If blood glucose becomes high, Beta cells act as a controller and detect this stimulus

Beta cells secrete insulin (a peptide hormone) into the blood

Insulin binds with a complementary cell surface receptor protein found on the surface of most body cells

Binding activates protein kinase enzymes to increase the rate of respiration (increase glucose consumption), increase glycogenesis (using many glucoses to form glycogen in liver and muscle cells), increase rate of lipogenesis (using glucose to synthesis lipid in liver cells), increase permeability of cells to glucose (more glucose transporter channels are inserted into the membrane)

Insulin binds to receptors on membrane of liver and muscle cells

Glucose transporters inserted into cell membrane. Glycogenesis, lipogenesis, increased respiration. Glucose removed from blood

If blood glucose becomes lower than normal, alpha cells in the pancreas act as receptors and detect this stimulus

Alpha cells secrete glucagon (peptide hormone) into the blood

Glucagon binds to complementary cell surface receptor proteins found on the surface of liver cells only.

Glucagon binds to a specific cell surface receptor protein on liver cell membranes.

This causes the membrane to change shape, activating a membrane bound enzyme called adenyl cyclase.

This enzyme converts ATP to cyclic AMP. cAMP activates the protein kinase enzymes. These enzymes cause increased glycogenolysis and gluconeogenesis.

This results in increased glucose concentration in cells and a faster rate of diffusion of glucose into the blood.

Adrenaline in another hormone that increases blood sugar levels in response to pain/shock 'fight or flight' response

Its produced in the adrenal glands and binds to complementary receptors on liver cell membranes and activates the same secondary messenger model as glucagon

It raises blood glucose by activating the enzyme that causes the breakdown of glycogen to glucose in the liver and inactivating an enzyme that synthesises glycogen