Which of the following occurs/occur during the cephalic phase of gastric acid secretion?
a. Stimulation of gastrin and histamine release
b. Direct stimulation of parietal cells
c. Inhibition of somatostatin release
d. Both a and b are correct
e. All of the above are correct

Verified step by step guidance

1. Understand the cephalic phase of gastric acid secretion: This phase is triggered by the sight, smell, taste, or thought of food. It is a neural response mediated by the vagus nerve, which stimulates the stomach to prepare for digestion.
2. Identify the key players in gastric acid secretion: Gastrin, histamine, and parietal cells are involved in stimulating acid production, while somatostatin inhibits acid secretion.
3. Analyze option (a): Stimulation of gastrin and histamine release occurs during the cephalic phase as the vagus nerve activates G cells (to release gastrin) and enterochromaffin-like cells (to release histamine).
4. Analyze option (b): Direct stimulation of parietal cells also occurs during the cephalic phase via acetylcholine released by the vagus nerve, which binds to receptors on parietal cells to promote acid secretion.
5. Analyze option (c): Inhibition of somatostatin release occurs because somatostatin normally suppresses acid secretion, and during the cephalic phase, the vagus nerve inhibits D cells (which produce somatostatin) to allow acid production to proceed. Based on this, evaluate whether all options (a, b, and c) are correct.

Key Concepts

Cephalic Phase of Digestion

The cephalic phase of digestion is the initial stage of gastric secretion triggered by the sight, smell, or thought of food. This phase prepares the stomach for food intake by stimulating the release of gastric juices, including hydrochloric acid and digestive enzymes, even before food enters the stomach.

Gastrin and Histamine Release

Gastrin is a hormone produced by G cells in the stomach lining that stimulates gastric acid secretion. Histamine, released by enterochromaffin-like cells, enhances the action of gastrin by binding to H2 receptors on parietal cells, leading to increased acid production. Both are crucial for effective digestion during the cephalic phase.

Parietal Cells and Acid Secretion

Parietal cells are specialized cells located in the gastric mucosa responsible for producing hydrochloric acid (HCl). During the cephalic phase, these cells are directly stimulated by neurotransmitters and hormones, leading to increased acid secretion, which is essential for the digestion of food and maintaining an acidic environment in the stomach.