Problem 5 - Entrance Test

Following a meal rich in proteins and fats, which sequence correctly outlines the hormonal responses and their primary physiological effects in coordinating digestion and absorption?

A. Chyme enters duodenum -> Secretin release -> Stimulates pancreatic bicarbonate secretion -> Inhibits gastric emptying.B. Chyme enters duodenum -> CCK release -> Stimulates gallbladder contraction and pancreatic enzyme secretion -> Inhibits gastric emptying.C. Acidic chyme enters stomach -> Gastrin release -> Stimulates gastric acid and pepsinogen secretion -> Inhibits pancreatic secretion.D. Glucose in small intestine -> GIP release -> Stimulates insulin secretion -> Stimulates gastric motility.

Correct: B

A. Secretin is released in response to acidic chyme in the duodenum. It primarily stimulates pancreatic bicarbonate secretion to neutralize the acid. While it can inhibit gastric emptying, its primary trigger is acidity, and the question specifies a meal rich in proteins and fats (which would also trigger CCK). B. Cholecystokinin (CCK) is released from the duodenal and jejunal mucosa mainly in response to the presence of fats and proteins (amino acids, fatty acids) in the chyme. CCK has several key roles: * Stimulates gallbladder contraction: This releases bile into the duodenum, which is essential for emulsifying fats. * Stimulates pancreatic enzyme secretion: Pancreatic lipase, proteases (trypsinogen, chymotrypsinogen), and amylase are crucial for digesting fats, proteins, and carbohydrates, respectively. * Inhibits gastric emptying: This slows down the rate at which chyme enters the duodenum, allowing adequate time for digestion and absorption. This option correctly describes the coordinated response to a protein and fat-rich meal. C. Gastrin is released primarily in response to food (especially proteins) in the stomach, distension of the stomach, and vagal stimulation. It stimulates gastric acid (HCl) and pepsinogen secretion. It does not inhibit pancreatic secretion; in fact, gastric acid promotes secretin release, which in turn stimulates pancreatic bicarbonate. The trigger here is acidic chyme entering the stomach, but Gastrin acts in the stomach, not in response to chyme entering the stomach in this context. D. Gastric Inhibitory Peptide (GIP), now also called Glucose-dependent Insulinotropic Peptide, is released primarily in response to glucose and fat in the small intestine. Its main role is to stimulate insulin secretion from the pancreas (an incretin effect). It inhibits gastric motility and acid secretion; it does not stimulate gastric motility.