Correct Option: B. Insulin
Detailed Explanation:
- Understanding Blood Glucose Regulation:
- Blood glucose levels are crucial for maintaining energy homeostasis in the body. When we consume food, especially carbohydrates, glucose enters the bloodstream, leading to an increase in blood glucose levels.
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The body has a sophisticated system to regulate these levels, primarily involving hormones produced by the pancreas.
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Role of Insulin:
- Insulin is a hormone produced by the beta cells of 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 (e.g., after eating), the pancreas releases insulin into the bloodstream. Insulin binds to insulin receptors on the surface of cells, triggering a series of events that allow glucose to enter the cells.
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Inside the cells, glucose can be used immediately for energy or stored as glycogen (in liver and muscle cells) for later use.
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Mechanism of Action:
- Insulin promotes the translocation of glucose transporter proteins (GLUT4) to the cell membrane, which increases the uptake of glucose from the bloodstream into the cells.
- Additionally, insulin inhibits gluconeogenesis (the production of glucose from non-carbohydrate sources) and glycogenolysis (the breakdown of glycogen into glucose), further helping to lower blood glucose levels.
Why Other Options Are Incorrect:
- A. Glucagon:
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Glucagon is produced by the alpha cells of the pancreas and has the opposite effect of insulin. It raises blood glucose levels by promoting glycogenolysis and gluconeogenesis in the liver. Therefore, glucagon is not responsible for promoting glucose uptake into cells; rather, it works to increase blood glucose when levels are low.
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C. Cortisol:
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Cortisol is a steroid hormone produced by the adrenal glands and is involved in the stress response. It increases blood glucose levels by promoting gluconeogenesis and reducing glucose uptake in non-essential tissues. While it plays a role in glucose metabolism, it does not primarily regulate glucose uptake into cells.
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D. Adrenaline (Epinephrine):
- Adrenaline is also produced by the adrenal glands and is involved in the "fight or flight" response. It increases blood glucose levels by stimulating glycogenolysis and inhibiting insulin secretion. Like cortisol, it does not promote glucose uptake into cells; instead, it prepares the body for immediate energy needs during stress.
Summary of Key Points:
- Insulin is the primary hormone responsible for lowering blood glucose levels by promoting glucose uptake into cells.
- It facilitates the translocation of glucose transporters to the cell membrane, allowing glucose to enter cells for energy or storage.
- Glucagon, cortisol, and adrenaline have opposing effects, primarily increasing blood glucose levels rather than promoting uptake.
- Understanding the roles of these hormones is crucial for grasping how the body maintains glucose homeostasis.