why is the figure considered to be an example of a negative feedback system, as opposed to a positive feedback system?
The figure is considered a negative feedback system because the response acts to oppose or reduce the original change, driving the system back toward its starting (set‑point) condition, instead of amplifying the change as a positive feedback system would.
Core idea in simple terms
- In a negative feedback loop, when something in the system goes up , the response tends to make it go down again (or vice versa).
- In a positive feedback loop, when something goes up , the response makes it go up even more , pushing the system further in the same direction.
So if, in your figure:
- A change (e.g., increase in temperature, hormone level, blood glucose, etc.) triggers a response that reverses that change (cooling down, lowering hormone, reducing glucose),
- And once the variable returns closer to normal, the response slows or stops ,
then it’s a negative feedback system, because the loop reduces the initial imbalance instead of reinforcing it.
How to check this in your specific figure
Look at the arrows and labels in the diagram:
- Identify the “variable” (the thing that changes first: temperature, concentration, output, etc.).
- See what the system does in response (the effector’s action, like sweating, insulin release, valve closing, decreased output).
- Ask: does that response move the variable back toward normal (negative feedback) or further away from normal (positive feedback)?
If the response moves it back toward normal and reduces the initial disturbance, that’s exactly why the figure is an example of a negative feedback system rather than a positive one.
Typical example: If body temperature rises, the body activates cooling mechanisms (sweating, vasodilation) that lower temperature back toward the set point — a classic negative feedback loop.