Thermoregulation

1. Thermoregulation Maintaining a stable body temperature

2. Why do organisms need to maintain a stable body temperature??

3. Optimum Temperatures • Organisms must keep their body temperature between a specific range in order to survive. • Enzyme activity • Metabolic processes

4. Body Temperature in animals • There are two types of organisms that maintain their body temperature in very different ways • Ectothermic organisms • Endothermic organisms • What do these terms mean? Can you give some examples of each?

5. Ecto (outside); therm (heat) • Use external environment to maintain body temperature. • Produce little heat • Lose heat quickly • Use less energy • Become very inactive when it gets cold • Fish, Reptiles, Insects

6. Endo (inside); therm (heat) • Maintain relatively constant body temperature • Generate a lot of heat from within via internal heat production • Generally have insulating structure to reduce heat loss (e.g. feathers, fur, fat) • Also develop behavioural and physiological adaptations to prevent heat loss

7. Endo (inside); therm (heat) • Mammals and birds

8. Homeothermic: organisms that can maintain a stable body temperature (e.g. mammals) • Poikilothermic: organisms whose body temperature varies considerably due to its surroundings (e.g. reptiles and insects)

9. Heat Transfer • Heat is a question of balance • Too HOT and animals must find ways to lose heat • Too COLD and animals must find ways to gain heat

10. Heat Transfer • To understand why animals do the things they do you must understand how heat can be transferred. QUESTION • What are the ways in which heat can be transferred?? How can animals lose or gain heat??

11. Heat Transfer • Conduction: transfer of heat from a hotter object to a cooler object via contact. • Radiation: transfer of heat from a hotter object to cooler object via infra-red waves.

12. Heat Transfer • Convection: Transfer of heat by warm air, or water, rising and being replaced by cooler air or water. • Evaporation: The process of changing a liquid into a gas. The heat from the body can evaporate water and cause a cooling effect.

13. Heat Transfer Heat transfer RAP!!!!

14. Heat Gain and Loss • Gain • Basic metabolic processes • Shivering • Exercise or other muscular activity • Radiation and conduction to the body • Loss • Evaporation sweat • Panting • Convection • Radiation and conduction from the body

15. Heat Loss and Gain VIDEO!!!!!

16. Systems Involved • Thermoregulation occurs via nerves and hormones • It involves many sensory inputs and several effector responses that act together to maintain a stable temperature

17. Linking to other systems • Thermoregulation is strongly related to the Nervous system and the Endocrine system Worksheet

18. Investigating Sweating • What you need to know: • How does sweating affect body temperature? • Why does sweating affect body temperature? • How can models help us investigate how the body works? • Question: • How does water evaporate?

19. For water to evaporate, it must absorb heat from its surroundings

20. Cotton wool Dry towelling cloth • Set up the equipment as shown opposite • Fill the conical flask with hot water from the kettle • Record the temperature and start your stop clock • Record the temperature every minute for 10 minutes. Record your data in a suitable table • Repeat with a wet towelling cloth

21. To Do: • Plot a graph of your data • Which flask cooled faster? • How do you explain your results? • Was your experiment a fair test – if not, why not? • How could you make this experiment more of a fair test?

22. Systems Involved • Brain – Hypothalamus • Lowering or raising the temperature of the hypothalamus initiates regulatory responses • Changes occur in heat production and heat exchange • Temperature cells act as misalignment detectors

23. Core body temperature >37°C Thermoreceptors Hypothalamus nerves Muscles of skin arteriole walls relax Sweat glands increase secretion Muscles reduce activity Skin arteries dilate More blood to the skin. More radiation & conduction of heat More water covers the skin. More evaporation Less heat generated

24. Systems Involved • Hypothalamus responds to receptors and coordinates appropriate nerve and hormonal responses

25. Systems Involved • The hypothalamus can release hormones that initiate the release of further hormones. • For example as the temperature drops the pituitary gland will be stimulated and release a thyroid stimulating hormone • The thyroid gland in turn produces hormones which increase the metabolic rate therefore increasing heat production

26. Systems Involved

27. Systems Involved • Skin – thermoreceptors act as disturbance detectors. • Detect change in external environment and triggers responses before it effects internal body temperature. • Responses include erector muscles of hairs contract and hairs stand up, blood vessels constrict. • These are the effectors for mediating change.

28. Skin

29. Negative feedback • Temperature regulation by the skin is part of a negative feedback system. • Output is fed back to receptors and becomes part of a new stimulus response cycle.

30. Muscles of skin arteriole walls relax Sweat glands increase secretion Core body temperature >37°C nerves Hypothalamus Thermoreceptors Muscles reduce activity NEGATIVE FEEDBACK Blood temperature Thermoreceptors Body loses heat Return to 37°C

31. Thermoregulation • VIDEO REVIEW

32. Summary • Ectothermic • Endothermic • Homeothermic • Poikilothermic • Heat transfer – Conduction, Convection, Radiation & Evaporation • Heat Gain and Loss • Endocrine and Nervous system involved

33. Review Questions • Page 256 of the text book. - Questions 17 - 21

34. Adaptations and Thermoregulation • Apart from physiological adaptations, animals also develop behaviours and physical structures that help them regulate their body temperature.

35. Heat Loss and Gain • Must remember the ways in which heat can be transferred. • These processes work on a temperature gradient. • Can you explain what this means?

36. Heat Loss and Gain • Temperature gradient simply refers to the difference in temperature between two things. • For example the lizard and the rock.

37. Heat Loss and Gain

38. Heat Loss and Gain • The rock is warmer than the lizard so the heat moves, via conduction, from the rock to the lizard. • As the lizard heats up and the gradient decreases and eventually changes the heat moves from lizard to rock.

39. Structural & Behavioural • The transfer of heat needs to be controlled. • What examples of structural and behavioural adaptations can you think of?

40. Behavioural Responses • Penguins huddling • Burrowing underground • Seeking shade • Basking • Fanning from honeybees

41. Behavioural Responses • VIDEO

42. Counter current heat exchange

43. Counter current heat exchange • The arteries and veins in certain areas, like the foot of the penguin, run very close to each other. • The warmer blood in the arteries heats the cooler blood in the veins.

44. Structural Responses • Animals need to control exchange. This can also be achieved through: • Insulation: - Fur - Feathers - Fat

45. Structural Adaptations • Feathers and fur insulate by trapping a thick layer of warm air next to the skin. • The layer of air has a protective insulating affect keeping the animal warm.

46. Structural Adaptations • The layer of air trapped by the otters fur helps reduce the temperature gradient between the otter and its surroundings. • Therefore reducing heat loss and gain.

47. Structural Adaptations • Blubber is also used as insulation. • Thick layers of fat are very effective in insulating animals against extremely cold conditions.

48. Structural Adaptation • Shape and size also play an important role. • How do you think shape and size of an animals can help?

49. Structural Adaptations • A large surface area to volume ratio increases heat loss • A small surface area to volume ratioreduces heat loss.

50. Structural Adaptations