For each of the examples of intestinal motility A–E, select the most appropriate stimulus from the following list of stimuli:

A. Option 2 Distension of the viscus wall. For this reflex, the distension of the stomach wall following ingestion of a meal is thought to stimulate colonic motility that results in defaecation.

B. Option 2 Distension of the viscus wall. When food is ingested, the smooth muscle in the stomach wall relaxes so that the added bulk can be accommodated without much increase in intragastric pressure.

C. Option 2 Distension of the viscus wall. When a bolus of food distends a hollow viscus it sets up a wave of contraction preceded by a wave of relaxation that carries the bolus along the viscus. Though peristalsis can be modified by autonomic nerves, the mechanism is based on local nerve networks in the wall of the viscus.

D. Option 4 Release of gastrin. Gastrin secreted in response to a meal increases tone in the cardiac sphincter and so prevents regurgitation of gastric contents into the oesophagus during stomach contractions.

E. Option 5 Release of CCK-PZ. CCK-PZ released from the bowel wall when fat enters the duodenum causes the gall bladder to contract to empty its contents into the second part of the duodenum. It also inhibits gastric emptying.