2. Homeostasis

3. SURVIVAL NEEDS Nutrients – for energy and cell building Nutrients – for energy and cell building Carbs, fats, proteins, minerals, vitamins Carbs, fats, proteins, minerals, vitamins Oxygen – 20% of air Oxygen – 20% of air Vital for Cellular respiration Vital for Cellular respiration Respiratory & cardiovascular systems Respiratory & cardiovascular systems

5. Survival Needs Water – 60-80% of body weight Water – 60-80% of body weight Provides fluid base for body secretions Provides fluid base for body secretions Body Temperature Body Temperature Must be maintained around 98 o F (37 0 C) Must be maintained around 98 o F (37 0 C) Too low : reactions slow & finally stop(death) Too low : reactions slow & finally stop(death) Too high: proteins begin to break down (death) Too high: proteins begin to break down (death) Body heat generated by activity of skeletal muscles Body heat generated by activity of skeletal muscles

7. Survival Needs Atmospheric Pressure- force per unit area exerted against a surface by the weight of air above that surface in the Earth’s atmosphere Atmospheric Pressure- force per unit area exerted against a surface by the weight of air above that surface in the Earth’s atmosphere Breathing and exchange of gas in lungs depend on proper pressure Breathing and exchange of gas in lungs depend on proper pressure High altitudes effect ability to carry out cellular metabolism – less O 2 High altitudes effect ability to carry out cellular metabolism – less O 2

9. 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.

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

11. FEEDBACK MECHANISMS

12. Negative Feedback Mechanism -Most homeostatic control mechanisms in body -Net effect of response to stimulus is to shut off or reduce the intensity of stimulus

14. Positive Feedback Mechanism More rare in body More rare in body Increase the stimulus and push variable farther from its original value Increase the stimulus and push variable farther from its original value

16. 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

17. Controlling body temperature Animals with a large surface area compared to their volume will lose heat faster than animals with a small surface area. Animals with a large surface area compared to their volume will lose heat faster than animals with a small surface area. Volume = _______ Surface area = ______ Volume : Surface area ratio = ___________ Volume = _______ Surface area = ______ Volume : Surface area ratio = ___________

18. Controlling body temperature Volume : Surface area ratio = 1:6 Volume : Surface area ratio = 1:5 For every 1 unit of heat made, heat is lost out of 6 sides For every 1 unit of heat made, heat is lost out of 5 sides

19. Controlling body temperature Volume : Surface area ratio = 1:6 Volume : Surface area ratio = 1:5 The bigger the Volume : Surface Area ratio is, the faster heat will be lost.

20. Penguins huddling to keep warm

21. 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.

22. Sweating The skin

23. 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!

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

25. 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.

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

27. 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.

29. 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

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

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

32. 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.

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

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

35. 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.

36. 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.

37. 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...

38. 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

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

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. 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.

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

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

44. 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)

45. 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

46. 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.