Biology / Unit 13 Bio 3199 short lesson, about 20 seconds
Cardiac Cycle: Systole and Diastole
Captions available
The idea
The cardiac cycle alternates systole, when heart chambers contract and eject blood, with diastole, when chambers relax and refill, repeating continuously to maintain circulation.
In practice
Blood pressure readings report systolic pressure over diastolic pressure, capturing both phases of a single cycle.
Where people slip
Atria and ventricles do not contract simultaneously — atrial contraction slightly precedes ventricular contraction within each cycle.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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