Abstract

The temporal organization of physiological functions such as sleep/wakefulness or body temperature are regulated by the circadian clock. This intrinsic clock starts ticking in the embryo, matures during development, and is attenuated in the elderly. This is illustrated by weakening synchrony, entrainment, and outputs of cellular circadian rhythms in the central circadian clock, located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The age-related diminution can contribute to susceptibility to diseases, such as sleep disorders, infertility, diabetes, and mental disorders. Over the course of our lives, a variety of internal and external factors come into play, under the influence of the circadian clock. The inherent developmental plasticity of the circadian system, the focus of the present issue, is critical for the establishment of normal bodily functions and their adaptation to the changing environment on earth.