Two Types of Feedback Mechanisms
Positive Feedback
Response enhances original stimulus until stimulus is shut off "Everyday world examples:" mass panic; student loans and tuition prices; addiction In physiology: Usually controls infrequent events that do not require continuous adjustment Examples in Physiology: Enhancement of labor contractions by oxytocin Platelet plug formation and blood clotting
more examples of negative feedback
A good example of a negative feedback mechanism is a home thermostat (heating system). The thermostat contains the receptor (thermometer) and control center. If the heating system is set at 70 degrees Fahrenheit, the heat (effector) is turned on if the temperature drops below 70 degrees Fahrenheit. After the heater heats the house to 70 degrees Fahrenheit, it shuts off effectively maintaining the ideal temperature. The control of blood sugar (glucose) by insulin is another good example of a negative feedback mechanism. When blood sugar rises, receptors in the body sense a change . In turn, the control center (pancreas) secretes insulin into the blood effectively lowering blood sugar levels. Once blood sugar levels reach homeostasis, the pancreas stops releasing insulin.
Positive Feedback examples more
A positive feedback mechanism is the exact opposite of a negative feedback mechanism. With negative feedback, the output reduces the original effect of the stimulus. In a positive feedback system, the output enhances the original stimulus. A good example of a positive feedback system is child birth. During labor, a hormone called oxytocin is released that intensifies and speeds up contractions. The increase in contractions causes more oxytocin to be released and the cycle goes on until the baby is born. The birth ends the release of oxytocin and ends the positive feedback mechanism. Another good example of a positive feedback mechanism is blood clotting. Once a vessel is damaged, platelets start to cling to the injured site and release chemicals that attract more platelets. The platelets continue to pile up and release chemicals until a clot is formed. Just remember that positive feedback mechanisms enhance the original stimulus and negative feedback mechanisms inhibit it.
Negative feedback
A type of regulation that responds to a change in conditions by initiating responses that will counteract the change. Maintains a steady state. Most common feedback mechanism in body Response reduces or shuts off original stimulus "Everyday world example:" Thermostat and heater Examples in Physiology: Regulation of body temperature (shivering and sweating) High blood sugar lowered by insulin secretion High blood CO2, low O2 increases heart and respiratory rate Thirst mechanism
