- 4 Reflexes:
- Enterogastric Reflex: Chyme entering the duodenum inhibits stomach muscle contraction.
- Gastroenteric Reflex: Stretching stomach leads to secretions in the gut.
- Gastroileal Reflex: Stretching stomach relaxes the ileocecal valve.
- Defecation Reflex: Stretching of anal sphincter has both long and short term reflexes.
- Short: Stretching of anal sphincter stimulates stretch receptors which in turn increase local peristalsis.
- Long: Stretching of anal sphincter stimulates neural system (parasympathetic); increases overall peristalsis and contracts external anal sphincter.
- 5 Hormones:
- Gastrin: Production of HCL, muscular contraction.
- GIP: Release of Insulin from pancreas.
- Secretin + CCK: Stimulates the secretion of pancreatic enzymes + buffers and release of bile from gallbladder.
- VIP: Dilates intestinal capillaries.
- Digestion in the stomach:
- 1. Hungry-related stimulus drives the CNS, and CNS interacts with chief cells, parietal cells, g cells, and mucous cells.
- 2. Chief cells produce Pepsinogen. Mucuous cells produce mucuous. Parietal cells produce HCL. G Cells produce gastrin into blood stream. pH is reduced.
- 3. Food enters the stomach, thus raising the pH. Distension of the stomach and raised pH drives a response to produce more pepsinogen, HCL, mucuous in order to digest food. Gastrin is also secreted to increase muscular contraction. Gastroenteric reflex.
- 4. pH is lowered as the food is transformed into chyme.
- 5. Chyme is emptied into duodenum. Enterogastric reflex inhibits contraction.
- 6. Lowered pH in the duodenum (chyme pH is lowered due to feedback loop to reduce pH in stomach) causes the secretion of secretin. Presence of lipids and carbohydrates cause secretion of CCK, GIP. Secretin, CCK, and GIP reduce chief/parietal/mucuous cell activity.
a guest May 10th, 2012 2,648 Never
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