1. Skin & Temperature Control
Homeostasis
Skin & Temperature Control

2. Learning Objectives 12.1 Principles of Homeostasis
a) Define homeostasis
(b) Explain the basic principles of homeostasis in terms of stimulus resulting from a change in the internal environment, a corrective mechanism and a negative feedback

3. Homeostasis
Homeostasis is defined as the maintenance of a constant internal environment.

4. The Need for Homeostasis
Changes in body temperature may result in enzyme inactivation or denaturation.
Any drastic changes in our blood and the surrounding tissues fluid will affect chemical reactions in the tissue cells and will harm the body.
Cells must be bathed in tissue fluid of the correct pH and water potential. Enzyme reaction will be affected.

5. Negative Feedback Control
The internal environment of our bodies MUST have certain conditions within tolerable limits to continue the healthy functioning.
Done by NEGATIVE FEEDBACK control.
Used to control blood sugar concentration, water concentration & temperature of the blood.

6. Negative Feedback
A stimulus, which is the change in the internal environment
A receptor that can detect the stimulus
A self-regulatory corrective mechanism
A negative feedback to the receptor

7. Receptors
detects it
Corrective
mechanism
Stimulus
Condition
increases
Normal
condition
Condition
decreases
Condition
rises
Stimulus
Condition
decreases
Corrective
mechanism
Receptor
detects it

8. Organs involved in Homeostasis
Skin (helps in temperature regulation)
Kidneys (helps in the water concentration of the body)
Brain (MASTERMIND)
Pancreas (produces insulin that helps in the control of sugar concentration in the blood)

9. Learning Objectives 12.2 Structure and function of the skin
(c) Identify on a diagram of the skin: hairs, sweat glands, temperature receptors, blood vessels and fatty tissue
(d) Describe the maintenance of a constant body temperature in humans in terms of insulation and the role of: temperature receptors in the skin, sweating, shivering, blood vessels near the skin surface and the co-ordinating role of the brain

10. Skin Largest organ of the human body. An important sense organ
Barrier between the body and the external environment
Organ that regulates our body temperature.

11. Skin

13. Epidermis outer layer of the skin :- Cornified layer (dead cells)
 Protects the body from water loss, invasion of microbes & mechanical, thermal & chemical damage.
b. Granular layer
 New cells undergo cell division
c. Malpighian layer
to replace dead cells from the cornified layer
pigmented cells (melanin) protects our skin against harmful UV light of the sun

14. Functions of the Epidermis
Layer is water-resistant (waterproof)
Prevents evaporation of water from skin
Prevents germs from entrying into the body.
Protective layer, preventing mechnical injury.

16. Dermis Consists mainly of fibrous tissue and many other structures:-
Blood vessels
numerous blood vessels
Arterioles that carry blood are controlled by vasometer nerves.
Nerves bring about contraction & dilation of the arteries.
Arterioles dilate (vasodilation) --> more blood is sent to the skin.
Arterioles contract (vasoconstriction) --> less blood is sent to the skin.

17. Dermis (b) Hair Common feature of mammals.
Grow inside the hair follicle
At the base of the follicle is a mass of tissue containing blood capillaries.
Attached to the hair follicles are the “hair erector” muscles. (contract --> causes the hair to stand)

19. Dermis (c ) Sweat glands sweat is secreted in the sweat glands.
Sweat glands ---> sweat duct ---> sweat pore
surface of skin.
Sweat = urea + water + salt (sodium chloride)

21. Dermis (d) Temperature receptors
nerve endings are found in the epidermis and dermis.
Form sense organs
Enable us to sense pain, pressure and temperature changes in the external environment.

22. NERVE ENDINGS

24. Dermis (e) Fatty Tissue
--> Fat cells are present where fat is stored.

25. Dermis (f) Sebaceous glands 2 glands open into each hair follicle.
Secreting an oily substance (sebum) into hair follicle.
Sebum lubricates the hair and keeps the skin soft and smooth.
Prevents dehydration of the skin.
Has an antiseptic action.

27. Control of body temperature

28. Skin Able to detect temperature change in the external environment.
A change in atmospheric temperature --> detected by temperature receptors on the skin
--> start some mechanisms to control the temperature.

29. The Brain Hypothalamus is the control centre for temperature.
Detects temperature changes in the blood.

30. What happens when temperature rises?
Hypothalamus triggers off the following:-
Decreased metabolic rate of the cells, resulting in less heat being produced.
Relaxation of skeletal muscles to reduce heat production. Causes the hair to lie flat
Vasodilation causing arterioles to increase blood supply to the skin . More heat can be lost through the skin.
More sweat is produced. As sweat is removed more latent heat is removed.

32. What happens when temperature falls?
Increased metabolic rate, resulting in more heat being produced.
Shivering due to the contraction of skeletal muscles. (increases heat production)
Causes hair to stand.
Vasoconstriction causing arterioles in the skin to constrict.
Blood is diverted from the skin to reduce heat loss.

33. Detected by
hypothalamus
Increased sweating
Vasodilation
Rise in Blood
Temperature
Heat loss
Heat released
During exercise
Body Temp
37 C
Body Temp
37 C
Cold
environment
Blood temp
rises
Drop in blood
temperature
Decreased sweating
Vasoconstriction
shivering
Detected by
hypothalamus

34. Regulating Body Temperature - on a Hot Day
21 April 2017
Figure 12.7 (modified) page 246, Figure 12.8 (modified) page 246 and Figure 12.9 page 248

35. Regulating Body Temperature - on a Hot Day
Stimulus
Blood and skin temperatures rise
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36. Regulating Body Temperature - on a Hot Day
Stimulus
Blood and skin temperatures rise
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
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21 April 2017 36

37. Regulating Body Temperature - on a Hot Day
hair follicle
hair
arteriole
blood capillaries
Stimulus
Blood and skin temperatures rise
erector muscle
Figure 12.7 (modified) page 246
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
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38. Regulating Body Temperature - on a Hot Day4
Greater heat loss
skin surface
Stimulus
Blood and skin temperatures rise
capillaries 1
Arterioles in skin dilate 3
Shunt vessels constrict
Figure 12.9 page 248
arteriole
Receptor
Temperature receptors detect changes and send nerve impulses to the brain 2
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
More blood flows to capillaries in skin
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21 April 2017 38

39. Regulating Body Temperature - on a Hot Day7
More latent heat lost as sweat evaporates
sweat pore
Stimulus
Blood and skin temperatures rise
sweat duct 6
Sweat production increases 5
Sweat glands more active
Figure 12.8 (modified) page 246
sweat gland
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
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21 April 2017 39

40. Regulating Body Temperature - on a Hot Day
hair follicle
hair
arteriole
blood capillaries 8
Hair erector muscles in skin relax
Stimulus
Blood and skin temperatures rise
erector muscle
Figure 12.7 (modified) page 246
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
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21 April 2017 40

41. Regulating Body Temperature - on a Hot Day
Stimulus
Blood and skin temperatures rise
Corrective Mechanism
Increase in heat loss and decrease in heat production
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
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21 April 2017 41

42. Regulating Body Temperature - on a Hot Day
Decreased metabolic rate reduces heat production
Stimulus
Blood and skin temperatures rise
Corrective Mechanism
Increase in heat loss and decrease in heat production
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
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21 April 2017 42

43. Regulating Body Temperature - on a Hot Day
Decreased metabolic rate reduces heat production
Blood temperature returns to normal levels
Stimulus
Blood and skin temperatures rise
Corrective Mechanism
Increase in heat loss and decrease in heat production
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
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21 April 2017 43

44. Regulating Body Temperature - on a Hot Day
Decreased metabolic rate reduces heat production
Blood temperature returns to normal levels
Stimulus
Blood and skin temperatures rise
Corrective Mechanism
Increase in heat loss and decrease in heat production
Negative
feedback
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
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21 April 2017 44

45. Regulating Body Temperature - on a Cold Day
21 April 2017
Figure 12.7 page 246, Figure 12.8 page 246 and Figure page 249

46. Regulating Body Temperature - on a Cold Day
Stimulus
Blood and skin temperatures fall
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21 April 2017 46

47. Regulating Body Temperature - on a Cold Day
Stimulus
Blood and skin temperatures fall
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
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21 April 2017 47

48. Regulating Body Temperature - on a Cold Day
hair follicle
hair
arteriole
blood capillaries
Stimulus
Blood and skin temperatures fall
erector muscles
Figure 12.7 page 246
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
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21 April 2017 48

49. Regulating Body Temperature - on a Cold Day4
Less heat loss
Stimulus
Blood and skin temperatures fall
skin surface
capillaries 1 3
Arterioles in skin constrict
Shunt vessels dilate
Figure page 249
arteriole
Receptor
Temperature receptors detect changes and send nerve impulses to the brain 2
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Less blood flows to capillaries in skin
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21 April 2017 49

50. Regulating Body Temperature - on a Cold Day7
Less latent heat lost
sweat pore
Stimulus
Blood and skin temperatures fall
sweat duct 6
Sweat production decreases 5
Sweat glands less active
Figure 12.8 page 246
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
sweat gland
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21 April 2017 50

51. Regulating Body Temperature - on a Cold Day
hair follicle
hair
arteriole
blood capillaries
Stimulus
Blood and skin temperatures fall 8
Hair erector muscles in skin contract
erector muscles
Figure 12.7 page 246
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
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21 April 2017 51

52. Regulating Body Temperature - on a Cold Day
Shivering occurs when insufficient heat is produced
Stimulus
Blood and skin temperatures fall
Corrective Mechanism
Decrease in heat loss and increase in heat production
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is
stimulated and sends nerve impulses to relevant body parts
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21 April 2017 52

53. Regulating Body Temperature - on a Cold Day
Increased metabolic rate increases heat production
Stimulus
Blood and skin temperatures fall
Corrective Mechanism
Decrease in heat loss and increase in heat production
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Copyright © Marshall Cavendish International (Singapore) Pte. Ltd.
21 April 2017 53

54. Regulating Body Temperature - on a Cold Day
Increased metabolic rate increases heat production
Blood temperature returns to normal levels
Stimulus
Blood and skin temperatures fall
Corrective Mechanism
Decrease in heat loss and increase in heat production
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Copyright © Marshall Cavendish International (Singapore) Pte. Ltd.
21 April 2017 54

55. Regulating Body Temperature - on a Cold Day
Increased metabolic rate increases heat production
Blood temperature returns to normal levels
Stimulus
Blood and skin temperatures fall
Corrective Mechanism
Decrease in heat loss and increase in heat production
Negative
feedback
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
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21 April 2017 55

56. Homeostasis (Concept Map)
21 April 2017
Concept Map page 251

57. HOMEOSTASIS The maintenance of a constant internal environment
Concept Map page 251
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58. Principles of Homeostasis
The maintenance of a constant internal environment
Principles of Homeostasis
Concept Map page 251
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21 April 2017 58

59. Principles of Homeostasis
The maintenance of a constant internal environment
Principles of Homeostasis
Stimulus
Change in internal environment
Concept Map page 251
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21 April 2017 59

60. Principles of Homeostasis
The maintenance of a constant internal environment
Principles of Homeostasis
Stimulus
Receptors
Change in internal environment
Detect the change
Concept Map page 251
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21 April 2017 60

61. Principles of Homeostasis Self-corrective Mechanism
The maintenance of a constant internal environment
Principles of Homeostasis
Stimulus
Receptors
Self-corrective Mechanism
Change in internal environment
Detect the change
To rectify the change
Concept Map page 251
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21 April 2017 61

62. Principles of Homeostasis Self-corrective Mechanism
The maintenance of a constant internal environment
Principles of Homeostasis
Stimulus
Receptors
Self-corrective Mechanism
Change in internal environment
Detect the change
To rectify the change
Examples
Concept Map page 251
Regulation of blood glucose concentration
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21 April 2017 62

63. Principles of Homeostasis Self-corrective Mechanism
The maintenance of a constant internal environment
Principles of Homeostasis
Stimulus
Receptors
Self-corrective Mechanism
Change in internal environment
Detect the change
To rectify the change
Examples
Concept Map page 251
Regulation of blood glucose concentration
Regulation of blood water potential
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21 April 2017 63

64. Principles of Homeostasis Self-corrective Mechanism
The maintenance of a constant internal environment
Principles of Homeostasis
Stimulus
Receptors
Self-corrective Mechanism
Change in internal environment
Detect the change
To rectify the change
Examples
Concept Map page 251
Regulation of blood glucose concentration
Regulation of blood water potential
Regulation of body temperature
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21 April 2017 64

65. Principles of Homeostasis Self-corrective Mechanism
The maintenance of a constant internal environment
Principles of Homeostasis
Stimulus
Receptors
Self-corrective Mechanism
Negative Feedback
Change in internal environment
Detect the change
To rectify the change
The reverse effect of the change
Examples
Concept Map page 251
Regulation of blood glucose concentration
Regulation of blood water potential
Regulation of body temperature
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21 April 2017 65