For any particular homeostatic response an animal may be a conformer or a regulator . Often survival is determined by the cellular tolerance to these changes. Regulators use physiologic mechanism to regulate their internal environment to the external changes. However, regulators have a limit in their regulatory ability and this zone of stability may be broad or narrow, depending on the organism. This requires a sensory system to gather the necessary information and relay it back to a controller.
Feedback can be either negative or positive .
A negative feedback system requires an inverter that reverses the sensory detection to up or down regulate . In other words if the sensory system detects a fall in temperature then the body heating system is up regulated, while a rise in body temperature past the set point would turn-off the heating mechanism. In contrast positive feedback does not invert the sensory signal but stimulate further fluctuation in the control system. Positive feedback would obviously lead to a very explosive and unstable response , unless the output was in some way limited at the high end. The transmission of a nerve impulse is an example of positive feedback.