This new weight reflects the newly established equilibrium between input and output. Note also the shape of the weight curve as it changes between the two steady levels. This shape often appears in physiological processes. Where it does, it usually reflects a balance where the pool size helps adjust either the input or output to that pool. You're missing a great java applet demonstrating balance Even though this system tends to reach steady values for its pool size, there really isn't much discrimination about what those values are.
Weight can still vary over a large range of possible values.
For many physiological processes, it is critical that the pool size be kept within very tight limits. Such close regulation requires something more than simple equilibria. They require a system that can adjust it's input and output to maintain a constant level in the pool. Go on the the next page to examine simple feedback systems . Copyright 1998, Joe Patlak, Department of Physiology, University of Vermont.