Control aspects of human temperature regulation

Abstract

Human body temperature control is characterized by a local dependence of system variables and parameters: receptors are thought to be distributed locally throughout the body. The integrative control centres appear to extend quasicontinuously from the spinal cord up to the hypothalamus. Finally, control actions obviously affect the passive system with distinct local dependence. The essential properties of non-linear distributed parameter control of human body temperature are demonstrated by way of experimental and mathematical results. With regard to the control strategy there are evidently five different concepts which claim to answer the question: ‘What is regulated and how?’ A control concept based on spatial integration of temperatures plus local effector actuation seems to be the one which is most adequately supported by system-theoretical as well as by experimental results. The discussion about ‘reference’ and ‘set-point’ of temperature regulation is still going on, and concentrates on four concepts. The concept of balance of passive and active processes, i.e. of controlling and of controlled subsystems, defines the steady-state as the only compatible operating point of the open loop functions in the closed control loop. It does not need an explicit neuronal reference input or difference of controller inputs and solves simultaneously the so-called problem of changing set-point due to fever or to circadian rhythm. This is explained as an adjustment of control parameters requiring another balance of controller and passive system.