8) the cardiac cycle

What are the two main phases of the cardiac cycle?

Systole (contraction) and diastole (relaxation).

What happens during atrial systole?

Atria contract, pushing blood into the ventricles.

What occurs during ventricular systole?

Ventricles contract, ejecting blood into the pulmonary trunk and aorta.

What is isovolumetric contraction?

Ventricles contract with all valves closed, increasing pressure without volume change.

What causes the AV valves to close?

Rising ventricular pressure during systole.

When do semilunar valves open?

When ventricular pressure exceeds pressure in the arteries.

What causes semilunar valves to close?

When ventricular pressure falls below arterial pressure during diastole.

What drives blood flow through the heart?

Pressure gradients between chambers and vessels.

What is the role of ventricular diastole?

Ventricles relax and fill with blood from the atria.

What is the end-diastolic volume (EDV)?

The volume of blood in the ventricles at the end of diastole.

What is stroke volume?

The amount of blood ejected by a ventricle during systole.

What does the first heart sound (S1) represent?

Closure of the AV valves.

What does the second heart sound (S2) represent?

Closure of the semilunar valves.

Why is understanding the cardiac cycle important clinically?

It helps interpret heart sounds, murmurs, and blood pressure dynamics.