Think about… 18.1 The concept of homeostasis 18.2 Regulation of blood glucose level

2. Think about… 18.1 The concept of homeostasis 18.2 Regulation of blood glucose level Recall ‘Think about…’ Summary concept map

3. 18.1 The concept of homeostasis Do you know what homeostasis is?

4. 18.1 The concept of homeostasis What is homeostasis? • ability of the body to maintain a stable internal environment - composition of blood and tissue fluid • body temperature • blood pressure • important for body to function properly

5. 18.1 The concept of homeostasis What is homeostasis? For example: Our body is exposed to changes in the external environment, e.g. air temperature homeostasis

6. 18.1 The concept of homeostasis What is homeostasis? blood For example: capillary The condition of blood and tissue fluid is kept constant for proper functions of cells body cell bathed in tissue fluid

7. 18.1 The concept of homeostasis Parameters of the internal environment to be kept stable What parameters must be kept constant in our body?

8. 18.1 The concept of homeostasis 1 Water content in blood water content in blood water potential of tissue fluid affects

9. 18.1 The concept of homeostasis 1 Water content in blood enter the cells or leave the cells If water potential of tissue fluid is different from that of the cells, water will …

10. 18.1 The concept of homeostasis 1 Water content in blood If too much water is gained …

11. 18.1 The concept of homeostasis 1 Water content in blood If too much water is lost …

12. 18.1 The concept of homeostasis 1 Water content in blood If too much water is lost … cells cannot function properly and may even die

13. 18.1 The concept of homeostasis 1 Water content in blood • regulated by kidneys (腎) ureters kidneys urinary bladder urethra mammalian urinary system

14. 18.1 The concept of homeostasis 2 Glucose level in blood • for respiration in cells energy + CO2 + water glucose + O2 - level in blood is kept steady to ensure a sufficient supply - as it is water soluble, any change in level affects water potential of the tissue fluid

15. 18.1 The concept of homeostasis 2 Glucose level in blood In humans, • normal range is 90–100 mg/cm3 • maintained by liver pancreas

16. 18.1 The concept of homeostasis 3 Gas content in blood • in respiration energy + CO2 + water glucose + O2 content in blood is kept steady to ensure a sufficient supply

17. 18.1 The concept of homeostasis 3 Gas content in blood • in respiration energy + CO2 + water glucose + O2 dissolves in blood too much / too little affects pH of blood and tissue fluid affects enzyme activity

18. 18.1 The concept of homeostasis 3 Gas content in blood • regulated by breathing heartbeat

19. 18.1 The concept of homeostasis 4 Body temperature • normal range is 36.5–37C • kept steady for enzymes to function properly • regulated by skin

20. 18.1 The concept of homeostasis 4 Body temperature What are the effects of failing to regulate body temperature?

21. 18.1 The concept of homeostasis 4 Body temperature C 44 death 42 CNS breakdown >37.5 fever 33 loss of consciousness 28 muscle failure

22. 18.1 The concept of homeostasis Mechanism of homeostasis • by negative feedback mechanism (負反饋機制)

23. 18.1 The concept of homeostasis Negative feedback mechanism Set point When the room temperature (RT) is higher than the set temperature (S) …

24. 18.1 The concept of homeostasis Negative feedback mechanism RT > S thermostat turns compressor on, cooling the air back to set temperature

25. 18.1 The concept of homeostasis Negative feedback mechanism When the room temperature (RT) is lower than the set temperature (S) …

26. 18.1 The concept of homeostasis Negative feedback mechanism thermostat turns compressor off, allowing room temperature to increase RT < S

27. 18.1 The concept of homeostasis Negative feedback mechanism Three components: Receptor Detects changes in the level of the parameter Control centre Processes information from receptor and coordinates different organs nervous system or endocrine system

28. 18.1 The concept of homeostasis Negative feedback mechanism When level of parameter is higher than normal, control centre receptor effector response to decrease the level back to normal normal level of parameter

29. 18.1 The concept of homeostasis Negative feedback mechanism response to increase the level back to normal control centre receptor effector When level of parameter is lower than normal,

30. Why is called “negative” feedback system???

31. Why is called “negative” feedback system??? The corrective action is always opposing to the deviation.

32. 18.1 The concept of homeostasis Negative feedback mechanism What are the Components in a feedback system??? RT > S thermostat turns compressor on, cooling the air back to set temperature

34. 18.1 The concept of homeostasis Negative feedback mechanism What are the Components in a feedback system??? Receptor Detects changes in the level of the parameter Control centre Processes information from receptor and coordinates different organs Produces a response opposite to the original change Effector

35. 18.1 The concept of homeostasis 1 is the ability of the body to maintain a stable internal environment. Homeostasis

37. 18.2 Regulation of blood glucose level

38. We are addicted to sugar

39. Importance of blood sugar • Hyperglycemia: blood glucose level goes above 7.0mmol/L. –The levels are increased in diabetes mellitus. • Hypoglycemia: blood glucose level falls below 3.0mmol/L, this would lead to a loss of consciousness (coma).

40. Importance of blood sugar regulation Health risks of Hyperglycaemia

41. 18.2 Regulation of blood glucose level Roles of liver and pancreas • they work together • pancreas secretes hormones insulin glucagon both act on liver but with opposite effects

42. 18.2 Regulation of blood glucose level Roles of liver and pancreas Insulin decreases blood glucose level liver cells excess glucose glycogen stored in muscles liver Body cells take in more glucose body cells glucose CO2 + water

43. 18.2 Regulation of blood glucose level Roles of liver and pancreas Glucagon increases blood glucose level liver cells stored glycogen glucose Let’s see how blood glucose level is regulated by negative feedback mechanism.

44. 18.2 Regulation of blood glucose level Roles of liver and pancreas higher than normal pancreas secretes more insulin and less glucagon liver cells and body cells normal blood glucose level

45. 18.2 Regulation of blood glucose level Roles of liver and pancreas higher than normal pancreas secretes more insulin and less glucagon liver cells and body cells Decrease level by: 1 converting more glucose to glycogen in liver cells 2 increasing glucose uptake and oxidation by body cells

46. 18.2 Regulation of blood glucose level Roles of liver and pancreas Increaselevel by: converting stored glycogen to glucose lower than normal pancreas secretes more glucagon and less insulin liver cells

47. 18.2 Regulation of blood glucose level Failing to regulate blood glucose level What will happen if blood glucose level is too high?

48. 18.2 Regulation of blood glucose level Failing to regulate blood glucose level blood glucose level too high water leaves cells by osmosis normal metabolism affected glucose passes out in urine diabetes mellitus

49. 18.2 Regulation of blood glucose level Failing to regulate blood glucose level it results when the pancreas fails to produce or does not produce enough insulin diabetes mellitus

50. 18.2 Regulation of blood glucose level blood glucose level (mg/100cm3) 200 healthy person level returns to normal within a short time 150 100 normal time (hrs) 1 2 3 glucose intake