The cardiac cycle is a description of the mechanical activity of the heart as it pumps blood. The cardiac cycle has been neatly broken down into four (4) stages. In each case, the stage is named after what is going on in the ventricle, as the ventricle is the structure that ejects blood from the heart under high (or relatively high) pressure.
In understanding the cardiac cycle, you must never forget that blood will always flow from an area of high pressure towards an area of low pressure. You need to also understand the Physiologist's view of the heart. Below is a labeled diagram of the heart seen throught the eyes of a physiologist. Note, it is not anatomically correct.
Stages of the Cardiac Cycle
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