| Date | November 2017 | Marks available | 2 | Reference code | 17N.3.SL.TZ0.16 |
| Level | Standard level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 16 | Adapted from | N/A |
Question
The diagram shows changes in the pressure and volume of the left ventricle during normal heartbeat. The phonocardiogram records heart sounds during the cardiac cycle.
[Source: Wiggers, Carl J. 1923. Modern Aspects of the Circulation in Health and Disease, 2nd ed. Philadelphia: Lea & Febiger, p. 97.]
State the relationship between pressure and volume in the left ventricle.
Explain the events that cause the sound shown on the phonocardiogram at the start of systole.
Outline reasons for fitting an artificial cardiac pacemaker.
Markscheme
as pressure increases volume decreases
OR
inverse correlation
Accept reverse argument
Do not accept “inversely proportional”
a. when the ventricle contracts blood presses/pressure acts on the AV valve
b. this closes the AV valve «which causes the sound»
The valve must be identified as the AV or atrioventricular valve
a. required when rate of heartbeat/heart contraction is too slow/irregular
b. produces electrical impulse that stimulates heartbeat/heart contraction
c. needed when SA node is defective
Accept “regulate the heartbeat” for marking point a
[Max 2 Marks]
