Medical Assistant Prep / Unit 22 MAS 528 short lesson, about 20 seconds
The Heart's Natural Pacemaker
Captions available
The idea
The sinoatrial, or SA, node is the heart's natural pacemaker.
In practice
One reference gives its normal rate as sixty to one hundred beats a minute; another says it fires roughly seventy to eighty times a minute on its own, before nerves adjust the rate.
Where people slip
Rates outside the normal range are reported, not explained.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
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