How it works
Each chart is a loop of boxes that says what happens at every step. The role of the step is blank: name it. The first loop is negative feedback, the second positive.
Read the full guide
Read the box, then name its role
Start at the top left box and follow the arrows. The step that changes first is the stimulus. The sensor detects it, the control center decides what to do, and the effector does it. On the first loop the result, the response, undoes the change. On the second the result makes the change bigger. The tag on the returning arrow asks which kind of feedback that is.
- Ask what the last step does to the first. Undoes it: negative feedback. Adds to it: positive feedback.
- A sensor is also called a receptor; both are accepted when you type.
Questions and answers
What are the three components of a feedback loop?
A sensor, a control center and an effector. The sensor monitors a value and reports it. The control center compares it with the normal range. The effector makes the change the control center orders.
What is the difference between negative and positive feedback?
Negative feedback reverses a change, bringing a value back toward its set point; most body systems work this way. Positive feedback intensifies a change, so the value moves farther from where it started until an end point stops it.
What is an example of positive feedback in the body?
Childbirth. Contractions push the baby against the cervix, nerve cells there signal the brain, oxytocin is released, and the contractions grow stronger. The cycle ends when the baby is born. Blood clotting is another example.
What is a set point?
The value that a normal range centers on. For human body temperature it is about 37 °C (98.6 °F). A feedback loop starts when a stimulus pushes the value too far from it.