Final answer:
Glucagon is a hormone stimulated by hypoglycemia, also known as low blood sugar, to raise blood glucose levels by converting glycogen to glucose in the liver. It is the counterpart to insulin, which is released when blood sugar levels are high to lower blood glucose levels.
Step-by-step explanation:
The hormone glucagon is stimulated by hypoglycemia, which means low blood sugar levels. The primary role of glucagon is to raise blood glucose levels. When blood glucose levels fall too low, glucagon is released from the alpha cells of the pancreas. This triggers the liver to convert stored glycogen into glucose, which is then released into the bloodstream to elevate the blood sugar level.
On the other hand, when there is a rise in blood glucose levels, this stimulates the secretion of insulin. Insulin is produced by the beta cells of the pancreas and helps to lower blood glucose levels by promoting the uptake of glucose into the cells and converting excess glucose to glycogen in the liver. Therefore, while insulin is responsive to high blood sugar, glucagon is the hormone that responds to low blood sugar.