Hormonal Regulation: Tissue Specific Metabolism & the Metabolic States

Hormonal Regulation Tissue Specific Metabolism & the Metabolic States: Absorptive state is a series of metabolic reactions that your body does when food is in plenty (store it for use later) The brain does not store energy, it just uses it (glucose that goes through the BBB) Post Absorptive State occurs when food is not in plenty and the body is in need of energy (breaking down molecules and releasing energy) Fatty acids cannot be broken down to make glucose, but glycerol can Insulin & Glucagon: Metabolism is simply the flow of energy throughout the body (energy is entered as food and absorbed as amino acids, fats, or carbohydrates) Insulin regulates the storage of glucose and glucagon regulated the release of glucose from storage Brain uses 60-70% of all energy we eat Glucose concentration wants to stay at around 70-120 mg/dL Anything above is known as hyperglycemia (leads to eye, nerve, and kidney disease which is known as diabetes → only need 1260 mg/dL to be diagnosed with it) and anything below is known as hypoglycemia (leads to being tired, lethargic, coma, and even death! → start to notice at around 40 mg/dL) Insulin causes glycolysis, glycogenesis (takes glucose and stores it in liver or muscle and is reversible) and also lipogenesis (make lipids/fatty acids which is irreversible forming adipose tissue) Glucagon causes glycogenolysis to occur, cause amino acids to undergo gluconeogenesis, and also cause ketogenesis (takes fatty acids and converts them to ketone bodies which is irreversible and ketone bodies are energy source ONLY for the heart and the brain) Insulin inhibits the release of glucagon Glucose, Insulin, & Diabetes: Glucose needs insulin in order to enter the cells (surface of the cells have insulin receptors that control glucose channels) Type I Diabetes occurs if insulin is not created properly by the pancreas (insulin receptors are still working there’s just no insulin Type II Diabetes occurs when insulin receptors aren’t working properly or a desensitization occurs to insulin (pancreas is still forming insulin properly) → leads to an individual need more insulin in order for the receptors to work properly Problems arising from diabetes include damage caused from too high of sugar levels in the blood or even causing you to have no energy because the sugar is never broken down into ATP Production of Insulin & Glucagon: The pancreas sits in the retroperitoneum and the liver sits in the peritoneum (or the abdomen) The pancreas not only receives oxygen rich arterial blood from the heart, but also nutrient rich blood from the small intestine through the portal venous system which triggers hormone release of insulin and glucagon (travels to the liver because it has a 4x greater effect in the liver) Islet of Langerhans is an area in the pancreas which has beta cells (release insulin if influx of calcium occurs) on the inside and alpha cells (release glucagon) on the outside Release of insulin: 1. Glucose enters the beta cells through GLUT-2 Transporters 2. Glucose undergoes processes such as glycolysis, cell cycle, etc. and produce ATP 3. ATP will bind to K+ channels and block them (not allow K+ from leaving the cell making [K+] increase) 4. The increase in [K+] causes depolarization of the membrane 5. The depolarization will cause the opening of voltage gated Ca2+ channels ([Ca2+] increases) 6. Calcium will then bind to insulin and allow it to fuse to the cell and leave the beta cell into the bloodstream via exocytosis to be sent to the liver in portal venous blood We don’t know much about glucagon release, but we do know amino acids trigger glucagon release Hormone Control of Hunger: Hormone levels tell you if you’re hungry or full The hypothalamus does this Insulin block receptors in the hypothalamus to indicate that you are full When you eat a fatty meal the body will release leptin (polypeptide hormone and doesn’t really change much because it is based on adipose tissue amount) which will also block receptors in the hypothalamus to indicate that you are full An empty stomach will cause the release of ghrelin (gastric peptide hormone) to tell the hypothalamus that we are hungry Hormones, Body Mass, & Obesity: Basal metabolic rate is the amount of energy we consume just at rest (about 2000 kcal/day) Without leptin, the hypothalamus will never tell us that we are full and therefore will cause us to be hungrier all the time BS Extra Notes: Pepsin is found in the stomach and Trypsin is found in the intestines (both are a part of the class of enzymes known as proteases)