G cells release gastrin in response to:W. Distension of the stomachX. Increase in pH caused by proteinsY. Increase in parasympathetic activityZ.  secretin from the small intestine

G cells, located in the stomach and duodenum, are responsible for the secretion of gastrin, a hormone that stimulates the production of gastric acid by the parietal cells of the stomach. Here's how they respond to each of the given factors:

W. Distension of the stomach: Yes, G cells release gastrin in response to distension of the stomach. When the stomach is stretched due to the presence of food, it triggers the G cells to release gastrin.

X. Increase in pH caused by proteins: Yes, G cells release gastrin in response to an increase in pH. When proteins are ingested, they buffer the stomach acid, causing an increase in pH. This triggers the G cells to release more gastrin to stimulate further acid production to aid in protein digestion.

Y. Increase in parasympathetic activity: Yes, G cells release gastrin in response to increased parasympathetic activity. The parasympathetic nervous system, specifically the vagus nerve, stimulates the release of gastrin during the cephalic phase of gastric secretion, which is activated by the sight, smell, and taste of food.

Z. Secretin from the small intestine: No, G cells do not release gastrin in response to secretin from the small intestine. Secretin primarily acts on the pancreas to stimulate the release of bicarbonate to neutralize the acidic chyme entering the duodenum. It does not directly stimulate gastrin release.