Excessive blood glucose is taken up by the liver cells and stored as glycogen. This requires optimum levels of insulin in the blood. When glucose levels are low, glycogen can again be broken down into glucose. This is done under the influence of another hormone, namely, glucagon.
When the glucose level are high ,the Beta cells of Islets of Langerhans in the pancreas release insulin. When the glucose levels are low, the Alpha-cells of Islets of Langerhans release glucagon.
Thus the liver and pancreas act as a ‘thermostat‘ maintaining the glucose levels in the blood, as shown in Figure4 below