blood that comes back into your heart called preload, and various other factors.