Alimentary And Digestive System Practice Test

Gastric acid secretion is driven by a balance of stimulatory and inhibitory signals. The stimulators are gastrin, histamine, and acetylcholine. Gastrin, released from G cells in the stomach, directly promotes parietal cell acid secretion and also encourages histamine release from enterochromaffin-like cells, which then acts on H2 receptors to boost acid production. Acetylcholine, released by vagal neurons, further enhances parietal cell activity. Inhibitors include somatostatin and secretin. Secretin is released in response to acidic chyme in the duodenum and works to reduce acid secretion both by dampening gastrin release and by directly inhibiting parietal cells. Somatostatin from D cells also suppresses acid secretion directly and inhibits gastrin release. So the correct pattern is stimulation by gastrin, histamine, and acetylcholine, and inhibition by somatostatin and secretin. The other statements misstate which hormones stimulate or inhibit acid secretion.