The cardiac style has two phases namely, diastole and systole.
In the diastole phase, blood returns to the heart from the superior and interior vena cava and flows into the right atrium. The pressure in the right atrium increases as the blood flows into it and exceeds the pressure of the right ventricle. As a result, the tricuspid valve opens and allows the blood to flow into the right ventricle.
Also, the oxygenated blood coming from the lungs flows into the left atrium and as the left atrial pressureincreases, the mitral valve opens and blood flows into the left ventricle.
In the systole phase, blood flows from the two atria into their respective ventricles. This blood flow occurs as a result of the contraction the atrial muscles due to the delpolarizationof the atria. Isovolumetric contraction is the period in which the ventricles contract but the pulmonary and aortic valves are closed as the ventricles do not have enough force to open them. The atrioventricular valves also remain closed during this period.
The semilunar valves open when the ventricular muscle contracts and generates blood pressure within the ventricle. When the heart muscle relaxes again the diastole phase begins.
