Dr. Andy Galpin

You might accidentally contract other ones.

Not good.

Remember, we want high precision and control of movement and skeletal muscle.

With cardiac tissue, we just want it all to go.

And so the fact that we have these open gates through these intercalated discs and through these gap junctions that says, hey, if for some reason we struggle to get intervention or activation of an action potential,

As long as we get it into one of the cells, it'll be able to leak into the rest of them as well.

So in this case, we want to hedge guaranteed contraction over control.

Now, on a similar point, if you go to skeletal muscle,

It exists in what are called motor units.

So you might have several hundred to even many thousands of muscle fibers, all innervated or controlled by one basic nerve is the way to think about that.

Okay, this allows you again to upregulate how many of your muscle fibers in your muscle are contracting at a given time by turning on or off more total motor units.

the heart doesn't have any there's no motor unit in the heart we don't want to have the consequences of what if a nerve fails or is blocked or dies and now we can't contract those fibers and so in fact the heart is not dependent upon nervous system activation to contract

Now, I'll say that again.

The heart does not require any nervous system activation to contract.

And this explains exactly why you can do really awesome and interesting things like in the movie Indiana Jones, Temple of Doom, where the gentleman reaches into the guy's heart and he pulls it directly out of it and he stares at that man's heart that's in his hand and it still continues to beat.

This happens because, again, unlike skeletal muscle, which requires nervous system activation, the cardiac tissue does not.

It has its own intricate rate and can spontaneously produce the electricity needed to contract independent of the nervous system.

Now, that does not mean the nervous system does not have a role in your heart.

It absolutely does, and we're going to talk a lot about that.

In fact, it's incredibly important to understand that as a way to monitor global fatigue, readiness, performance, and overall nervous system activation.