Cardiac Cycle and it's Control (Fri 20th)

Question 1

Cardiac Cycle?

Answer 1

1. Ventricular filling, atrioventricular valves are open but the semi-lunar valves are closed. DIASTOLE
2. Atria contract, atrioventricular valves are open but the semi-lunar valves are closed. DIASTOLE
3. Isovolumnic contraction: (Both AV & SL closed) SYSTOLE, but the ventricle is contracting, so called isovolumetric because the volume of blood doesn’t change but the pressure in the ventricle does.
4. Ventricular Ejection (AV closed, SL open). SYSTOLE, SL opens once pressure in ventricle greater than pressure in aorta / pulmonary artery
5. Isovolumic Relaxation (both AV & SL closed) DIASTOLE

Question 2

Max and min pressure changes in aorta?

Answer 2

Maximal during systole (peaks at ~120 mmHg), which declines to a minimum during diastole (lowest ~80 mmHg).

Question 3

How to calculate stroke volume?

Answer 3

End-diastolic volume, End-systolic volume (residual volume).

Stroke volume, SV = EDV-ESV

Question 4

What is the ejection fraction?

Answer 4

Ejection fraction = SV/EDV, normally about 0.6.

Question 5

What causes the first and second heart sounds (ba- dump)?

Answer 5

1. atrioventricular closing

2. semilunar opening

Question 6

What is a phonocardiogram?

Answer 6

a chart or record of the sounds made by the heart.

Question 7

Dichrotic notch?

Answer 7

where the semilunar valve closes causing a slight rebound of blood in aorta.

Question 8

Mean Atrial Pressure

Answer 8

DP plus a third (SP-DP)

Question 9

Diseases of the valves?

Answer 9

1. Incompetence: leaky, don’t close properly.

2. Stenosis: narrowing