* An example of a positive feedback loop occurs in which peptides cause acid and pepsinogen to be released and this in
turn causes more peptides in the stomach, which causes acid and pepsinogen to be released, etc..
* An example of a negative feedback loop iun the digestive system occurs in which the low pH of the stomach inhibits
gastrin secretion by the G cells which results in less acid secretion.
* Stimulation of HCl secretion:
1. The vagus nerve and amino acids in the stomach cavity stimulate the secretion of gastrin by G-cells
2. Gastrin stimulates the release of histamine by ECL cells
3. Histamine will stimulate the secretion of HCl by parietal cells.