Question

regulating blood glucose levels
what best describes the information shown in the diagram?
a. a positive feedback loop maintains homeostasis by returning blood glucose levels to normal.
b. a positive feedback loop maintains homeostasis by further decreasing blood glucose levels.
c. a negative feedback loop maintains homeostasis by further decreasing blood glucose levels.
d. a negative feedback loop maintains homeostasis by returning blood glucose levels to normal.

Explanation:

1. First, recall feedback loop types: Negative feedback counteracts changes to restore homeostasis; positive feedback amplifies changes.
2. The diagram shows blood glucose increase → pancreas releases glucagon → liver releases glucose (wait, no—wait, when glucose is low? Wait, no, the diagram: blood glucose level decreases → pancreas releases glucagon? Wait, no, the arrows: blood vessel (glucose) → when blood glucose level decreases, pancreas releases glucagon, which makes liver convert glycogen to glucose, releasing into blood, increasing glucose. Wait, no, the labels: "Blood glucose level increases" → then "Blood glucose level decreases" → pancreas releases glucagon? Wait, maybe I misread. Wait, the cycle: blood glucose level increases → then (after some steps) decreases. Wait, the key: negative feedback aims to return to set point (normal). Positive amplifies.
3. Analyze options:

• A: Positive feedback restoring? No, positive amplifies, so A wrong.
• B: Positive feedback further decreasing? No, positive doesn't do that.
• C: Negative feedback further decreasing? No, negative restores, not further decrease.
• D: Negative feedback loop maintains homeostasis by returning blood glucose levels to normal. Correct, because negative feedback counteracts the change (high glucose → mechanisms to lower it back to normal, or low → raise back; here the diagram shows the loop that brings glucose back to normal, which is negative feedback (opposing the initial change to restore balance).

Answer:

D. A negative feedback loop maintains homeostasis by returning blood glucose levels to normal.