Question 20N.3.HL.TZ0.22c
| Date | November 2020 | Marks available | [Maximum mark: 2] | Reference code | 20N.3.HL.TZ0.22c |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Describe | Question number | c | 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.]
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;
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