Effects Of Different Light Schedules On The Circadian Rhythm Of Endothelial Vasoactive Substances

Objective: Biological rhythms are universal phenomena in living organisms and enable them adapt to the environment much better. In human beings, the physiological function of almost every system, such as biochemistry phenomenon, physiological activity and individual psychological behavior, has some degree of cyclical fluctuation. Biological rhythms can be divided into 3 types on the basis of their cycle lengths: 1) circadian (or diurnal) rhythms with a period of approximately 24 hours; 2) ultradian rhythms, with a period significantly shorter than 24 hours (hours, minutes, or even seconds); and 3) infradian rhythms, with a period longer than 24 hours (days, months, or longer). Biologic rhythm is endogenous and hereditability, and meanwhile, it is conformed and adjusted by environment signals. Light signal is the main zeitgeber to induce and control biologic rhythms. Circadian rhythms of mammals are timed by an endogenous clock with a period of about 24 hours located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Light synchronizes this clock to the external environment by daily adjustments in the phase of the circadian oscillation. Recently, signaling pathways activated by light in the SCN have begun to be identified. Circadian rhythms, which...