What is a negative feedback loop in homeostasis?

• A. A stimulus triggers responses that amplify the deviation.
• B. A stimulus triggers responses that reverse the deviation, returning toward setpoint.
• C. The deviation is ignored by the system.
• D. Negative feedback always increases the deviation.

Answer: (B)

Negative feedback in homeostasis works by sensing a deviation from the body’s setpoint and triggering responses that oppose that change, bringing the system back toward the desired level. For example, if body temperature rises, cooling mechanisms like sweating and vasodilation kick in to lower it back to normal. If glucose rises after a meal, insulin is released to promote uptake of glucose and restore normal blood sugar. This opposition to the change is what keeps internal conditions stable.

The correct idea is that the stimulus triggers responses that reverse the deviation toward the setpoint. In contrast, positive feedback would amplify the deviation, which isn’t how most homeostatic controls operate (and some options describe ignoring the deviation, or always increasing it, which doesn’t maintain stability).