Lecture 25, 02 Dec 2003 Chapter 15, Feeding and Digestion Chapter 16, Energy Expenditure, Body Size

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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 Vertebrate Physiology 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 ABSORPTION: -Across epithelium of brush border (microvilli) -Glycocalyx has enzymes for final cleavage disaccharidases, aminopeptidases, phosphatases 3 -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 (15-37) 4

5 ABSORPTION -Active Transport -amino acids with ~specific transporters coupled to Na+ 5 -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 (15-38) Lipids 6 ER Golgi Lacteal

7 Nutrient Transport in Blood 7 -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 Water and Electrolyte Balance in Gut 8 -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 Chapter Energy Expenditure -temperature -size -activity

12 Metabolism 12 -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 Chemical Energy 13 (16-1)

14 Metabolic Rate 14 -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 Metabolic Rates 15 -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 Metabolic Rates 16 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 Specific Dynamic Action (SDA) -Metabolic Rate increases during digestion -2-3x resting metabolism in ectotherms 17 (16-5) Think about infrequently feeding snakes...

18 Measuring Metabolism Direct Calorimetry -measure heat produced -known mass of water surrounding chamber -not often used (maybe for small birds, mammals) 18 Indirect Calorimetry 1. Bomb calorimetry (food and waste) 2. Radioisotopes deuterium or tritium (H 3 ) labelled water oxygen radioisotopes (O 18 ) (doubly-labelled water) -measure loss of CO 2 and water over time -can be used in the field -measure metabolism and water flux 4kJ = 1kcal Power (W)= J/s

19 Measuring Metabolism Respirometry -measure O 2 consumption and CO 2 production -assumes primarily aerobic metabolism -closed vs. open 19 4kJ = 1kcal Power (W)= J/s

20 20 lungs gills skin (16-3)

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

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

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

24 Aerobic Scope Mammal MAS (max aerobic speed) 7.5x that of Lizard MAS (of similar body size) 24 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 VO 2 Measurement - Before, during, and after exercise 26 Desert Iguana Thomas Hancock: data and slides

27 Activity and Associated Oxygen Consumption 27 EEOC:Excess Exercise O xygen Consum ption EPOC: Excess Post-exercise O xygen Consum ption VO 2 EXERCISE RECOVERY Time (min)

28 Activity and Associated Oxygen Consumption 28 TEOC = TotalExcess O xygen Consum ption = EEOC + EPOC EEOC EPOC VO 2 EXERCISE RECOVERY Time (min)

29 Muscle Lactate 29 Lactate (mm) Gastrocnemius RIF WIF Exercise, Recovery Time (min)

30 Energy BudgetIm plications 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 Length of Bout is Important: 31 VO 2 Time (min)

32 32 VO 2 Time (min)

33 33 VO 2 Time (min)

34 34 VO 2 Time (min)

35 35 EPOC is now a large fraction of the net metabolic expenditure. VO 2 Time (min)

36 Phylogenetic Effects 36 FMR (kj/day) 100g reptile 100g mammal 100g bird (Nagy, Girard, Brown 1999) Energy Budgets Ecological Role

37 Scaling Effects 37 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 Knut Schmidt_Nielsen 1972 0.1mg/kg 0.

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

39 (16-8) 39

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

41 41 (16-8) MR = am b b = 0.75 logmr = loga + b(logm) (slope)

42 (16-7) 42

43 END xx

Digestion. Generalized Digestive System. Salivary glands (mucin) to lubricate. 2 (incl. stomach) Tongue for chemoreception.

Digestion. Generalized Digestive System. Salivary glands (mucin) to lubricate. 2 (incl. stomach) Tongue for chemoreception. Digestion 24 Generalized Digestive System Salivary glands (mucin) to lubricate 1 2 1 2 (incl. stomach) Tongue for chemoreception 3 3 4 4 (Eckert 25 15-13) 1 Foregut -Conducting, Storage, Digestion -Esophagus