State the functions of cells of islets of Langerhans.

(N/A) The islets of Langerhans are endocrine clusters within the pancreas. They contain two primary types of cells:
$1$. $\alpha$-cells: These cells secrete the hormone glucagon,which increases blood glucose levels by stimulating glycogenolysis in the liver.
$2$. $\beta$-cells: These cells secrete the hormone insulin,which decreases blood glucose levels by facilitating the cellular uptake and utilization of glucose.