Introduction to Animal Physiology

1. Introduction to Animal Physiology Homeostasis

2. Physiology • The study of the functions of living organisms • whole organisms • organ systems • organs • tissues • cells

3. Physiology • groups of cells with similar characteristics or specializations form tissues • different tissues combine to form organs • discrete structures with specific functions • organs which function together form organ systems

4. Physiology • tissues occur in four basic types • epithelial tissues form linings or coverings • perform functions appropriate to organ • connective tissues exist in a matrix • support and reinforce other tissues • muscle tissues contract • provide movement or propulsion • nervous tissues transmit and process information

5. tissues of the stomach wallFigure 41.2

6. Table 41.1

7. Homeostasis • most organ systems contribute to homeostasis • maintenance of a constant internal environment in spite of constant change • provides for material needs of cells • removes wastes from cells • regulates physical environment of cells • communicates among cells

8. homeostasis in a cellular suitcaseFigure 41.1

9. Homeostasis • homeostatic regulatory components • controlled systems - effectors • regulatory systems • acquire information • process information • integrate information • send commands

10. Homeostasis • homeostatic regulatory variables • setpoint • optimal chemical or physical condition • feedback information • actual current condition • error signal • discrepancy between setpoint and feedback value

11. Homeostasis • homeostatic regulatory inputs • negative feedback • reduces or reverses activity of effector • returns condition to set point • positive feedback • amplifies activity of effector • self-limiting activities • feedforward information • changes setpoint

12. the “responsible driver” exampleFigure 41.4

13. Homeostasis: thermoregulation • living cells cannot survive temperatures above or below fairly narrow limits • thermosensitivities of organisms vary • thermosensitivities of effectors vary • Q10 quantifies temperature sensitivity • ratio of physiological rate at one temperature to the rate at 10˚C lower temperature Q10 = RT / RT-10

14. Figure 41.5 biological range of Q10values

15. Homeostasis: thermoregulation • acclimatization can alter an animal’s temperature response • changes that allow optimal activity under different climatic conditions [e.g. seasonal temperature variation] • metabolic compensation • maintains metabolic rate in different seasons • accomplished with alternate enzyme systems (e.g.)

16. acclimatization may include metabolic compensationFigure 41.6

17. Homeostasis: thermoregulation • animals are classified by how they respond to environmental temperatures • homeotherm • maintains a constant body temperature as ambient temperature changes • poikilotherm • changes body temperature as ambient temperature changes

18. Homeostasis: thermoregulation • animals are classified by how they respond to environmental temperatures and • their sources (sinks) of body heat • ectotherm • external heat sources/sinks • endotherm • active heat generation and cooling

19. ectotherms and endotherms utilize different sources of body heatFigure 41.7

20. behavioral temperature regulation in an ectothermFigure 41.8

21. Homeostasis: thermoregulation • behavior is a common method of regulating body temperature • ectotherms • different microenvironments provide different temperatures • endotherms • behavioral temperature regulation reduces metabolic costs

22. behavioral temperature regulation in endothermsFigure 41.9

23. Homeostasis: thermoregulation • heat exchange between body and environment occurs through the skin • radiation - gain or loss • conduction - gain or loss • convection - gain or loss • evaporation - loss

24. Figure 41.10

25. Homeostasis: thermoregulation • heat exchange can be regulated by control of blood flow to the skin • constriction/dilation of blood vessels supplying the skin • change in heart rate

26. vegetarian marine iguanaFigure 41.11

27. an iguana regulates body temperature by altering heart rate in surf & sunFigure 41.11

28. muscular contraction generates heat brood warming by honey bees

29. Homeostasis: thermoregulation • some ectotherms use muscular contractions to generate heat • insects flex wing muscles • to achieve flight temperature • to warm brood above air temperature • Indian python flexes muscles to warm brood above air temperature • analogous to mammalian shivering

30. Homeostasis: thermoregulation • anatomical features allow some fish to retain muscular heat • in “cold” fish • blood is chilled in gills • cold blood is warmed by muscle mass • warmed blood returns to gills and is chilled

31. a cold fish dumps muscular heatFigure 41.12

32. Homeostasis: thermoregulation • anatomical features allow some fish to retain muscular heat • in “hot” fish • chilled blood from gills travels near skin • chilled blood enters muscle mass next to veins leaving muscle mass • countercurrent heat exchange warms blood entering muscle mass • countercurrent heat exchange removes heat from blood returning to the gills

33. a hot fish retains muscular heatFigure 41.12

34. Homeostasis: thermoregulation • thermal characteristics of endotherms • thermoneutral zone • temperature window with no regulation • basal metabolic rate • meets minimal metabolic needs • lower critical temperature • below which metabolic rate increases • upper critical temperature • above which active cooling occurs

35. basal metabolic rate vs. body massFigure 41.13

36. endotherms regulate body temperature metabolicallyFigure 41.14

37. Homeostasis: thermoregulation • thermal characteristics of endotherms • heat generation below the lower critical temperature • shivering heat production • contractions of opposed muscles • releases heat from ATP hydrolysis

38. Homeostasis: thermoregulation • thermal characteristics of endotherms • heat generation below the lower critical temperature • nonshivering heat production • occurs in brown fat tissue • due to thermogenin • uncouples respiratory electron transport from ATP synthesis

39. brown fat is highly vascularized, has a high density of mitochondria, and has smaller lipid dropletsFigure 41.15

40. reduced surface area andincreased insulation conserve body heatFigure 41.16

41. Homeostasis: thermoregulation • thermal characteristics of endotherms • anatomical features conserve heat below the lower critical temperature • reduced surface/volume ratio • increased thermal insulation • oil secretion resists wetting

42. increased surface area andreduced insulation release body heatFigure 41.16

43. Homeostasis: thermoregulation • thermal characteristics of endotherms • heat loss above the upper critical temperature • increased surface area/volume ratio • increased blood flow to skin • evaporation • sweat glands • panting

44. a thermostat controls the effectors (furnace and air conditioner) in a house

45. metabolic rate and body temperature respond to hypothalamic temperature changesFigure 41.17

46. ambient temperature(feedforward information)can alter the setpoint for metabolic heat productionFigure 41.18

47. Homeostasis: thermoregulation • mammalian thermal regulation • the mammalian thermostat is the hypothalamus • different effectors of thermal regulation have different set points • environmental temperature can act as feed forward information to alter set points • pyrogens increase the set point for metabolic heat production causing fever

48. Homeostasis: thermoregulation • torpor conserves metabolic resources • torpor is regulated hypothermia • some birds engage in daily torpor during inactive periods • in hibernating mammals, torpor may last hours, days, or weeks

49. decreased metabolism, lower temperatureFigure 41.19