List and describe 6 nervous and chemical (both food contents and cellular secretions) signals that regulate GI function. For each, describe the initial stimulus for secretion, source tissue/cells, target tissues, and final effects of their activities. [Suggestion: Make a table for comparison, with a brief caption.]
HORMONES -
1. VIP - vasoactive intestinal peptide.
Location - found in nerves of G.i.t , bloodbrain and autonomic nerves.
Stimulated by - fatty meals.
Actions - It markedly increases intestinal secretion of electrolytes and water.
2. CCK - pancreozymin -
Location - J-cells of duodenum and jejunum .
Stimulated by - peptides and aminoacids.
Action - contraction of gall bladder and relaxes sphincter of oddi.
3. Gastrin -
Location - G-cells of duodenum.
Stimulated by - peptides and aminoacids.
Action- H+ secretion by gastric parietal cells.
4. Secretin -
Location - S - cells of duodenum.
Stimulated by - H+ and fatty acids in duodenum.
Action - increases secretion of HC03- by pancreas and bile.
5. Somatostatin -
Location - by GIT.
Stimulated by - H+ in lumen.
Action - inhibit the secretion of GIT hormones and growth hormones.
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