Gastric juice is secreted by the wall of the stomach. Explain how the timing of secretion is controlled, with reference to the content of the juice.

a. nervous and hormonal control ✔

b. impulses from sight/smell of food stimulates brain to send nerve impulses ✔

c. impulses cause cells in stomach lining/ parietal cells to secrete acid/gastric juice ✔

d. food entering the stomach stimulates the chemoreceptors/stretch receptors ✔

e. chemoreceptors/stretch receptors send impulses to the brain ✔

f. vagus nerve/brain sends a nervous impulse to endocrine cells in wall of stomach ✔

g. endocrine cells release gastrin into the blood ✔

h. gastrin induces the release of gastric juice to digest proteins ✔

i. secretin/somatostatin decrease gastrin secretion ✔

Most candidates described the function of gastric juice rather than the control of its secretion. There was confusion regarding the different pathways and the responses for this question were very often badly structured and missed out details. For example, candidates often stated things like "the sight/smell of food triggers release of gastric juice" missing out some of the key steps in the pathway. So, although many candidates had a good understanding of the digestive processes in the gut, they could not express the pathways involved in the control of the timing of secretions in sufficient detail to gain full marks. Many students described the content of the juice or the enzymes involved in digestion and fails answer the question satisfactorily.