How is blood glucose concentration regulated, with reference to insulin, glucagon and the liver?

• The alpha and beta cells monitor the concentration of glucose in the blood • The normal blood glucose concentration is 90mg of glucoses in every 100cm³ of blood • If the concentration rises or falls away from this concentration then the cells in the Islets of Langerhans detect the change and either alpha or beta cells will release a hormone depending on whether the blood glucose level is too high or too low If blood glucose level rises too high • A high blood glucose concentration is detected by the Beta cells • In response the Beta cells secrete insulin into the blood • Insulin binds to complementary shaped receptors on its target cells • Insulin’s target cells are the hepatocytes and also muscle cells • Hepatocytes are liver cells • Once insulin binds at its target cells it causes a change in its tertiary structure, this causes a change in shape of the cell surface membrane, which activates adenyl cyclase • Inside the target cells, adenyl cyclase converts ATP to cAMP • cAMP activates a series of enzyme controlled reactions inside the cell • In muscle cells the rate of respiration is increased so that more glucose is used up • In the hepatocytes glucose is converted to glycogen for storage (glycogenesis) If blood glucose level drops too low • The low blood glucose concentration is detected by Alpha cells • In response the Alpha cells secrete the hormone glucagon • Glucagon binds to complementary shaped receptors on the target cells • Its target cells are the hepatocytes • Once Glucagon binds at its target cells it causes a change in its tertiary structure, this causes a change in shape of the cell surface membrane, which activates adenyl cyclase • Inside the target cells adenyl cyclase converts ATP to cAMP • cAMP activates a series of enzyme controlled reactions inside the cell • The conversion of glycogen to glucose is stimulated (glycogenolysis) so that more glucose is released into the blood • cAMP also activates the production of glucose by conversion from amino acids and lipids (gluconeogenesis)