Medical Assistant Prep / Unit 4 MAS 080 short lesson, about 20 seconds
The Heart's Own Pacemaker
Captions available
The idea
The heart starts its own beat: the sinoatrial node fires rhythmic impulses without any signal from the brain.
In practice
Left alone, the node fires roughly seventy to eighty times a minute; the autonomic nerves then speed the rate up or slow it down to match the body's needs.
Where people slip
This electrical system is what an electrocardiogram records, the subject of units twenty-two and twenty-three.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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