Overview of circadian rhythms

The daily light-dark cycle governs rhythmic changes in the behavior and/or physiology of most species. Studies have found that these changes are gover ned by a biological clock, which in mammals is located in two brain areas c alled the suprachiasmatic nuclei. The circadian cycles established by this clock occur throughout nature and have a period of approximately 24 hours. In addition, these circadian cycles can be synchronized to external time si gnals but also can persist in the absence of such signals. Studies have fou nd that the internal clock consists of an array of genes and the protein pr oducts they encode, which regulate various physiological processes througho ut the body. Disruptions of the biological rhythms can impair the health an d well-being of the organism.