Transcript Glucose2
1QQ # 3 Name on top edge, back side of paper Answer on blank side of paper. 1. You’re called to the football field and asked to assist with a player who has stopped drilling on a hot humid summer day. How will you determine whether the athlete is experiencing heat exhaustion or heat stroke? What symptoms will you be looking for in each condition? 2. What type of drug would you take to control a fever? What is the mechanism of action of such drugs? Would you take that drug if your fever were 100 degrees Farenheit? Why or why not? Absorptive Phase Fig. 16.01 Lipoprotein Lipase =sink Hepatic Portal System Once inside, glucose is converted to something else, thereby maintaining a concentration gradient for facilitated diffusion of glucose into cells. Liver Typical vasculature: Artery-Arteriole-Capillary-Venule-Vein-Heart Islets of Langerhans Alpha cells secrete glucagon Beta cells secrete insulin Delta cells secrete somatostatin Route of blood Hepatic portal system Artery-Arteriole-Capillary-Portal Vessel- Capillary-Venule-Vein-Heart Fig. 16.02 Special case: Muscle wasting of starvation Glucose Sparing Special term: Glycogenolysis & Gluconeogenesis Post-absorptive phase Note: Nervous tissue can use glucose and ketones Major Points • Absorptive phase lasts ~ 4 hours, cells “burn” glucose. • During absorptive phase, energy needs provided by recently digested food • During absorptive phase, excess is converted to stored fuel • During post-absorptive phase, energy need met by release of stored fuels, most cells “burn” fatty acids, nervous tissue uses glucose and ketones. • Fasting defined as greater than 12 hours after previous meal (some say 24 hrs) • Fasting for several days has little effect on plasma glucose levels The Issues • How do cells “know” which fuel to “burn?” • How do cells “know” when to synthesize glycogen or lipids and when to break down glycogen or lipid? • What is responsible for the transitions from the absorptive and post-absorptive states? • How does glucose get into “sink” cells? Identify sensors, afferent pathway, integrator, efferent pathway, effectors Fig. 16.07 How is insulin secretion affected if plasma glucose is lower than set point? Which cell types have insulin receptors? Exercise (via an undescribed mechanism) increases the number of glucose transporters in muscle cell membrane Peptide hormone GLUT-4 Activates some enzymes, inactivates others: see next slide! ↑ plasma glucose →↑insulin secretion→↑glucose uptake into cells →↓ plasma glucose Diabetes mellitus: T1DM =beta cells fail to produce adequate insulin (5%) T2DM = target cells “resistant” (less responsive) to insulin Stimulatory actions of insulin in green Inhibitory actions of insulin in dashed red Absorptive Phase Post-Absorptive Phase Thinking about food Factors that influence Insulin Secretion ? FF WHY? The Integrator integrates multiple inputs FF Glucose uptake, Storage, Lipogenesis Another hormone that regulates plasma glucose concentration Glucagon prevails during postabsorptive phase Transition from absorptive to postabsorptive phase? Graph your daily caloric intake over a 48 hour period Plasma Glucose Calories consumed 100 65 6am Noon 6pm MN 6am Noon 6pm MN 6am Overlay INSULIN SECRETION on the graph Overlay GLUCAGON SECRETION on the graph Noon Glucose-counterregulatory controls (oppose effects of insulin) Glucagon Epinephrine Cortisol (permissive effect) Growth hormone (permissive effect) Fig. 16.10 EPI, yet another horomone in glucose homeostasis, effects opposite of Insulin Don’t fret about receptors, afferent pathway, and integrator for this feedback loop. Who Cares? A Case Study • On our website at • http://webs.wofford.edu/davisgr/bio342/oggt.htm A Case Study of Glucose Homeostasis A 35 year old male presented with the following complaints: frequent severe headaches upon awakening at 4:30 am, blurred vision, and fatigue due to excessive stress at work. The patient complained of routine 16 hr workdays followed by a midnight snack of breakfast cereal. An OGTT was ordered and provided the following results: During the second hour of the OGTT, the patient exhibited anxiety, paleness, hunger, tremulousness, and cold sweat. No additional tests were ordered. The patient was instructed to replace the midnight snack of cereal with a protein-rich snack. Oral Glucose Tolerance Test • Overnight fast, no beverages other than water • Fasting blood sample • Ingest 75 grams glucose • Blood samples every 0.5 hours for 3-5 hours • Plot plasma glucose concentration over time • Compare curves Sugar content of Red Bull? 60 Stress, Emergency (fight or flight), Exercise Effect on Alpha Cells Effect on Beta cells The Answer to the Problem? • Rationale for substituting protein for carbohydrate midnight snack?