Question

Acid secretion in stomach is stimulated by
A) Gastrin
B) Histamine
C) Both A and B
D) None of the above

Answer 1

Hint: Acid secretion in stomach is neural as well as hormonally regulated. Parietal cell has the receptors for acetylcholine, Gastrin and histamine. All these three stimulate the HCl secretion from the parietal cell (present in the stomach).

Complete answer:
Mechanism:
There are three phases of gastric secretion:
Cephalic /neural phase: In this case smell of food/ thought of food/ tactic sensation of food in the mouth sends nervous impulses to the medulla oblongata, these impulses cause parasympathetic neuron, Vagus nerve to stimulate secretion of Hydrochloric acid and pepsin in the stomach.
Parasympathetic stimulation also results in stimulation of Gastrin from the lower part of the stomach. This hormone travels through the bloodstream and further stimulates Hydrochloric acid and pepsin secretion in the upper and middle part of the stomach.
Gastric phase: In this phase food has entered the stomach . This action activates parasympathetic reflex via the medulla oblongata . This has a direct stimulatory effect on the gastric glands. This results in continuous secretion of Hydrochloric acid and pepsin.
Intestinal phase: In this phase of gastric secretion, Chyme has entered the duodenum , so gastric secretion is no longer needed. When the chyme contains lipids from the digestion of fats or contain enough Hydrochloric acid to bring its pH below 2, gastric secretion is inhibited.

Hence, the correct answer is option (C)

Note: There are several types of secretion secreted by different kinds of cell present in gastric
1) Mucous cells: they secretes mucus which protects stomach lining from Hydrochloric Acid .
2) Parietal cells: secretes Hydrochloric acid.
3) Chief cells: secretes pepsinogens.