2. 1

3. 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

4. 3 Heatstroke ( 中暑 ) often occurs among marathon runners, especially on hot and humid days.

5. 4 They fail to lose heat efficiently and the body temperature may rise to as high as 43 ℃.

6. 5 They feel dizzy and may become unconscious.

7. 6 Heatstroke can be deadly if not treated immediately.

8. 7 Why is heatstroke more likely to occur under hot and humid conditions 1

9. 8 Why may death result when the body temperature is too high 2

10. 9 What are the treatments and precautions for heatstroke 3

11. 10 2.1 Importance of regulating body temperature How does the environmental temperature affect our body temperature?

12. 11 human body temperature ( o C) environmental temperature ( o C) 10 20 30 40 0 2.1 Importance of regulating body temperature body temperature kept at about 37 o C

13. 12 metabolic activities are controlled by enzymes only work efficiently within a narrow range of temperature 2.1 Importance of regulating body temperature

14. 13 metabolic activities are controlled by enzymes  keeps enzyme activity and metabolic rate steady stable body temperature  we stay active at all times 2.1 Importance of regulating body temperature

15. 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

16. 15 2.1 Importance of regulating body temperature Heat loss exhalation evaporation of sweat convection due to air current urination and defaecation Radiation?

17. 16 2.1 Importance of regulating body temperature Heat loss Heat gain = stable body temperature

18. 17 skin is the major organ involved in regulating body temperature 2.1 Importance of regulating body temperature

19. 18 1 A stable body temperature allows enzymes 2.1 Importance of regulating body temperature properly, so that the metabolic rate can be kept and we can stay active at all times. in cells to function steady

20. 19, 2 Heat is transferred between the body and the environment by radiation 2.1 Importance of regulating body temperature conduction convection and evaporation.

21. 20 2.2 The role of skin epidermis ( 表皮 ) dermis ( 真皮 ) two layers: Structure and functions of skin

22. 21 2.2 The role of skin Structure and functions of skin

23. 22 Skin on different parts of the body

24. 23 Skin two layers: epidermis dermis

25. 24 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 Scanning electron microscope (SEM) picture of normal skin E. coli on the surface of human skin.

26. 25

27. 26 epidermis dermis 2.2 The role of skin 1 Epidermis three layers:

28. 27 2.2 The role of skin 1 Epidermis three layers: i) Innermost layer produces new cells by mitotic cell division

29. 28 contains melanin ( 黑素 ) 2.2 The role of skin 1 Epidermis three layers: i) Innermost layer absorbs UV light protects the body

30. 29 contains melanin ( 黑素 ) 2.2 The role of skin 1 Epidermis three layers: i) Innermost layer determines skin colour

31. 30 produces vitamin D when exposed to sunlight 2.2 The role of skin 1 Epidermis three layers: i) Innermost layer

32. 31 consists of living cells 2.2 The role of skin 1 Epidermis three layers: ii) Middle layer: pushed towards surface die and flatten outermost layer

33. 32 consists of dead cells 2.2 The role of skin 1 Epidermis three layers: iii) Outermost layer constantly worn away and replaced by new cells

34. 33 2.2 The role of skin 1 Epidermis three layers: iii) Outermost layer reduce water loss consists of dead cells

35. 34 2.2 The role of skin 1 Epidermis three layers: iii) Outermost layer protect from mechanical injury consists of dead cells

36. 35

37. 36 2.2 The role of skin 1 Epidermis three layers: iii) Outermost layer prevent entry of pathogens consists of dead cells

38. 37 i) Sensory receptors 2.2 The role of skin 2 Dermis pain receptor touch receptor thermoreceptor pressure receptor detect stimuli

39. 38 ii) Hair follicles ( 毛囊 ) 2.2 The role of skin 2 Dermis new hair cells produced from the base

40. 39 2.2 The role of skin 2 Dermis root of hair new hair cells produced from the base ii) Hair follicles ( 毛囊 )

41. 40 iii) Erector muscles ( 豎毛肌 ) 2.2 The role of skin 2 Dermis and hairs

42. 41 2.2 The role of skin 2 Dermis erector muscle contracts  hair pulled upright erector muscle relaxes  hair lies flat and hairs iii) Erector muscles ( 豎毛肌 )

43. 42 Goose bumps

44. 43 Goose bumps

45. 44 iv) Sweat glands ( 汗腺 ) 2.2 The role of skin 2 Dermis form sweat contains mainly water, salts, urea and other metabolic waste

46. 45 2.2 The role of skin 2 Dermis sweat duct ( 汗管 ) iv) Sweat glands ( 汗腺 ) sweat pore ( 汗孔 )

47. 46 2.2 The role of skin 2 Dermis sweat coming out to the skin surface  sweating iv) Sweat glands ( 汗腺 )

48. 47 2.2 The role of skin 2 Dermis sweat coming out to the skin surface  sweating for regulating body temperature iv) Sweat glands ( 汗腺 )

49. 48 2.2 The role of skin 2 Dermis sweat coming out to the skin surface  sweating for excretion iv) Sweat glands ( 汗腺 )

50. 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…

51. 50 v) Blood vessels 2.2 The role of skin 2 Dermis circulation of blood supplies oxygen and nutrients

52. 51 v) Blood vessels 2.2 The role of skin 2 Dermis circulation of blood removes waste

53. 52 v) Blood vessels 2.2 The role of skin 2 Dermis circulation of blood distributes heat

54. 53 v) Blood vessels 2.2 The role of skin 2 Dermis vasoconstriction and vasodilation ‘vessel’

55. 54 v) Blood vessels 2.2 The role of skin 2 Dermis vasoconstriction and vasodilation regulate heat loss by controlling the amount of blood flowing to the body surface

56. 55 v) Blood vessels 2.2 The role of skin 2 Dermis vasoconstriction and vasodilation arteriole capillary venule shunt vessel ( 分流血管 )

57. 56 v) Blood vessels 2.2 The role of skin 2 Dermis vasoconstriction and vasodilation 1 arteriole constricts 2 less blood to capillary 3 more blood through shunt vessel less heat is lost Under cold conditions

58. 57 v) Blood vessels 2.2 The role of skin 2 Dermis vasoconstriction and vasodilation 1 arteriole dilates 2 more blood to capillary 3 less blood through shunt vessel more heat is lost Under hot conditions

59. 58 Vasoconstriction and vasodilation occur in the capillaries.  2.2 The role of skin

60. 59 2.2 The role of skin Capillaries cannot constrict or dilate because they have no muscle walls.

61. 60 2.2 The role of skin It is the arterioles in the deeper part of the dermis that constrict or dilate.

62. 61 vi) Sebaceous glands 2.2 The role of skin 2 Dermis secrete sebum ( 皮脂 ) keeps hairs and skin supple and waterproof

63. 62 vi) Sebaceous glands 2.2 The role of skin 2 Dermis secrete sebum ( 皮脂 ) a natural antiseptic

64. 63 2.2 The role of skin hair follicle epidermis sweat duct sebaceous gland mammalian skin (L.S)

65. 64 Pimples – inflamed

66. 65 insulates the body to reduce heat loss 2.2 The role of skin Subcutaneous fat as energy reserve

67. 66 2.1 Examination of the mammalian skin 1 Examine a prepared slide of mammalian skin or a skin model. 2.2 The role of skin 2 Identify the structures.

68. 67 2.2 The role of skin Functions of structures of the skin: Epidermis: 1 Innermost layer produces by mitotic cell division new cells contains which protects the body against ultraviolet light melanin

69. 68 2.2 The role of skin Functions of structures of the skin: Epidermis: 1 Innermost layer produces vitamin D

70. 69 2.2 The role of skin Functions of structures of the skin: Epidermis: 2 Middle layer when pushed towards the surface, cells die and form the outermost layer

71. 70 2.2 The role of skin Functions of structures of the skin: Epidermis: 3 Outermost layer reduces by evaporation water loss protects the body from mechanical injury

72. 71 2.2 The role of skin Functions of structures of the skin: Epidermis: 3 Outermost layer prevents the entry of pathogens

73. 72 2.2 The role of skin Functions of structures of the skin: Dermis: 1 Sensory receptors detect stimuli 2 Hair follicles produce new hairs

74. 73 2.2 The role of skin Functions of structures of the skin: Dermis: 3 Erector muscles and hairs help regulate body temperature 4 Sweat glands secrete for excretion and body temperature regulation sweat

75. 74 2.2 The role of skin Functions of structures of the skin: Dermis: 5 Blood vessels supply and to skin cells and remove waste from them nutrients oxygen

76. 75 2.2 The role of skin Functions of structures of the skin: Dermis: 5 Blood vessels help regulate body temperature by and vasodilation vasoconstriction

77. 76 2.2 The role of skin Functions of structures of the skin: Dermis: 6 Sebaceous glands secrete that keeps the hairs and skin supple and waterproof, and reduces the growth of harmful microorganisms sebum

78. 77 2.2 The role of skin Functions of structures of the skin: Subcutaneous fat: acts as a layer heat insulating acts as reserve energy

79. 78 How does skin regulate body temperature? 2.2 The role of skin 3D animation by controlling heat loss

80. 79 2.2 The role of skin 1 erector muscles contract to pull hairs upright Under cold conditions

81. 80 2.2 The role of skin 2 sweating is reduced Under cold conditions

82. 81 2.2 The role of skin 3 vasoconstriction Under cold conditions

83. 82 2.2 The role of skin 4 layer of subcutaneous fat becomes Under cold conditions less heat is lost thicker (long-term response)

84. 83 2.2 The role of skin Under hot conditions 1 erector muscles relax and hairs lie flat

85. 84 2.2 The role of skin Under hot conditions 2 sweating increases 3 vasodilation

86. 85 2.2 The role of skin Under hot conditions 4 layer of subcutaneous fat becomes thinner (long-term response) more heat is lost

87. 86 Sweat is produced only when the body temperature increases.  2.2 The role of skin

88. 87 2.2 The role of skin Sweat is produced most of the time to remove metabolic waste.

89. 88 Structure Response under cold conditions 1 Erector muscles 2 Hairs 3 Sweat glands Contract Pulled upright 2.2 The role of skin Secrete less sweat

90. 89 Structure Response under cold conditions 4 Arterioles 5 Subcutaneous fat Constrict (vasoconstriction) 2.2 The role of skin Becomes thicker (long-term)

91. 90 Structure Response under hot conditions 1 Erector muscles 2 Hairs 3 Sweat glands Relax Lie flat 2.2 The role of skin Secrete more sweat

92. 91 Structure Response under hot conditions 4 Arterioles 5 Subcutaneous fat Dilate (vasodilation) 2.2 The role of skin Becomes thinner (long-term)

93. 92 2.3 Other mechanisms of body temperature regulation Muscle contraction metabolism in muscle cells generates heat shivering ( 顫抖 ) - skeletal muscles contract involuntarily

94. 93 Action of hormone 2.3 Other mechanisms of body temperature regulation body temperature is also regulated by thyroxine ( 甲狀腺素 ) increases metabolic rate  generates heat to keep the body warm increases metabolic rate  generates heat to keep the body warm

95. 94 Action of hormone 2.3 Other mechanisms of body temperature regulation thyroid gland secretes body temperature is also regulated by thyroxine ( 甲狀腺素 )

96. 95 Action of hormone 2.3 Other mechanisms of body temperature regulation increased thryoxine secretion is a long-term response body temperature is also regulated by thyroxine ( 甲狀腺素 )

97. 96 2.3 Other mechanisms of body temperature regulation Under cold conditions 1 A decrease in blood temperature stimulates the hypothalamus to secrete TSH-releasing hormone (TRH). hypothalamus TRH

98. 97 2.3 Other mechanisms of body temperature regulation Under cold conditions 2 TRH stimulates the pituitary gland to secrete thyroid stimulating hormone (TSH). hypothalamus TRH pituitary gland TSH

99. 98 2.3 Other mechanisms of body temperature regulation Under cold conditions 3 TSH stimulates the thyroid gland to secrete thyroxine. hypothalamus TRH pituitary gland TSH thyroxine

100. 99 2.3 Other mechanisms of body temperature regulation Under cold conditions 4 Thyroxine increases the metabolic rate of body cells and more heat is generated. hypothalamus TRH pituitary gland TSH thyroxine

101. 100 2.3 Other mechanisms of body temperature regulation Under cold conditions thyroxine inhibits secretions of TRH and TSH (negative feedback) hypothalamus TRH pituitary gland TSH thyroxine

102. 101 Change of behaviour 2.3 Other mechanisms of body temperature regulation voluntary behaviour also plays a part in regulating body temperature

103. 102 2.3 Other mechanisms of body temperature regulation Under cold conditions wear more clothes turner on the heater take in warm food/drinks

104. 103 2.3 Other mechanisms of body temperature regulation wear fewer clothes turner on the fan take in cold food/drinks Under hot conditions

105. 104 1 in muscle cells generates heat to maintain the body temperature. Metabolism also generates heat. Shivering provides extra amount of heat to keep us warm under cold conditions. Muscle contraction 2.3 Other mechanisms of body temperature regulation

106. 105 2 increases the metabolic rate of most cells, so that more heat can be generated to keep the body warm. Increased thyroxine secretion is a response to a cold environment. long-term Thyroxine 2.3 Other mechanisms of body temperature regulation

107. 106 a Under cold conditions, we can reduce heat loss and increase heat gain by means like wearing more clothes, turning on the heater and taking in more food and drinks. 3 Behavioural mechanisms that help regulate body temperature: 2.3 Other mechanisms of body temperature regulation warm

108. 107 b Under hot conditions, we can promote heat loss and reduce heat gain by means like wearing fewer clothes, turning on the fan and taking in more food and drinks. 3 Behavioural mechanisms that help regulate body temperature: 2.3 Other mechanisms of body temperature regulation cold

109. 108 2.4 The thermoregulatory centre in hypothalamus has thermoreceptors that detect the temperature of blood passing through it receives nerve impulses about changes in external temperature from the thermoreceptors in the skin

110. 109 2.4 The thermoregulatory centre heat loss centre thermoregulatory centre in hypothalamus normal body temp thermo- receptors rises heat gain centre

111. 110 2.4 The thermoregulatory centre heat loss centre normal body temp thermo- receptors rises initiates mechanisms normal body temp falls heat gain centre

112. 111 2.4 The thermoregulatory centre Mechanisms to promote heat loss and decrease heat gain: relaxation of erector muscles increased sweating vasodilation decreased secretion of thyroxine (long-term) Physiological

113. 112 2.4 The thermoregulatory centre Mechanisms to promote heat loss and decrease heat gain: thinner layer of subcutaneous fat (long-term) Structural

114. 113 2.4 The thermoregulatory centre Mechanisms to promote heat loss and decrease heat gain: wear fewer clothes Behavioural turn on the fan take in more cold food

115. 114 2.4 The thermoregulatory centre heat loss centre heat gain centre normal body temp thermo- receptors rises initiates mechanisms normal body temp falls thermo- receptors initiates mechanisms rises

116. 115 2.4 The thermoregulatory centre Mechanisms to reduce heat loss and increase heat gain: contraction of erector muscles reduced sweating vasoconstriction shivering Physiological

117. 116 2.4 The thermoregulatory centre Mechanisms to reduce heat loss and increase heat gain: increased secretion of thyroxine (long-term) Physiological

118. 117 2.4 The thermoregulatory centre Mechanisms to reduce heat loss and increase heat gain: thicker layer of subcutaneous fat (long-term) Structural

119. 118 2.4 The thermoregulatory centre Mechanisms to reduce heat loss and increase heat gain: wear more clothes Behavioural turn on the heater take in more warm food

120. 119 in skin detect changes in external temperature and send nerve impulses to the thermoregulatory centre in the. Thermoreceptors hypothalamus 2.4 The thermoregulatory centre 1a

121. 120 Thermoreceptors in the hypothalamus detect changes in the temperature of passing through it. blood 2.4 The thermoregulatory centre 1b

122. 121 Skin or blood temperature rises heat loss 2.4 The thermoregulatory centre 2a centre stimulated mechanisms erector muscles and hairs relax lie flat sweating increases occurs vasodilation

123. 122 Skin or blood temperature rises heat loss 2.4 The thermoregulatory centre 2a centre stimulated mechanisms thyroxine secretion decreases subcutaneous fat becomes thinner, e.g. wear fewer clothes, turn on the fan behavioural mechanisms

124. 123 Skin or blood temperature falls heat gain 2.4 The thermoregulatory centre 2b centre stimulated mechanisms erector muscles and hairs are contract pulled upright sweating decreases and shivering occur vasoconstriction

125. 124 2.4 The thermoregulatory centre thyroxine secretion increases subcutaneous fat becomes thicker behavioural mechanisms, e.g. wear more clothes, turn on the heater Skin or blood temperature falls heat gain 2b centre stimulated mechanisms

126. 125 Why is heatstroke more likely to occur under hot and humid conditions? 1 High humidity lowers the rate of evaporation of sweat, so the body cannot lose heat effectively and heatstroke is likely to occur.

127. 126 Why may death result when the body temperature is too high? 2 When the body temperature is too high, enzymes cannot work properly and cells fail to function.

128. 127 What are the treatments and precautions for heatstroke? 3 To treat heatstroke, we should move the person to shaded areas and wrap the body with cool wet towels.

129. 128 What are the treatments and precautions for heatstroke? 3 To prevent heatstroke, we should avoid doing vigorous exercise in a hot environment.

130. 129 maintained by balancing A stable body temperature heat gain thermoregulatory centre in hypothalamus controlled by heat loss

131. 130 thermoregulatory centre in hypothalamus through mechanisms that involve skin

132. 131 structures involved skin subcutaneous fat erector muscles and hairs sweat glands blood vessels

133. 132 thermoregulatory centre in hypothalamus through mechanisms that involve blood circulation distribution of heat controls vasoconstriction and vasodilation by

134. 133 thermoregulatory centre in hypothalamus through mechanisms that involve skeletal muscles under cold conditions production of more heat leads to shiver

135. 134 thermoregulatory centre in hypothalamus through mechanisms that involve thyroid gland secretes metabolic rate increases thyroxine

136. 135 thermoregulatory centre in hypothalamus through mechanisms that involve cerebrum brings about behavioural mechanisms