Negative feedback is?

• A. A mechanism that reduces a stimulus after a response
• B. A mechanism of response in which a stimulus initiates reactions that reduce the stimulus
• C. A process that initiates growth
• D. A system that maintains constant temperature without feedback

Answer: (B)

Negative feedback is a control process that keeps conditions stable by opposing a deviation from a set point. When a variable changes, sensors detect it and trigger effects that reverse that change, bringing the variable back toward the normal range. This creates a loop where the initial stimulus is opposed by the response, reducing the stimulus as the response happens. For example, when body temperature rises, sweating and increased blood flow to the skin help cool the body; when blood glucose rises after a meal, insulin is released to lower glucose levels. The mechanism described in the option that states a stimulus initiates reactions that reduce the stimulus best fits this idea. The other ideas either describe growth rather than regulation, or claim there is no feedback while maintaining a constant temperature.