Gastrin (protein digestion)

The endocrine system maintains many body conditions within normal limits with feedback loops. Each endocrine feedback loop maintains homeostasis using the following components: • Stimulus - a change in a body condition. • Production cell - an endocrine cell that produces a hormone after being affected by stimulus. • Hormone - the signaling chemical. • Target cell - a cell receptive to the hormone. • Action - what the cell does when affected by the hormone. • Response - the overall change in controlled body condition as a result of the feedback loop. • The gastric phase of digestion begins as the stomach fills with food (especially proteins). • Receptors sense distension and the increased gastric pH. • Stimulated receptors prompt G cells in mucosa of stomach to secrete gastrin. • Gastrin binds to parietal and chief cells in gastric mucosa. • Stimulated parietal cells produce more hydrochloric acid. • Chief cells produce more pepsinogen, the precursor to pepsin. • Increased pepsin and gastric acid increase the stomach's ability to digest proteins.

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