The Cardiac Cycle

Question 1

Describe what’s happening during late diastole

Answer 1

Both sets of chambers are relaxed. The AV valve opens and blood passively fills the atria from veins and gravity allows the ventricles to fill.

Question 2

Describe what’s happening during atrial systole

Answer 2

Atrial contraction forces a small amount of blood into the ventricles. Some blood flows back into the veins as there isn’t any valves to stop this third flow - this creates a pulse observed by the jugular venous pressure.

Question 3

Describe what is happing at isovolumic ventricular contraction. (systole)

Answer 3

First phase of ventricular contractor forces AV valves to close (creating the S1 sound) but this doesn’t create enough pressure to open semi-luner valves. Isovolumic means pressure is changing with no change in volume.

Question 4

Describe what is happing at ventricular ejection. (systole)

Answer 4

As the ventricles pressure exceeds the arteries pressure the semi-luner valves open and blood is ejected at high speed. At this point the AV valves remain closed.

Question 5

Describe what is happing at isovolumic ventricular relaxation (diastole)

Answer 5

As the ventricles relax pressure in the ventricle decreases and blood in the arteries flows back causing the cusps of the semi-luner valves to close - creating the S2 sound.