Question 434 of 782

Which hormone is primarily responsible for regulating blood glucose levels by lowering them after a meal?

  • Glucagon
  • Insulin
  • Adrenaline
  • Thyroxine

Correct Answer: B

Explanation
The correct option is B. Insulin. Detailed Explanation:
  1. Understanding Blood Glucose Regulation:
  2. Blood glucose levels fluctuate throughout the day, especially after meals when we consume carbohydrates. The body needs to maintain these levels within a narrow range to ensure proper functioning of cells and organs.
  3. Role of Insulin:
  4. Insulin is a hormone produced by the beta cells of the pancreas. Its primary function is to lower blood glucose levels after a meal. When you eat, carbohydrates are broken down into glucose, which enters the bloodstream. In response to rising glucose levels, the pancreas releases insulin.
  5. Insulin facilitates the uptake of glucose by cells, particularly muscle and fat cells, allowing them to use glucose for energy or store it as glycogen for later use. This process effectively lowers the amount of glucose in the bloodstream.
  6. Mechanism of Action:
  7. When insulin binds to its receptors on target cells, it triggers a series of cellular responses:
    • Increased Glucose Uptake: Cells increase the number of glucose transporters (GLUT4) on their surface, allowing more glucose to enter.
    • Glycogenesis: Insulin promotes the conversion of glucose to glycogen in the liver and muscle cells for storage.
    • Inhibition of Gluconeogenesis: Insulin suppresses the production of glucose from non-carbohydrate sources in the liver.
  8. Why Other Options Are Incorrect:
  9. A. Glucagon: This hormone is produced by the alpha cells of the pancreas and has the opposite effect of insulin. Glucagon raises blood glucose levels by promoting glycogenolysis (the breakdown of glycogen to glucose) and gluconeogenesis. It is released when blood glucose levels are low, not after a meal.
  10. C. Adrenaline: Also known as epinephrine, this hormone is released during stress or "fight or flight" situations. It increases blood glucose levels by stimulating glycogen breakdown and inhibiting insulin secretion. While it plays a role in glucose regulation, it does not primarily lower blood glucose after meals.
  11. D. Thyroxine: This hormone, produced by the thyroid gland, regulates metabolism and energy expenditure but does not have a direct role in lowering blood glucose levels after meals. It influences overall metabolic rate and can affect how the body uses glucose, but it does not directly lower blood glucose like insulin does.
Summary of Key Points:
  • Insulin is the primary hormone responsible for lowering blood glucose levels after meals.
  • It promotes glucose uptake by cells and storage as glycogen.
  • Glucagon raises blood glucose levels, while adrenaline and thyroxine have different roles in metabolism and stress response.
  • Understanding the functions of these hormones is crucial for grasping how the body maintains glucose homeostasis.
Revision Summary:
  • Insulin lowers blood glucose levels after meals by facilitating glucose uptake and storage.
  • Glucagon raises blood glucose levels when they are low.
  • Adrenaline and thyroxine have different metabolic roles and do not primarily regulate post-meal glucose levels.
  • The balance between insulin and glucagon is essential for maintaining stable blood glucose levels.
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