Library · Physiology
Heart rate
Make it clearer
Heart rate is simply how many times the heart beats in a minute. From age ten on, at rest, the usual range is 60 to 100 beats per minute.
What sets the rhythm is the sinoatrial node, a small group of myocytes, that is, muscle cells of the heart, tucked into the upper wall of the right atrium, the chamber where blood returning from the body comes in. Those cells have something the others do not: they never rest. Ordinary heart cells sit still waiting for a signal; these depolarize on their own, meaning they take on an electrical charge by themselves, over and over. A metronome that takes no rest between beats: one has barely ended and the next has begun.
Working on top of that rhythm is the autonomic system, the part of the nervous system that runs without the person thinking about it. Its parasympathetic branch slows the production of action potentials, those electrical pulses, and the heart slows down. The sympathetic branch does the opposite and speeds it up.
In brief
Heart rate is the number of beats per minute; at rest, from age ten on, it is 60 to 100 beats per minute.
The sinoatrial node sets it: myocytes in the upper wall of the right atrium that, unlike the rest, have no resting phase and depolarize on their own.
A metronome that takes no rest between beats: one has barely ended and the next has begun.
The autonomic system adjusts it: parasympathetic input slows the production of action potentials and sympathetic input speeds it up.
Sources (2)
- MedlinePlus, U.S. National Library of MedicinePulse, MedlinePlus Medical EncyclopediaPublished
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Sinoatrial Node, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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