Cardiac Cycle Overview and Phases

The complete sequence of events that occur in the heart during one heartbeat, encompassing contraction and relaxation phases.

The phase when the heart muscle contracts and pumps blood out of the chambers.

The phase when the heart muscle relaxes and the chambers refill with blood.

A rapid heart rate.

The changes in volume and pressure within the heart chambers, arteries, and veins during each cardiac cycle.

The opening and closing of the heart valves, allowing blood to flow in one direction.

The electrical activation of the heart that triggers the mechanical events of the cardiac cycle.

The way in which the electrical signals of the heart are conducted and spread throughout the heart.

The atria function as volume pumps, adding a little extra blood to the ventricles during diastole.

The length of time it takes for one complete cardiac cycle (systole and diastole).

The normal cardiac cycle duration at a heart rate of 75 beats per minute is approximately 0.8 seconds.

Diastole takes up about two-thirds of the cardiac cycle, while systole takes up about one-third.

As heart rate increases, the total cardiac cycle duration shortens, with a greater decrease in diastole duration compared to systole.

At a heart rate of 200 beats per minute, the cardiac cycle duration is 0.3 seconds, with both systole and diastole lasting 0.15 seconds each.

The period when the ventricles contract but no blood is ejected yet. The heart chambers are closed, and pressure builds up inside the ventricles.

The period during which blood is rapidly ejected from the ventricles into the aorta, driven by the strong ventricular contraction.

The phase when the rate of blood ejection from the ventricles slows down, with the ventricular pressure still above aortic pressure.

The very brief period between the end of ventricular ejection and the opening of the AV valves for the next inflow of blood.

The period when the ventricles relax and the heart chambers are closed, allowing the pressure in the ventricles to decrease below the pressure in the aorta.

The period when the AV valves open and blood starts flowing from the atria into the ventricles, rapidly filling the ventricles.

The final phase of ventricular filling, where the inflow of blood slows down as the ventricles approach their maximum volume.

The interval of time during which the AV valves close and the semilunar valves remain closed. This phase marks the beginning of ventricular contraction.

A brief period of ventricular contraction where the pressure increases rapidly due to a closed system. It's the phase where the heart muscle actively contracts.

The pressure inside the ventricles begins to rise rapidly during Isovolumetric Contraction. This is because the heart muscle is contracting, putting pressure on the blood within the ventricles.

During Isovolumetric Contraction, the A-V valves bulge into the atria due to the rising ventricular pressure, creating a small bump known as the "c" wave in the atrial pressure curve.

During Isovolumetric Contraction, the volume of blood within the ventricles remains constant. This means no blood is entering or leaving the ventricles.

The semilunar valves remain closed during Isovolumetric Contraction, and so the blood ejected during the previous heartbeat continues to flow to the periphery. Because the semilunar valves are closed, no new blood enters the aorta or pulmonary artery.

The AV valves and the semilunar valves are both closed during Isovolumetric Contraction, preventing blood from entering or exiting the ventricles.

The rapid ejection phase is part of systole (heart contraction), where most blood is ejected from the ventricle into the aorta and pulmonary artery.

The rapid ejection phase starts with the opening of the semilunar valves.

During the rapid ejection phase, atrial pressure decreases due to the pull of the ventricles on the A-V fibrous skeleton, leading to a negative wave in the atrial pressure and JVP.

During the rapid ejection phase, the ventricular volume decreases significantly as the majority of blood is ejected.

Ventricular pressure reaches its maximum value during rapid ejection, which is equal to the highest pressure in the aorta and pulmonary arteries.

Aortic pressure increases rapidly during rapid ejection, reaching its maximum value (systolic blood pressure) as blood flows into the aorta.

During rapid ejection, more blood leaves the ventricle than escapes from the aorta to the periphery.

During rapid ejection, the A-V valves are closed, and the semilunar valves are open.

The period following the rapid ejection phase of the heart's contraction, where blood continues to flow out of the ventricle, but at a slower rate.

During the Reduced Ejection Phase, the pressure inside the ventricle slowly decreases, paralleling the decrease in aortic pressure.

The aortic pressure also decreases during the Reduced Ejection Phase, primarily because the blood flowing outward to the body exceeds the amount ejected by the ventricle.

Atrial pressure gradually increases during the Reduced Ejection Phase as venous blood continuously returns to the atria, while the atrioventricular valves remain closed.

The ventricular volume considerably decreases during the Reduced Ejection Phase due to blood ejection. The volume reaches its minimum at the end of this phase, known as the end systolic volume (ESV).