2.04 - The Cardiac Cycle

Question 1

List the four heart valves and the structures they seperate

Answer 1

Tricuspid: Right atrium and right ventricle

Pulmonary: Right ventricle and pulmonary artery

Mitral (Biscuspid): Left atrium and left ventricle

Aortic: Left ventricle and ascending aorta

Question 2

Define systole

Answer 2

Period between S₁ and S₂. Period of contraction and ejection

Question 3

Define diastole

Answer 3

Period between S₂ and S₁

Period of relaxation and filling

Question 4

Does the length of diastole or systole change with heart rate?

Answer 4

Systole is more of less constant.

However diastole varies with heart rate

Question 5

In relation to an ECG recording when do the heart sound occur?

Answer 5

S₁ occurs during (later part) of the QRS complex

S₂ occurs at the end of systole, after the T wave

Question 6

List and describe the heart sounds heard using the stethoscope

Answer 6

S₁: closure of the mitral/tricuspid valves

S₂: closure of the aortic/pulmonary valves

S₃: Faint rumble, opening of mitral/tricuspid valve with flow murmur in to ventricles (typically heard in young people

S₄: faint rumble, flow murmur causes by atrial contraction

Question 7

What is the Peak Diastolic Volume, End Diastolic Volume, Stroke Volume and pressure range in the left ventricle

Answer 7

PDV: 120mL

EDV: 40mL

SV: 80mL

Pressure range: 0-120mmHg

Question 8

What do the notches in an aortic trunk pressure curve represent?

Answer 8

Movements of the valves

Question 9

What is the pressure range in the aorta?

Answer 9

120mmHg during systole and 80mmHg during diastole

Question 10

Describe the drop in to negative flow in the aorta

Answer 10

The dip in to negative flow in the aorta is due to back flow of blood. The Aortic valve acts as a cushion and needs this back flow of blood in order to close

Question 11

Describe valvular plane displacement

Answer 11

Contraction of the heart during systole moves the valvular plane (the line the atrioventricular valves make) towards the apex of the heart (i.e. away from the vena cava). This motion results in mechanical suction on the atria and vena cave, resulting in suction of blood in to the atria during systole

Question 12

List the phases of the cardiac cycle

Answer 12

1. Isovolumetric contraction
2. Fast ejection
3. Slow ejection (aortic valve then closes)
4. Isovolumetric relaxation. “Elastic recoil”, mitral valve opens
5. Rapid ventricular filling
6. Slow ventricular filling
7. Atrial contraction

Question 13

Draw the Cardiac Cycle graph.

Answer 13