Unit 8 Flashcards
Describe the glucostatic theory of appetite regulation.
Works in a short time manner
- suggests that levels of blood glucose are an important feeding or satiety signal
- low levels of blood glucose stimulate the “feeding center” in the hypothalamus causing hunger
- high levels of blood glucose stimulate the “satiety center” in the HT and reduces appetite
Lipostatic theory of appetite regulation
Based on long term regulation of body fat via the hormone leptin
- increased leptin from fat cells causes a decrease in appetite (receptors in HT)
- decreased leptin from a low % body fat cause increase in appetite
Distinguish between the endocrine and exocrine secretions of the pancreas.
Endocrine secretions come from clusters of cells called islets and include the hormones insulin and glucagon
Exocrine secretions include digestive enzymes and a watery solution of sodium bicarb (to help neutralize stomach acid)
Carbohydrate digestion
Digested by amylase coming from saliva and the pancreas. Broken down into mono and disaccharides
How are disaccharides broken down further into monosaccharides
By the enzyme disaccharidase
Protein digestion
Proteins are broken down into peptides and amino acids by proteases and peptidases from the small intestine and exocrine cells of the pancreas
What begins protein digestion
Pepsin which is secreted from the stomach
Pepsinogen is the inactive form of pepsin which is activated by HCL (low pH)
Lipid digestion
Lipids are broken down by bile salts which emulsify large blobs into small blobs. The small blobs are broken down into fatty acids and monoglycerides by lipase.
How is glucose and amino acids absorbed
Secondary active transport and leave the cell by facilitated diffusion
How do large proteins get absorbed
This mostly happens in infants but are absorbed by endocytosis and leave by exocytosis
How do fatty acids and cholesterol enter/exit the cell?
Enter by simple diffusion and the form a chylomicron which leaves the cell by exocytosis
Cephalic phase of digestion
Anticipation of food stimulates the parasympathetic neurons which stimulate salivary glands to secrete water, enzymes, and mucous. The enteric nervous system is also stimulated which causes:
Stomach: to increase motility and secretions
Intestines: to increase motility and secretions
Sphincter of Oddi: to relax
Gall bladder: to increase contraction
Gastric phase of digestion
Increase parasympathetic activity, gastric stretch, aa and fa in gastric chyme and pH stimulate the hormone gastrin which is secreted by the G cells of the antrum of the stomach.
What are the target cells of gastrin secretion in the gastric phase of digestion
- Parietal cells of the stomach which the increase HCl secretion (converting pepsinogen to pepsin)
- Chief cells of the stomach which increase pepsinogen secretion
- Lower esophageal sphincter which increase contraction
- illeum and colon which increase contraction to make room for incoming food
Intestinal phase of digestion
Acidic chyme enter the small intestines
-Increased H+ causes the duodenal cells to secrete secretin which causes a decrease in gastric motility and decreased emptying of the stomach. Also causes in increase in pancreatic juice secretion (esp. bicarb)
Increased fatty acids and amino acids cause jejunal cells the release cholecystokinin (CCK) which causes in increase in pancreatic juice secretion (esp. bicarb), decreased gastric motility and emptying of the stomach, and cause contraction of the gall bladder
Increased carbohydrates cause the duodenal cells to secrete glucose-dependent insulinotropic peptide which cause the beta cells of the pancreas to secrete insulin
