1 Control, Coordination and Feedback

2 Blood glucose control What is glucose? Why is glucose in the blood? Where does it come from? Where does it go? What is it there for? How much is there? How do you measure it? When does the concentration increase? When does the concentration decrease?

3 Blood glucose regulation

4 Glucose concentration 80 to 120 mg 100 cm -3 blood This is the ‘normal’ range The concentration fluctuates Below 60 mg 100 cm -3 – coma Above 180 mg 100 cm -3 exceeds renal threshold and glucose appears in the urine

5 Blood glucose What goes wrong when the concentration decreases? What goes wrong when the concentration increases?

6 Blood glucose What goes wrong when the concentration decreases too far? Hypoglycaemia The symptoms associated with low blood sugar are: tiredness, confusion, dizziness, headaches, mood swings, muscle weakness, shaking

7 Blood glucose What goes wrong when the concentration increases too far? Hyperglycaemia The symptoms include: Excessive thirst; frequent urination; fatigue; unexplained weight loss; vision problems, such as blurring; increased susceptibility to infections such as thrush.

8 Blood glucose concentration Keep within narrow limits Corrective action if it increases Corrective action if it decreases Control mechanism needs to respond to fluctuations –Negative feedback – reduces the difference between actual and ideal / norm / set point

9 Feedback system Input Receptor Control centre Effector(s) Communication system Corrective actions Negative feedback

10 Liver cells Binucleate cell central vein

11 Liver cell

12 Liver cell protein metabolism lipid metabolism carbohydrate metabolism

13 Carbohydrate metabolism glucose absorbed across membrane by facilitated diffusion glucose stored as glycogen glucose  glucose 6 phosphate glucose 6 phosphate  glucose 1 phosphate glucose units added onto end of glycogen molecule (glycosidic links) glycogen synthetase

14 Carbohydrate metabolism glycogen broken down to glucose glucose 1 phosphate molecules formed glucose phosphorylase glucose 1 phosphate  glucose 6 phosphate glucose 6 phosphate to glucose glucose diffuses out of cell through protein carriers

15 Glucose storage glucose concentration in blood increases beta cells in pancreas release insulin insulin stimulates liver cells to store glucose as glycogen insulin stimulates lipid synthesis insulin stimulates protein synthesis insulin helps to conserve resources

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17 Islet of Langerhans exocrine tissue endocrine tissue

18 Alpha cells Beta cells

19 Structure of insulin

20 Insulin receptor

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22 Secondary messengers Glucagon and insulin are both proteins Do not cross membranes Signalling transduction at cell membrane Secondary messenger produced inside membrane 2 o messenger transmits signal to enzymes within cytoplasm

23 Cyclic AMP Produced just inside cell membrane ATP  cyclic AMP Catalysed by Adenylate cyclase Cyclic AMP combines with a protein Starts a ‘chain reaction’ following stimulation by glucagon

24 Amplification Quick response required from many enzymes Signal is amplified Chain reaction: A  B  C  D Enzyme cascade Final enzyme converts glycogen  glucose

25 Glucagon

26 Glucagon

27 Insulitis

28 Modern technology BiosensorInsulin mini-pump