How do our hearts beat 24/7 without needing to take a break/rest period?
In: 1
It doesn’t.
All the individual muscle fibers are essentially resting for over 2/3 of the cycle.
There are rest periods built into every beat cycle.
The atrial beat (“top half”of the heart) pushes blood down into the ventricles (“bottom half”).
When that finishes, the ventricular beat begins – a few things are all happening at the same time here:
1- ventricles start squeezing – pushing blood out to the lungs and body
2- the valve flaps get pressed to close by the pressure build up created by this squeeze, preventing backward flow to the atria
3- the atrial muscles are resting, allowing those chambers to refill
4- A very slight atrial vacuum is created while the muscle wall elasticity pulls the atrial walls back to filled and ready to pump position
As the ventricular pumping finishes, those chambers begin their rest period.
Now, for a short time NO muscle contraction is happening – both chamber sets are resting, filling slightly by passive drainage. There is detectable electrical activity as ions are passing across membranes, preparing for the next beat cycle to begin.
Next beat cycle starts – atrial beat begins, ventricles are still resting – refer back to the Atrial beat above, and repeat indefinitely.
If your question is more HOW this keeps working without conscious control – then the answer is that the process is controlled by a self-exciting bundle of nerve fibers referred to as the SA (sino-atrial) node, which begins the beat cycle directly. The atrial signal then stimulates the rest of the non-self excitory electro-conducive mediation of the beat cycle.
Latest Answers