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The heart's electrical conduction system
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The heart's electrical conduction system is the wiring that decides when the heart beats. Its starting point is the sinoatrial node, a cluster of cells within the heart muscle itself that works as the normal pacemaker: that is where the impulse starts before traveling through the heart and making it contract.
From the sinoatrial node the impulse passes down to the atrioventricular node, the next stop on the way to the ventricles. From there the bundle of His, a bridge of specialized muscle, picks it up and spreads it through its two branches, the right and the left, down to the ventricles, which therefore contract at the same time instead of each on its own.
The striking part is the start. The pacemaker cells of the sinus node never rest: as soon as one action potential ends they begin depolarizing on their own, that is, changing their electrical charge, to fire the next one. It is a relay race where the first runner takes off with no starting gun.
In brief
The heart's electrical conduction system carries the impulse from the sinoatrial node, its normal pacemaker, and makes the myocardium contract.
From the sinoatrial node it passes to the atrioventricular node, and the bundle of His carries it through the right and left bundle branches to the ventricles, which contract together.
The pacemaker cells of the sinus node have no resting phase: they begin depolarizing on their own as soon as the previous action potential ends.
It is a relay race where the first runner takes off with no starting gun.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Sinoatrial Node, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Bundle of His, StatPearlsPublished
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