How negative and positive feedback loops keep the body's internal variables inside a set point, the way HESI A2 Biology tests it with blood glucose and other clinical examples.
ObjectiveB.1.3Read4 minExam weightFoundations of Biology ≈ 24% of Biology
This lesson is part of the full Study Guide
Unlock every lesson, unit, and quiz across every subject. The Biology foundations of biology unit is included.
Define homeostasis and name the four parts of a negative feedback loop.
Explain why almost every regulated variable in the body uses negative, not positive, feedback.
Give at least two clinical examples each of negative and positive feedback.
What the lesson concludes
Homeostasis is the body's tendency to hold internal variables inside a narrow set point range, not to keep them perfectly fixed.
A negative feedback loop runs stimulus, sensor, control centre, effector, and the effector's response opposes the original stimulus.
Blood glucose regulation by insulin and glucagon is the textbook negative feedback example and the one HESI reaches for most often.
Positive feedback pushes a variable further from its set point and is rare, used only where an event needs to finish quickly, such as childbirth contractions or blood clotting.
Confusing negative feedback with something bad, or positive feedback with something good, is the single most common wrong answer on this objective.