ABSTRACT
Chronobiology is the science of biological rhythms. Circadian rhythms refer to cyclical fluctuations that recur regularly each solar day. The term is based on the Latin words circa (about) and dies (a day), reflecting that the endogenous rhythm (determined in constant conditions in an isolation unit) exceeds 24 h but is fine-tuned to a 24-h period by exogenous factors. These include light, temperature, habitual activity and social influences.
