Final answer:
Insulin, secreted by the pancreas' beta cells, lowers blood sugar levels by promoting glucose uptake and glycogen formation. When blood sugar levels fall, insulin secretion stops and glucagon is released to increase blood sugar, maintaining homeostasis.
Step-by-step explanation:
Regulation of Blood Glucose Levels by Insulin
When the blood glucose levels rise, the beta cells of the pancreas release the hormone insulin, which facilitates the uptake of glucose by body cells and promotes the conversion of glucose to glycogen in the liver. These actions of insulin result in a decrease in blood glucose levels. Conversely, when blood sugar levels drop, insulin secretion is inhibited, and the alpha cells of the pancreas secrete glucagon.
This hormone stimulates the liver to convert glycogen back into glucose and to release this glucose into the bloodstream, thus elevating the blood sugar levels to normal. This system of hormonal regulation ensures that blood glucose levels remain within a normal range, which is critical for maintaining homeostatic balance and preventing conditions such as hypoglycemia (low blood sugar) and hyperglycemia (high blood sugar), the latter of which is a characteristic of diabetes mellitus. Insulin and glucagon play complementary roles in this regulatory mechanism, demonstrating the dynamic nature of the endocrine system in responding to changes in blood glucose concentrations.