what is the correct sequence for cardiac cycle

Sequence 1: a. Atrial systole b. Ventricular systole c. Combined diastole

Sequence2 a. Atrial systole/Ventricular diastole b. Ventricular systole/atrial diastole c.Atrial systole/Ventricular diastole

In internet I found sequence 1 but however in my book sequence 2 is followed. So can anyone clear my doubt?

  • They're actually the same except that sequence 2 includes the beginning of the next heart beat as step C. It's just two ways of writing the same thing.
    – Carey Gregory
    Jul 9, 2021 at 14:16

1 Answer 1


They read very similarly to each other but I am sure they are viewing the cardiac cycle from different points.

2 is to explain atrium and ventricle are contracting alternatively(they are not in systole at the same time). 1 is to explain there are three distinct periods in the cardiac cycle: atrial systole, ventricular systole, both diastole.

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