What effects are created by the negative feedback system controlling digestion once chyme has left the stomach?

A negative feedback loop occurs in which the low pH of the stomach inhibits gastrin secretion by the G cells which results in less acid secretion.





Gastrin release is inhibited by:





鈽籘he presence of acid (primarily the secreted HCl) in the stomach (a case of negative feedback).





鈽籗omatostatin also inhibits the release of gastrin, along with secretin, GIP (gastroinhibitory peptide), VIP, glucagon and calcitonin.





One inhibitory factor is acidity (pH below 3) - a negative feedback mechanism, exerted via the release of somatostatin from 未 cells in the stomach, inhibits gastrin and histamine release.





Another inhibitory factor is somatostatin, which acts on somatostatin-2 receptors on G cells in a paracrine manner via local diffusion in the intercellular spaces, but also systemically through its release into the local mucosal blood circulation; it inhibits acid secretion by acting on parietal cells.





Other inhibitory factors are gastric inhibitory peptide (GIP), secretin, somatostatin, glucagon, calcitonin, all of which are released into the circulatory system.





Chemoreceptors in the stomach monitor the pH level of the chyme, and trigger the negative feedback loop. Nerve impulses propagate to the submucosal plexus, where they innervate parasympathetic and enteric neurons. During the intestinal phase of digestion, gastric peristalsis and secretion of gastric juice are inhibited.

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