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Hormonal Control of the Digestive system: Gastrin: A peptide hormone, that calls for the secretion of gastric juices from chief and parietal cells, also stimulates stomach to churn. Produced in G-cells in the gastric pits of the stomach lining and secreted into the blood stream. The release of gastrin is triggered by the presence of food in the stomach lumen especially protein. Gastrin is inhibited by low pH (less than 3)…. What kind of feedback is this? Secretin: A peptide hormone, that calls for the secretion of pancreatic juices. Produced in the S- cells in the duodenum and secreted into the blood stream. The release of secretin is triggered by the lowering of pH in the duodenum. What would trigger the lowering of pH? Cholecystokinin CCK: A peptide hormone, that calls for release of pancreatic juice and bile (empties gall bladder). Produced by cells lining the duodenum and secreted into bloodstream. Triggered by the presence of fat and partially digested proteins. This hormone also acts as a hunger suppressant. If someone was really hungry and ate quickly, how would this effect their food intake? Nerve Regulation of the Digestive system: Two types of nerves help to control the action of the digestive system: Extrinsic and Intrinsic Extrinsic (outside) nerves come to the digestive organs from the unconscious part of the brain or from the spinal cord. They release a chemical called acetylcholine and another called adrenaline. Acetylcholine causes the muscle of the digestive organs to squeeze with more force and increase the "push" of food and juice through the digestive tract. Acetylcholine also causes the stomach and pancreas to produce more digestive juice. Adrenaline relaxes the muscle of the stomach and intestine and decreases the flow of blood to these organs. Intrinsic (inside) nerves, which make up a very dense network embedded in the walls of the esophagus, stomach, small intestine, and colon. The intrinsic nerves are triggered to act when the walls of the hollow organs are stretched by food. They release many different substances that speed up or delay the movement of food and the production of juices by the digestive organs.