The role of glucagon and the alpha cells of the pancreas

• The alpha cells of the islets of Langerhans detect a fall in blood glucose concentration and respond by secreting the hormone glucagon directly into the blood plasma.
• Glucagon has three main actions in order to have the overall effect of increasing the concentration of glucose in the blood to restore it to the optimum concentration. By raising the blood glucose concentration, the alpha cells in turn reduce the secretion of glucagon. This creates a negative feedback loop.
• One of the main actions of glucagon is attaching to specific protein receptors on the cell-surface membrane of liver cells.
• One of the main actions of glucagon is activating enzymes that convert glycogen to glucose.
• One of the main actions of glucagon is activating enzymes involved in the conversion of amino acids and glycerol into glucose (gluconeogenesis).