Question

When blood glucose concentration rises above 80-110 mg/dL, beta cells of the pancreas sense the increase and secrete the hormone insulin. Insulin travels in the blood to all cells of the body and causes the cells to move glucose from the blood into the cells. Which of the following statements is true of this homeostatic mechanism?

Options:
A. The cells of the body are the integration center in this feedback loop.
B. This is an example of a positive feedback loop.
C. Insulin concentration in the blood is the regulated variable.
D. The set point is 80-110 mg/dL.

Answer 1

The set point for blood glucose concentration is 80-110 mg/dL, and insulin release by beta cells is part of a negative feedback loop to maintain this set point by lowering high glucose levels.

Step-by-step explanation:

When blood glucose levels rise, the beta cells of the pancreas release insulin to prompt cells to absorb glucose, thereby reducing blood sugar levels. Insulin thus maintains homeostasis by lowering glucose when it is above the normal range of 80-110 mg/dL. The correct answer to the question is D. The set point for blood glucose concentration is 80-110 mg/dL.

Insulin secretion by the beta cells acts as part of a negative feedback loop, where high blood glucose levels trigger insulin release to lower glucose levels, after which insulin secretion diminishes. In contrast, a positive feedback loop would involve an output that enhances or accelerates the initial stimulus, which is not the case with insulin-mediated glucose regulation.

Insulin concentration is a response, not the variable being regulated. The cells of the body are not the integration center; they are the targets of insulin's action. The integration center, which involves the pancreas sensing glucose levels and releasing insulin, orchestrates the process of maintaining glucose levels within a narrow range.