Overview of Circadian Rhythms
First published: 2001
Brief summary
Introductory overview of circadian rhythms, endogenous clocks, entrainment and the suprachiasmatic nucleus.
Article
Circadian rhythms are internally generated changes in behaviour and physiology with periods close to 24 hours. They are normally synchronised to the environmental light-dark cycle but continue under constant conditions, demonstrating that they are produced by an endogenous timing system rather than by direct responses to daylight alone.
In mammals, the principal circadian pacemaker is located in the paired suprachiasmatic nuclei of the anterior hypothalamus. Light information from the retina reaches this region and adjusts the phase of the clock, allowing internal rhythms to remain aligned with local day and night.
The clock is based on interacting genes and proteins that form regulatory feedback loops. Signals from the central pacemaker coordinate rhythms in sleep and wakefulness, hormone secretion, body temperature, metabolism and many other processes, while additional clocks operate in tissues throughout the body.
Circadian disruption can result from shift work, rapid travel, illness, ageing or mistimed light exposure. Loss of alignment between internal rhythms, behaviour and the external environment can impair sleep, cognition, hormonal regulation, gastrointestinal function, performance and general well-being.
Source details and credits
- Source / publisher: PMC
- Source type: Review
- URL type: WWW
- Credits: PMC
- URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC6707128/