Which hormone is secreted by the cells of the pancreatic islets to increase the amount of glucose in the blood?
A insulin
B calcitonin
C glucagon
D estrogen
The correct answer and explanation is:
The correct answer is C: glucagon.
Glucagon is a hormone secreted by the alpha cells of the pancreatic islets (also known as the islets of Langerhans). Its primary function is to increase the amount of glucose in the blood, especially when blood glucose levels are low. This process is essential for maintaining homeostasis in the body, ensuring that the brain and other tissues that rely on glucose for energy have a continuous supply.
When blood glucose levels fall, glucagon is released into the bloodstream. It then travels to the liver, where it stimulates the breakdown of glycogen into glucose (a process called glycogenolysis). Additionally, glucagon promotes the production of new glucose molecules from non-carbohydrate sources, such as amino acids, in a process called gluconeogenesis. Both of these actions raise blood glucose levels.
This mechanism of glucagon counterbalances the effect of insulin, which is secreted by the beta cells of the pancreatic islets. Insulin lowers blood glucose levels by promoting the uptake of glucose into cells for energy or storage as glycogen in the liver and muscles.
The release of glucagon is typically triggered when blood glucose levels drop below a certain threshold, often after periods of fasting or intense physical activity. It acts as a vital counter-regulatory hormone, ensuring that the body’s energy needs are met during times when glucose is in short supply.
In contrast, insulin (choice A) works to decrease blood glucose levels, calcitonin (choice B) regulates calcium levels in the blood, and estrogen (choice D) is a hormone involved in reproductive functions but does not regulate blood glucose.