Keywords Feedback loop

Positive feedback loop

Negative feedback loop

Homeostasis

Dynamic equilibrium

Set point

Stimulus

Receptor

Modulator

Effector

Feedback loops A feedback system or feedback loop is a situation

where the response to a stimulus modifies the stimulus

Feedback loops maintain homeostasis

Example:

Stimulus = high body temperature

Response = sweating

Result = lower body temperature (stimulus has been modified)

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Positive Feedback

When positive feedback occurs, the response to a stimulus reinforces and intensifies the stimulus

Example: childbirth

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Negative Feedback The response has the effect of reducing the stimulus

that caused it

This is called negative feedback

Many of the body’s homeostatic mechanisms fluctuate and are in dynamic equilibrium

The point around which conditions fluctuate is called the set point

Example:

glucose levels in the blood: set point = 90mg/100ml6

Feedback systemsNegative feedback systems consist of:

The stimulus is the change in the environment

The receptor detects the change

The modulator is a control centre responsible for processing information

The effector carries out a response counteracting the effect of the stimulus (or change in the environment)

Feedback loopsNegative feedback loop – adrenal glands

http://bcs.whfreeman.com/thelifewire/content/chp42/4202b.swf