Cardiac Cycle

Question 1

Heart sounds

Answer 1

Normally heart valves produce a sound when they shut.

They don’t produce a sound when they open.

Question 2

Cardiac Cycle

Answer 2

Sequence of events which take place from the beginning of one heart beat to the beginning of the next.

Question 3

Systole

Answer 3

Ventricles contract
RV: pumps blood to pulmonary artery
LV: pumps blood to aorta

Question 4

Diastole

Answer 4

Heart relaxes and fills with blood

Question 5

1. Passive filling

Answer 5

AV valves (tricuspid and mitral) are open
Aortic and pulmonary valves are shut
Venous return flows through the atria and into ventricles
Ventricles become around 80% full

Question 6

2. Atrial contraction

Answer 6

Occurs during the PR interval of ECG

Atria are squeezed so any remaining blood can get to the ventricles

Question 7

3. Isovolumetric ventricular contraction

Answer 7

Occurs at the ST segment of the ECG
Ventricular pressure continues to rise
When ventricular pressure exceeds atrial pressure the AV valves (tricuspid and mitral) shut.
This produces the first heart sound “LUB”
This establishes the beginning of systole.
Tension continues to rise in the closed volume of the ventricle as both the AV and aortic/pulmonary valves are shut so blood in ventricles can’t escape.

Question 8

4. Ventricular ejection

Answer 8

When pressure in the ventricles exceeds the aortic/pulmonary pressure, the atrial and pulmonary valves open.
SV is ejected from the ventricles and the aortic and pulmonary pressures rise.
Ventricles then begin to relax.
When aortic/pulmonary pressure exceeds ventricular pressure, the aortic/pulmonary valves shut.
This produces the second heart sound “DUB”.
This establishes the beginning of diastole.

Question 9

5. Isovolumetric ventricular relaxation

Answer 9

Ventricle is now a closed box again as both the AV vaves and the aortic/pulmonary valves are shut.
When ventricular pressure is less than atrial pressure, the AV valves reopen and the cycle starts again

Question 10

Auscultatory areas

Answer 10

Aortic valve - 2nd ICS, right sternal edge
Pulmonary valve - 2nd ICS, left sternal edge
Tricuspid valve - 4th ICS, left sternal edge
Mitral valve - 5th ICS, mid-clavicular line

Question 11

Heart sounds

Answer 11

S1 - closure of the tricuspid and mitral valves, beginning of systole
S2 - closure of the pulmonary and aortic valves, beginning of diastole
S3 - physiological/pathological added sound
S4 - added sound, always pathological