Cardiac Cycle

Diastole : heart relaxes

Systole : heart contracts. increase in pressure in the heart as it decreases the volume within the chambers of the heart. only 1 type of chamber is contracted at any 1 time.

—> in different phases, the AV and SL valves open and close.
—> the closing of the valves is what creates the noise of a heart beat called ‘lub dub’.

—> ventricles relax
—> atria contract increasing the pressure in the atria

—> this forces the blood through the atrioventricular valves into the ventricles.
—> the valves are already open.

—> atria relax
—> ventricles contract increasing the pressure in the ventricles

—> this closes the AV valves as the blood pushes the valves.
—> the valves don’t flip due to the chordae tendineae

—> this opens the SL valves in the arteries as the blood pushes the valves
—> allows blood to be pumped into the arteries (aorta & pulmonary)

—> atria and ventricles relax

—> this closes the SL valves in the arteries as the blood pushes the valves

—> the atria begin to fill with blood from the veins (vena cava and pulmonary)
—> this causes the AV valves to open and blood trickles into the ventricles