Think about… 2.1 Importance of regulating body temperature 2.2 The role of skin

2. Think about… 2.1 Importance of regulating body temperature 2.2 The role of skin 2.3 Other mechanisms of body temperature regulation 2.4 The thermoregulatory centre Recall ‘Think about…’ Summary concept map

3. Deadly enemy of marathon runners Heatstroke (中暑) often occurs among marathon runners, especially on hot and humid days.

4. Deadly enemy of marathon runners They fail to lose heat efficiently and the body temperature may rise to as high as 43℃.

5. Deadly enemy of marathon runners They feel dizzy and may become unconscious.

6. Deadly enemy of marathon runners Heatstroke can be deadly if not treated immediately.

7. 1 Why is heatstroke more likely to occur under hot and humid conditions

8. 2 Why may death result when the body temperature is too high

9. 3 What are the treatments and precautions for heatstroke

10. 2.1 Importance of regulating body temperature How does the environmental temperature affect our body temperature?

11. 2.1 Importance of regulating body temperature 40 30 20 10 0 30 40 10 20 body temperature kept at about 37oC human body temperature (oC) environmental temperature (oC)

12. 2.1 Importance of regulating body temperature • metabolic activities are controlled by enzymes only work efficiently within a narrow range of temperature

13. 2.1 Importance of regulating body temperature • metabolic activities are controlled by enzymes • stable body temperature  keeps enzyme activity and metabolic rate steady  we stay active at all times

14. 2.1 Importance of regulating body temperature Heat gain radiation from the sun liver metabolism respiration in cells muscle contraction conduction from hot sand

15. 2.1 Importance of regulating body temperature Heat loss Radiation? exhalation evaporation of sweat convection due to air current urination and defaecation

16. 2.1 Importance of regulating body temperature Heat loss Heat gain = stable body temperature

17. 2.1 Importance of regulating body temperature • skin is the major organ involved in regulating body temperature

18. 2.1 Importance of regulating body temperature 1 A stable body temperature allows in cells to function enzymes properly, so that the metabolic rate can be kept and we can stay active at all times. steady

19. 2.1 Importance of regulating body temperature 2 Heat is transferred between the body and the environment by radiation conduction , , and evaporation. convection

20. 2.2 The role of skin Structure and functions of skin • two layers: epidermis (表皮) dermis (真皮)

21. 2.2 The role of skin Structure and functions of skin

22. Skin on different parts of the body

23. Skin • two layers: epidermis dermis

24. Scanning electron microscope (SEM) picture of normal skin E. coli on the surface of human skin. Human hair and skin layers. scanning electron micrograph (SEM) of a section through human skin with a hair (upper centre) emerging from the surface. The skin layers, from top to bottom, are the stratum corneum (flaky, brown), composed of flattened, dead skin cells that form the surface of the skin. The dead cells from this layer are continuously being shed and replaced by cells from the living epidermal layer below (red, extending downwards around hair follicle). The lowest layer seen here is the dermis (grey-brown, lower centre). This is a thick layer of fibrous connective tissue that supports and nourishes the epidermis. Magnification: x100

26. 2.2 The role of skin 1 Epidermis • three layers: epidermis dermis

27. 2.2 The role of skin 1 Epidermis • three layers: i)Innermost layer • produces new cells by mitotic cell division

28. 2.2 The role of skin 1 Epidermis • three layers: i)Innermost layer • contains melanin (黑素) absorbs UV light protects the body

29. 2.2 The role of skin 1 Epidermis • three layers: i)Innermost layer • contains melanin (黑素) determines skin colour

30. 2.2 The role of skin 1 Epidermis • three layers: i)Innermost layer • produces vitamin D when exposed to sunlight

31. 2.2 The role of skin 1 Epidermis • three layers: ii)Middle layer: • consists of living cells pushed towards surface die and flatten outermost layer

32. 2.2 The role of skin 1 Epidermis • three layers: iii)Outermost layer • consists of dead cells constantly worn away and replaced by new cells

33. 2.2 The role of skin 1 Epidermis • three layers: iii)Outermost layer • consists of dead cells reduce water loss

34. 2.2 The role of skin 1 Epidermis • three layers: iii)Outermost layer • consists of dead cells protect from mechanical injury

36. 2.2 The role of skin 1 Epidermis • three layers: iii)Outermost layer • consists of dead cells prevent entry of pathogens

37. 2.2 The role of skin 2 Dermis i)Sensory receptors • detect stimuli pain receptor touch receptor thermoreceptor pressure receptor

38. 2.2 The role of skin 2 Dermis ii)Hair follicles (毛囊) • new hair cells produced from the base

39. 2.2 The role of skin 2 Dermis ii)Hair follicles (毛囊) • new hair cells produced from the base root of hair

40. 2.2 The role of skin 2 Dermis iii)Erector muscles (豎毛肌) and hairs

41. 2.2 The role of skin 2 Dermis iii)Erector muscles (豎毛肌) and hairs • erector muscle contracts  hair pulled upright • erector muscle relaxes  hair lies flat

42. Goose bumps

43. Goose bumps

44. 2.2 The role of skin 2 Dermis iv)Sweat glands (汗腺) • form sweat contains mainly water, salts, urea and other metabolic waste

45. 2.2 The role of skin 2 Dermis iv)Sweat glands (汗腺) sweat pore (汗孔) sweat duct (汗管)

46. 2.2 The role of skin 2 Dermis iv)Sweat glands (汗腺) • sweat coming out to the skin surface  sweating

47. 2.2 The role of skin 2 Dermis iv)Sweat glands (汗腺) • sweat coming out to the skin surface  sweating for regulating body temperature

48. 2.2 The role of skin 2 Dermis iv)Sweat glands (汗腺) • sweat coming out to the skin surface  sweating for excretion

49. Male Sweat Boosts Women’s Hormone Levels ..Sweat has been the main focus of research on human pheromones, and in fact, male underarm sweat has been shown to improve women’s moods and affect their secretion of luteinizing hormone, which is normally involved in stimulating ovulation…

50. 2.2 The role of skin 2 Dermis v)Blood vessels • circulation of blood supplies oxygen and nutrients