Trace feedback direction and each substance’s gradient
Physiology questions often describe a system rather than ask for an isolated word. Homeostasis involves regulation around a reference range. In a negative-feedback model, a change triggers a response that counteracts the deviation. A sensor detects a value, a control centre compares information with the reference, and an effector produces a response. “Negative” describes that relationship; it does not mean harmful, absent or numerically less than zero. For an original nonclinical model, let a regulated value rise above its reference range. A sensor reports the rise, a controller increases removal, and the value falls back toward the range. The last relationship is compensatory. If the response instead amplified the initial rise, that direction would not fit this negative-feedback description. This abstract model helps read human physiology explanations; it does not diagnose a person or specify a treatment, target measurement or care procedure. Membrane movement requires a different kind of directional reasoning. For a permeant substance undergoing passive diffusion, initial net movement follows its own concentration gradient from higher to lower concentration. Suppose substance P is 6 units on side A and 2 on side B, while substance Q is 1 on A and 4 on B. With permeability to both and passive diffusion only, net P movement is A→B and net Q movement is B→A. Adding the concentrations of different substances would lose the two separate gradients. Equilibrium does not mean that individual molecules stop moving. It means no net directional transfer for the substance at equilibrium under the specified conditions. Selective permeability also matters: a concentration difference alone does not establish movement through a barrier that does not permit that substance to cross. This unit supports selected cellular and regulatory foundations. It leaves major anatomy, organ-system, genetics and molecular-biology content for further study rather than presenting these models as full TEAS Science coverage.
In a nonclinical model of temperature regulation, a rise above a reference range is sensed. A controller then increases heat loss, and the model’s temperature moves back toward that range. Which relationship makes the loop negative feedback?
- Negative feedback is defined by reversal of a deviation. Here the response moves temperature downward after an upward deviation. Detection, temporal order and a positive numerical amount of heat loss do not by themselves identify feedback type. This is conceptual physiology, not a care instruction.
Compare the other answer choices
That sequence identifies signal flow but does not distinguish negative from positive feedback.
The word negative refers to the relationship to the deviation, not a negative numerical response value.
Events occur over time in many mechanisms; temporal order alone does not identify negative feedback.
Try it, then explain it.
Complete a short set without looking at the example. After each answer, explain which evidence or rule supports your decision and why the alternatives do not fit.
Sources & authorship
Original Slope explanations and examples. References support the concepts; they are not the source of copied questions. Independent educator review is pending.
OpenStax Anatomy and Physiology 2 e §1.5 HomeostasisOpenStax Biology 2 e §5.2 Passive Transport