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Date May 2019 Marks available 4 Reference code 19M.3.SL.TZ1.18
Level Standard level Paper Paper 3 Time zone Time zone 1
Command term Explain Question number 18 Adapted from N/A

Question

Hypochlorhydria is a condition whereby patients produce low quantities of stomach acid. Outline the effect this might have on the normal processes within the stomach.

[3]
a.

Explain the mechanisms that regulate the composition of gastric juices.

[4]
b.

Markscheme

a. reduced resistance to pathogens ✔

b. pH not optimum for pepsin activity ✔

c. activation of enzymes/pepsinogen is reduced ✔

d. reduced food/protein digestion ✔

a.

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 ✔

b.

Examiners report

This was often answered in terms of the functions of stomach acid rather than hypochlorydria, however this was not penalised. The effect on pathogens and reduced digestion were most often stated, and activation of enzymes very rarely.

a.

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.

b.

Syllabus sections

Option D: Human physiology » Option D: Human physiology (Core topics) » D.2 Digestion
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Option D: Human physiology » Option D: Human physiology (Core topics)
Option D: Human physiology

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