Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Wertheim cung cấp cho các bạn kiến thức về ngành y đề tài: Circadian light. | Rea et al. Journal of Circadian Rhythms 2010 8 2 http content 8 1 2 REVIEW JOURNAL OF CIRCADIAN RHYTHMS Open Access Circadian light Mark S Rea Mariana G Figueiro Andrew Bierman John D Bullough Abstract The present paper reflects a work in progress toward a definition of circadian light one that should be informed by the thoughtful century-old evolution of our present definition of light as a stimulus for the human visual system. This work in progress is based upon the functional relationship between optical radiation and its effects on nocturnal melatonin suppression in large part because the basic data are available in the literature. Discussed here are the fundamental differences between responses by the visual and circadian systems to optical radiation. Brief reviews of photometry colorimetry and brightness perception are presented as a foundation for the discussion of circadian light. Finally circadian light CLA and circadian stimulus CS calculation procedures based on a published mathematical model of human circadian phototransduction are presented with an example. Introduction The suprachiasmatic nuclei SCN in the hypothalamus host the master circadian clock that organizes and orchestrates the timing of all daily biological functions from complicated physiological systems to single cells. The SCN in humans have on average an intrinsic period slightly greater than 24 hours 1 that is modulated by the temporal pattern of light and dark on the retina. As a result of the earth s rotation on its axis the temporal pattern of light and dark on the retina synchronizes the SCN to a matching 24-h period. Recent research has demonstrated that disruption of the natural 24-h pattern of light and dark from rapid flight across time zones or from rotating shift work can lead to a wide variety of maladies from poor performance to sleep loss weight gain and even breast cancer 2-9 . Because it is increasingly evident that retinal light and dark .
