内分泌的周期规律生物界的若干活动和现象是周期规律性的;植物和动物,单细胞动物和高等动物包括人类在内,莫不表现有各种各样周期性生理活动。候鸟年度季节性定向长途飞行,某些脊椎动物冬眠,人类夜间睡眠和月经周期,以及24小时的体温变化等是人所共知的例子。许多激素的分泌释放也是周期性的,或者在24小时内的一个特定时间(昼夜规律)或者生殖周期,在 Endocrine cycle laws Several activities and phenomena in the biological world are cyclical; plants and animals, unicellular animals, and higher animals, including humans, show a variety of cyclical physiological activities. Migratory birds seasonal seasonal long-haul flights, some vertebrate hibernation, human sleep and the nighttime menstrual cycle, as well as 24-hour temperature changes are well-known examples. The secretion of many hormones is also cyclical, or at a specific time within 24 hours (circadian rhythm) or the reproductive cycle, at