In the regulation of stomach secretions, distension of the stomach activates local reflexes and a parasympathetic reflex. This is called the ______ phase.

Correct Answer: B

Rationale: The correct answer is B: gastric phase. This phase is activated by the distension of the stomach, triggering local reflexes and parasympathetic reflexes to stimulate gastric secretions. The cephalic phase (A) is triggered by the sight, smell, or thought of food. The intestinal phase (C) inhibits gastric secretions and motility. The enterogastric phase (D) inhibits gastric motility and secretion when chyme enters the duodenum. Thus, the gastric phase is specifically related to the distension of the stomach, making it the correct answer.

Correct Answer: B

Rationale: The correct answer is B: inhibit the defecation reflex. Stimulation of the internal anal sphincters by the sympathetic nervous system or stimulation of the external anal sphincter by the somatic motor nervous system leads to constriction of the anal sphincters, preventing the passage of feces. This inhibits the defecation reflex by maintaining continence. The other choices are incorrect because: A: Stimulating the anal sphincters does not promote the defecation reflex; it actually inhibits it. C: Mass movements are related to the movement of feces through the large intestine, not directly influenced by anal sphincter stimulation. D: Inhibiting mass movements is not a direct effect of anal sphincter stimulation.

Correct Answer: A

Rationale: The correct answer is A because it accurately states that the products of protein digestion can be absorbed as free amino acids or as di- or tripeptides. This is true as the final breakdown products of proteins, whether they are individual amino acids or smaller peptide chains, can be absorbed through the intestinal wall into the bloodstream. Choice B is incorrect because not all proteins are digested equally in the stomach, and the efficiency of digestion can vary based on factors like protein structure and presence of inhibitors. Choice C is incorrect because chymotrypsin, elastase, and carboxypeptidase A are actually produced and secreted by the pancreas, not the gastric zymogenic cells. Choice D is incorrect because there are more than 14 different amino acid transporters involved in the absorption of digested protein products, not just one. Therefore, choice A is the most correct statement regarding protein digestion and absorption.

Correct Answer: B

Rationale: Correct Answer: B Rationale: - Brunner's glands secrete an alkaline mucous-rich fluid for protection, not digestive enzymes. - A is correct as Brunner's glands are found in the duodenal wall. - C is correct as they are located in the submucosal layer. - D is correct as they empty secretions into the crypts of Lieberkuhn, aiding in digestion.

Correct Answer: B

Rationale: An increase in the ratio of glucagon to insulin signals a state of low blood glucose, promoting lipolysis in adipose tissue to release fatty acids for energy production. Glucagon activates hormone-sensitive lipase in adipose tissue, leading to increased breakdown of triglycerides. This process releases fatty acids and glycerol into the bloodstream to be used as fuel. Therefore, choice B is correct. Choices A and C are incorrect as glucagon promotes glucose production in the liver and inhibits glucose uptake by muscle cells, respectively. Choice D is incorrect as the increased glucagon to insulin ratio has a physiological effect on lipolysis.