1. The maintenance of a constant internal environment

2. Learning Objectives How you keep conditions inside your body constant How cells get rid of waste products How the body monitors its temperature How blood sugar level is controlled

3. The main things that need to be controlled are Body temperature Water content Salt content Blood sugar content Urea Carbon dioxide

4. Cooling the Body Down Too hot- enzymes denature, can’t catalyse cell reactions Core temperature too high – skin capillaries dilate More blood flows through skin - flush- lose heat - radiation Too low- blood capillaries to skin constrict, reduce blood flow to skin

6. BODY TEMPERATURE Enzymes in the human body work best at about 37 C The brain has a thermoregulator control centre to maintain this It controls nerve receptors sensitive to blood temperature in the brain It also receives information from the skin temperature receptors

7. WATER CONTENT Kidneys control amount of water retained in the body Act as Filters to keep a balance of a) water, b) urea, c) ions in the blood

8. SALT CONTENT Ions e.g., of sodium are taken into the blood after digestion of food This may cause the salt content of the blood to be too high, drawing water into the cells by osmosis Excess ions are removed from the blood by the kidneys to maintain a correct body water balance

9. Sweat Rate goes up if too hot Sweat mainly water, salt As water evaporates, it cools the skin Heat is lost from the body in sweat In humid conditions, sweat does not evaporate very easily

10. BLOOD SUGAR Eating foods containing carbohydrate means the carbohydrates are digested into sugars which are absorbed into the blood Levels of blood glucose must be controlled Insulin is the hormone which controls the level of sugar in your blood.

11. Regulation of blood Glucose The pancreas detects sugar levels If they are too high the cells in the pancreas secrete insulin Insulin causes liver and muscles to take up glucose to form glycogen this is the form the energy is stored Insulin causes the blood glucose levels fall

12. Pancreas and Insulin

13. Diabetes A person who has this does not produce enough of the hormone insulin So their blood sugar levels can rise to a fatally high level This can cause come and death

14. Treatment of Diabetes Careful attention to diet Injecting insulin into the body

15. Frederick Banting and Charles Best

16. Experiments carried out by Frederick Banting and Charles Best These were the first scientists to isolate insulin They removed a pancreas from a dog and took an extract from it They injected this extract into diabetic dogs and observed the effects on blood sugar levels They found that it caused the dogs blood sugar levels to drop dramatically

17. What was in this dogs pancreas? The chemical was isolated and it was INSULIN Today genetically modified bacteria are used to manufacture human insulin

18. Check your Knowledge Which organ detects blood sugar levels? What hormone does it secrete? What does this hormone convert blood sugar to Why is this such an important hormone? Where does this conversion of blood sugar to glycogen take place?

19. UREA Surplus amino acids from digestion are converted to fats and carbohydrates in the liver The Liver produces the waste product – urea which travels in the blood to the kidneys. The kidneys filter it out of the blood. It becomes concentrated, to be excreted as urine

20. CARBON DIOXIDE Carbon dioxide is a waste product of respiration This is breathed out from the lungs, some dissolved in water vapour.