How do our hearts beat 24/7 without needing to take a break/rest period?
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They actually take a few milli seconds of mini break in between beats. It’s a really really short break, it’s like a smol tiny power nap.
It’s because the heart is made of cardiomyocytes, not skeletal muscle.
In regular muscle, three things cause fatigue.
* Nerves get overstimulated making it harder for them to sustain a signal. So you need to push harder to make a muscle respond the same
* Muscles run out of fuel to meet the demands they need. Normally they taken in glucose to fuel oxidative phosphorylation and generate those muscle contractions. However, when a muscle is used too much, the ability of them to make energy from fuel is far lower than how much they need so they run out of fuel
* Muscles themselves get tired due to accumulation of things like lactic acid, impacting ability of Ca2+ and other critical components to work as well.
In cardiac muscle, these 3 things don’t really happen
* Cardiac muscle doesn’t have nerve innvervation. They rely on either themselves (cardiac muscle can beat themselves) or through their neighbors (which is how the wave of contractions in the heart occur).
* Muscles have more than 10x more energy production (mitochrondria), so doesn’t run out
* Cardiomyocytes can actually use lactic acid as well as other molecules as fuel to make energy, so those things are less likely to accumulate. If you overwork your muscle though, you can get acidosis but that occurs far after all your other muscles have tired out
They do rest, between every single beat, otherwise it would just be one long sustained contraction LOL
The heart is made of a different muscle configuration. The fibers arre smaller and tighter and far more interconnected than other muscles. This means that minor damage can be repaired and other fibers can simply bear the load and the muscle tears much less easily.
You can still overload a heart of course and obviously this is not recommended, but the key to your question is that heart muscles are simply configured differently and optimized for their role in a somewhat different way that sacrifices raw power for interconneced structures that allow minor damage to be easily repaired..
https://en.wikipedia.org/wiki/Cardiac_muscle
Got an echocardiogram yesterday and walked out pondering this exact question. Whoosh! Whoosh! Whoosh! Heart never gets a break.
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