Which is an example of a positive feedback loop in physiology?

• A. Sweating to cool the body.
• B. Insulin release after a high blood glucose.
• C. Oxytocin release during labor.
• D. Regulation of blood pressure by vasoconstriction.

Answer: (C)

Positive feedback loops amplify a change rather than dampen it, driving a process to a completion. In labor, oxytocin makes uterus contractions stronger; those contractions stretch the cervix even more, which releases more oxytocin and strengthens the contractions again. This self-reinforcing cycle continues until the baby is born, which ends the stimulus. The other examples illustrate negative feedback, where the response counteracts the change to bring things back toward normal: cooling the body through sweating, insulin reducing high blood glucose, and vasoconstriction regulating blood pressure to oppose deviations.