Circadian Rhythms Fact Sheet
First published: 2023
Brief summary
NIH overview of circadian rhythms, sleep-wake timing, metabolism and health.
Article
Circadian rhythms are physical, mental and behavioural changes that recur over approximately 24 hours. They are found in animals, plants and microorganisms, and in humans they influence sleep, hormone release, appetite, digestion, body temperature and the timing of functions in many organs and tissues.
Light and darkness are the strongest environmental influences on circadian timing, although food intake, activity, stress, temperature and social conditions can also affect it. A biological clock made from interacting genes and proteins generates the rhythm, while a master clock in the suprachiasmatic nucleus coordinates clocks elsewhere in the body.
Molecular feedback loops are central to clock function. Clock proteins accumulate, interact and regulate the expression of the genes that produce them, creating repeated daily changes in protein abundance and gene activity that can be adjusted by environmental signals.
Jet lag, night work, neurological disease, genetic variation and light exposure at night can place circadian rhythms out of synchrony. Short-term effects include drowsiness, impaired coordination and reduced concentration, while persistent disruption is associated with increased risks affecting metabolic, cardiovascular and mental health.
Source details and credits
- Source / publisher: NIGMS / NIH
- Source type: Educational article
- URL type: WWW
- Credits: NIGMS / NIH
- URL: https://www.nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx