ABSTRACT
The thermoregulatory system is a controlled system requiring sensors, a controller, and effectors. Sensation of temperature occurs in the skin, deep body tissues, and within the central nervous system (CNS) through specialized thermoreceptive fibers and neurons. Information about body temperature is integrated and compared to a reference temperature. This function is distributed in a number of CNS sites but is most highly concentrated in the hypothalamus. The hypothalamus utilizes endocrine, behavioral, and autonomic outputs to alter heat flow to the environment and to alter heat production. These functions are mediated by sympathetic fibers to a number of end organs, including vascular smooth muscle, sweat glands, and brown adipose tissue, and by outputs to both respiratory and skeletal muscles. There is a close relationship between the thermoregulatory system and the control of metabolic rate for purposes of body weight regulation. Under environmental extremes or in the case of pathology, hypothermia or hyperthermia may result. These conditions, which represent a breakdown of normal thermoregulatory control, are in contrast to fever, which is a regulated elevation of body temperature in response to cytokines and which is thought to be useful to the individual in fighting disease. An additional possible beneficial effect of altered body temperature is in the case of controlled hypothermia as a treatment for ischemic brain injury.
