The Cardiac Cycle

These flashcards cover key concepts related to the cardiac cycle, including definitions, phases, and important volumes.

What is the cardiac cycle?

The period between the start of one heartbeat and the beginning of the next.

What is the typical duration of a cardiac cycle?

800 msec

What are the two main phases of the cardiac cycle?

Systole (contraction) and Diastole (relaxation).

What happens during atrial systole?

The atria contract, forcing blood into the ventricles.

What happens during ventricular systole?

The ventricles contract to eject blood.

What occurs during diastole?

The heart relaxes and refills with blood.

How long does atrial systole lasts?

100 ms

How long does atrial diastole last for?

700 ms

How long does ventricular systole last for?

approx. 270 ms

How long does ventricular diastole last for?

approx. 530 ms

How much blood remains in each ventricle at the end of a contraction (retained blood)?

approx. 60ml

How much blood enters the ventricles through passive filling?

approx. 45ml

During atrial systole, how much additional blood is forced into each ventricle?

approx. 25ml

What is the typical end-diastolic volume (EDV) in each ventricle?

approx. 130ml (60 ml + 45 ml + 25 ml)

What is stroke volume?

The amount of blood ejected by each ventricle, typically 70ml.

What are the two phases of ventricular systole?

Isovolumetric contraction and ventricular ejection.

What occurs during Isovolumetric contraction?

Ventricular pressure rises enough to close the AV valves, but not enough to open the semilunar valves.

What is the End-Systolic Volume (ESV)?

The volume remaining after contraction, approx. 60 ml

What characterize Early Ventricular Diastole?

The heart muscle relaxes and the atria fill, but all valves are closed, so no blood enters the ventricles yet

What happens during Late Ventricular Diastole?

Atrial pressure opens the AV valves, allowing blood to flow passively into the ventricles.

What causes the S1 (“lub“) heart sound?

The closing of the AV valves during ventricular systole

What causes the S2 (“dub“) heart sound?

The closing of the semilunar valves during ventricular diastole

What causes heart murmurs?

Abnormal heart sounds that can indicate changes in heart health and efficiency.

What is the significance of the heart sounds?

They provide insight into how well the valves are functioning.