How is blood glucose controlled in homeostasis?

Blood glucose concentration is controlled mainly by the pancreas. If there is a rise in blood glucose concentration the pancreas will detect this and the beta cells will secrete insulin. At the same time the alpha cells will stop secreting glucagon as we no longer want glycogen being converted to glucose. The insulin can now bind to receptors on liver and muscle cells. Insulin will cause cells to take up more glucose, glycogenesis is activated (synthesis of glycogen) and cells will respire more glucose. Overall these steps will ensure the blood glucose concentration will fall to the normal level again.

The pancreas can also detect a low blood glucose concentration. This time it will activate alpha cells to secrete glucagon. The beta cells will stop secreting insulin as this increases glucose concentration and we don't want that. Glucagon will travel in the blood and bind to receptors on liver cells (not muscle cells like insulin). It will activate; glycogenolysis (break down of glycogen), gluconeogenesis (making glucose from non-carbon compounds such as amino acids) and cells will respire less glucose. Each of these steps lead to an increase in blood glucose therefore the blood glucose concentration will return to normal again.

An easy way to remember the key biological terms here (such as gluconeogenesis, glycogenolysis) is to remember 'lysis' means breaking and 'genesis' means making. For example, if you want to remember the term for making glycogen, remember 'genesis' is at the end therefore it must be glycogenesis.