Question 19M.3.SL.TZ1.b
| Date | May 2019 | Marks available | [Maximum mark: 4] | Reference code | 19M.3.SL.TZ1.b |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Explain | Question number | b | Adapted from | N/A |
Explain the mechanisms that regulate the composition of gastric juices.
[4]
a. regulated by both hormonal and nervous systems ✔
b. smell/sight of food causes the brain to send nerve impulses ✔
c. via the «vagus» nerve from the medulla «oblongata» ✔
d. «gland» cells in the stomach wall are stimulated to secrete gastric juice ✔
e. chemoreceptors in the stomach wall detect food «and send an impulse to the brain» ✔
f. stretch receptors detect stretching/distension of the stomach «and send impulses to the brain» ✔
g. release of «hormone» gastrin ✔
h. gastrin stimulates secretion of acid
OR
pepsinogen by exocrine gland cells in the stomach wall ✔
i. secretin and somatostatin inhibit gastrin secretion if the pH in the stomach falls too low ✔
There were few excellent answers to this question, perhaps because the wording of the question led some candidates to discuss composition of digestive juices rather than their control. The medulla and gastrin were often mentioned and occasionally chemo- and stretch receptors. Often a mark was awarded from different sections of the answer, as responses lacked clarity.
