Experimental gastric function monitoring in healthy subjects before, during and after a meal shows an initial rise, peak, and then decline in gastric acid production. Which of the following helps most to down-regulate gastric secretion after a meal?

Question

Experimental gastric function monitoring in healthy subjects before, during and after a meal shows an initial rise, peak, and then decline in gastric acid production.  Which of the following helps most to down-regulate gastric secretion after a meal?

Quizplus · Accepted Answer

Classically, the stimulation of acid secretion within the stomach is separated into three phases: cephalic, gastric, and intestinal. The cephalic phase is mediated primarily by cholinergic and vagal mechanisms, and is triggered by the thought, sight, smell, and taste of food. The gastric phase is mediated by the presence of gastrin (which stimulates histamine secretion and therefore, indirectly, acid secretion), and is triggered by the chemical stimulus of food and distension of the stomach. The intestinal phase is initiated when protein-containing food enters the duodenum, but this phase plays only a minor role in stimulating gastric acid secretion. In fact, intestinal influences are effective in down-regulating gastric acid secretion after a meal. The ileum and colon release peptide YY, which binds to receptors on the endocrine, histamine-containing cells described as enterochromaffin-like (ECLs). Such binding counteracts the cephalic and gastric phases of acid secretion by inhibiting gastrin-stimulated histamine release from ECLs. Other factors that inhibit acid secretion include somatostatin and prostaglandins. (Choice A) Basal gastric secretion has been defined as the gastric juices secreted in the absence of intentional or avoidable stimuli (essentially, the "baseline" gastric acid secretion). Basal gastric secretion is not an important factor in the down-regulation of postprandial gastric secretion. (Choices B and C) The cephalic and gastric phases both stimulate gastric acid secretion, not down-regulate it. (Choice E) Receptive relaxation is a reflex that allows the gastric fundus to dilate in anticipation of food passing through the pharynx and esophagus. It is not an important factor in the down-regulation of postprandial gastric secretion. (Choice F) Postprandial alkaline tide is defined as an increase in plasma HCO₃‾ and decrease in plasma Cl‾ secondary to the surge of acid within the gastric lumen. It is not an important factor in the down-regulation of postprandial gastric secretion. Educational Objective: The cephalic and gastric phases stimulate gastric acid secretion, while intestinal influences tend to reduce gastric acid secretion.

Experimental Gastric Function Monitoring in Healthy Subjects Before, During and After