Positive and Negative Feedback Loops

A. Negative Feedback

CO2O2

• 1. Control System that counteracts any change in the body that moves conditions above or below a set point.

• 2. Keeps internal environment stable. (Homeostasis!!)• 3. Shuts off original stimulus or reduces intensity.

Negative Feedback

Equilibrium

Starting Situation

Starting Situation

Example of Negative Feedback

Example of Negative Feedback

Sympathetic Nervous System

Parasympathetic Nervous System

Fight Or Flight Response Calming return to Equilibrium

B. Positive Feedback

• 1.Control system that uses information from sensors to increase the rate of change away from set points.

• 2.Not common, only used when rapid change is needed.

• 3.Turns on Stimulus.

Positive Feedback

Explosion

Blocking

No Equilibrium

Example of Positive Feedback

MicrophoneAmplifier

Explosion

Example of Positive Feedback

Pancreas Releases Insulin

to Lower Blood Sugar

Liver Releases Glucagon

to Raise Blood Sugar

Positive Feedback

NegativeFeedback