Questions: Homeostasis and Feedback Loops

Question 1

In a homeostatic feedback loop, which component detects deviations from the set point and sends a signal to the control center?

• A. Effector
• B. Control center
• C. Sensor (receptor)
• D. Hormone

Answer: (C)

The sensor (or receptor) monitors the regulated variable and detects when it deviates from the set point. In body temperature regulation, thermoreceptors in the skin and hypothalamus are the sensors. The control center (hypothalamus) processes the signal, and effectors (sweat glands, skeletal muscles) execute the response. Confusing the control center with the sensor is a common error — the control center decides what to do, but it relies on the sensor to know what is happening.

Question 2

Positive feedback loops are generally pathological and represent a breakdown of normal homeostasis.

• T. True
• F. False

Answer: False

Positive feedback loops are normal physiological mechanisms used whenever a self-amplifying response toward a threshold event is needed. Uterine contractions during childbirth, blood clotting cascade, and the LH surge triggering ovulation all use positive feedback. They are purposeful mechanisms that drive a process to completion; the key difference from negative feedback is that they are self-terminating once the triggering event is resolved.

Question 3

Explain why homeostasis does not mean the internal environment is perfectly constant.

Model answer: Homeostasis maintains physiological variables within a functional range around a set point, not at a single fixed value. The variable continuously oscillates as the feedback system responds to deviations, and the set point itself can shift with physiological state (e.g., body temperature set point rises during fever). The system is better described as dynamic equilibrium than perfect constancy.

A thermostat analogy is useful: even a thermostat set to 68°F allows room temperature to drop to 66°F before the furnace activates, then overshoots slightly to 70°F. Biological systems work similarly — there is always lag time in sensor detection and effector response, so the regulated variable oscillates around the set point rather than being held at an exact value.