circadian rhythm


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Related to circadian rhythm: melatonin, Circadian rhythm sleep disorder

circadian rhythm

n.
A daily rhythmic activity cycle, based on 24-hour intervals, that is exhibited by many organisms.

cir·ca·di·an rhythm

(sər-kā′dē-ən)
A daily cycle of biological activity based on a 24-hour period and influenced by regular variations in the environment, such as the alternation of night and day.
Did You Know? Why do you sometimes wake up on time even if your alarm clock doesn't ring? How do nocturnal animals know when it is time to wake up? It's because you—and most other animals—have a kind of internal clock that controls the cycle of the day's biological activities, such as sleeping and waking. These daily biological activities are known as circadian rhythms because they are influenced by the regular intervals of light and dark in each 24-hour day. While the process underlying circadian rhythm is not completely understood, it is mainly controlled by the release of hormones. The brain regulates the amount of hormone released in response to the information it gets from light-sensitive cells in the eye, called photoreceptors. Circadian rhythms can be disrupted by changes in this daily schedule. For example, biologists have observed that birds exposed to artificial light for a long time sometimes build nests in the fall instead of the spring. In humans who travel long distances by air, the local time of day no longer matches the body's internal clock, causing a condition known as jet lag.

circadian rhythm

The regular recurrence of life activities in 24-hour cycles.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.circadian rhythm - a daily cycle of activity observed in many living organisms
biological time - the time of various biological processes
Translations

cir·ca·di·an rhythm

n. ritmo circadiano, ref. a variaciones rítmicas biológicas en un ciclo de 24 horas.
References in periodicals archive ?
Once the experimenters re-imposed the 24-hour cycle of light and dark, however, subjects' bodies re-established a 24-hour circadian rhythm.
Circadian rhythm in mammals is controlled mainly by neurons in the hypothalamus, says study coauthor Patricia V.
For combined wakefulness and sleepiness, it may be best to try to shift the patient's circadian rhythm, said Dr.
The most well-known circadian rhythm is that of body temperature, which varies daily only a degree or two in a healthy person, peaking in late afternoon and dropping during early morning hours.
GlobalData's clinical trial report, Circadian Rhythm Global Clinical Trials Review, H2, 2011" provides data on the Circadian Rhythm clinical trial scenario.
Plants, like animals, have a 24 hour 'body-clock' known as the circadian rhythm.
Cortisol is a key regulatory hormone which exhibits a strong circadian rhythm, usually rising in the early morning and falling in the evening.
If sleep problems include both wakefulness and sleepiness, it may be best to try to shift the patient's circadian rhythm.
lung function was found to have a natural circadian rhythm, where it is at its peak during the late afternoon hours and at its lowest around midday.
PHILADELPHIA -- Worsening of asthma at night may be caused by circadian rhythm, rather than sleep, according to a study presented at the annual meeting of the Associated Professional Sleep Societies.
Crossing time zones causes jet lag (known as transient desynchronization of the circadian rhythm to medical experts).
Gene Block of the University of Virginia in Charlottesville and his colleagues study how the body's natural timekeeping, or circadian rhythm, changes with age.

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