In mammals, daily rhythms in physiology and behavior are under control of a circadian pacemaker situated in the suprachiasmatic nucleus (SCN). This master clock receives photic input from the retina and coordinates peripheral oscillators present in other tissues, maintaining all rhythms in the body synchronized to the environmental light–dark cycle. In line with its function as a master clock, the SCN appears to be well protected against unpredictable stressful stimuli. However, available data indicate that stress and stress hormones at certain times of day are capable of shifting peripheral oscillators in, e.g., liver, kidney and heart, which are normally under control of the SCN. Such shifts of peripheral oscillators may represent a temporary change in circadian organization that facilitates adaptation to repeated stress. Alternatively, these shifts of internal rhythms may represent an imbalance between precisely orchestrated physiological and behavioral processes that may have severe consequences for health and well-being.

在哺乳动物中，生理和行为的日常节律由位于视交叉上核 (SCN) 中的昼夜节律起搏器控制。这个主时钟接收来自视网膜的光输入并协调存在于其他组织中的外围振荡器，保持身体中的所有节律与环境光暗循环同步。与其作为主时钟的功能一致，SCN 似乎可以很好地防止不可预测的压力刺激。然而，现有数据表明，一天中某些时间的压力和压力荷尔蒙能够改变外周振荡器，例如肝脏、肾脏和心脏，这些通常受 SCN 控制。外围振荡器的这种变化可能代表昼夜节律组织的暂时变化，有助于适应反复的压力。或者，