circadian rhythm

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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 ?
The brain controls the circadian clock that regulates sleeping, digestion and brain activity to suit the different demands of day and night--but new research shows that individual cells also appear to have 'clocks' that are affected by a series of genes.
The circadian clock is the human body's natural tendency to follow a 24 hour cycle; this internal pattern is strongly regulated by light and dark with most people yearning for sleep between the hours of midnight and 6 AM (NSF, 2007)The circadian clock controls the body temperature, hormones, heart rate and other body functions;as a result, 10-20% of shift workers report falling asleep on the job (NSF, 2007).
The area of the brain called the hypothalamus, which links the nervous system to the endocrine system by synthesizing and secreting neurohormones that affect sleep, emotions, body temperature, hunger and thirst, is the mainspring of our circadian clock.
In most organisms there is a daily, or circadian, rhythm in visual sensitivity that is believed to be an output of the circadian clock in the retina.
When the light hits the retina, it resets the circadian clock," he says.
Within part II, the chapter on Drosophila, by Jeff Price, is an excellently organized telling of the fascinating story of how the mysteries of the fruit fly circadian clock were unraveled by methods as disparate as Konopka's tenacious brute force discovery of clock mutants to beautiful molecular genetic magic that has fleshed out how the circadian clock actually works in this signal organism.
In mammals, the circadian clock resides in two dusters of nerve cells called the suprachiasmatic nuclei (SCN), which are located in a region at the base of the brain called the anterior hypothalamus.
A joint team of Japanese and American researchers has discovered that restricted feeding entrains the circadian clock in the liver, according to a report published in the Friday edition of U.
Until now most scientists have assumed that the circadian clock, which regulates the body's daily cycles, does not start working until around the time of birth or even later.
Czeisler said he was surprised to find that people's circadian clock - an area deep in the brain that regulates sleep and other functions - runs on a cycle of 24 hours, 11 minutes.
The natural circadian clock is set on a 24 hour, 11 minute cycle.
There are several published studies of daily motor activity patterns in leech species, but no evidence that leeches possess a circadian clock.