Question 20N.3.HL.TZ0.22
| Date | November 2020 | Marks available | [Maximum mark: 5] | Reference code | 20N.3.HL.TZ0.22 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Describe, Evaluate, State | Question number | 22 | Adapted from | N/A |
Blood pressure changes in chimpanzees (Pan troglodytes) fed a salt-supplemented diet during a two-and-a-half-year treatment period were compared to the blood pressure of those fed a normal diet. The graph shows the mean systolic and diastolic blood pressure (± standard deviation) before, during and after the treatment period.
[Source: Republished with permission of American Society for Clinical
Investigation, from The Journal of Clinical Investigation, O’Shaughnessy, K.M. and Karet, F.E., 113, 8, 2004;
permission conveyed through Copyright Clearance Center, Inc.]
Evaluate the effect of salt on blood pressure using the data in the graph.
[2]
a. systolic pressure increases with salt in diet during treatment;
b. diastolic pressure is slightly higher/no change with salt during treatment
OR
diastolic pressure only changes towards the end of the period;
c. (blood) pressure goes back to normal after treatment
OR
salt causes increased (blood) pressure;
d. standard deviation values overlap therefore not statistically significant;
The majority could evaluate that salt increased blood pressure, most comparing the effect on systolic and diastolic blood pressure.
State the instrument used by doctors to measure blood pressure.
[1]
sphygmomanometer/blood pressure monitor;
Although strong candidates could state sphygmomanometer or blood pressure monitor, too many irrelevant or blank answers were seen.
Describe the mechanism by which the heartbeat is initiated.
[2]
a. sinoatrial node/SAN initiates contraction of atria;
b. SAN sends messages to the atrioventricular/AV node;
c. AV node initiates ventricular contraction;
d. through conducting fibres;
Most candidates did well in this question, strongest candidates distinguishing themselves by complete and very detailed answers.