anim_hormonal_control_digestive_activities_answer_key.doc

Hormonal Control of Digestive Activities To complete this worksheet, select: Module: Energy Acquisition Activity: Animations Title: Hormonal Control of Digestive Activities Introduction 1. Hormones regulate several digestive activities. As review, describe each of the following parts of an endocrine feedback loop. Stimulus – a change in body condition. Production Cell –an endocrine cell that produces a hormone after being affected by the stimulus. Hormone – the signaling chemical. Target Cell - the cell(s) receptive to the hormone. Action – what the cell(s) do(es) when affected by the hormone. Response – The overall change in controlled body condition as a result of the feedback loop. Gastrin (increased stomach distention) 2. Describe the two events that stimulate gastrin secretion. The two events are the presence of food that causes distention and the release of HCl and change in pH. 3. Describe G cell function. G cells located in the mucosa produce gastrin that binds to and stimulates parietal and chief cells. The stimulated parietal cells produce more HCl and the chief cells produce more pepsinogen. 4. What are the gastrin target cells and where are they located? The target cells for gastrin are the parietal and chief cells located in the mucosa. 5. Describe the response of gastric mucosal target cells to gastrin. Parietal Cells - produce more HCl. Chief Cells - produce more pepsinogen. 6. Describe the stomach’s response to increased pepsin and gastric acid. Increased pepsin and gastric juice increase the stomach’s ability to digest proteins. 7. What effects does gastrin have on smooth muscle cells of the muscularis? Gastrin binds to smooth muscle cells causing increased gastric motility, opening of the pyloric sphincter and increased gastric emptying. Secretin (increased stomach distention) 8. Acidic chyme entering the duodenum is the stimulus. Identify the production cells - The S cells in the intestinal mucosa. Identify the hormone – the hormone is secretin. 9. a. What is the secretin target? Secretin targets the pancreatic Acinar cells. b. What is the target response? Secretin stimulates the pancreas to produce and deliver more bicarbonate to the small intestine. c. What is the affect of bicarbonate? Bicarbonate buffers the acidity of the gastric chyme and protects intestinal tissue. 10. a. Describe the stomach mucosa’s response to secretin. Secretin also targets the acid-producing parietal cells of the gastric mucosa and inhibits gastric acid secretion. With less gastric acid the chyme enters the small intestine is less acidic. Cholecystokinin (increased acidic chyme) 11. What stimulates production of cholecystokinin (CCK)? CCK is stimulated by the entrance of fatty chyme into the duodenum. 12. a. Identify CCK target cells. The enteroendocrine cells are targeted to produce CCK which then targets the pancreas. b. What is the target cell response? The pancreas responds by delivering pancreatic lipase and bile to the small intestine to promote the digestion of fats in the chyme. c. How does this endocrine loop address increased chyme fat? As more fatty chyme undigested protein enters the duodenum more CCK will be released to stimulate the pancreas to release more pancreatic lipase and bile. It will also trigger closing of the pyloric sphincter and inhibit gastric emptying. 13. Describe the enterogastric reflex. What stimulates the reflex? The presence of fatty chyme What is the CCK target and its response? Pancreatic acinar cells to secrete pancreatic lipase and biliary system to release bile into the small intestine for fat emulsification.. Explain the necessity of the enterogastric reflex. Regulate the movement and digestion of fatty substances since these take the longest to digest.