Correct Option: A. Insulin
Detailed Explanation:
- Understanding Blood Glucose Regulation:
-
Blood glucose levels are crucial for maintaining energy homeostasis in the body. The body needs a stable supply of glucose, especially for the brain and muscles, which rely heavily on it for energy.
-
Role of the Pancreas:
-
The pancreas is a vital organ that plays a key role in digestion and blood sugar regulation. It contains clusters of cells known as the islets of Langerhans, which are responsible for producing hormones, including insulin and glucagon.
-
Function of Insulin:
- Insulin is a peptide hormone produced by the beta cells of the islets of Langerhans in the pancreas. Its primary function is to lower blood glucose levels by facilitating the uptake of glucose into cells, particularly muscle and fat cells.
-
When blood glucose levels rise after eating, insulin is secreted into the bloodstream. It promotes:
- Glucose Uptake: Insulin binds to receptors on cell membranes, allowing glucose to enter the cells.
- Glycogenesis: It stimulates the liver to convert excess glucose into glycogen for storage.
- Lipogenesis: Insulin encourages the conversion of glucose into fat for long-term energy storage.
-
Why Other Options Are Incorrect:
- B. Adrenaline:
- Adrenaline (or epinephrine) is a hormone produced by the adrenal glands, primarily in response to stress. It increases blood glucose levels by promoting glycogenolysis (the breakdown of glycogen to glucose) and gluconeogenesis (the production of glucose from non-carbohydrate sources). While it does raise blood glucose, it is not the primary regulator under normal conditions.
- C. Thyroxine:
- Thyroxine (T4) is a hormone produced by the thyroid gland that regulates metabolism, including the rate at which the body uses energy. While it can influence glucose metabolism, it does not directly regulate blood glucose levels like insulin does.
-
D. Cortisol:
- Cortisol is a steroid hormone produced by the adrenal cortex, often released in response to stress. It increases blood glucose levels by promoting gluconeogenesis and inhibiting glucose uptake in non-essential tissues. However, it is not the primary hormone for regulating blood glucose under normal physiological conditions.
-
Common Pitfalls:
- Students may confuse the roles of different hormones, especially under stress conditions where adrenaline and cortisol are involved. It’s important to remember that while these hormones can influence blood glucose levels, insulin is the primary hormone for maintaining glucose homeostasis in a non-stressful state.
Revision Summary:
- Insulin is the primary hormone secreted by the pancreas that regulates blood glucose levels.
- It facilitates glucose uptake into cells and promotes glycogen storage in the liver.
- Other hormones like adrenaline, thyroxine, and cortisol can influence blood glucose but are not the main regulators.
- Understanding the specific roles of these hormones is crucial for grasping how the body maintains energy balance.