The body’s goal of homeostasis – keeping a relatively stable internal environment despite changing external conditions, is vital. The body is not unchanging or static. In fact, to maintain homeostasis, every organ system is constantly working and interacting to balance the body’s optimum chemical, thermal, and neural conditions. The basic mechanism to maintain homeostasis involves receptors that monitor changes to the environment. When there is a stimulus, they send that information to the control center (integrating center) which interprets what the body needs and triggers a response with an effector. The effector elicits a feedback response to the stimulus. The feedback can influence the stimulus by depressing it with negative feedback or enhancing it with positive feedback.
This communication of stimulus and response is mainly between the nervous system and the endocrine system. The nervous system uses electrical impulses and the endocrine system uses hormones released into the blood to get their messages to where they need to go.
Most responses to stimuli for maintaining homeostasis are negative feedback to counter the stimuli and reduce its effect – protect the body from sudden severe changes. This is how the body maintains its temperature, heart rate, blood pressure, blood sugar levels, etc. This is by far the more common way to regulate and maintain homeostasis.
Positive feedback in the body is a way to respond to a stimuli by increasing it. This is much rarer than negative feedback, but is a powerful, rare response (cascade effect) when needed. An important example of this is blood clotting.
After reading about feedback mechanisms and studying the illustrated diagrams, try the Feedback Mechanism - Model Building Investigation.