2. Hormones and Homeostasis IB Biology Topic 6

3. Group Activity Which group can come up with the biggest list of hormones you have already come across in biology? You have 2 min!

7. Negative Feedback control

11. Involuntary responses Mechanisms of temperature regulation are involuntary Controlled at a subconscious level by the hypothalamus

12. Vasodilation Skin becomes dilated Large volume of blood flows through capillaries near skin surface Blood able to lose heat by radiation

13. Increase in rate of sweating Heat energy from body Convert sweat into water vapour Lowers body temperature

14. Vasoconstriction Arterioles leading to skin become constricted Small volume of blood flow to surface capillaries Little heat lost by radiation

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

16. Decreased rate of sweating Sweating reduced to a minimum Heat conserved

17. Contraction of erector muscles Wide layer of air trapped between body and external environment Air poor conductor of heat Layer of insulation reduces heat loss

19. Voluntary responses Body temperature drops below normal Nerve impulses transmit this information to cerebrum Person ‘feels cold’ Takes appropriate action to correct problem -puts on a jacket -has a cup of tea etc.

22. EVERYONE (except Alonso!) Write down as a group EVERYTHING you know or heard about diabetes under these three headings 1.The science of the disease 2.The lifestyle change for the individual 3.The cure/medication Then Alonso or I will check it! Not This Cure!!

23. Control of blood sugar level Living cells need a continuous supply of energy Most of this energy released by oxidation of glucose Cells using up glucose present in bloodstream (blood sugar)

24. Homeostatic Mechanism Body only obtains supplies of glucose when food is eaten Need to guarantee regular supply of glucose regardless of how often food is consumed Body employs a homeostatic mechanism

25. The Liver 100g of glucose stored as glycogen in the liver Glucose can be added or removed from this reservoir of stored carbohydrate

26. Rise in blood sugar level 1.Detected by β cells in regions of pancreas called Islets of Langerhans 2.Receptor cells produce insulin 3.Hormone transported in bloodstream to the liver 4.Insulin activates an enzyme which catalyses glucoseglycogen 5.Blood sugar concentration brought down to normal

27. Drop in blood sugar level Detected in α cells by Islets of Langerhans Release the hormone glucagon Glucagon transported to the liver and activates a different enzyme which catalyses the reaction glycogenglucose

30. Diabetes mellitus 2 types of diabetes Type I diabetes Type II diabetes

31. Type I diabetes Insufficient insulin produced Causes body produces antibodies against insulin and/or β cells in Islets of Langerhans Treatment Inject insulin (why can´t you just take a tablet?) Transplant pancreas or β cells

32. Type II diabetes Insufficient insulin produced Body cells become less sensitive to insulin Causes Obesity, age, familiy history Treatment Eat less carbs Exercise and lose weight Medication (lower blood glucose and increase insulin production)

33. Absence of insulin Cells unable to use glucose efficiently Fat stores become depleted Weight loss Tissue wastage