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Biology Lecture #3 - Regulation of the Digestive System.docx

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BIOL 103
Virginia K Walker

Biology Lecture #3 – Regulation of Digestion System  Topics to be covered – regulatory physiology, pioneering discoveries, the peptic ulcer Stomach  Why aren’t cells in stomach lining hydrolyzed by pepsin nor damaged by hydrochloric acid?  Gastric glands lining stomach produce pepsin in an inactive form called pepsinogen, and this combined with hydrochloric acid becomes pepsin  Parietal cells that produce HCl don’t accumulate all at once, rather they are formed after secretion and then the reaction between H+ and Cl- ions that are delivered via pumps that push against a 1: 3 000 000 gradient (largest gradient that must be overcome inside the human body)  Cells that line the stomach produce a mucous that has a pH of 6 that protects against the acid Regulation of Digestion  Nervous system has two main functions  Control of muscular and glandular activity by local nerves  Regulation by the brain  Hormones  Secreted mainly be cells that are in the epithelium of the stomach and small intestine that tend to directly affect those organs  Gastrin  secreted by stomach in response to a meal that stimulates muscle contraction and acid production, returns to stomach via blood  Secretin and CCK  secreted by movement of acidic chime into small intestine, stimulates secretion of digestive enzymes and bicarbonate from pancreas  stimulates the contraction of gallbladder to release bile  food particles lead to release of gastrin which increases the acidity of the stomach, which then leads to the release of secretin and feedbacks and blocks gastrin  cystic fibrosis , recessive disease that causes disruption in a transporter protein, CFTR  pathology associated with the defective protein is that the secretion of mucous is thick and sticky, and therefore has much effect on body such as not being able to clear the mucous  mucous blocks the ducts from the stomach down into the small intestine and blocks enzymes from reaching their destinations, resulting in symptoms of malnourishment  patients therefore have to be on antibiotics for much of life  Targe
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