Dr. Andy Galpin

Remember this.

We're going to come back to this later in the episode when we talk about

determinants of VO2 max, what to improve in some of these other numbers, and why that relates to your resting heart rate, your maximum heart rate, why that's not trainable, why there's no difference in maximum heart rate between highly fit people and unfit people, and things like that.

So the ability of your heart to fill back up with blood is critical.

So it's gotta contract, allow enough time for blood to fill back into the atria or ventricle, and then contract again.

So big, long, smooth contractions

Not a lot of plasticity in the tissue itself.

We want to hedge against having lots of fine motor control.

We want consistency over specificity here.

So another way to build on top of that is going back to what I said a second ago.

How does it produce a contraction independent of the nervous system?

I gave you the potentially a little bit crude example from the Indiana Jones movie.

But another way to think about this is how can my heart beat if I'm unconscious, right?

If I've got the brain turned offline.

Well, it will continue to do that because it has this intrinsic rate.

You've got four or what are called pacemakers in your heart.

The one I want to cover and talk about the most is the SA node.

So the senoatrial node, this is in the right atria.

And it controls, for the most part, your heart rate.

Now, you've got other ones like the AV node, Purkinje fibers, and bundles of his and things like that.