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What is the pacemaker of the heart?In: Human Anatomy |
Answer
The pacemaker of the heart is a bundle of cells that tells the heart when to beat. These cells are connected to the rest of the cells of the heart and communicate with them through electrical signals. The pacemaker cells set the pace (or rate) of the heartbeat.
The actual structure that serves as the heart's primary pacemaker is called the sinoatrial node (SA node). As described above, the SA node is a little bundle of cells located in the wall of the right atrium, the small upper chamber on the right side of the heart.
What if the SA node is knocked out for some reason? There are actually other regions of the heart that can act as pacemakers. These regions are known as latent pacemakers and include the atrioventricular node (AV node) and other cells that make up the electrical communication system of the heart (including special cells that make up the so-called Purkinje fibers of the heart). Even the cells that make up the large ventricles of the heart can set the pace of the heart.
Interestingly, each of the pacemakers described above has a different inherent rate that it "wants" the heart to beat at. For example, the SA node gets excited spontaneously at a rate of about 100 per minute. Some of the latent pacemakers might spontaneously get excited at a rate of 65 per minute or 45 per minute.
If that's the case, then wouldn't the heart just beat chaotically? How is it possible that the heart beats in a regular way with all of these different pacemakers lying around?
The reason is that under normal circumstances, only the SA node is active; all of the other latent pacemakers are basically inactive. Now, should the SA node fail, the AV node can take over. Likewise, if the AV node fails, cells that make up the Purkinje fibers can take over. And if even they fail, then the ventricular cells can take over as a last resort. There's lots of redundancy for this all-important organ.
Another type of pacemaker is the type that gets implanted by physicians. In patients with abnormal heart rates or rhythms, an artificial pacemaker can be implanted. These pacemakers serve the same purpose as the natural pacemakers of the heart: they control the regular rate and rhythm of the heart.
First answer by Diberri. Last edit by Diberri. Contributor trust: 119 [recommend contributor]. Question popularity: 22 [recommend question]
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