heart - systole/diastole on graph?

[smoutera]

Hello,
I was given an assignment to label the following graph with atrial systole, atrial diastole, ventricular systole and ventricular diastole. They are gram/sec graphs measured on frog heart. Can someone help me with it? I cannot decide whether it is starting with atrial or ventricular ones..
Thank you from now.

Whole Beat :


First Incline :


First Decline :


Second Incline :


Second Decline :



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