Question

which of the following describes a negative feedback loop?

• when the heart rate is too high, the body sends hormones that continually increase the heart rate higher.
• when a pregnant woman is in labor, the body sends hormones that increase the intensity of contractions, which then increases the secretion of the same hormones.
• when blood sugar is too low, the body sends hormones that raise blood sugar until it reaches a typical level and hormone secretion slows.
• when a person is jogging, the body sends hormones that continually decrease the rate of oxygen supply to the legs.

Explanation:

To determine the negative feedback loop, we recall that negative feedback counteracts a change to return to a set point.

• Option 1: Increases heart rate further (positive feedback, amplifies change).
• Option 2: Labor contractions increasing hormone secretion (positive feedback, amplifies labor).
• Option 3: Blood sugar too low → hormones raise it to normal, then secretion slows (counteracts low blood sugar, returns to set point: negative feedback).
• Option 4: Hormones continually decrease oxygen supply (not a feedback to stabilize, and description is inconsistent with negative feedback).

So the correct option is the one about blood sugar regulation.

Answer:

When blood sugar is too low, the body sends hormones that raise blood sugar until it reaches a typical level and hormone secretion slows.