G. Metabolic Thermoregulation 4. How is body temperature maintained in wild?

1. G. Metabolic Thermoregulation • 4. How is body temperature maintained in wild? • a. thermoreceptors in CNS, skin • b. hypothalamic set point

2. c. If TB < set point, warm up • usually because TA < TB causes heat loss • (1) high BMR • (2) active heat production • Thermogenesis • shivering: asynchronous motor units • nonshivering: increase cellular calorigenesis

3. These are E expensive • must be adapted to gain large amounts of E and O2 • 10 X intestinal surface area, 15 X lung surface area of ectotherms

4. (3) cheaper alternative • adaptations to reduce heat loss • (a) Insulation • external pelage: fur or feathers • internal fat: blubber • (b) keep heat from environment by peripheral vasoconstriction: pale

5. d. If TB > set point, cool down • occurs if TA > TB • also occurs if metabolic heat production increases • e.g. activity • insulation increases danger of overheating

6. Cooling achieved by: • (1) passive heat loss: heat lost across skin by conductance • peripheral vasodilation: flushing • (2) active heat loss: increase mr to activate mechanisms to lose heat • evaporation • cutaneous water loss: sweating • respiratory water loss: panting

7. Therefore, in endotherms: • at high temperatures: animal must work to cool • at low temperatures: animal must work to heat • in between, heat produced by BMR adequate to maintain TB

8. e. Animal in trouble at extremes • (1) Hypothermia: heat loss exceeds maximum metabolic production • (2) Hyperthermia: heat gain exceeds maximum cooling capacity • Q10 effect becomes important

9. 5. Some animals well adapted to survive at extremes • a. Coldest environments for homeotherms • Polar terrestrial and aquatic • Adaptive strategy: • (1) conserve E rather than increase expenditure • Slope of curve depends on thermal conductivity across animal’s skin

10. Ways to reduce thermal conductivity of skin • (a) improve pelage length and density to trap more air • (b) improve internal insulation with thick blubber • low thermal conductivity • low vascular supply • doesn’t require air to insulate • blood can bypass to shed heat if necessary

11. (2) Large size reduces heat loss • (3) Alternatively, give up • (a) Hibernation: • prolonged regulation of TB 1° above TA • 95% energy conservation • (b) Torpor: • brief drops in TB (overnight) • small mammals and birds

12. b. Survival in hot environments • Limited to small range • (1) MR increases to support evaporation • Requires water vapor pressure gradient between animal and environment • Lung: 47 mm Hg H2O vapor • Hot, dry environments: 10-30 mm Hg • Hot, humid environments: reduce v.p. gradient • Hot, humid environments are stressful

13. Rarely give up in hot environments • (2) Heat storage • large animals (camels) allow TB to increase during the day • returns to normal at night • Cool blood going to brain with inspired air • (3) Behavior: nocturnal, burrow

14. 7. Characteristics of Endotherms: • a. Big • b. Require lots of food and oxygen • c. Insulation • d. Sustained activity • e. Fast growth • f. Broad geographical range • All these describe dinosaurs

15. IX. GAS TRANSPORT • A. Principles of Gas Supply and Exchange • 1. Respiration: acquisition of O2 for aerobic metabolism • Diffusion is limited to 1 mm, so systems must exist for supply

16. 2. Pressure • Movement of gas is strictly a passive process • No active transport is used • Animals can't pump gas • a. Basic force: • Diffusion down pressure gradients

17. b. Total atmospheric P at sea level, 20˚ • 760 mm Hg • c. Equals sum of partial pressures of all constituent gases • Each gas contributes in proportion to its % composition of air • e.g., O2 = 159 mm Hg

18. Partial Pressure (mm Hg) Clean Dry Air at Sea Level % Composition Etc. < 1% < 7 CO2 0.03% 0.23 O2 20.9% 159 N2 78% 593

19. 3. Factors can modify this pressure • a. Altitude • Increased altitude decreases total and partial pressures • b. Presence of other gases • Additional gases in air will displace oxygen

20. (1) H2O vapor • all tissues are saturated with water • surrounded with water vapor • (a) water vapor displaces 02 • (b) depending on “relative humidity” • air saturated with H2O vapor = 100% relative humidity • (c) ability of air to hold water vapor is temperature dependent

21. Partial Pressure (mm Hg) • Displaces O2: Clean, moist air at sea level, 37° % Composition CO2, Etc. < 1% < 9 O2 19.6% 149 N2 73% 555 H2O 6.2% 47

22. (2) CO2 • (a) Produced by metabolism inside animal

23. Partial Pressure (mm Hg) • (b) Further displaces O2:Mammal lung, 37°, 100% r.h. % Composition Etc. < .3% < 1 O2 13% 100 N2 74.5% 568 CO2 6% 45 H2O 6.2% 47

24. 4. Animals also concerned with gas concentrations • a. concentration = number of molecules/unit volume • b. In air, [O2] is high • e.g. at 24˚, 192 ml O2/L air

25. c. Aquatic environments • [O2] is low • because solubility of O2 in water is low • O2 in air diffuses into water until pressures are equal

26. c. Aquatic environments • [O2] is low • because solubility of O2 in water is low • O2 in air diffuses into water until pressures are equal 159 pO2 0

27. c. Aquatic environments • [O2] is low • because solubility of O2 in water is low • O2 in air diffuses into water until pressures are equal 159 0

28. c. Aquatic environments • [O2] is low • because solubility of O2 in water is low • O2 in air diffuses into water until pressures are equal 159 159

29. c. Aquatic environments • [O2] is low • because solubility of O2 in water is low • O2 in air diffuses into water until pressures are equal [O2] = 192 ml/L pO2 159 [O2] = 6.6 ml/L 159

30. d. [O2] also decreases with increasing T • 760 mm, pO2=159, 15˚: • 7.8 ml O2/L H2O • 760 mm, pO2=159, 35˚: • 5.0 ml O2/L H2O • Therefore, for aquatic environments, [O2] is low and temperature dependent

31. B. Animals therefore exist in 2 distinct respiratory environments: • 1. Terrestrial: air is respiratory medium • a. low viscosity and density • b. relatively high [O2] • c. rapid diffusion of gas: homogeneous • 2. Aquatic: water is medium • a. high viscosity and density • b. relatively low [O2] (down to 0) • c. slow diffusion: heterogeneous

32. C. Respiratory Transport Scheme • 1. Sum of all gas transport mechanisms used in an animal • Reflects animal’s function as system to convert O2 to CO2

34. External Internal TISSUES SKIN

35. External Internal pO2: 160 mm < 25 mm

36. External Internal pO2: 160 mm < 25 mm

37. External Internal pO2: 160 mm < 25 mm pCO2: 0.2 mm up to 50 mm

38. External Internal pO2: 160 mm < 25 mm pCO2: 0.2 mm up to 50 mm O2 Gradient

39. External Internal pO2: 160 mm < 25 mm pCO2: 0.2 mm up to 50 mm O2 Gradient CO2 Gradient

40. C. Respiratory Transport Scheme • 1. Sum of all gas transport mechanisms used in an animal

41. 2. Animals can still speed gas movement • a. Make it easy for gas to to cross membranes • b. Provide gas transport systems which facilitate diffusion

42. 3. Adaptations to facilitate diffusion • a. Specialized organ at interface of animal and medium • Respiratory Organ

43. < 25 mm Respiratory Organ up to 50 mm

44. b. Specialized internal transport mechanism to speed diffusion over distances • Blood

45. < 25 mm BLOOD up to 50 mm

46. c. Specialized mechanism in ECF to facilitate diffusion from blood to cells • Carrier Proteins

47. < 25 mm Carriers up to 50 mm

48. < 25 mm Carriers up to 50 mm D. Respiratory Organs

49. Generalized Structure of Respiratory Organs

50. Generalized Structure of Respiratory Organs RESPIRATORY EPITHELIUM