Why the heart doesn’t get tired from being active 24/7 but other muscles do?
In: Biology
Heart muscles are almost entirely composed of contracting fibers and mitochondria so they can work tirelessly.
They do this by sacrificing storage space, they store no energy reserves and must be supplied with huge volumes of oxygenated blood continuously. That would be a problem way down in your toes, but it’s no trouble in your heart – unless something blocks the flow.
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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. – that’s what i found on google, not 100% sure
If you look at it closely, the heart is not working all the time.
The heart can be said to consist of four chambers, namely two atria and two ventricles. The two pairs of chambers work in such a way that either the atria or the ventricles or both get a rest at a given time:
Every single heartbeat includes three major stages: atrial systole, ventricular systole, and complete cardiac diastole.
Atrial systole is the contraction of the atria that causes ventricular filling.(The ventricles ate realxed here) Takes about 0.1seconds
Ventricular systole is the contraction of the ventricles in which blood is ejected into the pulmonary artery or aorta, depending on side.( The atria are relaxed here)Takes about 0.3 seconds
Complete cardiac diastole occurs after systole. The blood chambers of the heart relax and fill with blood once more, continuing the cycle.
(Both are relaxed during this point)Takes about 0.4 seconds.
So in a cardiac cycle of about 0.8s the
·Ventricles are resting for about 0.5s
·Atria are resting for about 0.7s
Some more info:
https://courses.lumenlearning.com/boundless-ap/chapter/physiology-of-the-heart/
The special nature of the heart muscles have been explained very well by the other comments, so I will refrain from talking about that.
So before we start any of this, there are different types of muscles.
* Cardiac muscle – muscle in the heart, also the one we are talking about here
* Striated Muscle – Muscle in biceps, triceps, abdominal region. This is what we go to the gym to work out.
* Smooth muscle – This is your stomach, intestines, and really most internal organs.
There are more but I’m not about to pull out my freshman year bio textbook.
Striated muscles are used all day when we are awake, these have to propel the body forward and do day to day tasks, your brain has to send out electric impulses to do these things and even though you may not think about it, you move these muscles consciously.
Cardiac and Smooth muscles however work on their own, there are parts of your brain (like I believe the stem) that are devoted to **involuntary actions** such as your heart beating, digesting food, blinking, and similar things.
Now you’re probably blinking voluntarily now so sorry, but that proves that **some** involuntary actions can be done **voluntarily**. Other ones like your heart beating are done fully involuntary.
Also the Cardiac Muscles are much more important than Striated Muscles. The energy from eating goes towards keeping your heart going first as it’s a lot more vital than your biceps.
Hope it wasn’t too much :p
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