Explain the control of blood glucose levels in humans (8)
- Blood-glucose levels are maintained within narrow limits so that there are sufficient amounts of glucose in the blood (for respiring cells) but also not too high levels that will disturb the osmotic balance. This is regulated by a negative feedback system. Pancreatic islet cells are able to detect changes in blood glucose concentration and can act accordingly: -If blood glucose levels are too high (e.g. after a meal- hyperglycaemia): Pancreatic B cells secrete the hormone insulin. Insulin causes liver & muscle cells to store the excess glucose as glycogen. -If the blood glucose levels are too low (i.e. in starvation, hypoglycaemia): Pancreatic A cells secrete the hormone glucagon. Glucagon causes the catabolism of glycogen sources to produce glucose hence the blood glucose level is returned to its normal.
