Cardiac

Heart Sounds

The sounds produced by the closing of heart valves, commonly described as 'lub-dup'.

Lub (S₁)

The sound created by the closure of the AV valves at the start of systole.

Dup (S₂)

The sound produced by the closure of the semilunar (SL) valves at the start of diastole.

Murmurs

Abnormal heart sounds caused by valve problems.

Cardiac Cycle

One complete heartbeat consisting of systole and diastole phases of the atria and ventricles.

Atrial Systole

The phase where the atria contract to push blood into the ventricles.

Ventricular Systole

The phase where the ventricles contract, beginning with the closure of the AV valves.

Ventricular diastole:

 relaxation; SL valves close → isovolumetric relaxation → AV valves reopen → filling begins.

Isovolumetric Contraction

ventricular contraction when the AV valves close (first heart sound “lub”) but the semilunar valves have not yet opened so no blood leaves yet.

Ventricular Ejection

once ventricular pressure is higher than pressure in the aorta/pulmonary trunk → semilunar valves open and blood is pumped out of the ventricles

Early Diastole

ventricular contraction during which the ventricles relax and the semilunar valves close (second heart sound “dup”).

Isovolumetric Relaxation

early diastole where the ventricles relax, and the AV valves are still closed until pressure falls.

Ventricular Filling

The phase in the cardiac cycle during diastole when blood fills the ventricles.

AV Valves- Ventricular Filling

Atrioventricular valves (tricuspid and mitral) that open to allow blood flow from the atria to the ventricles.

Semilunar Valves- Ventricular Filling

Valves (aortic and pulmonary) closed

Atrial Pressure

The pressure in the atria that influences the opening of the AV valves during diastole.

Cardiac Cycle Average Duration

Approximately 0.8 seconds at a heart rate of 75 beats per minute.

 Ventricular Systole (Ventricular Contraction)

ventricles contract, pumping blood into the aorta and pulmonary artery. It follows atrial systole and precedes ventricular diastole.