Body temperature cycles
نویسندگان
چکیده
Body temperature in mammals is homeostatically regulated around a set point, which renders it independent of large variations in environmental temperature. Hypothalamic regions, including the preoptic area, act as thermoregulatory centers that receive temperature inputs from the core body through hypothalamic receptors and from the environment through skin receptors. Thermogenic and heatdissipative processes in tissues, such as muscles, brown adipose tissue, skin and vascular tissue, are regulated to counterbalance temperature deviations in order to maintain a relatively constant body temperature. While the thermoregulatory system aims to maintain the body temperature at a fixed target value, this set point itself fluctuates throughout the course of a day, resulting in circadian variations of body temperature. In humans, the maximal body temperature is reached in the late afternoon and drops to the nadir value at the end of the sleep phase. The circadian component in body temperature is under the control of the suprachiasmatic nuclei (SCN), which project to the preoptic area. The SCN is continuously entrained by light signals from the retinohypothalamic tract and, in turn, synchronizes circadian body temperature cycles to environmental light-dark cycles. In addition to body temperature cycles, the SCN governs a plethora of neuronal and humoral signals with daily oscillations, and these rhythmic SCN outputs control diverse physiological functions, either directly or indirectly through the synchronization of circadian oscillators in peripheral tissues. Peripheral clocks, which are operative in Body temperature cycles Gatekeepers of circadian clocks
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عنوان ژورنال:
دوره 12 شماره
صفحات -
تاریخ انتشار 2013