The goal of the negative feedback pathway: Maintain a constant level of water in the funnel. Try to maintain the level at exactly the line on the funnel. We are simulating what might be happening to glucose levels in the muscle during exercise. Glucose is being used (modeled by the water flowing out of the funnel) and is being replaces by increased glucose production and delivery by the liver and other tissues (this is modeled by the responder dumping measured amounts of water back into the funnel).

The detector: Watches the level of water and report it to the afferent pathway. Uses terms such as "below", "slightly below", "very much above". Reports only the water level in the funnel - does not make suggestions about what the response should be.

The afferent pathway: Takes the report from the detector to the integrator. Returns to the detector for the next report.

The integrator: Listens to the report from the afferent path. Makes a decision about what the response should be. Tells the efferent path. The timing of the response can be varied - the efferent path will only be activated when the integrator instructs. Also, the amount of the response can be varied. 15 ml or 50 ml of fluid can be added to the funnel.

The efferent pathway: Takes the decision from the integrator to the effector (responder).

The effector (responder): Performs exactly the instructions received from the efferent pathway.