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Homeostasis

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homeostasis - high school

homeostasis - high school

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  • 1. Homeostasis This Powerpoint is hosted on www.worldofteaching.com Please visit for 100’s more free powerpoints
  • 2. Glossary  Maintain – keep up.  Constant – the same.  Internal – inside the body.  Environment – surroundings of the body.  Feedback - a cycle in which the output of a system “feeds back” to modify or reinforce the actions of the system in order to maintain homeostasis.
  • 3. Glossary  Negative feedback - a change causes system 1 to send a message to system 2 to restore homeostasis. When system 1 detects that system 2 has acted, it stops signaling for action and system 2 stops (turned off).  Positive feedback - the original stimulus is promoted rather than stopped. Positive feedback is rarely used to maintain homeostasis. An example of positive feedback is childbirth.
  • 4. What is Homeostasis?  Body cells work best if they have the correct  Temperature  Water levels  Glucose concentration  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.  Human beings have a body temperature of about 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
  • 7. Controlling body temperature  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 = ___________
  • 8. 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
  • 9. 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.
  • 10. Penguins huddling to keep warm
  • 11. What mechanisms are there to cool the body down? 1. Sweating  When your body is hot, sweat glands are stimulated to release sweat.  The liquid sweat turns into a gas (it evaporates)  To do this, it needs heat.  It gets that heat from your skin.  As your skin loses heat, it cools down.
  • 12. Sweating The skin
  • 13. What mechanisms are there to cool the body down? 2. Vasodilation  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.  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!
  • 14. If the temperature rises, the blood vessel dilates (gets bigger). This means more heat is lost from the surface of the skin
  • 15. What mechanisms are there to warm the body up? 1. Vasoconstriction  This is the opposite of vasodilation  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.
  • 16. If the temperature falls, the blood vessel constricts (gets shut off). This means less heat is lost from the surface of the skin
  • 17. What mechanisms are there to warm the body up? 2. Piloerection  This is when the hairs on your skin “stand up” .  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 air becomes an insulating layer.
  • 18. Controlling Glucose levels  Your cells also need an exact level of glucose in the blood.  Glucose moves into the cells for cellular respiration  Excess glucose gets turned into glycogen in the liver  This is regulated by 2 hormones (chemicals) from the pancreas called: Insulin Glucagon
  • 19. If there is too much glucose in the blood, Insulin converts some of it to glycogen the rest moves into the cells for use in cellular respiration. Glycogen Glucose in the blood
  • 20. If there is not enough glucose in the blood, Glucagon converts some glycogen into glucose. Glycogen Glucose in the blood
  • 21. Diabetes  Some people do not produce enough insulin.  When they eat food, the glucose levels in their blood cannot be reduced.  This condition is known as DIABETES.  Diabetics sometimes have to inject insulin into their blood. They have to be careful of their diet.
  • 22. Time Glucose Concentration Meal eaten Insulin is produced and glucose levels fall to normal again. Glucose levels rise after a meal. Normal
  • 23. Time Glucose Concentration Meal eaten Insulin is not produced so glucose levels stay high Glucose levels rise after a meal. Diabetic
  • 24. The glucose in the blood increases. Glycogen Glucose in the blood But there is no insulin to convert it into glycogen. Glucose concentration rises to dangerous levels.
  • 25. Pancreas produces Insulin Glucose into cells Out of blood Blood glucose increases Homeostasis Blood glucose decreases ( High ) (Low) Glucose out of cells Into blood Pancreas produces Glucagon Blood Glucose Feedback Mechanism
  • 26. Controlling water levels  The control of water levels is carried out by the KIDNEYS.  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 contains the element Nitrogen.
  • 27. 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...
  • 28. 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
  • 29. The kidney tubule now contains lots of blood components including: Glucose: Ions: Water: Urea:
  • 30. 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.
  • 31. 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.
  • 32. 3. Reabsorb water Water and ions are the next to be absorbed. It depends on how much is needed by the body.
  • 33. 3. Reabsorb water Water and ions are the next to be absorbed. It depends on how much is needed by the body.
  • 34. 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)
  • 35. 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
  • 36. Summary of urine production  Urea is a waste product made in the LIVER  Water content of the body is controlled in the KIDNEYS  Urea, water and other waste makes up URINE.  Urine travels down the URETER and is stored in the BLADDER  Urine is excreted through the URETHRA.
  • 37.  Temperature regulation, glucose level control and water level control are all examples of NEGATIVE FEEDBACK MECHANISMS.
  • 38. Homeostasis in Plants  Control of water levels in the plant is important to the survival of the plant.  This is achieved by a number of methods:  Waxy cuticle on leaves  Storage of water  Opening and closing of stomates
  • 39. Stoma Open Stoma Closed Guard Cells Stoma Function of Stomata Guard Cells CO2 O2 H2O What goes in? What goes out? •What process involves using CO2 and H2O releasing O2 as a waste product? •Photosynthesis •What is the plant using this process to make? •Carbohydrates-glucose •If the plant needs water for photosynthesis, why is water coming out of the stoma?
  • 40. Stoma Open Stoma Closed Guard Cells Function of Guard Cells Guard Cells•These stomata (leaf openings) naturally allow water to evaporate out. •Why would the plant close stomata with guard cells? •Prevent excess water loss through transpiration. (conserve water) •So what is the point of having stomata? •Allow gas exchange for photosynthesis
  • 41.  The opening and closing of the stomata maintains water balance in the plant and thus maintains homeostasis.