| Date | November 2016 | Marks available | 2 | Reference code | 16N.3.SL.TZ0.15 |
| Level | Standard level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Outline | Question number | 15 | Adapted from | N/A |
Question
The QT interval corresponds to the time it takes for the ventricles of the heart to contract and then start to refill with blood before beginning the next contraction. Measures of QT interval were taken from 15-year-old female patients with anorexia nervosa and compared to healthy females of the same age. The body mass, heart rate and the mass of the left ventricle were also measured and the mean values are shown in the table.
Outline the reasons that the female patients with anorexia nervosa have a lower mean ventricle mass than healthy females.
Suggest a reason for the difference in QT interval between females with anorexia nervosa and healthy females.
State the two causes of normal heart sounds.
Markscheme
a. patients with anorexia nervosa do not eat sufficient food/protein/amino acids. Starving = insufficient food
b. heart muscles used as an energy source
c. reduced body mass reduces requirement for muscle mass in ventricle
decreased left ventricle mass/pressure therefore more time needed to contract
atriaventricular/AV valve closing and semilunar/SV valves closing
Both valves need to be addressed for the mark.
