1. Homeostasis L.O: to define homeostasis and explain how homeostasis occurs Starter: Year 11 homeostasis quiz – what can you remember from two years ago??!

2. Homeostasis Definition Definition: Homeostasis is maintenance of a constant internal environment within a living organism. Homeo = same Stasis = state

3. Negative Feedback A series of changes that result in a substance being restored its normal / optimum level. Can you put the parts of a negative feedback system in the correct order? Then match up the sections with their correct description. Ask me to check before you glue them down! Once you’ve done, try to write an example of negative feedback next to each section. E.g a waterbath getting too hot – what would happen?

4. Section Set Point / Optimum Level InputReceptorControllerEffectorOutput Feedback Loop Description The normal /optimum level A detectable change Measures the level of change Receives and controls info from receptor Carries out the change needed to restore to norm System is returned to normal / optimum level Informs the receptor about the changes made by the effector Example Waterbath on at 40c Water temperatu re rises to 42c Thermosta t detects change Heating element is turned off Water temperatu re falls Negative Feedback A series of changes that result in a substance being restored its normal / optimum level.

5. What needs to be regulated by such a control system?

6. Examples of Homeostasis (in a quiz stylee!) 1:

7. 2:

8. 3:

9. Examples of Homeostasis 1)Glucoregulation = keeping blood sugar levels constant 2)Thermoregulation = keeping body temperature constant at …?...°c 3)Osmoregulation = keeping water and ion levels constant

10. Osmoregulation If your blood water conc falls…

11. Osmoregulation If your blood water conc falls… This is detected by osmoreceptors in the hypothalamus…

12. Osmoregulation If your blood water conc falls… This is detected by osmoreceptors in the hypothalamus… Pituitary gland releases ADH (anti-diuretic hormone) into the blood…

13. Osmoregulation If your blood water conc falls… This is detected by osmoreceptors in the hypothalamus… Pituitary gland releases ADH (anti-diuretic hormone) into the blood… This makes your kidney tubules more permeable to water…

14. Osmoregulation If your blood water conc falls… This is detected by osmoreceptors in the hypothalamus… Pituitary gland releases ADH (anti-diuretic hormone) into the blood… This makes your kidney tubules more permeable to water… So you absorb more water!

15. Osmoregulation However… Alcohol interferes and reduces the effect of ADH… what consequences does this have on your body?? Interestingly… Boxers and jockeys who want to lose weight use diuretic drugs… how would this work??