The shivering response in animals and man.

The physiological response to body cooling may be regarded as a homeostatic response embracing the concept of negative feedback. The metabolic response to falling body temperature is normally both appropriate and adequate. However, there are reports of inadequate or absent responses to body cooling and of non-febrile animals shivering at elevated body temperature. The reasons for these paradoxical findings are not fully understood, particularly since the controller of body temperature receives the largest proportion of its thermal afferent information from temperature sensors located within the body core. During anaesthesia and certain phases of sleep the shivering response to hypothermia may be impaired. It also appears that other factors such as the rate of cooling and disturbances of the circadian machinery (altered light conditions, phase shifting of activity patterns) may be of importance. These factors are relevant for people working in the arctic, especially since many of them are shift workers.