Feedback is a process or control mechanism where the level of a product feeds back to control the rate of its own production.

Small flucuations above and below the optimal levels do not cause a response.

When the level rises significantly above the normal level, it is reduce by negative feedback (Note the portion of the curve above the "dashed" optimal environment in the graph above!).

When the level falls significantly below the normal level, it is increased through negative feedback (Note the portion of the curve below the "dashed" optimal environment in the graph above!).

Negative Feedback is a control mechanism which has a stabilizing effect upon a system because a change in levels always causes the opposite change.

Simple examples of negative feedback include:

A rise in levels feeds back to decrease production and reduce the level. Example: The carbon dioxide level increases in the blood (as a result of holding the breath or exercise). The body responds by directing the diaphragm and lungs to increase the rate of ventilation, which moves carbon dioxide from the blood and out into the air. As blood carbon dioxide levels return to normal, the rate of ventilation decreases.

A decrease in level feeds back to stimulate an increase in production to raise the level. Example: The carbon dioxide level in the blood has decreased far below normal (due to hyperventilation). The diaphragm and lungs are directed to slow the ventilation rate, so that carbon dioxide againbuilds up in the blood and returns to the normal condition.

[Negative Feedback & Control of Body Temperature] ----- [Negative Feedback & Control of Blood Glucose Level]