Off the wall question for the Docs.

[pmanton]

The heart muscle does its thumpty thump thing 24-7. It never takes a rest. In my case it has been doing it for 83 years.

How does this muscle differ from the muscles in my arms and legs? Why do my arms and legs tire, but my heart does not?

Curious old fart wants to know.
Paul
Salome, AZ.

 

[whitepines]

Not a doc, but happen to know in this case it's the type of muscle that comprises the heart. There's more energy storage in each cell (more mitochondria), plus the muscle cells have specific features (T-tubles) to increase contraction efficiency. Basically it's "designed" to run 24/7 under that load without running out of energy and starting to build up lactic acid etc. like other muscles.

 

[Cervieres]

Cardiac muscle has more metabolic flexibility than skeletal muscle (it can change energy sources based on what’s available). Also, you have plenty of other non-cardiac muscles which are working more or less nonstop most of your life like your diaphragm and the muscles of your chest wall, neck, and trunk.

 

[WDD]

It does rest - between beats. Just like your diaphragm does which also runs 24 7.

 

[whitepines]

Cardiac muscle has more metabolic flexibility than skeletal muscle (it can change energy sources based on what’s available).

Neat, I didn't know that. What energy source can it use that normal muscle cannot?

 

[Cervieres]

Lipids, ketones and lactate. Skeletal muscle likes glucose and fatty acids. Cardiac muscle preferentially uses fatty acids followed by glucose, but can switch over to the others when times are bad.

The useless crap you remember from med school...

 

[steingar]

Cardiac muscle is actually constructed somewhat differently than skeletal muscles.

 

[lbfjrmd]

Cardiac muscle resists fatigue so well because it’s got more mitochondria than skeletal muscle. With so many power plants at its disposal, the heart doesn’t need to stop and chill out. It also has a steady supply of blood bringing it oxygen and nutrients.

 

[AggieMike88]

because it’s got more mitochondria

I’m waiting for someone’s spell check to try a Jedi mind trick and use “midichlorians”