This course gives students the skills to interpret or predict the behavior of physiologic systems in order to study normal and pathologic phenomena. The body uses many feedback control mechanisms to maintain homeostasis, the keeping of a constant interior environment (eg. pH, temperature, blood pressure, balance, bone stress, muscle length). Transfer functions characterize organ physiology. These functions are the building blocks of an organ system model. By studying these models, complex behavior can often be easily interpreted. Further, these models often suggest ways to make noninvasive physiologic measurements. Applications include: vicious cycles, such as hyperventilation syndrome, and how to break them; hierarchical, parallel, and other redundant systems; causes of instabilities such as Cheyne-Stokes breathing; open and closed loop control of anesthesia and artificial organs. Reference will be made to several common mechanisms such as the thermostat. Lecture demonstrations include pulmonary and cardiovascular measurement. A term paper on a topic of the student's choice is required.