Question

Which of the following statements regarding glucagon is false?

• A. It is secreted by the alpha cells of the islets of Langerhans.
• B. It decreases the blood sugar level.
• C. It acts antagonistically to insulin.
• D. It is secreted by a heterocrine gland.

Answer 1

The correct option is B It decreases the blood sugar level.

The pancreas is a heterocrine gland, i.e., it has both exocrine and endocrine functions. The endocrine pancreas consists of ‘islets of Langerhans’. The two main types of cells in the islet of Langerhans are called $\alpha$-cells and $\beta$-cells. The $\alpha$-cells secrete a hormone called glucagon and the $\beta$-cells secrete insulin.

Glucagon acts mainly on the liver cells (hepatocytes) and stimulates the breakdown of glycogen to form glucose (glycogenolysis) resulting in an increased blood sugar level. It also stimulates the process of formation of glucose (gluconeogenesis). Glucagon reduces the cellular glucose uptake and utilisation.

Insulin decreases blood glucose levels. It acts on hepatocytes and adipocytes and enhances the uptake and utilisation of glucose by these cells, which results in decreased blood glucose levels. Insulin also stimulates the conversion of glucose to glycogen (glycogenesis) in the target cells. Thus, insulin and glucagon have antagonistic (opposite) functions.