1. By Sila Topcu UoB Foundation

2. What is homeostasis ? Same and steady Why is it important ? Rates of biochemical reactions Movement of water all depend on it …

3. How is homeostasis brought about ? Negative feedback http://health.howstuffworks.com/adam- 200092.htm http://health.howstuffworks.com/adam- 200092.htm

4. What must be kept constant ?

5. The control of blood glucose concentration In 1859 Claude Bernard was the first to recognise the importance of homeostasis.

6. There are three sources of blood glucose : Digestion of carbohydrates in the diet Breakdown of glycogen [ glycogenesis]. Conversion of non- carbohydrate compounds.

7. Mechanism of blood glucose control Pancreas has a vital role The islets of Langerhans

8. High blood glucose concentration Detected by  - cells Insulin is released

9. Low blood glucose concentration Detected by  - cells Glucagon is secreted

10. Summary

11. What happens when homeostasis goes wrong ? DIABETES ! !! There are two types Type I And Type II And of course it is treatable !

12. Past Exam Question The graph shows the blood glucose and glucagon concentrations in a healthy person during and after eating a meal.

13. (i)From where is glucagon secreted? (ii)Explain the changes that occur in the glucagon concentration over the period on the graph. (b)Explain how the information shown in the graph provides an example of negative feedback.

14. Answers (a)(i)Cells of islets of Langerhans / pancreas / a cells; (ii)High glucagon because – eg stimulated by low glucose/ glycogen must be converted to glucose; Low glucagon because – e.g. body has absorbed glucose; (b)Clear understanding that a change from the set level initiates mechanism returning it; low glucose secretion of glucagon glucose level increases/ glucagon increase glucose increase ® glucagon decrease;

15. END OF THE PRESENTATION Referencing "Homeostasis." 25 February 2005. HowStuffWorks.com. 02 May 2010. “Homeostasis” www.biologymad.com http://www.biologymad.com/resources/A2%20H omeostasis.pdf accessed on 28 th of Aprilwww.biologymad.com http://www.biologymad.com/resources/A2%20H omeostasis.pdf Baker M. Indge B. Rowland M. (2001) Further Studies in Biology, Unit 9 Pages 174 - 193