Make note of differences in the morphology of right and left heart. Now consider the sequence of events involved in excitation that leads to synchronized contraction of the heart. Results in delay of excitation between atrium and ventricles that is functionally significant. Bundle of His, right and left branches then to purkinje fibers. Note that this arrangement leads to a wave of excitation from the apex of the heart towards the top.
Total time is approx.
Diastole relaxation and filling lasts about 0.5 sec Systole - contraction and ejection, lasts about 0.3 sec. Direction of blood flow as well as opening and closing of values can be explained based upon pressure changes between two points. Start at the end of diastole marked by a period call isovolumetric contraction. Note that the figure only shows cardiac cycle for the left heart and the systemic circulation. During diastole, the AV valves are open left atrial pressure is slightly higher that left ventricular pressure, therefore left ventricle fills.