IMAT 2014 Q28 [Blood Glucose]

Which one of the following names the structure, in humans, that directly detects a change in blood glucose level and then the structure that responds to the change?

A. Pituitary gland and liver
B. Pancreas and pancreas
C. Hypothalamus and pituitary gland
D. Adrenal gland and pancreas
E. Liver and adrenal gland

The answer to this question is B.

The main concept for this question is blood glucose homeostasis, thus you must be aware of the organ that mainly contributes to the balance of blood glucose concentration. We can then take this systematically to eliminate the choices that are evidently incorrect. Firstly, recall that the maintenance of this aspect of homeostasis is governed by 2 main hormones, insulin and glucagon. This should prompt you to think of the pancreas, which is tasked with secreting this hormones. Thus you can eliminate the choices that do not include pancreas, leaving you with choices B and D.

Let us then analyze the question to arrive at the correct choice:

  • There are 2 parts of what the question is asking from you, first is, the structure that detects the change, and second, the structure that responds to the change.
  • As mentioned at the start of this answer, that the pancreas is the structure that responds to the change given its ability to secrete insulin and glucagon in the blood stream.
  • You will now have to discern which among pancreas (choice B) or the adrenal gland (choice D) is the structure responsible for detecting the change in blood glucose.
  • To answer, it is the beta cells of the pancreas that can be found in the islets of Langerhans, that has the ability to detect the changes in blood concentration. To summarize how beta cells are able to do this, they basically monitor the catabolic products of glucose when it enters the beta cells. Glucose enters the beta cell and undergoes mitochondrial metabolism. Beta cells “sense” the products of this catabolism, ATP to be more specific, because ATP is needed ultimately to induce the exocytosis of insulin out of beta cells. Thus overall, the beta cells will vary the rate of insulin synthesis and secretion based on the blood glucose levels.

Thus, the answer to this question is choice B, the pancreas monitors and controls blood glucose levels.