File:Heart function.jpg

Summary
Figure 11.21 In each cardiac cycle, a series of contractions (systoles) and relaxations (diastoles) pumps blood through the heart and through the body. (a) During cardiac diastole, blood flows into the heart while all chambers are relaxed. (b) Then the ventricles remain relaxed while atrial systole pushes blood into the ventricles. (c) Once the atria relax again, ventricle systole pushes blood out of the heart. Concepts of Biology-1st Canadian Edition 11.3 Circulatory and Respiratory Systems by Charles Molnar and Jane Gair License: Creative Commons Attribution 4.0 International License

Source: https://opentextbc.ca/biology/chapter/11-3-circulatory-and-respiratory-systems/