2. Homeostasis

3. Glossary Maintain – keep up. Maintain – keep up. Constant – the same. Constant – the same. Internal – inside the body. Internal – inside the body. Environment – surroundings of the body. Environment – surroundings of the body.

4. What is Homeostasis? Body cells work best if they have the correct Body cells work best if they have the correct Temperature Temperature Water levels Water levels Glucose concentration Glucose concentration Your body has mechanisms to keep the cells in a constant environment. Your body has mechanisms to keep the cells in a constant environment.

5. What is Homeostasis? The maintenance of a constant environment in the body is called Homeostasis

6. Controlling body temperature All mammals maintain a constant body temperature. All mammals maintain a constant body temperature. Human beings have a body temperature of about 37ºC. Human beings have a body temperature of about 37ºC. E.g. If your body is in a hot environment your body temperature is 37ºC E.g. If your body is in a hot environment your body temperature is 37ºC If your body is in a cold environment your body temperature is still 37ºC If your body is in a cold environment your body temperature is still 37ºC

7. Penguins huddling to keep warm

8. To provide the optimum conditions for enzyme-catalysed reactions to be carried out. To provide the optimum conditions for enzyme-catalysed reactions to be carried out. Why do we need to regulate: Internal body temperature

9. Body Temperature Normal internal body temperature is 37 0 C. Normal internal body temperature is 37 0 C. Temperatures above this: Temperatures above this: denature enzymes and block metabolic pathways Temperatures below this: Temperatures below this: slow down metabolism and affect the brain.

10. Control of homeostasis through feedback Feedback system- cycle of events in which the status of a body condition is continually monitored, evaluated, changed, re-monitored, re-evaluated, etc. Feedback system- cycle of events in which the status of a body condition is continually monitored, evaluated, changed, re-monitored, re-evaluated, etc.

11. 1) receptor 1) receptor sensor that responds to changes (stimuli) sensor that responds to changes (stimuli) 2) control centre 2) control centre sets range of values, evaluates input and sends output sets range of values, evaluates input and sends output 3) effector 3) effector receives output from control centre and produces a response receives output from control centre and produces a response 3 basic components of a feedback system

12. Body Temperature Control The hypothalamus acts as a thermostat and receives nerve impulses from heat and cold thermoreceptors in the skin. The hypothalamus acts as a thermostat and receives nerve impulses from heat and cold thermoreceptors in the skin. There are also receptors in the hypothalamus- called central thermoreceptors. There are also receptors in the hypothalamus- called central thermoreceptors. These detect changes in blood temperature.

13. What mechanisms are there to cool the body down? 1. Sweating When your body is hot, sweat glands are stimulated to release sweat. When your body is hot, sweat glands are stimulated to release sweat. The liquid sweat turns into a gas (it evaporates) The liquid sweat turns into a gas (it evaporates) To do this, it needs heat. To do this, it needs heat. It gets that heat from your skin. It gets that heat from your skin. As your skin loses heat, it cools down. As your skin loses heat, it cools down.

14. Sweating The skin

15. What mechanisms are there to cool the body down? 2. Vasodilation Your blood carries most of the heat energy around your body. Your blood carries most of the heat energy around your body. There are capillaries underneath your skin that can be filled with blood if you get too hot. There are capillaries underneath your skin that can be filled with blood if you get too hot. This brings the blood closer to the surface of the skin so more heat can be lost. This brings the blood closer to the surface of the skin so more heat can be lost. This is why you look red when you are hot! This is why you look red when you are hot!

16. Vasoconstriction and Vasodilatation

17. Correction of overheating 1. Detected by thermoreceptors in the hypothalamus. 2. Causes vasodilation. 3. Sweating

18. If the temperature rises, the blood vessel dilates (gets bigger). This means more heat is lost from the surface of the skin

19. Sweating How does it work? Heat energy in the body is used to convert the water in sweat to vapour cooling down the body.

20. Cooling down When it's hot and you need to cool down, muscles at each hair relax.hair Hairs lie close to the skin. Air does not act as an insulating layer.

21. What mechanisms are there to warm the body up? 1. Vasoconstriction This is the opposite of vasodilation This is the opposite of vasodilation The capillaries underneath your skin get constricted (shut off). The capillaries underneath your skin get constricted (shut off). This takes the blood away from the surface of the skin so less heat can be lost. This takes the blood away from the surface of the skin so less heat can be lost.

22. Correction of overcooling 1. Detected by thermoreceptors in the hypothalamus. 2. Causes vasoconstriction. 3. Decreased sweating 4. Shivering

23. If the temperature falls, the blood vessel constricts (gets shut off). This means less heat is lost from the surface of the skin

24. What mechanisms are there to warm the body up? 2. Piloerection This is when the hairs on your skin “stand up”. This is when the hairs on your skin “stand up”. It is sometimes called “goose bumps” or “chicken skin”! It is sometimes called “goose bumps” or “chicken skin”! The hairs trap a layer of air next to the skin which is then warmed by the body heat The hairs trap a layer of air next to the skin which is then warmed by the body heat The air becomes an insulating layer. The air becomes an insulating layer.

25. Keeping warm When it's cold, the muscle contracts pulls the hair up. A layer of warm air accumulates around the hair and insulates the organism. Heat retained

27. END Temperature Regulation Refer to text section 7.1 and 7.2 Define positive and negative feedback. Copy Figure 5 for your notes and answer the accompanying “Applying Inquiry Skills” question #8 on page 341.

28. Controlling Glucose levels Your cells also need an exact level of glucose in the blood. Your cells also need an exact level of glucose in the blood. Excess glucose gets turned into glycogen in the liver Excess glucose gets turned into glycogen in the liver This is regulated by 2 hormones (chemicals) from the pancreas called: This is regulated by 2 hormones (chemicals) from the pancreas called:InsulinGlucagon

29. If there is too much glucose in the blood, Insulin converts some of it to glycogen Glycogen Insulin Glucose in the blood

30. If there is not enough glucose in the blood, Glucagon converts some glycogen into glucose. Glycogen Glucagon Glucose in the blood

31. Diabetes Some people do not produce enough insulin. Some people do not produce enough insulin. When they eat food, the glucose levels in their blood cannot be reduced. When they eat food, the glucose levels in their blood cannot be reduced. This condition is known as DIABETES. This condition is known as DIABETES. Diabetics sometimes have to inject insulin into their blood. They have to be careful of their diet. Diabetics sometimes have to inject insulin into their blood. They have to be careful of their diet.

32. Time Glucose Concentration Meal eaten Insulin is produced and glucose levels fall to normal again. Glucose levels rise after a meal. Normal

33. Time Glucose Concentration Meal eaten Insulin is not produced so glucose levels stay high Glucose levels rise after a meal. Diabetic

34. The glucose in the blood increases. Glycogen Insulin Glucose in the blood But there is no insulin to convert it into glycogen. Glucose concentration rises to dangerous levels.

35. Controlling water levels The control of water levels is carried out by the KIDNEYS. The control of water levels is carried out by the KIDNEYS. It is closely linked to the excretion of urea. It is closely linked to the excretion of urea. Urea is a waste product that is made when the LIVER breaks down proteins that are not needed by the body. Urea is a waste product that is made when the LIVER breaks down proteins that are not needed by the body. Urea contains the element Nitrogen. Urea contains the element Nitrogen.

36. The kidneys The kidneys “clean” the blood of waste products and control how much water is kept in the body. The waste products and water make up urine which is excreted via the ureter. “Dirty” blood enters the kidney through the renal artery. Then, several things happen to clean the blood...

37. Blood enters the tubule area in a capillary. The capillary forms a small “knot” near the kidney tubule. The blood is filtered so all the small particles go into the tubule. The capillary then carries on to run next to the tubule. 1. Filtration

38. The kidney tubule now contains lots of blood components including: Glucose: Ions: Water: Urea:

39. 2. Reabsorb sugar The body needs to have sugar in the blood for cells to use in respiration. So all the sugar is reabsorbed back into the capillary.

40. 2. Reabsorb sugar The body needs to have sugar in the blood for cells to use in respiration. So all the sugar is reabsorbed back into the capillary.

41. 3. Reabsorb water Water and ions are the next to be absorbed. It depends on how much is needed by the body.

42. 3. Reabsorb water Water and ions are the next to be absorbed. It depends on how much is needed by the body.

43. Reabsorbing water If you have too little water in your blood, you will produce very concentrated urine. (very little water in it) If you have too much water in your blood, you will produce very dilute urine. (lots of water in it)

44. 5. Excrete the waste Everything that is left in the kidney tubule is waste: All the urea Excess water This waste is called urine. It is excreted via the ureter and is stored in the bladder. The “clean” blood leaves the kidney in the renal vein. Renal vein Ureter

45. Summary of urine production Urea is a waste product made in the LIVER Urea is a waste product made in the LIVER Water content of the body is controlled in the KIDNEYS Water content of the body is controlled in the KIDNEYS Urea, water and other waste makes up URINE. Urea, water and other waste makes up URINE. Urine travels down the URETER and is stored in the BLADDER Urine travels down the URETER and is stored in the BLADDER Urine is excreted through the URETHRA. Urine is excreted through the URETHRA.

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