In the context of homeostasis, what best describes negative feedback?

• A. A mechanism in which a change in a physiological variable triggers responses that counteract the change and return the variable toward its set point
• B. A mechanism that maintains internal conditions only by anticipating future changes rather than responding to deviations
• C. A mechanism in which a change in a physiological variable triggers responses that amplify the change, pushing the variable farther from its set point
• D. A mechanism in which the effector initiates the stimulus without involvement of a receptor or control center

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the concept of homeostasis, which is the process by which biological systems maintain stable internal conditions despite external changes.
2. Step 2: Recognize that negative feedback is a regulatory mechanism where a change in a physiological variable triggers a response that counteracts or reverses that change.
3. Step 3: Identify the key components of negative feedback: a receptor that detects the change, a control center that processes the information, and an effector that produces a response to restore the variable to its set point.
4. Step 4: Contrast negative feedback with positive feedback, where the response amplifies the change rather than reversing it, and with feedforward mechanisms that anticipate changes without responding to deviations.
5. Step 5: Conclude that negative feedback best describes a mechanism where responses counteract changes to maintain stability, which matches the description: 'A mechanism in which a change in a physiological variable triggers responses that counteract the change and return the variable toward its set point.'