This document introduces a set of ideas from systems theory (stocks, flows, dynamic equilibrium, control, and feedback).

The first section defines terms, using the stocks-and-flows framework and the feedback-loop framework. These frameworks are applied to the example of maintaining the level of water in a basin.

The second section applies the same ideas and frameworks to maintaining indoor air temperature, first with heating and then with heating and cooling, establishing a “comfort range”, which is maintained. A new framework, time-within-range, is introduced.

The third section uses the ideas and frameworks described earlier to understand diabetes.

The fourth section describes the complex ecology in which insulin management systems operate.

For a copy of the document, please send me an email.