Why does the heart-muscle never tire?

[LennoxLewis]

During high-school I've read an explanation for this, but unfortunately i forgot. I think heart muscle-tissue was built differently than normal muscles, but that begs the question... why are some often used muscles, like the thighs, not made the same way? Would it require too much energy or protein to sustain them? (that is of course, assuming the diet of a human living in the wild).

 

[somasimple]

Brain!
http://www.somasimple.com/pdf_files/spinal_supraspinal.pdf
http://www.somasimple.com/central_governor

 

[MATLABdude]

It's the only striated involuntary muscle in the body:
http://en.wikipedia.org/wiki/Heart
http://en.wikipedia.org/wiki/Muscle

 

[LennoxLewis]

It's the only striated involuntary muscle in the body:
http://en.wikipedia.org/wiki/Heart
http://en.wikipedia.org/wiki/Muscle

Thanks for the links, but could you explain why this kind of tissue is not being used by other often-used muscles?

 

[fluidistic]

I might be wrong, but I think some muscles in eyes/ears does not tire either. This would be much stranger than the heart if these muscles doesn't have any difference from common muscles (i.e. not like the heart).

 

[MATLABdude]

Thanks for the links, but could you explain why this kind of tissue is not being used by other often-used muscles?

They are! Striated muscles are your commonly-encountered skeletal muscles, except that these are usually under voluntary control (i.e. you can make your arm go up and down at will). Smooth muscle is used everywhere else to control valves, and make (non-heart) organs work, and are under involuntary control (i.e. you can't make your stomach not digest).

I think it's just that the heart can keep going all the time, because it's always supplied with fresh nutrients, and waste products are removed on a timely basis at your heart's usual level of exertion / beating (as opposed to your skeletal muscles, where lactic acid builds up and glycogen is burnt up when you work out strenuously, or do a moderate amount over a long duration).

 

[somasimple]

http://en.wikipedia.org/wiki/Catatonia

Catatonic patients will sometimes hold rigid poses for hours and will ignore any external stimuli.

The problem is that catatonic patients do not experience pain.
They may change their posture after many hours without a whisper.

 

[LennoxLewis]

They are! Striated muscles are your commonly-encountered skeletal muscles, except that these are usually under voluntary control (i.e. you can make your arm go up and down at will). Smooth muscle is used everywhere else to control valves, and make (non-heart) organs work, and are under involuntary control (i.e. you can't make your stomach not digest).

I think it's just that the heart can keep going all the time, because it's always supplied with fresh nutrients, and waste products are removed on a timely basis at your heart's usual level of exertion / beating (as opposed to your skeletal muscles, where lactic acid builds up and glycogen is burnt up when you work out strenuously, or do a moderate amount over a long duration).

So basically, what really distinguishes the heart muscles from most other ones is a constant abundance of oxygen as well as constant "maintenance" ?

 

[MATLABdude]

So basically, what really distinguishes the heart muscles from most other ones is a constant abundance of oxygen as well as constant "maintenance" ?

Pretty much. Why do our skeletal muscles get 'tired'? We build up too many waste products, run out of the energy stored in the cells (and deplete our glucose reserves), or aren't getting enough oxygen.

Well, that and a heart is capable of getting started / maintaining itself (until it runs out of fuel / oxygen).

 

[KingOfChaos]

The heart is also worked, constantly. As such, it doesn't get tired because of the work load it is used to maintaining 24/7.

 

[shredder666]

1. Simply because they're adapted to, myocardium is actually a separate category in the muscle groups in some textbooks.
2. If you look at the cardiac cycle, the heart is actually resting a bit longer than it's working
3. as for the waste product thing, my hypothesis is that when blood gets fresh oxygen from the lungs, it's first stop is the heart through the coronary arteries with its rich oxygen content and other resources, the heart gets plenty of "food" :D

Other muscles get sore after exercise simply because they produce acid faster than cells could metabolize them.