SME
Principles of Biology II · Problem type
Negative and positive feedback loops
Use this for “After a meal, blood glucose rises. Trace the loop that brings it back, and say whether it is negative or positive feedback.”
Explore
Core temperature climbs past about 37 °C during a long run.
Heat is shed until the core cools, and then the effectors ease off: negative feedback.
Assumptions
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A loop runs stimulus, sensor, control center, effector, response; the set point is the value it holds.
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Negative feedback opposes the change, so the variable returns toward its set point and the loop quiets.
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Positive feedback amplifies the change until an outside event, such as birth or a sealed wound, ends it.
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