Topic overview

Start with the big picture

The lesson begins with Claude Bernard’s concept of the milieu intérieur and the distinction between plasma, interstitial fluid, and intracellular fluid. It relates the different ionic compositions of ECF and ICF to membrane potentials, then introduces homeostasis as dynamic regulation rather than a fixed state. You will encounter key regulated variables and the parts of a control system, including sensors, pathways, integrators, and effectors. The topic also compares negative feedback, positive feedback, and feed-forward control, and explains how gain describes control effectiveness. Further sections connect capillary and membrane transport, lymphatic return, and buffer systems to the maintenance of fluid balance and ECF pH.