Acid Secretion
Omeprazole is a proton pump inhibitor that irreversibly blocks the H+/K+ ATPase, the final step of acid secretion.
What our notes say
- Omeprazole is a proton pump inhibitor that irreversibly blocks the H+/K+ ATPase, the final step of acid secretion. (Clinical Pharmacology I (MBPL 4400) main exam: 25 January 2023)
- Histamine receptor antagonists and proton pump inhibitors suppress gastric acid secretion (Paediatrics end of 2nd semester exam (MBPE 4300): 5 October 2021, 50 MCQs)
- Sucralfate and dimethicone also suppress gastric acid secretion (Paediatrics end of 2nd semester exam (MBPE 4300): 5 October 2021, 50 MCQs)
- It works through H2 receptor to stimulate acid secretion in the stomach (Biochemistry I End of Year MCQs — September 2020 (Past Paper))
- Reduces gastric motility and acid secretion, slowing emptying to allow neutralisation. (END YEAR PP1 & PP2 2025 Physiology: MCQs for Medical School Exams)
- Stimulates gastric acid secretion and gastric motility, promoting emptying. (END YEAR PP1 & PP2 2025 Physiology: MCQs for Medical School Exams)
Study material on Acid Secretion
- Gastric Acid Secretion and Thyroid Disorders
- Comprehensive Guide to Nutrient Digestion and Absorption
- Medical Physiology Year Two – Paper Two MCQs
- Liver Function Tests (LFTs)
- CLINICAL BIOCHEMISTRY LAQs & SAQs
- LECTURE 7: GI tract Hormones
- Paediatrics end of 2nd semester exam (MBPE 4300): 5 October 2021, 50 MCQs
- Paediatrics main exam (MBPE 4300): 24 January 2022, Paper One, 100 MCQs, 2 short essays and 2 long essays
- END YEAR PP1 & PP2 2025 Physiology: MCQs for Medical School Exams
- Medical Physiology Section A - Complete Questions and Comprehensive Answers
- Gastric Acid Secretion and Thyroid Disorders
- Gastric Acid Secretion and Thyroid Disorders
- Weekly Year 2: GIT Physiology Exam - March 20, 2026 (Section A: MCQs)
- Weekly Year 2: GIT Physiology Exam - March 27, 2026 (Section A: MCQs)
Practice questions on Acid Secretion
H2 receptor antagonists like ranitidine reduce gastric acid secretion by
- Directly inhibiting the proton pump
- Blocking histamine stimulation of parietal cell H2 receptors
- Increasing prostaglandin synthesis in gastric mucosa
- Neutralizing already secreted acid
Answer: B. H2 blockers competitively antagonize histamine at H2 receptors on gastric parietal cells, preventing the histamine-mediated activation of adenylyl cyclase and subsequent stimulation of the proton pump. They do not directly block the pump itself (that's the mechanism of PPIs like omeprazole). ---
Which of the following inhibits gastric acid secretion?
- Acetylcholine
- Histamine
- Somatostatin
- Gastrin
Answer: C. Somatostatin is the 'universal inhibitor' in the GIT and directly inhibits parietal cell acid secretion.
Which of the following inhibits gastric acid secretion?
- Vagal stimulation
- Gastrin
- Enterogastric reflex (distension of duodenum)
- Histamine
Answer: C. The enterogastric reflex, triggered by acid or distension in the duodenum, inhibits gastric motility and gastric acid secretion (the 'brakes').
Potentiation in gastric acid secretion refers to:
- The inhibition of Gastrin by Secretin
- The synergistic effect of Acetylcholine, Gastrin, and Histamine
- The role of the liver in neutralizing acid
- The conversion of pepsinogen to pepsin
Answer: B. Potentiation occurs when the combined effect of multiple stimuli (ACh, Gastrin, Histamine) is greater than the sum of their individual effects.
Which of the following hormones *inhibits* gastric acid secretion?
- Gastrin
- Histamine
- Acetylcholine
- Somatostatin
Answer: D. Somatostatin, released by D cells in the stomach and duodenum, acts locally to inhibit gastrin release and directly inhibits parietal cell acid secretion, thereby decreasing gastric acid output.
Regarding the regulation of gastric acid secretion, which statement is TRUE?
- Antral distension primarily inhibits gastric acid secretion.
- Acetylcholine directly inhibits parietal cell function.
- Prostaglandins stimulate HCl secretion.
- Histamine, released from ECL cells, is a potent stimulator of parietal cells.
Answer: D. Histamine, released from enterochromaffin-like (ECL) cells in response to gastrin and acetylcholine, acts on H2 receptors on parietal cells, strongly stimulating HCl secretion.