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PET3361EXAM II STUDY GUIDE1. Define postabsorptive and postprandial states and explain how each of the macronutrients is absorbed into the system.• Postabsorptive state = Fasting stateo After an overnight fast, blood glucose is maintained by glycogenolysis (break down of glycogen) and gluconeogenesis (formation of glucose from non-carbohydrate source) in the livero Glycogenolysis provides 65-75% of the glucose releasedo Gluconeogenesis provides the remaining 25-35% of the glucose released by the liver.o Muscle glycogen cannot be converted to blood glucose• Postprandial sate = Fed stateo Absorbed glucose is being stored as glycogen (glycogenesis) in skeletal muscles and livero Most cells of the body are removing glucose for energy (glycolysis), especially neurons and red blood cellso Adipose cells remove glucose to form glycerol needed for triglycerides formation and fatty acids• Absorption of Carbohydrates:o Monosaccharides are absorbed through the wall of the small intestine into capillaries leading to the portal veino Glucose and Galactose are absorbed by secondary active transport coupled to Na+ transport into the epithelial cells and then move into the blood by facilitated diffusiono Fructose is absorbed through epithelial cells and into the blood by facilitated diffusion• Fats and water are absorbed through – Passive absorption• Fructose is absorbed through – Facilitated absorption• Amino Acids and Glucose are absorbed through – Active absorption2. Which hormones control blood glucose and how? How does exercise influence these responses?o Insulino Secreted from Beta cells in the Pancreaso Released when blood glucose higho Causes active transport of amino acids into tissue cellso Causes facilitated diffusion of glucose into tissue cellso Leads to a decrease in Blood glucose and increase in stored glycogeno Gradually decreases as exercise intensity increases (blunted response)o Glucagono Secreted from Alpha cells in the Pancreaso Released when blood glucose is lowo Stimulates glycogenolysis and gluconeogenisiso Stimulates fat breakdowno Causes increased Blood glucose levelo Epinephrine & Norepinephrineo Work in conjunction with Glucagon to raise blood glucose levelso Stimulate fat breakdowno Stimulate glycogenolysis and gluconeogenesiso Exercise causes increase in Epinephrine and Norepinephrine levels3. What factors influence CHO use during exercise and how?• Exercise Intensityo The greater the intensity of exercise = the quicker the depletion of stored glycogeno As you increase exercise intensity you increase reliance on CHO and decrease your reliance on fat• Exercise Durationo The longer the exercise goes, the more depleted glycogen stores get• Initial Glycogen Levelso A higher carbohydrate intake causes higher levels of glycogen stores during exercise. o Higher levels will last longer, will not be depleted as quickly as if the initial glycogen levels were low• Training Statuso The more trained you are, the more efficiently you can use fuels4. What is the recommended timing for the feeding of CHO before exercise?• Timingo 30-60 minutes before exercise Some studies with heavy exercise reported reductions in endurance Studies using moderate intensity reported no significant difference Probably better for moderate intensity activityo 3 or more hours before exercise This has been found to improve performance5. What are the general guidelines for a pre-competition meal?• Pre-competition meal general guidelines:o Carbohydrate feeding 3-4 hours before exerciseo 150-300 grams of carbohydrates (3-5 grams/kilogram body weight)o Solid or liquido Relatively little fat or fiber (avoid fried foods) These cause discomfort, digestive rate slows, potentially doesn’t allow access to other fuelso Limit protein (controversy)6. When is it most beneficial to feed CHO during exercise? What are the guidelines?• Feeding glucose or glucose polymers during exercise improves endurance (only if the exercise lasts more than 60 minutes)o Feeding during exercise spares muscle glycogen (type I), and maintains your blood glucose levelo A glucose-electrolyte drink between 4-8% is optimal• Feeding glucose during performance DOES NOT help when:o Subjects are hyperthermico During high intensity exercise when fatigue is due to accumulation of H+ in muscles (lasting 20-30 minutes)o During events lasting 30-45 minutes7. How does CHO feeding during recovery influence muscle glycogen?• Immediate feeding post-exercise causes greater glycogen synthesis for the first 2 hours• Early feeding (post-exercise) has an increased muscle glycogen storage compared to later feeding (post-exercise) for up to 4 hours8. What factors enhance glycogen synthesis and how?• Glycogen depletiono When depleted, this increases the percentage of activated GS I-form, the more active form of glycogen synthase.• Presence of Insulino Insulin enhances glycogen synthesis and uptake of glucose from the blood• Exerciseo Exercise can activate GS I-form of glycogen synthase, and causes Glut-4 to be present at the cell membrane (transporter)9. Know the recovery feeding guidelines for enhancing muscle glycogen storage.• Guidelines for Post-exercise carbohydrates:o Feed approximately 1-1.5g /kg each hour for the first 4 hours after exerciseo Within the first 6 hours after exercise, high GI foods or simple CHO provide the best glycogen replacemento These foods increase insulin levels in the blood, stimulating glucose transport into the cell and glycogen synthesiso Provide CHO replacement beverage with 70-90 g CHO immediately after exercise if the athlete are eating self-selected diets, are unable to eat within 2 hours, or are not hungry• Carbohydrates after exercise:o High glycemic, carbohydrate-rich foodso Either a single large meal or small frequent meals will replenish glycogen storeso SHOULD BE CONSUMED AS SOON AS POSSIBLE AFTER EXERCISEo Avoid fructose and other slow-digesting carbohydrates10. How does muscle damage influence glycogen resynthesis?• Eccentric exercise causing muscle soreness and damage is accompanied by reduced muscle glycogen resynthesiso This may be due to the damage to the sarcolemma and interference with glucose transport into the muscle fibero May also be due to the inflammatory response and increased glucose oxidation by neutrophils11. What are the guidelines for daily CHO intake?• Daily CHO intake:o Feed 5-7 g/kg body weight over 24 hour period for

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FSU PET 3361 - Exam 2

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