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Lecture 25, 02 Dec 2003 Chapter 15, Feeding and Digestion

1. Lecture 25, 02 Dec 2003 Chapter 15, Feeding and Digestion Chapter 16, Energy Expenditure, Body Size Vertebrate Physiology ECOL 437 University of Arizona Fall 2003 instr: Kevin Bonine t.a.: Bret Pasch. 2. Vertebrate Physiology 437. 1. Feeding and Digestion (CH15)

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Lecture 25, 02 Dec 2003 Chapter 15, Feeding and Digestion

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  1. 1 Lecture 25, 02 Dec 2003 Chapter 15, Feeding and Digestion Chapter 16, Energy Expenditure, Body Size Vertebrate Physiology ECOL 437 University of Arizona Fall 2003 instr: Kevin Bonine t.a.: Bret Pasch

  2. 2 Vertebrate Physiology 437 1. Feeding and Digestion (CH15) 2. ~Energy Expenditure (CH16) 3. Announcements… - Term paper 04 Dec. - Seminar write-up 09 Dec. - Powerpoint (file to us on 09 Dec.) - Oral Presentations 10 Dec. (8min) - Movie and Thanksgiving Assgt due Wed - Read Ch17 for Thurs lecture - Friday Physiology Seminar (calcium regulation in endothelial cells)

  3. 3 ABSORPTION: -Across epithelium of brush border (microvilli) -Glycocalyx has enzymes for final cleavage disaccharidases, aminopeptidases, phosphatases -Simple Diffusion 1 fat-soluble substances 2 small water soluble substances through regulated aquaporins 3 down concentration or electrochemical gradients -Facilitated Diffusion 1 monosaccharides and amino acids 2 transporter proteins 3 down conc. gradient or 4 coupled to Na+ gradient (Na/K-ATPase)

  4. 4 (15-37)

  5. 5 ABSORPTION -Active Transport -amino acids with ~specific transporters coupled to Na+ -Lipids -products cross into epithelial cells (monoglycerides, fatty acids, glycerol) -reconstructed into triglycerides -formed into chylomicrons using cholesterol and phospholipids -chylomicrons exocytosed -taken into central lacteal and into lymph system

  6. 6 Lipids ER Golgi Lacteal (15-38)

  7. 7 Nutrient Transport in Blood • lipids (chylomicrons) into blood from lymph at • thoracic duct • -sugars and amino acids into capillaries of villi • -to liver via hepatic portal vein • sugars converted to glycogen for storage

  8. 8 Water and Electrolyte Balance in Gut • Lots of water and electrolytes secreted into • lumen • Need to recover • Most via lower small intestine (ileum) • Osmotic gradient b/c absorb salts, carbos, amino acids • Tips of villi • Countercurrent exchange with high Na+ (Cl- follows) to • facilitate water reabsorption

  9. 9 Secretions etc. ileum (15-39) =

  10. 10 Nutritional Requirements… (Essential?)

  11. 11 Chapter 16 Energy Expenditure -temperature -size -activity

  12. 12 Metabolism -Chemical reactions in the body -Temperature dependent rates -Not 100% efficient, energy lost as heat (not ‘lost’ if used to maintain Tb) 1. Anabolic -creation, assembly, repair, growth (positive nitrogen balance) 2. Catabolic -energy release from complex molecules (carbos, fats, proteins) -energy storage in phosphate bonds (ATP) and metabolic intermediates (glucose, lactate)

  13. 13 Chemical Energy (16-1)

  14. 14 Metabolic Rate -measurable conversion of chemical energy into heat -used to understand: -energy budgets -dietary needs -body size implications -habitat effects -costs of various activities -mode of locomotion -cost of reproduction

  15. 15 Metabolic Rates -Basal Metabolic Rate, BMR -minimal environmental and physiological stress (appropriate ambient temperature, post-digestive, resting etc.) -Standard Metabolic Rate, SMR -similar to BMR, but at a given Tb -Field Metabolic Rate, FMR -average metabolic rate of animal in natural setting -hard to measure

  16. 16 Metabolic Rates Basal Metabolic Rate, BMR -important components: 1. Membrane form and function maintenance of electrochemical gradients -proton pumps in mitochondrial membranes -Na/K-ATPase pumps in plasma membrane 2. Protein synthesis 3. ATP formation

  17. 17 Specific Dynamic Action (SDA) -Metabolic Rate increases during digestion -2-3x resting metabolism in ectotherms (16-5) Think about infrequently feeding snakes...

  18. 18 Measuring Metabolism Direct Calorimetry -measure heat produced -known mass of water surrounding chamber -not often used (maybe for small birds, mammals) Indirect Calorimetry 1. Bomb calorimetry (food and waste) 2. Radioisotopes deuterium or tritium (H3) labelled water oxygen radioisotopes (O18) (doubly-labelled water) -measure loss of CO2 and water over time -can be used in the field -measure metabolism and water flux 4kJ = 1kcal Power (W)= J/s

  19. 19 Measuring Metabolism Respirometry -measure O2 consumption and CO2 production -assumes primarily aerobic metabolism -closed vs. open 4kJ = 1kcal Power (W)= J/s

  20. 20 lungs gills skin (16-3)

  21. 21 RQ, Respiratory Quotient Rate of CO2 production RQ= Rate of O2 consumption 4kJ = 1kcal Power (W)= J/s Value depends on substrate oxidized: Energy Storage

  22. 22 RE, Respiratory Exchange Ratio RE = instantaneous ratio of O2 consumption and CO2 production (16-4)

  23. 23 Metabolic Scope Aerobic Metabolic Scope = max sustainable metabolic rate / BMR -usually measured as O2 consumption -often = 10-15 x BMR -does not include anaerobic contributions -best measured at steady-state, sustainable levels

  24. 24 Aerobic Scope Mammal MAS (max aerobic speed) 7.5x that of Lizard MAS (of similar body size) Anaerobic Scope Mammal and Lizard maximal speed equivalent at a given body mass -ecological implications? -both tend to increase with increasing body mass

  25. 25 Oxygen Debt -repay anaerobic contribution to elevated metabolism -oxidize anaerobic products (e.g., lactate) (16-2)

  26. 26 VO2 Measurement - Before, during, and after exercise Desert Iguana Thomas Hancock: data and slides

  27. 27 Activity and Associated Oxygen Consumption EPOC: Excess Post-exercise Oxygen Consumption EEOC: Excess Exercise Oxygen Consumption VO2 EXERCISE RECOVERY 0 15 30 45 Time (min)

  28. 28 Activity and Associated Oxygen Consumption TEOC = Total Excess Oxygen Consumption = EEOC + EPOC EEOC EPOC VO2 EXERCISE RECOVERY 0 15 30 45 Time (min)

  29. 29 Muscle Lactate Exercise,

  30. Energy Budget Implications 30 • Costs for Exercise and Recovery:- A Single Bout: 15 seconds at Maximum intensity • Traditional Estimates: 0.7% of daily energy expenditure • Inclusion of EPOC: 4.6% of daily energy expenditure

  31. 31 Length of Bout is Important: VO2 Time (min)

  32. 32 VO2 Time (min)

  33. 33 VO2 Time (min)

  34. 34 VO2 Time (min)

  35. EPOC is now a large fraction of the net metabolic expenditure. 35 VO2 Time (min)

  36. 36 Phylogenetic Effects FMR (kJ/day) 11.8 100g reptile 100g mammal 142 100g bird 242 (Nagy, Girard, Brown 1999) Energy Budgets… Ecological Role…

  37. 37 Scaling Effects Allometry - changes in body proportions as animals get larger (mouse vs. elephant) Metabolic Rate - mass-specific metabolic rate decreases with increasing body mass (16-6) linear cubed squared

  38. 38 Knut Schmidt_Nielsen 1972 0.1mg/kg 0.2mg for 70 kg (a) = elephant freaked out and died (1960’s) -What is the correct dose? -Importance of Scaling!

  39. 39 (16-8)

  40. 40 Scaling How do morphology and metabolism change with body mass? Body mass Power Functions: Scaling exponent MR = aMb Metabolic rate Y-intercept (of log-log plot) Take log of both sides logMR = loga + b(logM) (Linearizes) Can look at mass-specific rates by dividing through by M

  41. 41 (16-8) MR = aMb b = 0.75 (slope) logMR = loga + b(logM)

  42. 42 (16-7)

  43. xx END

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