1. 17-1 G. Metabolic Thermoregulation 4. How is body temperature maintained in wild? a. thermoreceptors in CNS, skin b. hypothalamic set point

2. 17-2 c. If T B < set point, warm up usually because T A < T B causes heat loss (1) high BMR (2) active heat production Thermogenesis shivering: asynchronous motor units nonshivering: increase cellular calorigenesis

3. 17-3 These are E expensive must be adapted to gain large amounts of E and O 2 10 X intestinal surface area, 15 X lung surface area of ectotherms

4. 17-4 (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. 17-5 d. If T B > set point, cool down occurs if T A > T B also occurs if metabolic heat production increases e.g. activity insulation increases danger of overheating

6. 17-6 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. 17-7 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 T B

8. 17-8 e. Animal in trouble at extremes (1) Hypothermia: heat loss exceeds maximum metabolic production (2) Hyperthermia: heat gain exceeds maximum cooling capacity Q 10 effect becomes important

9. 17-9 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. 17-10 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. 17-11 (2) Large size reduces heat loss (3) Alternatively, give up (a) Hibernation: prolonged regulation of T B 1° above T A 95% energy conservation (b) Torpor: brief drops in T B (overnight) small mammals and birds

12. 17-12 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 H 2 O vapor Hot, dry environments: 10-30 mm Hg Hot, humid environments: reduce v.p. gradient Hot, humid environments are stressful

13. 17-13 Rarely give up in hot environments (2) Heat storage large animals (camels) allow T B to increase during the day returns to normal at night Cool blood going to brain with inspired air (3) Behavior: nocturnal, burrow

14. 17-14 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. 17-15 IX. GAS TRANSPORT A. Principles of Gas Supply and Exchange 1. Respiration: acquisition of O 2 for aerobic metabolism Diffusion is limited to 1 mm, so systems must exist for supply

16. 17-16 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. 17-17 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., O 2 = 159 mm Hg

18. 17-18 N2N2 O2O2 Etc. Clean Dry Air at Sea Level % Composition 78% 20.9% 0.03% < 1% CO 2 593 159 0.23 < 7 Partial Pressure (mm Hg)

19. 17-19 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. 17-20 (1)H 2 O vapor all tissues are saturated with water surrounded with water vapor (a) water vapor displaces 0 2 (b) depending on “relative humidity” air saturated with H 2 O vapor = 100% relative humidity (c) ability of air to hold water vapor is temperature dependent

21. 17-21 N2N2 O2O2 CO 2, Etc. % Composition 73% 19.6% 6.2% < 1% 555 149 47 < 9 Partial Pressure (mm Hg) Displaces O 2 : Clean, moist air at sea level, 37° H2OH2O

22. 17-22 (2) CO 2 (a) Produced by metabolism inside animal

23. 17-23 % Composition Partial Pressure (mm Hg) N2N2 O2O2 Etc. 74.5% 13% 6.2% <.3% 568 100 47 < 1 CO 2 H2OH2O 6%45 (b) Further displaces O 2 :Mammal lung, 37°, 100% r.h.

24. 17-24 4. Animals also concerned with gas concentrations a. concentration = number of molecules/unit volume b. In air, [O 2 ] is high e.g. at 24˚, 192 ml O 2 /L air

25. 17-25 c. Aquatic environments [O 2 ] is low because solubility of O 2 in water is low O 2 in air diffuses into water until pressures are equal

26. 17-26 159 0 pO 2 c. Aquatic environments [O 2 ] is low because solubility of O 2 in water is low O 2 in air diffuses into water until pressures are equal

27. 17-27 159 0 c. Aquatic environments [O 2 ] is low because solubility of O 2 in water is low O 2 in air diffuses into water until pressures are equal

28. 17-28 159 c. Aquatic environments [O 2 ] is low because solubility of O 2 in water is low O 2 in air diffuses into water until pressures are equal

29. 17-29 159 [O 2 ] = 192 ml/L [O 2 ] = 6.6 ml/L pO 2 c. Aquatic environments [O 2 ] is low because solubility of O 2 in water is low O 2 in air diffuses into water until pressures are equal

30. 17-30 d. [O 2 ] also decreases with increasing T 760 mm, pO 2 =159, 15˚: 7.8 ml O 2 /L H 2 O 760 mm, pO 2 =159, 35˚: 5.0 ml O 2 /L H 2 O Therefore, for aquatic environments, [O 2 ] is low and temperature dependent

31. 17-31 B. Animals therefore exist in 2 distinct respiratory environments: 1. Terrestrial: air is respiratory medium a. low viscosity and density b. relatively high [O 2 ] c. rapid diffusion of gas: homogeneous 2. Aquatic: water is medium a. high viscosity and density b. relatively low [O 2 ] (down to 0) c. slow diffusion: heterogeneous

32. 17-32 C. Respiratory Transport Scheme 1. Sum of all gas transport mechanisms used in an animal Reflects animal’s function as system to convert O 2 to CO 2

33. 17-33

34. 17-34 ExternalInternal SKIN TISSUES

35. 17-35 ExternalInternal pO 2 :160 mm< 25 mm

36. 17-36 ExternalInternal pO 2 :160 mm< 25 mm

37. 17-37 ExternalInternal pO 2 :160 mm< 25 mm pCO 2 :0.2 mmup to 50 mm

38. 17-38 ExternalInternal pO 2 :160 mm< 25 mm pCO 2 :0.2 mmup to 50 mm O 2 Gradient

39. 17-39 ExternalInternal pO 2 :160 mm< 25 mm pCO 2 :0.2 mmup to 50 mm O 2 Gradient CO 2 Gradient

40. 17-40 C. Respiratory Transport Scheme 1. Sum of all gas transport mechanisms used in an animal

41. 17-41 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. 17-42 3. Adaptations to facilitate diffusion a. Specialized organ at interface of animal and medium Respiratory Organ

43. 17-43 Respiratory Organ < 25 mm up to 50 mm

44. 17-44 b. Specialized internal transport mechanism to speed diffusion over distances Blood

45. 17-45 up to 50 mm < 25 mm BLOOD

46. 17-46 c. Specialized mechanism in ECF to facilitate diffusion from blood to cells Carrier Proteins

47. 17-47 up to 50 mm < 25 mm Carriers

48. 17-48 up to 50 mm < 25 mm D. Respiratory Organs Carriers

49. 17-49 Generalized Structure of Respiratory Organs

50. 17-50 RESPIRATORY EPITHELIUM Generalized Structure of Respiratory Organs

51. 17-51 MEDIUM Generalized Structure of Respiratory Organs ENVIRONMENT High pO 2

52. 17-52 MEDIUM BLOOD Generalized Structure of Respiratory Organs High pO 2

53. 17-53 MEDIUM BLOOD Generalized Structure of Respiratory Organs High pO 2 VASCULAR ENDOTHELIUM

54. 17-54 BLOOD Generalized Structure of Respiratory Organs ECF MEDIUM High pO 2

55. 17-55 MEDIUM High pO 2 BLOOD ECF Generalized Structure of Respiratory Organs

56. 17-56 MEDIUM BLOOD Generalized Structure of Respiratory Organs High pO 2 High pCO 2

57. 17-57 MEDIUM BLOOD High pCO 2 Generalized Structure of Respiratory Organs

58. 17-58 1. Diffusion Rate of Gas Governed by Fick Equation (1870)

59. 17-59 1. Diffusion Rate of Gas Governed by Fick Equation (1870) M = D A (P EXT - P INT ) L

60. 17-60 1. Diffusion Rate of Gas Governed by Fick Equation (1870) M = D A (P EXT - P INT ) L Movement of gas/unit time (M) depends on:

61. 17-61 a. Permeability of epithelium to gas D = Diffusion coefficient for given gas L = Thickness of epithelium Higher the permeability, more gas can cross

62. 17-62 Permeability is usually as high as possible because epithelium is thin (1-2 cells)

63. 17-63 Permeability is usually as high as possible because epithelium is thin (1-2 cells)

64. 17-64 b. Surface area of epithelium: A Larger the epithelium, more gas can cross Therefore, have very large respiratory organs Lots of branching surfaces to increase surface area

65. 17-65 c. Pressure gradient across epithelium: (P EXT -P INT ) Greater the difference in pressure between the medium and blood, the more gas diffuses Animals work to maximize this gradient Achieved by ventilation of epithelium removes CO 2 brings in new O 2 at highest pressures

66. 17-66 E. Three Basic Types of Respiratory Organs 1. Lung Medium is air a. Structure: bronchioles alveoli Blood 0.2 to 0.6 micrometers from air

67. 17-67 b. Fick Characteristics Thin epithelia for permeability Branching structure for large surface area 1 cc = 300 cm 2 Ventilation insures gradient “tidal” ventilation

68. 17-68 c. Lung/Terrestrial Breathing Advantages (1) Air has high O 2 content (2) Low density makes air very cheap to breathe only 1-2% of total E for ventilation (3) Respiratory epithelium protected inside animal immune system, filtration

69. 17-69 d. Disadvantages (1) internal, so must keep moist and warm inhale: humidify and heat air exhale: release heat and water (2) closed sac tends to trap CO 2 and H 2 O at elevated pressures reduces pO 2 at epithelium from 160 to 100

70. 17-70 Can improve gas pressures Birds very high O 2 demand pump air through flow-through lung flushes out CO 2 (28 mm vs 45mm ) increases gradients for both O 2 uptake and CO 2 removal

71. 17-71 e. Control of lung ventilation Medullary reflex arc

72. 17-72 Increased Blood pCO 2 Decreased Blood O 2

73. 17-73 Increased Blood pCO 2 Decreased Blood O 2 O 2, CO 2 Chemoreceptors in Aortic and Carotid Bodies

74. 17-74 Increased Blood pCO 2 Decreased Blood O 2 O 2, CO 2 Chemoreceptors in Aortic and Carotid Bodies Medulla

75. 17-75 Increased Blood pCO 2 Decreased Blood O 2 O 2, CO 2 Chemoreceptors in Aortic and Carotid Bodies Medulla Increase Ventilation Rate

76. 17-76 In terrestrial vertebrates both O 2 and CO 2 being measured, but CO 2 of primary importance in ventilation control low O 2 : inc. vent. rate 1.5 fold high CO 2 : inc. vent. rate 10 fold This reflex is extensively modified by other blood chemistry characteristics activity muscle stretch voluntary control