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Overview of human circadian biological clock with some physiological parameters.
.A circadian rhythm is a roughly 24-hour cycle in the biochemical, physiological or behavioural processes of living entities, including plants, animals, fungi and cyanobacteria (see bacterial circadian rhythms).^ Therefore, a circadian rhythm is a cycle that takes about 24 hours in order to complete.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

^ Circadian rhythm describes the approximately 24-hour cycles that are generated by an organism.
  • Sleeplessness and Circadian Rhythm Disorder: eMedicine Neurology 10 February 2010 13:27 UTC emedicine.medscape.com [Source type: Academic]

^ Photosynthesis is an important circadian rhythm in plants.
  • COORDINATING PHOTOSYNTHETIC ACTIVITY: CIRCADIAN RHYTHMS 10 February 2010 13:27 UTC www.tiem.utk.edu [Source type: Academic]

.The term "circadian" comes from the Latin circa, "around", and diem or dies, "day", meaning literally "approximately one day". The formal study of biological temporal rhythms such as daily, tidal, weekly, seasonal, and annual rhythms, is called chronobiology.^ The term circadian comes from Latin words that literally mean “around the day.” .

^ The study of these is called ‘Chronobiology’.
  • Circadian Rhythm Definition | Circadian Rhythms and Sleep | Short Articles - Science, Technology, Computers 10 February 2010 13:27 UTC www.explainstuff.com [Source type: Academic]

^ The word circadian comes from the Latin circa diem meaning about a day, which starts out as a good definition for circadian rhythms.
  • Circadian Rhythms and Sleep | Serendip's Exchange 10 February 2010 13:27 UTC serendip.brynmawr.edu [Source type: FILTERED WITH BAYES]

.Although circadian rhythms are endogenous, they are adjusted (entrained) to the environment by external cues called zeitgebers, the primary one of which is daylight.^ External factors that affect the circadian rhythm are called zeitgebers.
  • Circadian Rhythms and Sleep | Serendip's Exchange 10 February 2010 13:27 UTC serendip.brynmawr.edu [Source type: FILTERED WITH BAYES]

^ Circadian rhythms are endogenously generated, and can be entrained by external cues, called zeitgebers, the primary one of which is daylight.
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

^ This is called the biological clock or circadian rhythm .
  • Circadian rhythm@Everything2.com 10 February 2010 13:27 UTC www.everything2.com [Source type: FILTERED WITH BAYES]

Contents

History

.The earliest known account of a circadian rhythm dates from the 4th century BC, when Androsthenes, a ship captain serving under Alexander the Great, described diurnal leaf movements of the tamarind tree.^ The study of circadian rhythms dates back to the 19 th century.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]

^ We can describe circadian rhythms by the following equation: .
  • COORDINATING PHOTOSYNTHETIC ACTIVITY: CIRCADIAN RHYTHMS 10 February 2010 13:27 UTC www.tiem.utk.edu [Source type: Academic]

^ The earliest known account of a circadian rhythm dates from the 4th century BC, when Androsthenes, a ship captain serving under Alexander the Great, described diurnal leaf movements of the tamarind tree.
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

[1] .The first modern observation of endogenous circadian oscillation was by the French scientist Jean-Jacques d'Ortous de Mairan in the 1700s; he noted that 24-hour patterns in the movement of the leaves of the plant Mimosa pudica continued even when the plants were isolated from external stimuli.^ All animals, including humans, have an internal 24-hour clock or circadian rhythm that creates a daily oscillation of body temperature, brain activity, hormone production and metabolism.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ Circadian rhythm disorders are disruptions in a person’s circadian rhythm—a name given to the “internal body clock” that regulates the (approximately) 24-hour cycle of biological processes in animals and plants.

^ For example, in 1729, a French scientist discovered that circadian movements were not dependent on the daily cycling of light and dark, even though they were synchronized with it.
  • COORDINATING PHOTOSYNTHETIC ACTIVITY: CIRCADIAN RHYTHMS 10 February 2010 13:27 UTC www.tiem.utk.edu [Source type: Academic]

.In 1918, J. S. Szymanski showed that animals are capable of maintaining 24-hour activity patterns in the absence of external cues such as light and changes in temperature.^ All animals, including humans, have an internal 24-hour clock or circadian rhythm that creates a daily oscillation of body temperature, brain activity, hormone production and metabolism.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ More recent research shows that adults of all ages free-run at an average of 24 hours and 11 minutes.

^ The circadian clock coordinates physiological and behavioral processes on a 24-hour rhythm, allowing animals to anticipate changes in their environment and prepare accordingly.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

[2] Joseph Takahashi discovered the genetic basis for the rodent circadian rhythm in 1994.[3][4]
.The term "circadian" was coined by Franz Halberg in the late 1950s.^ The term circadian was coined when Franz Halberg, a scientist at the University of Minnesota, published a paper in 1959 showing blood count varied according to a strict rhythm that was about a day.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
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^ The term "circadian", coined by Franz Halberg, comes from the Latin circa, "around," and diem or dies, "day", meaning literally "approximately one day."
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

[5]

Criteria

To differentiate genuinely endogenous circadian rhythms from coincidental or apparent ones, three general criteria must be met: 1) the rhythms persist in the absence of cues, 2) they persist equally precisely over a range of temperatures, and 3) the rhythms can be adjusted to match the local time:
.
  • The rhythm persists in constant conditions (for example, constant dark) with a period of about 24 hours.^ The period is approximately 24 hours (p = 24).
    • COORDINATING PHOTOSYNTHETIC ACTIVITY: CIRCADIAN RHYTHMS 10 February 2010 13:27 UTC www.tiem.utk.edu [Source type: Academic]

    ^ If the rhythms were exogenously driven, they should persist with a period of exactly 24 hours.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    ^ Instead of 2 p , the period is 24 hours.
    • COORDINATING PHOTOSYNTHETIC ACTIVITY: CIRCADIAN RHYTHMS 10 February 2010 13:27 UTC www.tiem.utk.edu [Source type: Academic]

    .The rationale for this criterion is to distinguish circadian rhythms from those "apparent" rhythms that are merely responses to external periodic cues.^ Figure 1 Circadian rhythm responses to light.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    ^ In order for scientists to identify endogenous circadian rhythms a subject must be isolated from sunlight, clocks, environmental sounds, and to all other cues of time .
    • Circadian rhythm@Everything2.com 10 February 2010 13:27 UTC www.everything2.com [Source type: FILTERED WITH BAYES]

    ^ Strictly speaking, a diurnal rhythm should not be called circadian until it has been shown to persist under constant environmental conditions and thereby can be distinguished from those rhythms that are simply a response to 24-hour environmental changes.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    .A rhythm cannot be declared to be endogenous unless it has been tested in conditions without external periodic input.
  • The rhythm is temperature-compensated, i.e., it maintains the same period over a range of temperatures.^ The influence of temperature on circadian rhythms is particularly interesting in that a change in temperature can affect the phase of a cycle without substantially altering the rate of cycling.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    ^ When heart rate, mean arterial pressure and activity were recalculated according to the endogenous Circadian periods of each individual mouse, the amplitudes of the Circadian rhythm s ("subjective night"-"subjective day" differences) were maintained for all variables studied.
    • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

    ^ Circadian rhythms are endogenously generated, and can be entrained by external cues, called zeitgebers, the primary one of which is daylight.
    • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

    .The rationale for this criterion is to distinguish circadian rhythms from other biological rhythms arising due to the circular nature of a reaction pathway.^ This is called the biological clock or circadian rhythm .
    • Circadian rhythm@Everything2.com 10 February 2010 13:27 UTC www.everything2.com [Source type: FILTERED WITH BAYES]

    ^ In order for scientists to identify endogenous circadian rhythms a subject must be isolated from sunlight, clocks, environmental sounds, and to all other cues of time .
    • Circadian rhythm@Everything2.com 10 February 2010 13:27 UTC www.everything2.com [Source type: FILTERED WITH BAYES]

    ^ View Pathway: Circadian rhythm Login Apropos .
    • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

    .At a low enough or high enough temperature, the period of a circular reaction may reach 24 hours, but it will be merely coincidental.
  • The rhythm can be reset by exposure to an external stimulus.^ All animals, including humans, have an internal 24-hour clock or circadian rhythm that creates a daily oscillation of body temperature, brain activity, hormone production and metabolism.
    • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

    ^ Some studies show that morning bird sounds and high-density negative ionization also play a role in resetting the circadian rhythm.
    • Circadian Rhythm Sleep Disorders 10 February 2010 13:27 UTC www.talkaboutsleep.com [Source type: FILTERED WITH BAYES]

    ^ The circadian clock coordinates physiological and behavioral processes on a 24-hour rhythm, allowing animals to anticipate changes in their environment and prepare accordingly.
    • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

    .The rationale for this criterion is to distinguish circadian rhythms from other imaginable endogenous 24-hour rhythms that are immune to resetting by external cues and, hence, do not serve the purpose of estimating the local time.^ B. Resetting the circadian rhythm .
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    ^ Environmental cues are external cues, which resets the circadian clock.
    • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

    ^ This multi-purpose hormone regulates other hormones responsible for circadian rhythm (the body's rhythm during a 24-hour period of time - i.e.
    • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

    .Travel across time zones illustrates the necessity of the ability to adjust the biological clock so that it can reflect the local time and anticipate what will happen next.^ No one mentioned using Melatonin as an aid to adjusting to different time zones.
    • How to deal with jetlag | Gadling.com 10 February 2010 13:27 UTC www.gadling.com [Source type: General]

    ^ Humans have biological rhythms, known as circadian rhythms, which are controlled by a biological clock and work on a daily time scale.

    ^ When the sleep-wake cycle is out of phase with the rhythms that are con-trolled by the circadian clock (e.g., during shift work or rapid travel across time zones), adverse effects may ensue.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    Until rhythms are reset, a person usually experiences jet lag.

Origin

.Photosensitive proteins and circadian rhythms are believed to have originated in the earliest cells, with the purpose of protecting the replicating of DNA from high ultraviolet radiation during the daytime.^ Cycling Cells - The circadian rhythm .
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

^ Some studies show that morning bird sounds and high-density negative ionization also play a role in resetting the circadian rhythm.
  • Circadian Rhythm Sleep Disorders 10 February 2010 13:27 UTC www.talkaboutsleep.com [Source type: FILTERED WITH BAYES]

^ Circadian rhythm is an innate gene-genome characteristic, inborn-brought-about at the energetic conditions during the genesis of genes in the process of phasing from chemical olygomers to replicating life, to living genes which are base life energy packages.
  • Circadian Rhythms and Sleep | Serendip's Exchange 10 February 2010 13:27 UTC serendip.brynmawr.edu [Source type: FILTERED WITH BAYES]

As a result, replication was relegated to the dark. .The fungus Neurospora, which exists today, retains this clock-regulated mechanism.^ Regulation of the Drosophila protein timeless suggests a mechanism for resetting the circadian clock by light.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

^ A clock is a term to describe the entire biological mechanism that regulates natural occurring rhythms in an organism.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

.Circadian rhythms allow organisms to anticipate and prepare for precise and regular environmental changes; they have great value in relation to the outside world.^ These rhythms allow organisms to anticipate and prepare for precise and regular environmental changes.
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

^ The circadian clock coordinates physiological and behavioral processes on a 24-hour rhythm, allowing animals to anticipate changes in their environment and prepare accordingly.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ Shift work Pregnancy Time zone changes Medications Changes in routine Common Circadian Rhythm Disorders .
  • Circadian Rhythm Disorders 10 February 2010 13:27 UTC www.webmd.com [Source type: General]

.The rhythmicity appears to be as important in regulating and coordinating internal metabolic processes, as in coordinating with the environment.^ The circadian clock coordinates physiological and behavioral processes on a 24-hour rhythm, allowing animals to anticipate changes in their environment and prepare accordingly.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ Studies have found that the internal clock consists of an array of genes and the protein products they encode, which regulate various physiological processes throughout the body.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

[6] .This is suggested by the maintenance (heritability) of circadian rhythms in fruit flies after several hundred generations in constant laboratory conditions,[7] as well as in creatures in constant darkness in the wild, and by the experimental elimination of behavioural but not physiological circadian rhythms in quail.^ The circadian clock coordinates physiological and behavioral processes on a 24-hour rhythm, allowing animals to anticipate changes in their environment and prepare accordingly.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ Finally, not only may alcohol consumption affect circadian rhythms, but circadian factors, such as the light-dark cycle, may also influence alcohol consumption.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Thus, almost all diurnal rhythms that occur under natural conditions continue to cycle under laboratory conditions devoid of any external time-giving cues from the physical environment (e.g., under constant light or constant darkness).
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

[8][9]
.The simplest known circadian clock is that of the prokaryotic cyanobacteria.^ Cyanobacteria are the simplest known form of life that has circadian rhythms.
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^ The circadian clock in cyanobacteria controls photosynthesis, nitrogen fixation, cell division, respiration, amino acid uptake, and carbohydrate synthesis (6) .
  • Circadian Rhythms and Sleep | Serendip's Exchange 10 February 2010 13:27 UTC serendip.brynmawr.edu [Source type: FILTERED WITH BAYES]

^ Humans have biological rhythms, known as circadian rhythms, which are controlled by a biological clock and work on a daily time scale.

.Recent research has demonstrated that the circadian clock of Synechococcus elongatus can be reconstituted in vitro with just the three proteins of their central oscillator.^ Circadian oscillators are biological clocks.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

^ That’s because the body’s internal clock, or circadian rhythm , may play a role in metabolism, researchers say.
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

^ Recently, however, researchers have been surprised to find that circadian rhythms could persist in isolated lungs, livers, and other tissues grown in a culture dish (i.e., in vitro) that were not under the control of the SCN (Yamazaki et al.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.This clock has been shown to sustain a 22-hour rhythm over several days upon the addition of ATP.^ The circadian clock coordinates physiological and behavioral processes on a 24-hour rhythm, allowing animals to anticipate changes in their environment and prepare accordingly.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ Chronotherapy is a progressive advancement or delay (1-2 hours per day) of sleep time depending on the type and the severity of the disorder.

^ Circadian Light Therapy Resets and Stabilizes the Circadian Clock Light is the most effective way to synchronize the body with the twenty-four hour day.
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.Previous explanations of the prokaryotic circadian timekeeper were dependent upon a DNA transcription / translation feedback mechanism.^ As discussed previously, the properties of circadian clocks suggested cyclic changes in the expression of certain genes as a possible mechanism underlying the internal pacemaker.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Central to the timekeeping mechanism of the body and mind are Suprachaismatic nuclei or SCN. The SCN is the master clock the circadian rhythm that controls all other rhythms of the body.
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^ Central to the timekeeping mechanism of the body and mind are Suprachaismatic nuclei or SCN. The SCN is the master clock – the circadian rhythm that controls all other rhythms of the body.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]

.It is an unanswered question whether circadian clocks in eukaryotic organisms require translation/transcription-derived oscillations, for, although the circadian systems of eukaryotes and prokaryotes have the same basic architecture (input – central oscillator – output), they do not share any homology.^ Circadian oscillators are biological clocks.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

^ The circadian rhythm describes the internal biological clock that controls an organism's daily activity cycles.
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

^ The period, or frequency, of oscillation of the central circadian pacemaker is relatively insensitive to external and internal environmental influences.
  • Melatonin and Circadian Rhythm Disorder | May-June 2002 | Sleep Review 10 February 2010 13:27 UTC www.sleepreviewmag.com [Source type: Academic]

This implies probable independent origins.
.In 1971, Ronald J. Konopka and Seymour Benzer first identified a genetic component of the biological clock using the fruit fly as a model system.^ SLEEP 101: Sleep is actually a combination of 2 systems, your sleep drive (like hunger) and a biological clock that tells you when to sleep.
  • Dr. Michael J. Breus: Sleep Hygiene 101: How To Ensure A Better Night's Rest 10 February 2010 13:27 UTC www.huffingtonpost.com [Source type: General]

^ Jan 6; 303(1): 19 Chang HJ Circadian rhythm s in Neurospora crassa: Dynamics of the clock component frequency visualized using a fluorescent reporter.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Researchers used chemical agents to introduce numerous, random mutations into the DNAs of the fruit fly, Drosophila melanogaster, and of the filamentous fungus Neurospora .
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.Three mutant lines of flies displayed aberrant behaviour: one had a shorter period, another had a longer one, and the third had none.^ PER (period) protein continues to cycle up to three days after a fly's head has been removed, whether or not the corpse is exposed to periods of light and dark.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

.All three mutations mapped to the same gene, which was named period.^ We propose that Period clock gene mutations promote tumorigenesis by unique molecular pathways.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Whereas all patients with DSPS exhibited a 24-hour periodicity of oral temperature rhythm, three of seven patients with ISWP lacked such a daily rhythm.

^ Human tumors show Period gene mutations or decreased expression.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

[10] .The same gene was identified to be defective in the sleep disorder FASPS (Familial advanced sleep phase syndrome) in human beings thirty years later, underscoring the conserved nature of the molecular circadian clock through evolution.^ Phase advance of the circadian sleep-wake cycle as an anti-depressant.
  • To Sleep, Perchance to Reset Your Body Clock - Psychiatric Times 10 February 2010 13:27 UTC www.psychiatrictimes.com [Source type: FILTERED WITH BAYES]

^ Advanced Sleep Phase Syndrome: Advanced sleep phase syndrome is a disorder in which the major sleep episode is advanced in relation to the desired clock time.
  • Circadian Rhythm Disorders 10 February 2010 13:27 UTC www.webmd.com [Source type: General]

^ In human beings circadian rhythm disorders can result that lead to sleeping...
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

.Many more genetic components of the biological clock are now known.^ Its synthesis and release into the general circulation are timed by one or more biologic clocks(in a circadian rhythmic fashion) but in humans they occur only in darkness.
  • Melatonin and Circadian Rhythm Disorder | May-June 2002 | Sleep Review 10 February 2010 13:27 UTC www.sleepreviewmag.com [Source type: Academic]

^ Humans have biological rhythms, known as circadian rhythms, which are controlled by a biological clock and work on a daily time scale.

.Their interactions result in an interlocked feedback loop of gene products resulting in periodic fluctuations that the cells of the body interpret as a specific time of the day.^ Since the discovery of the Clock gene in mice, the list of circadian clock genes identified in mammals has grown in a remarkably short period of time (see table 1).
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ The disruption results from either a malfunction in the “internal body clock” or a mismatch between the “internal body clock” and the external environment regarding the timing and duration of sleep.

^ If you have a circadian rhythm disorder, your body is likely producing melatonin at the wrong time of day, when you need to be active.
  • Circadian Rhythm Sleep Disorders 10 February 2010 13:27 UTC www.talkaboutsleep.com [Source type: FILTERED WITH BAYES]

.A great deal of research on biological clocks was done in the latter half of the 20th century.^ This remarkable research points to the biological clock’s role in...
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

.It is now known that the molecular circadian clock can function within a single cell; i.e., it is cell-autonomous.^ The circadian "clock" in humans is located mainly in the suprachiasmatic nucleus (SCN), which is a group of cells located in the hypothalamus (a portion of the brain).
  • Circadian Rhythm Disorders 10 February 2010 13:27 UTC www.webmd.com [Source type: General]

^ UC Irvine researchers have found a molecular link between circadian rhythms – our own body clock – and metabolism.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ The circadian clock in cyanobacteria controls photosynthesis, nitrogen fixation, cell division, respiration, amino acid uptake, and carbohydrate synthesis (6) .
  • Circadian Rhythms and Sleep | Serendip's Exchange 10 February 2010 13:27 UTC serendip.brynmawr.edu [Source type: FILTERED WITH BAYES]

[11] .At the same time, different cells may communicate with each other resulting in a synchronized output of electrical signaling.^ This means that the cycle may start at an earlier or later-than-normal time but still have the same length.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ It results from an inability to synchronize one's normal rhythm to rapidly changing time shifts of environmental cues.
  • Sleeplessness and Circadian Rhythm Disorder: eMedicine Neurology 10 February 2010 13:27 UTC emedicine.medscape.com [Source type: Academic]

^ Other factors that may affect severity of jet lag are age, ability to sleep while traveling, the time of the day at destination, and exposure to light.
  • Sleeplessness and Circadian Rhythm Disorder: eMedicine Neurology 10 February 2010 13:27 UTC emedicine.medscape.com [Source type: Academic]

.These may interface with endocrine glands of the brain to result in periodic release of hormones.^ Apparently, the body clock begins to cycle too quickly during the second half of the menstrual cycle, and may be a reason why these reproductive hormones deplete too quickly.
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^ These results indicate that the role of GPR7 may be subtle or limited in relation to the Circadian clock despite its robust expression in the SCN. Scientists probe brain's role in obesity.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Because your daily cycle, or circadian rhythm is not operating properly, your pineal gland may be releasing the night time hormone melatonin during your day cycle, causing you to feel tired in the at various times during the day.
  • Circadian Rhythm Sleep Disorders 10 February 2010 13:27 UTC www.talkaboutsleep.com [Source type: FILTERED WITH BAYES]

.The receptors for these hormones may be located far across the body and synchronize the peripheral clocks of various organs.^ Since metabolic rates are known to change in a circadian fashion, we investigated the temporal variations of biophoton emission across the day from healthy human body.
  • Yes, You Too Glow in The Dark 10 February 2010 13:27 UTC www.medgadget.com [Source type: FILTERED WITH BAYES]

^ Apparently, the body clock begins to cycle too quickly during the second half of the menstrual cycle, and may be a reason why these reproductive hormones deplete too quickly.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ Circadian Light Therapy Resets and Stabilizes the Circadian Clock Light is the most effective way to synchronize the body with the twenty-four hour day.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

.Thus, the information of the time of the day as relayed by the eyes travels to the clock in the brain, and, through that, clocks in the rest of the body may be synchronized.^ Thus, the body is ready for sleep and for wakefulness at different times of the day.

^ Dawn Simulation has also been clinically proven in sleep labs and universities to help treat DCR. Dawn simulation helps maintain a consistent circadian rhythm by sending a properly timed signal of light through the retina of the eye to the brain's Suprachaismatic nucleus, or body clock in the hypothalamus.
  • Circadian Rhythm Sleep Disorders 10 February 2010 13:27 UTC www.talkaboutsleep.com [Source type: FILTERED WITH BAYES]

^ The most useful measure of a person’s internal body-clock time—circadian time (CT) is the time of dim light melatonin onset (DLMO).
  • To Sleep, Perchance to Reset Your Body Clock - Psychiatric Times 10 February 2010 13:27 UTC www.psychiatrictimes.com [Source type: FILTERED WITH BAYES]

.This is how the timing of, for example, sleep/wake, body temperature, thirst, and appetite are coordinately controlled by the biological clock.^ Genes controlling insulin can alter timing of biological clock .
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ They are generally able to get enough sleep if allowed to sleep and wake at the times dictated by their body clocks.

^ Any suggestions for resetting his biological body clock ...
  • Circadian Rhythms and Sleep | Serendip's Exchange 10 February 2010 13:27 UTC serendip.brynmawr.edu [Source type: FILTERED WITH BAYES]

Importance in animals

.Circadian rhythmicity is present in the sleeping and feeding patterns of animals, including human beings.^ Circadian rhythms are important in determining human sleeping patterns.
  • Circadian Rhythm Disorders 10 February 2010 13:27 UTC www.webmd.com [Source type: General]

^ In human beings circadian rhythm disorders can result that lead to sleeping...
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

^ All animals, including humans, have an internal 24-hour clock or circadian rhythm that creates a daily oscillation of body temperature, brain activity, hormone production and metabolism.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

.There are also clear patterns of core body temperature, brain wave activity, hormone production, cell regeneration and other biological activities.^ There are patterns of brain wave activity, hormone production, cell regeneration, and other biological activities linked to this 24-hour cycle.
  • Circadian Rhythm Disorders 10 February 2010 13:27 UTC www.webmd.com [Source type: General]

^ These changes in biological rhythms can be measured in physical strength, aerobic capacity, body temperature, blood pressure, mental alertness, production and secretion of neurotransmitters & hormones, and many other body functions.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ On the other hand, temperature compensation also is rather puzzling, because most kinds of biological processes (e.g., biochemical reactions in the body) are accelerated or slowed by temperature changes.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.In addition, photoperiodism, the physiological reaction of organisms to the length of day or night, is vital to both plants and animals, and the circadian system plays a role in the measurement and interpretation of day length.^ The circadian clock coordinates physiological and behavioral processes on a 24-hour rhythm, allowing animals to anticipate changes in their environment and prepare accordingly.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ Some studies show that morning bird sounds and high-density negative ionization also play a role in resetting the circadian rhythm.
  • Circadian Rhythm Sleep Disorders 10 February 2010 13:27 UTC www.talkaboutsleep.com [Source type: FILTERED WITH BAYES]

^ That’s because the body’s internal clock, or circadian rhythm , may play a role in metabolism, researchers say.
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

.Timely prediction of seasonal periods of weather conditions, food availability or predator activity is crucial for survival of many species.^ It is well-known that in many species, activity does in fact follow daily patterns.
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

.Although not the only parameter, the changing length of the photoperiod ('daylength') is the most predictive environmental cue for the seasonal timing of physiology and behavior, most notably for timing of migration, hibernation and reproduction.^ For those who consistently work the same shift, only environmental issues affect sleep quality once the biological clock adjusts to the new time.
  • Sleeplessness and Circadian Rhythm Disorder: eMedicine Neurology 10 February 2010 13:27 UTC emedicine.medscape.com [Source type: Academic]

^ Correspondingly, almost all species exhibit daily changes in their behavior and/or physiology.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ It results from an inability to synchronize one's normal rhythm to rapidly changing time shifts of environmental cues.
  • Sleeplessness and Circadian Rhythm Disorder: eMedicine Neurology 10 February 2010 13:27 UTC emedicine.medscape.com [Source type: Academic]

[12]

Impact of light–dark cycle

.The rhythm is linked to the light–dark cycle.^ Melatonin is secreted by the pineal gland and secretion is suppressed by exposure to light and is entrained by the light-dark cycle.
  • Melatonin and Circadian Rhythm Disorder | May-June 2002 | Sleep Review 10 February 2010 13:27 UTC www.sleepreviewmag.com [Source type: Academic]

^ Keep yourself exposed to the natural light and dark cycles of your destination.
  • How to deal with jetlag | Gadling.com 10 February 2010 13:27 UTC www.gadling.com [Source type: General]

^ This cycle becomes disrupted when you suddenly become displaced in a different time zone with light and dark cycles to which your body is not accustomed.
  • How to deal with jetlag | Gadling.com 10 February 2010 13:27 UTC www.gadling.com [Source type: General]

.Animals, including humans, kept in total darkness for extended periods eventually function with a freerunning rhythm.^ For example, when functioning properly, the human circadian rhythm will respond to the morning light of a new day.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ Melatonin, when administrated to animals and humans, shifts circadian rhythms according to a phase-response curve.
  • Melatonin and Circadian Rhythm Disorder | May-June 2002 | Sleep Review 10 February 2010 13:27 UTC www.sleepreviewmag.com [Source type: Academic]

^ Nearly all physiological and behavioral functions in humans occur on a rhythmic basis, which in turn leads to dramatic diurnal rhythms in human performance capabilities.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.Each "day", their sleep cycle is pushed back or forward, depending on whether their endogenous period is shorter or longer than 24 hours.^ Ultradian rhythms are those which cycle in less than 24 hours.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

^ Treatment Recommendations for Non 24-hour Sleep/Wake Cycles .
  • Circadian Rhythm Sleep Disorders 10 February 2010 13:27 UTC www.talkaboutsleep.com [Source type: FILTERED WITH BAYES]

^ An infardian rhythm is a cycle that is greater than 24 hours.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

.The environmental cues that each day reset the rhythms are called Zeitgebers (from the German, Time Givers).^ Zeitgeber: A German word literally meaning “time-giver.” A time cue capable of entraining circadian rhythms.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Zeitgebers: The Bodys Way of Synchronizing In order for to reconcile the difference between natures exact twenty-four hour cycle and the internal circadian rhythms we free-run on, nature has given us zeitgebers, a German word that means time givers.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ To maintain a 24 hour day/night cycle, the biological clock needs regular environmental time cues, e.g.

[13] It is interesting to note that totally-blind subterranean mammals (e.g., blind mole rat Spalax sp.) are able to maintain their endogenous clocks in the apparent absence of external stimuli. .Although they lack image-forming eyes, their photoreceptors (detect light) are still functional; as well, they do surface periodically.^ There is some evidence that although these clock genes are different for different functions they maybe quite similar in their composition (Lee et al., 1998).
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

^ They suggest that although light can entrain a behavioral rhythm, the eyes are not a required medium for the light to cause a shift in a rhythm.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

[citation needed]
.Freerunning organisms that normally have one consolidated sleep episode will still have it when in an environment shielded from external cues, but the rhythm is, of course, not entrained to the 24-hour light/dark cycle in nature.^ Circadian rhythm describes the approximately 24-hour cycles that are generated by an organism.
  • Sleeplessness and Circadian Rhythm Disorder: eMedicine Neurology 10 February 2010 13:27 UTC emedicine.medscape.com [Source type: Academic]

^ Ultradian rhythms are those which cycle in less than 24 hours.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

^ An infardian rhythm is a cycle that is greater than 24 hours.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

.The sleep–wake rhythm may, in these circumstances, become out of phase with other circadian or ultradian rhythms such as temperature and digestion.^ Circadian Rhythm Disorders Out of Synch: what is circadian rhythm disorder?
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ The Circadian rhythm of body temperature.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Symptoms of Circadian rhythm sleep disorder .
  • Circadian rhythm sleep disorder Symptoms, Diagnosis, Treatments and Causes - WrongDiagnosis.com 10 February 2010 13:27 UTC wrongdiagnosis.com [Source type: Academic]

[citation needed]
.Recent research has influenced the design of spacecraft environments, as systems that mimic the light/dark cycle have been found to be highly beneficial to astronauts.^ Finally, not only may alcohol consumption affect circadian rhythms, but circadian factors, such as the light-dark cycle, may also influence alcohol consumption.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Melatonin is secreted by the pineal gland and secretion is suppressed by exposure to light and is entrained by the light-dark cycle.
  • Melatonin and Circadian Rhythm Disorder | May-June 2002 | Sleep Review 10 February 2010 13:27 UTC www.sleepreviewmag.com [Source type: Academic]

^ Such a curve can predict the manner in which an organism will entrain not only to shifts in the light-dark cycles but also to unusual light cycles, such as non-24-hour cycles or different light:dark ratios.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

[citation needed]

Arctic animals

.Norwegian researchers at the University of Tromsø have shown that some Arctic animals (ptarmigan, reindeer) show circadian rhythms only in the parts of the year that have daily sunrises and sunsets.^ All animals, including humans, have an internal 24-hour clock or circadian rhythm that creates a daily oscillation of body temperature, brain activity, hormone production and metabolism.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ The circadian clock coordinates physiological and behavioral processes on a 24-hour rhythm, allowing animals to anticipate changes in their environment and prepare accordingly.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ The term circadian was coined when Franz Halberg, a scientist at the University of Minnesota, published a paper in 1959 showing blood count varied according to a strict rhythm that was about a day.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
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.In one study of reindeer, animals at 70 degrees North showed circadian rhythms in the autumn, winter, and spring, but not in the summer.^ Some studies show that morning bird sounds and high-density negative ionization also play a role in resetting the circadian rhythm.
  • Circadian Rhythm Sleep Disorders 10 February 2010 13:27 UTC www.talkaboutsleep.com [Source type: FILTERED WITH BAYES]

^ One early pioneer was Curt Paul Richter, a professor of psychobiology at Johns Hopkins Medical School whose innovative concepts are the foundation for established concepts and methods for studying circadian rhythms in humans.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ Medical news articles related to Circadian rhythm sleep disorder include: Circadian Rhythm Plays Role in Memory Studies Link Circadian Rhythm, Metabolism, Longevity to One Protein more health news...» Source: HealthDay News .
  • Circadian rhythm sleep disorder Symptoms, Diagnosis, Treatments and Causes - WrongDiagnosis.com 10 February 2010 13:27 UTC wrongdiagnosis.com [Source type: Academic]

.Reindeer at 78 degrees North showed such rhythms only autumn and spring.^ Finally, not only may alcohol consumption affect circadian rhythms, but circadian factors, such as the light-dark cycle, may also influence alcohol consumption.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ It has been demonstrated in the melon fly that specific activities, such as mating, and wing vibration only occur during a specific time during a daily activity rhythm (Miyatake, 1997).
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

.The researchers suspect that other Arctic animals as well may not show circadian rhythms in the constant light of summer and the constant dark of winter.^ Figure 1 Circadian rhythm responses to light.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Circadian rhythm disorders and light therapy .
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

^ Other Disorders that show a circadian Pattern .
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]

[14][15]
.However, another study in northern Alaska found that ground squirrels and porcupines strictly maintained their circadian rhythms through 82 days and nights of sunshine.^ Circadian rhythm disorder can be treated with melatonin; however, because of its unpredictable effects, further research in chronobiotics is needed .
  • Melatonin and Circadian Rhythm Disorder | May-June 2002 | Sleep Review 10 February 2010 13:27 UTC www.sleepreviewmag.com [Source type: Academic]

^ The Master Clock Significant progress is being made in the field of chronobiology, the formal name for the medical science that studies circadian rhythms.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ For example, the sleep pattern of a housefly is a circadian rhythm while traffic congestion over the course of a day is rhythmic; it is not a circadian rhythm.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

.The researchers speculate that these two small mammals see that the apparent distance between the sun and the horizon is shortest once a day, and, thus, a sufficient signal to adjust by.^ Researchers believe these hormones may deplete too quickly, and not allow enough time for the body to adjust.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
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^ Studies have found that these changes are governed by a biological clock, which in mammals is located in two brain areas called the suprachiasmatic nuclei.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ To further elucidate the regulation of circadian rhythms, researchers need a better understanding of the nature of circadian signal output from the SCN and of how these output signals may be modified once they reach their target systems.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

[16]

Butterfly migration

.The navigation of the fall migration of the Eastern North American monarch butterfly (Danaus plexippus) to their overwintering grounds in central Mexico uses a time-compensated sun compass that depends upon a circadian clock in their antennae.^ An example would be the annual migration of monarch butterflies from North America to Mexico.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

^ Jan 6; 303(1): 19 Chang HJ Circadian rhythm s in Neurospora crassa: Dynamics of the clock component frequency visualized using a fluorescent reporter.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Pacemaker is an internal mechanism, which keeps time for the circadian clock by either coordinating or constructing rhythms.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

[17][18]

Biological clock in mammals

Diagram illustrating the influence of light and darkness on circadian rhythms and related physiology and behaviour through the suprachiasmatic nucleus in humans.
.The primary circadian "clock" in mammals is located in the suprachiasmatic nucleus (or nuclei) (SCN), a pair of distinct groups of cells located in the hypothalamus.^ Suprachiasmatic nucleus or nuclei (SCN): A cluster of nerve cells located in the brain region called the hypothalamus that is responsible for generating and coordinating circadian rhythmicity in mammals.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ In mammals, the circadian clock resides in two clusters of nerve cells called the suprachiasmatic nuclei (SCN), which are located in a region at the base of the brain called the anterior hypothalamus.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ THE CIRCADIAN CLOCK The circadian oscillator is located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus.
  • Melatonin and Circadian Rhythm Disorder | May-June 2002 | Sleep Review 10 February 2010 13:27 UTC www.sleepreviewmag.com [Source type: Academic]

.Destruction of the SCN results in the complete absence of a regular sleep–wake rhythm.^ The sleep-wake cycle, which constitutes a central aspect of circadian rhythms in particular, is subject to modification by alcohol; alcohol’s effects on the sleep of nonalcoholics and alcoholics are discussed by Drs.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Pattern of sleep-wake cycle: This is an important part of the history in patients with circadian rhythm disturbances.
  • Sleeplessness and Circadian Rhythm Disorder: eMedicine Neurology 10 February 2010 13:27 UTC emedicine.medscape.com [Source type: Academic]

^ People with circadian rhythm sleep disorders are unable to sleep and wake at the times required for normal work, school, and social needs.

.The SCN receives information about illumination through the eyes.^ When the eye is exposed to circadian light the SCN receives this signal and utilizes it as it regulates the circadian cycle.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
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.The retina of the eye contains not only the "classical" photoreceptors which are used for vision but ganglion cells which respond to light and are called photosensitive ganglion cells.^ Wake therapy is only necessary for the first night if used with bright light each successive morning.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
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.These cells contain the photo pigment melanopsin and their signals follow a pathway called the retinohypothalamic tract, leading to the SCN. If cells from the SCN are removed and cultured, they maintain their own rhythm in the absence of external cues.^ Circadian rhythm abnormalies have been hypothesized to account for these aspects of SAD, and they provide a rationale for the therapeutic use of light therapy.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Circadian rhythms that are expressed in the absence of any 24-hour signals from the external environment are called free running.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ When it comes time for birds to migrate south and then, back north they are signaled by circannual rhythms.
  • Circadian Rhythms and Sleep | Serendip's Exchange 10 February 2010 13:27 UTC serendip.brynmawr.edu [Source type: FILTERED WITH BAYES]

.The SCN takes the information on the lengths of the day and night from the retina, interprets it, and passes it on to the pineal gland, a tiny structure shaped like a pine cone and located on the epithalamus.^ Melatonin is produced by the pineal gland and it has a day/night function.
  • Circadian Rhythms and Sleep | Serendip's Exchange 10 February 2010 13:27 UTC serendip.brynmawr.edu [Source type: FILTERED WITH BAYES]

^ Circadian axis is a name for a group of body parts comprised of the retinas, the pineal complex (of which the pineal gland is a photoreceptor, a circadian oscillator, and produces melatonin) and the suprachiasmatic nucleus (SCN) which is located in the region of the brain called the hypothalamus.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

^ These structures include certain regions of the brain (i.e., the optic and cerebral lobes) in insects; the eyes in certain invertebrates and vertebrates; and the pineal gland, which is located within the brain, in nonmammalian vertebrates.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.In response the pineal secretes the hormone melatonin.^ Melatonin Melatonin is an important hormone secreted by the pineal gland in the brain.
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

^ Because the circadian rhythm is running fast, the pineal gland releases the nighttime hormone melatonin prematurely, causing one to feel tired earlier in the evening.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
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^ Melatonin is a hormone produced in the brain by the pineal gland, from the amino acid tryptophan.
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

.Secretion of melatonin peaks at night and ebbs during the day and its presence provides information about night-length.^ It peaks during darkness and lowers during the day.
  • Circadian Rhythms and Sleep | Serendip's Exchange 10 February 2010 13:27 UTC serendip.brynmawr.edu [Source type: FILTERED WITH BAYES]

^ David, I have to agree with Mary Jo's comment about staying awake during the day to adjust better with local time.
  • How to deal with jetlag | Gadling.com 10 February 2010 13:27 UTC www.gadling.com [Source type: General]

^ Nature, through its twenty-four hour cycle of day and night, has provided us with a template or a pattern that anticipates what we need to be healthy.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
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.The circadian rhythms of humans can be entrained to slightly shorter and longer periods than the Earth's 24 hours.^ In this case, the body clock is running slower than a normal circadian rhythm (24 hour period).
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^ Stability, precision, and newar 24-hour period of the human circadian pacemaker.
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^ The hypothesis that such uncontrolled geomagnetic cues might play a role in the persistence of rhythmicity can be refuted by a second characteristic feature of circadian rhythms: These cycles persist with a period of close to, but not exactly, 24 hours.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.Researchers at Harvard have recently shown that human subjects can at least be entrained to a 23.5-hour cycle and a 24.65-hour cycle (the latter being the natural solar day-night cycle on the planet Mars).^ There are patterns of brain wave activity, hormone production, cell regeneration, and other biological activities linked to this 24-hour cycle.
  • Circadian Rhythm Disorders 10 February 2010 13:27 UTC www.webmd.com [Source type: General]

^ Therefore, a circadian rhythm is a cycle that takes about 24 hours in order to complete.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

^ Introduction Background Circadian rhythm describes the approximately 24-hour cycles that are generated by an organism.
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

[19]

Determining the human circadian rhythm

The classic phase markers for measuring the timing of a mammal's circadian rhythm are[20]
  • melatonin secretion by the pineal gland and
  • core body temperature.
.For temperature studies, people must remain awake but calm and semi-reclined in near darkness while their rectal temperatures are taken continuously.^ When subjects are studied under near-dark conditions, the onset and shutoff of melatonin secretion have been used to determine the phase position of the circadian oscillator.
  • Melatonin and Circadian Rhythm Disorder | May-June 2002 | Sleep Review 10 February 2010 13:27 UTC www.sleepreviewmag.com [Source type: Academic]

The average human adult's temperature reaches its minimum at about 05:00 (5 a.m.), about two hours before habitual wake time, though variation is great among normal chronotypes.
Melatonin is absent from the system or undetectably low during daytime. Its onset in dim light, dim-light melatonin onset (DLMO), at about 21:00 (9 p.m.) can be measured in the blood or the saliva. Its major metabolite can also be measured in morning urine. .Both DLMO and the midpoint (in time) of the presence of the hormone in the blood or saliva have been used as circadian markers.^ When out of balance, quantity, quality and timing of hormone and neurotransmitter secretion suffer and our bodies suffer from a circadian rhythm disorder (CRD).
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^ A circadian rhythm disorder means your body is producing hormones, chemicals and neurotransmitters in the wrong amounts and/or at the wrong time of the day.
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^ Light is a very common cue used by circadian pacemakers to keep time.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

.However, newer research indicates that the melatonin offset may be the most reliable marker.^ These observations indicate that most cells and tissues of the body may be capable of modulating their activity on a circadian basis.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Race has been associated with variations in incidence of obstructive sleep apnea (OSA) ; however, many variables may be associated with these differences, and further research is necessary to evaluate this.
  • Sleeplessness and Circadian Rhythm Disorder: eMedicine Neurology 10 February 2010 13:27 UTC emedicine.medscape.com [Source type: Academic]

.Benloucif et al. in Chicago in 2005 found that melatonin phase markers were more stable and more highly correlated with the timing of sleep than the core temperature minimum.^ The sleep-wake cycle resynchronized to the melatonin rhythm by either phase-advance or -delay shifts in the free-run session.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ In those older than 40 years, women are 1.3 times more likely to report insomnia than men.
  • Sleeplessness and Circadian Rhythm Disorder: eMedicine Neurology 10 February 2010 13:27 UTC emedicine.medscape.com [Source type: Academic]

^ Sauman et al (1996) found that PER is critical for egg hatching in silkmoths.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

.They found that both sleep offset and melatonin offset were more strongly correlated with the various phase markers than sleep onset.^ Studies have found that the internal clock consists of an array of genes and the protein products they encode, which regulate various physiological processes throughout the body.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ On the other hand, the Circadian melatonin rhythm was significantly phase-delayed in the both groups, showing internal desynchronization of the Circadian rhythm s.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Antidepressant action of melatonin in the treatment of Delayed Sleep Phase Syndrome.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

.In addition, the declining phase of the melatonin levels was more reliable and stable than the termination of melatonin synthesis.^ In the case of a phase delay, the peak levels are reached later than they would be had the rhythm not been shifted.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ As Pers and Crys accumulate, they inhibit their own synthesis, and the protein levels decline.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Furthermore, melatonin secretion rhythm as a Circadian phase marker was assessed by measuring urinary 6-sulphatoxymelatonin levels.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

[20]
.One method used for measuring melatonin offset is to analyse a sequence of urine samples throughout the morning for the presence of the melatonin metabolite 6-sulphatoxymelatonin (aMT6s).^ The QDC method is useful for analyzing glycemic control in patients on IIT. Diagnostic utility of daytime salivary melatonin levels in Smith-Magenis syndrome.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Samples were collected starting 12-hours before surgery and throughout the following 72-hours, using a CMA 600 (CMA(R) - Solna, Sweden) microdialysis analyser.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Furthermore, melatonin secretion rhythm as a Circadian phase marker was assessed by measuring urinary 6-sulphatoxymelatonin levels.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

.Laberge et al. in Quebec in 1997 used this method in a study that confirmed the frequently found delayed circadian phase in healthy adolescents.^ Jan 6; 303(1): 19 Chang HJ Circadian rhythm s in Neurospora crassa: Dynamics of the clock component frequency visualized using a fluorescent reporter.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ On the other hand, the Circadian melatonin rhythm was significantly phase-delayed in the both groups, showing internal desynchronization of the Circadian rhythm s.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Katzenberg et al suggested genetic correlation (ie, clock polymorphisms) to circadian rhythm patterns.
  • Sleeplessness and Circadian Rhythm Disorder: eMedicine Neurology 10 February 2010 13:27 UTC emedicine.medscape.com [Source type: Academic]

[21]

Outside the "master clock"

.More-or-less independent circadian rhythms are found in many organs and cells in the body outside the suprachiasmatic nuclei (SCN), the "master clock". These clocks, called peripheral oscillators, are found in the oesophagus, lungs, liver, pancreas, spleen, thymus, and the skin.^ These can be temporary or due to a lack in the circadian rhythm in the body.
  • Circadian Rhythms and Sleep | Serendip's Exchange 10 February 2010 13:27 UTC serendip.brynmawr.edu [Source type: FILTERED WITH BAYES]

^ The Circadian rhythm of body temperature.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Central to the timekeeping mechanism of the body and mind are Suprachaismatic nuclei or SCN. The SCN is the master clock the circadian rhythm that controls all other rhythms of the body.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

[22] Though oscillators in the skin respond to light, a systemic influence has not been proven so far.[23][24] .There is some evidence that also the olfactory bulb and prostate may experience oscillations when cultured, suggesting that also these structures may be weak oscillators.^ There is some evidence that although these clock genes are different for different functions they maybe quite similar in their composition (Lee et al., 1998).
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

.Furthermore, liver cells, for example, appear to respond to feeding rather than to light.^ For example, when functioning properly, the human circadian rhythm will respond to the morning light of a new day.
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^ For example, the aversion of a nocturnal rodent to bright light results in its activity onset appearing to coincide with the absence of light, or “lights off,” when the animal actually has been awake for hours.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.Cells from many parts of the body appear to have freerunning rhythms.^ The digestive tract may be controlled by a rhythm, as is a single cell, and as does a part of a cell such as a nucleus.
  • Terms of Circadian Rhythm 10 February 2010 13:27 UTC www.colostate.edu [Source type: Academic]

Light and the biological clock

.Light resets the biological clock in accordance with the phase response curve (PRC).^ Any suggestions for resetting his biological body clock ...
  • Circadian Rhythms and Sleep | Serendip's Exchange 10 February 2010 13:27 UTC serendip.brynmawr.edu [Source type: FILTERED WITH BAYES]

^ Circadian Light Therapy Resets and Stabilizes the Circadian Clock Light is the most effective way to synchronize the body with the twenty-four hour day.
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^ In addition to resetting the clock, light has a direct and positive impact by increasing brain serotonin levels.
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.Depending on the timing, light can advance or delay the circadian rhythm.^ Circadian Rhythm - Time 4-26-07 .
  • Circadian Rhythm on Yahoo! Music 10 February 2010 13:27 UTC new.music.yahoo.com [Source type: FILTERED WITH BAYES]

^ Figure 1 Circadian rhythm responses to light.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Finally, not only may alcohol consumption affect circadian rhythms, but circadian factors, such as the light-dark cycle, may also influence alcohol consumption.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.Both the PRC and the required illuminance vary from species to species and lower light levels are required to reset the clocks in nocturnal rodents than in humans.^ Circadian Light Therapy Resets and Stabilizes the Circadian Clock Light is the most effective way to synchronize the body with the twenty-four hour day.
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^ Virtually all species show similar phase-dependent-resetting responses to light, which can be expressed as a phase-response curve.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ This hypothesis was supported by the demonstration in a number of species that the expression of genes and the production of proteins encoded by those genes were required for normal clock function.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.Lighting levels that affect circadian rhythm in humans are higher than the levels usually used in artificial lighting in homes.^ Figure 1 Circadian rhythm responses to light.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Circadian rhythm disorders and light therapy .
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

^ Levels and Circadian rhythm of PER2 in Apc(Min/+) mouse intestine are markedly decreased, and selective abnormalities in intestinal clock gene and clock-controlled gene expression are seen.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

.According to some researchers[25] the illumination intensity that excites the circadian system has to reach up to 1000 lux striking the retina.^ The challenge for researchers and clinicians now is to determine not only the cause but also the consequences for human health and disease of disruptions in the temporal organization of the circadian system.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ To further elucidate the regulation of circadian rhythms, researchers need a better understanding of the nature of circadian signal output from the SCN and of how these output signals may be modified once they reach their target systems.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.In addition to light intensity, wavelength (or colour) of light is a factor in the entrainment of the body clock.^ Circadian Light Therapy Resets and Stabilizes the Circadian Clock Light is the most effective way to synchronize the body with the twenty-four hour day.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ In addition to resetting the clock, light has a direct and positive impact by increasing brain serotonin levels.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
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^ Both of these studies concluded that specific wavelengths, intensities and color spectrum of light, (not available in ordinary room lighting) could reset the circadian clock and create circadian balance.
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.Melanopsin is most efficiently excited by blue light, 420–440 nm[26] according to some researchers while others have reported 470–485 nm.^ Some studies demonstrate that narrow-band short wavelength "blue" light, naturalistic dawn simulation, and high-density negative air ionization are effective.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Thus, exposure to brighter light intensities can lengthen the period in some species and shorten it in other species.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.It is thought that the direction of the light may have an effect on entraining the circadian rhythm;[25] light coming from above, resembling an image of a bright sky, has greater effect than light entering our eyes from below.^ Figure 1 Circadian rhythm responses to light.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Circadian rhythm disorders and light therapy .
  • Circadian Rhythm - Kosmix : Reference, Videos, Images, News, Shopping and more... 10 February 2010 13:27 UTC www.kosmix.com [Source type: Academic]

^ Finally, not only may alcohol consumption affect circadian rhythms, but circadian factors, such as the light-dark cycle, may also influence alcohol consumption.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.According to a 2010 study completed by the Lighting Research Center, daylight has a direct effect on circadian rhythms and, consequently, on performance and well-being.^ Figure 1 Circadian rhythm responses to light.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Finally, not only may alcohol consumption affect circadian rhythms, but circadian factors, such as the light-dark cycle, may also influence alcohol consumption.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ The sleep-wake cycle, which constitutes a central aspect of circadian rhythms in particular, is subject to modification by alcohol; alcohol’s effects on the sleep of nonalcoholics and alcoholics are discussed by Drs.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.The research showed that students who experience disruption in lighting schemes in the morning consequently experience disruption in sleeping patterns.^ Research described in the open access journal BMC Neuroscience showed that red light, which does not stimulate the circadian system, is just as effective at...
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ Because CRD's disrupt the sleep pattern, they may contribute to narcolepsy, sleep apnea, snoring, etc.
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^ They may only experience a few hours of sleep each night, and feel worse in the morning time.
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.The change in sleeping patterns may lead to negatively impacted student performance and alertness.^ Patients with irregular sleep-wake cycles demonstrate no consistent pattern of alertness.
  • Sleeplessness and Circadian Rhythm Disorder: eMedicine Neurology 10 February 2010 13:27 UTC emedicine.medscape.com [Source type: Academic]

^ Doctors will sometimes prescribe lifestyle changes that encourage new sleep patterns or reduced stress.
  • Circadian Rhythm Disorder | LIVESTRONG.COM 10 February 2010 13:27 UTC www.livestrong.com [Source type: FILTERED WITH BAYES]

^ Because CRD's disrupt the sleep pattern, they may contribute to narcolepsy, sleep apnea, snoring, etc.
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.Removing circadian light in the morning delays the dim light melatonin onset by 6 minutes a day, for a total of 30 minutes for five days.^ Circadian Light Therapy Resets and Stabilizes the Circadian Clock Light is the most effective way to synchronize the body with the twenty-four hour day.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ At the same time circadian light therapy has a depressing affect on daytime melatonin.
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^ The Circadian rhythm in plasma melatonin was measured on the baseline day before phase-shift, on the 4th day of shift schedule and the 5th day of free-run.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

[27]

Enforced longer cycles

.Modern research under very controlled conditions has shown the human period for adults to be just slightly longer than 24 hours on average.^ For most animals, the timing of sleep and wakefulness under natural conditions is in synchrony with the circadian control of the sleep cycle and all other circadian-controlled rhythms.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Both of these observations raise the intriguing possibility that the homeostatic and circadian controls may be more interrelated than researchers previously thought.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ These studies conclude that, if left alone, healthy humans undergo changes based on an internal clock that is longer than twenty-four hours.
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.Czeisler et al. at Harvard found the range for normal, healthy adults of all ages to be quite narrow: 24 hours and 11 minutes ± 16 minutes.^ Typical values for a resting, healthy adult human are approximately 120 mmHg (16 kPa) systolic and 80 mmHg (11 kPa) diastolic (written as 120/80 mmHg, and spoken as "one twenty over eighty") with large individual variations.
  • High Blood Pressure Remedies from the Earth Clinic Community. 10 February 2010 13:27 UTC www.earthclinic.com [Source type: General]

^ The clinical term for this disorder is Advanced Circadian Rhythm Disorder or ACR. ACR happens when the body clock is running faster than a normal 24-hour period.
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^ In this case, the body clock is running slower than a normal circadian rhythm (24 hour period).
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

.The "clock" resets itself daily to the 24-hour cycle of the Earth's rotation.^ Circadian Light Therapy Resets and Stabilizes the Circadian Clock Light is the most effective way to synchronize the body with the twenty-four hour day.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ The 24-hour cycling comes about as the BMAL1 and Clock proteins induce increased production of Per and Cry proteins.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Such a curve can predict the manner in which an organism will entrain not only to shifts in the light-dark cycles but also to unusual light cycles, such as non-24-hour cycles or different light:dark ratios.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

[28]
.The 28-hour day is presented as a concept of time management.^ Zeitgeber time (ZT): A standardized 24-hour notation of the phase in an entrained circadian cycle in which ZT 0 indicates the beginning of day, or the light phase, and ZT 12 is the beginning of night, or the dark phase.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ The sleep schedule was phase-advanced by 8 hours from their habitual sleep times for 4 days, which was followed by a free-run session for 6 days where the subjects were deprived of time cues.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

[29] .It builds on the fact that the week of seven days at 24 hours and a "week" of six days at 28 hours both equal a week of 168 hours.^ Zeitgeber time (ZT): A standardized 24-hour notation of the phase in an entrained circadian cycle in which ZT 0 indicates the beginning of day, or the light phase, and ZT 12 is the beginning of night, or the dark phase.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Because the body clock is running too fast, ACR sufferers tend to run out of energy before the 'day' or 24 hour period is through.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ Circadian: A term derived from the Latin phrase “circa diem,” meaning “about a day”; refers to biological variations or rhythms with a cycle of approximately 24 hours.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.To live on the 28-hour day and six-day week would require staying awake for 19 to 20 hours and sleeping for eight to nine hours.^ The sleep schedule was phase-advanced by 8 hours from their habitual sleep times for 4 days, which was followed by a free-run session for 6 days where the subjects were deprived of time cues.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

.Each "day" on this system has a unique light/dark pattern.^ Zeitgeber time (ZT): A standardized 24-hour notation of the phase in an entrained circadian cycle in which ZT 0 indicates the beginning of day, or the light phase, and ZT 12 is the beginning of night, or the dark phase.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.Studies by Nathaniel Kleitman[30] in 1938 and by Derk-Jan Dijk and Charles Czeisler[31][32] in 1994/5 have put human subjects on enforced 28-hour sleep–wake cycles, in constant dim light and with other time cues suppressed, for over a month.^ The sleep-wake cycle, which constitutes a central aspect of circadian rhythms in particular, is subject to modification by alcohol; alcohol’s effects on the sleep of nonalcoholics and alcoholics are discussed by Drs.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ When the sleep-wake cycle is out of phase with the rhythms that are con-trolled by the circadian clock (e.g., during shift work or rapid travel across time zones), adverse effects may ensue.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Jan 6; Wu T, Ni Y, Dong Y, Xu J, Song X, Kato H, Fu Z Although studies involving the Circadian response to external time cues indicate that the peripheral clocks are dominated mainly by food cues, whether and how changes in the light and food cues affect the Circadian rhythm of the renal clock is still largely unknown.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

.Because normal people cannot entrain to a 28-hour day,[33] this is referred to as a forced desynchrony protocol.^ Zeitgeber time (ZT): A standardized 24-hour notation of the phase in an entrained circadian cycle in which ZT 0 indicates the beginning of day, or the light phase, and ZT 12 is the beginning of night, or the dark phase.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Circadian: A term derived from the Latin phrase “circa diem,” meaning “about a day”; refers to biological variations or rhythms with a cycle of approximately 24 hours.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Because the body clock is running too fast, ACR sufferers tend to run out of energy before the 'day' or 24 hour period is through.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

.Sleep and wake episodes are uncoupled from the endogenous circadian period of about 24.18 hours and researchers are allowed to assess the effects of circadian phase on aspects of sleep and wakefulness including sleep latency and other functions.^ The hypothesis that such uncontrolled geomagnetic cues might play a role in the persistence of rhythmicity can be refuted by a second characteristic feature of circadian rhythms: These cycles persist with a period of close to, but not exactly, 24 hours.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ The sleep-wake cycle, which constitutes a central aspect of circadian rhythms in particular, is subject to modification by alcohol; alcohol’s effects on the sleep of nonalcoholics and alcoholics are discussed by Drs.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ MISTLBERGER, R.E.; BERGMANN, B.M.; AND RECHTSCHAFFEN, A. Relationships among wake episode lengths, contiguous sleep episode lengths, and electroencephalographic delta waves in rats with suprachiasmatic nuclei lesions.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

[34]
.Early research into circadian rhythms suggested that most people preferred a day closer to 25 hours when isolated from external stimuli like daylight and timekeeping.^ Circadian Light Therapy Resets and Stabilizes the Circadian Clock Light is the most effective way to synchronize the body with the twenty-four hour day.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ Central to the timekeeping mechanism of the body and mind are Suprachaismatic nuclei or SCN. The SCN is the master clock the circadian rhythm that controls all other rhythms of the body.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ Depressive Disorders Clinical Depression Researchers report that depression is closely tied to circadian rhythm disorders because almost all depression sufferers have sleep problems and feel worse at a particular time of day as well as in the winter.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

.Early investigators determined the human circadian period to be 25 hours or more.^ Human’s Free-running rhythm Beginning in 1980, several studies were conducted to learn more about the human circadian rhythm.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]

^ The challenge for researchers and clinicians now is to determine not only the cause but also the consequences for human health and disease of disruptions in the temporal organization of the circadian system.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ In this case, the body clock is running slower than a normal circadian rhythm (24 hour period).
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

.They went to great lengths to shield subjects from time cues and daylight, but they were not aware of the effects of indoor electric lights.^ Diurnal rhythms may persist when the organism is placed in an environment devoid of time cues, such as constant light or constant darkness.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Circadian rhythms are self-sustaining (i.e., free running), meaning that they will persist when the organism is placed in an environment devoid of time cues, such as constant light or constant darkness.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ A third characteristic property of circadian rhythms is their ability to be synchronized, or entrained, by external time cues, such as the light-dark cycle.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.The subjects were allowed to turn on light when they were awake and to turn it off when they wanted to sleep.^ If you are awake, turn on the light and read something difficult or mildly boring.
  • Dr. Michael J. Breus: Sleep Hygiene 101: How To Ensure A Better Night's Rest 10 February 2010 13:27 UTC www.huffingtonpost.com [Source type: General]

^ For example, the aversion of a nocturnal rodent to bright light results in its activity onset appearing to coincide with the absence of light, or “lights off,” when the animal actually has been awake for hours.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ One of the easiest things to help you go back to sleep, biologically: Do not turn on the lights!
  • Dr. Michael J. Breus: Sleep Hygiene 101: How To Ensure A Better Night's Rest 10 February 2010 13:27 UTC www.huffingtonpost.com [Source type: General]

.Electric light in the evening delayed their circadian phase.^ One of these properties is the rhythms’ ubiquity in nature: Circadian rhythms exist in a broad array of biological processes and organisms, with similar properties and even similar phase-response curves to light.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Exposure to light during the early part of the animal’s night causes a phase delay, whereas exposure to light in the latter part of the animal’s night causes a phase advance.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ On the other hand, the Circadian melatonin rhythm was significantly phase-delayed in the both groups, showing internal desynchronization of the Circadian rhythm s.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

These results became well known.[28] .Researchers allowed subjects to keep electric lighting on in the evening, as it was thought at that time that a couple of 60W bulbs would not have a resetting effect on the circadian rhythms of humans.^ Figure 1 Circadian rhythm responses to light.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ B. Resetting the circadian rhythm .
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Circadian Light Therapy Resets and Stabilizes the Circadian Clock Light is the most effective way to synchronize the body with the twenty-four hour day.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

.More recent research[citation needed] has shown that adults have a built-in day, which averages just over 24 hours, that indoor lighting does affect circadian rhythms and that most people attain their best-quality sleep during their chronotype-determined sleep periods.^ How does light affect you?
  • How do I fix my circadian rhythm? - Other Topics Forum - Discuss Pop Culture, Arts and Entertainment 10 February 2010 13:27 UTC forumserver.twoplustwo.com [Source type: General]

^ Figure 1 Circadian rhythm responses to light.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Circadian Light Therapy Resets and Stabilizes the Circadian Clock Light is the most effective way to synchronize the body with the twenty-four hour day.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

Human health

.Timing of medical treatment in coordination with the body clock may significantly increase efficacy and reduce drug toxicity or adverse reactions.^ Apparently, the body clock begins to cycle too quickly during the second half of the menstrual cycle, and may be a reason why these reproductive hormones deplete too quickly.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ When the sleep-wake cycle is out of phase with the rhythms that are con-trolled by the circadian clock (e.g., during shift work or rapid travel across time zones), adverse effects may ensue.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Light therapy and antidepressant medication are effective treatment options, with limited evidence for the efficacy of psychotherapy.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

.For example, appropriately timed treatment with angiotensin converting enzyme inhibitors (ACEi) may reduce nocturnal blood pressure and also benefit left ventricular (reverse) remodelling.^ If you would be courteous enough to email me a respone and give me your opinion as to what I may be doing wrong to control my blood pressure, I would truly appreciate it!
  • High Blood Pressure Remedies from the Earth Clinic Community. 10 February 2010 13:27 UTC www.earthclinic.com [Source type: General]

^ Took 2 tsp 3 times a day for 3 weeks and it did absolutely nothing to lower my blood pressure.
  • High Blood Pressure Remedies from the Earth Clinic Community. 10 February 2010 13:27 UTC www.earthclinic.com [Source type: General]

^ I decided to read up a little more about the benefits of ACV for my high blood pressure.
  • High Blood Pressure Remedies from the Earth Clinic Community. 10 February 2010 13:27 UTC www.earthclinic.com [Source type: General]

[citation needed]
A short nap during the day does not affect circadian rhythms.
.A number of studies have concluded that a short period of sleep during the day, a power-nap, does not have any effect on normal circadian rhythm, but can decrease stress and improve productivity.^ Because the circadian rhythm influences so much of how a person feels or sleeps, if a person desires optimal health, they need to manage their circadian rhythm.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
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^ The sleep-wake cycle, which constitutes a central aspect of circadian rhythms in particular, is subject to modification by alcohol; alcohol’s effects on the sleep of nonalcoholics and alcoholics are discussed by Drs.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Since the discovery of the Clock gene in mice, the list of circadian clock genes identified in mammals has grown in a remarkably short period of time (see table 1).
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

[35][36]
.There are many health problems associated with disturbances of the human circadian rhythm, such as seasonal affective disorder (SAD), delayed sleep phase syndrome (DSPS) and other circadian rhythm disorders.^ Circadian Rhythm Disorders Out of Synch: what is circadian rhythm disorder?
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ Antidepressant action of melatonin in the treatment of Delayed Sleep Phase Syndrome.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ CRD's contribute to other sleep disorders .
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]

[37] .Circadian rhythms also play a part in the reticular activating system, which is crucial for maintaining a state of consciousness.^ Although studies of unicellular organisms point to the cellular nature of the system generating circadian rhythms, the circadian pacemaker in higher organisms is located in cells of specific structures of the organism.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ These issues also include the question of what role alcohol may play in the disruption of normal circadian rhythms and the biological clock.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Thus, Per1 and Clock may play important roles in the light-induced resetting of the Circadian rhythm s in the kidney.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

.In addition, a reversal in the sleep–wake cycle may be a sign or complication of uremia,[38] azotemia or acute renal failure.^ Their sleep-wake cycles were monitored everyday by polysomnography and/or weight sensor equipped with a bed.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ When the sleep-wake cycle is out of phase with the rhythms that are con-trolled by the circadian clock (e.g., during shift work or rapid travel across time zones), adverse effects may ensue.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ The sleep-wake cycle, which constitutes a central aspect of circadian rhythms in particular, is subject to modification by alcohol; alcohol’s effects on the sleep of nonalcoholics and alcoholics are discussed by Drs.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.Studies have also shown that light has a direct effect on human health because of the way it influences the circadian rhythms.^ Figure 1 Circadian rhythm responses to light.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ One early pioneer was Curt Paul Richter, a professor of psychobiology at Johns Hopkins Medical School whose innovative concepts are the foundation for established concepts and methods for studying circadian rhythms in humans.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ Circadian Light Therapy Resets and Stabilizes the Circadian Clock Light is the most effective way to synchronize the body with the twenty-four hour day.
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

[39][40][41][42]

Disruption

Disruption to rhythms usually has a negative effect. .Many travellers have experienced the condition known as jet lag, with its associated symptoms of fatigue, disorientation and insomnia.^ The symptoms of jet lag are similar to depression, and will persist until the body clock can respond to the new time.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
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^ When our body is out of sync with nature, we suffer from a Circadian Rhythm Disorder , of which Chronic Fatigue, SAD, Depression, Anxiety, and Insomnia are the most common symptoms .
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ In addition to the sleep disturbances associated with jet lag or shift work, sleep disorders can occur for many other known and unknown reasons.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

.A number of other disorders, for example bipolar disorder and some sleep disorders, are associated with irregular or pathological functioning of circadian rhythms.^ Circadian Rhythm Disorders Out of Synch: what is circadian rhythm disorder?
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ Following are some examples of how circadian rhythm disorder affects specific kinds of mood and sleep disorders.
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^ CRD's contribute to other sleep disorders .
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]

.Recent research suggests that circadian rhythm disturbances found in bipolar disorder are positively influenced by lithium's effect on clock genes.^ Circadian Rhythm Disorders Out of Synch: what is circadian rhythm disorder?
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ Illnesses caused by Circadian Rhythm Disorder .
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ What causes circadian rhythm disorder?
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
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[43]
.Disruption to rhythms in the longer term is believed to have significant adverse health consequences on peripheral organs outside the brain, particularly in the development or exacerbation of cardiovascular disease.^ Disruptions of the biological rhythms can impair the health and well-being of the organism.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ The challenge for researchers and clinicians now is to determine not only the cause but also the consequences for human health and disease of disruptions in the temporal organization of the circadian system.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

[44] .The suppression of melatonin production associated with the disruption of the circadian rhythm may increase the risk of developing cancer.^ Shift work and nocturnal light exposure are associated with Circadian clock disruption and with increased cancer risk.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

^ Finally, not only may alcohol consumption affect circadian rhythms, but circadian factors, such as the light-dark cycle, may also influence alcohol consumption.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ The authors have previously found that altered patterns of Circadian rest-activity rhythm s are significantly and independently associated with the severity of fatigue and anorexia in patients with metastatic colorectal cancer.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

[45]

Effect of drugs

.Circadian rhythms and clock genes expressed in brain regions outside the SCN may significantly influence the effects produced by drugs such as cocaine.^ Finally, not only may alcohol consumption affect circadian rhythms, but circadian factors, such as the light-dark cycle, may also influence alcohol consumption.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

^ Because the circadian rhythm influences so much of how a person feels or sleeps, if a person desires optimal health, they need to manage their circadian rhythm.
  • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
  • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

^ The sleep-wake cycle, which constitutes a central aspect of circadian rhythms in particular, is subject to modification by alcohol; alcohol’s effects on the sleep of nonalcoholics and alcoholics are discussed by Drs.
  • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

[46][47] .Moreover, genetic manipulations of clock genes profoundly affect cocaine's actions.^ Moreover, the re-entrainment of the clock genes was greatly enhanced after the reversal of both the feeding schedule and the LD cycle.
  • View Pathway: Circadian rhythm 10 February 2010 13:27 UTC apropos.mcw.edu [Source type: Academic]

[48]

See also

References

Bibliography

  • Aschoff J (ed.) (1965) Circadian Clocks. North Holland Press, Amsterdam
  • Avivi A, Albrecht U, Oster H, Joel A, Beiles A, Nevo E (November 2001). ."Biological clock in total darkness: the Clock/MOP3 circadian system of the blind subterranean mole rat".^ These issues also include the question of what role alcohol may play in the disruption of normal circadian rhythms and the biological clock.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    Proceedings of the National Academy of Sciences of the United States of America 98 (24): 13751–6. doi:10.1073/pnas.181484498. PMID 11707566.
     
  • Avivi A, Oster H, Joel A, Beiles A, Albrecht U, Nevo E (September 2002). ."Circadian genes in a blind subterranean mammal II: conservation and uniqueness of the three Period homologs in the blind subterranean mole rat, Spalax ehrenbergi superspecies".^ Since the discovery of the Clock gene in mice, the list of circadian clock genes identified in mammals has grown in a remarkably short period of time (see table 1).
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    ^ However, considerable frustration ensued as researchers sought to isolate the equivalent genes in mammals (i.e., mammalian homologs).
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    Proceedings of the National Academy of Sciences of the United States of America 99 (18): 11718–23. doi:10.1073/pnas.182423299. PMID 12193657.
     
  • Ditty JL, Williams SB, Golden SS (2003). ."A cyanobacterial circadian timing mechanism". Annual Review of Genetics 37: 513–43. doi:10.1146/annurev.genet.37.110801.142716.^ Annual Review of Genetics 34:533-562, 2000.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    ^ LOWREY, P.L., AND TAKAHASHI, J.S. Genetics of the mammalian circadian system: Photic entrainment, circadian pacemaker mechanisms, and post-translational control.
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    .PMID 14616072. 
  • Dunlap JC, Loros J, DeCoursey PJ (2003) Chronobiology: Biological Timekeeping.^ The mechanisms underlying the biological timekeeping systems and the potential consequences of their failure are among the issues addressed by researchers in the field of chronobiology.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    Sinauer, Sunderland
  • Dvornyk V, Vinogradova O, Nevo E (March 2003). ."Origin and evolution of circadian clock genes in prokaryotes".^ Since the discovery of the Clock gene in mice, the list of circadian clock genes identified in mammals has grown in a remarkably short period of time (see table 1).
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    ^ As discussed previously, the properties of circadian clocks suggested cyclic changes in the expression of certain genes as a possible mechanism underlying the internal pacemaker.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    ^ Some of the pro-posed circadian clock genes have been identified solely based on their similarity in sequence to Drosophila clock genes and have not been confirmed to have clock function based on an examination of the behavior of the corresponding mutants.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    Proceedings of the National Academy of Sciences of the United States of America 100 (5): 2495–500. doi:10.1073/pnas.0130099100. PMID 12604787.
     
  • Koukkari WL, Sothern RB (2006) Introducing Biological Rhythms. Springer, New York
  • Martino T, Arab S, Straume M, et al. (April 2004). ."Day/night rhythms in gene expression of the normal murine heart". Journal of Molecular Medicine 82 (4): 256–64. doi:10.1007/s00109-003-0520-1.^ The first few days will be hard but after a while you will find you are a dapting to a normal pattern and you're body is telling you to ge to sleep at a certain every time every night.
    • How do I fix my circadian rhythm? - Other Topics Forum - Discuss Pop Culture, Arts and Entertainment 10 February 2010 13:27 UTC forumserver.twoplustwo.com [Source type: General]

    ^ This hypothesis was supported by the demonstration in a number of species that the expression of genes and the production of proteins encoded by those genes were required for normal clock function.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    PMID 14985853.
     
  • Refinetti R (2006) Circadian Physiology, 2nd ed. CRC Press, Boca Raton
  • Takahashi JS, Zatz M (September 1982). "Regulation of circadian rhythmicity". Science 217 (4565): 1104–11. doi:10.1126/science.6287576. PMID 6287576. 
  • Tomita J, Nakajima M, Kondo T, Iwasaki H (January 2005). ."No transcription-translation feedback in circadian rhythm of KaiC phosphorylation". Science 307 (5707): 251–4. doi:10.1126/science.1102540.^ The Master Clock Significant progress is being made in the field of chronobiology, the formal name for the medical science that studies circadian rhythms.
    • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

    ^ Circadian science The study of circadian rhythms dates back to the 19 th century.
    • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

    ^ Significant progress is being made in the field of chronobiology, the formal name for the medical science that studies circadian rhythms.
    • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]

    PMID 15550625.
     
  • Moore-Ede, Martin C.; Sulszman, Frank M.; Fuller, Charles A. (1982). .The Clocks that Time Us: Physiology of the Circadian Timing System.^ Since the discovery of the Clock gene in mice, the list of circadian clock genes identified in mammals has grown in a remarkably short period of time (see table 1).
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    Cambridge, MA: Harvard University Press. ISBN 0-674-13581-4.
     

Notes

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External links

  • Circadian rhythm at the Open Directory Project
  • Forger D, Gonze D, Virshup D, Welsh DK (June 2007). ."Beyond intuitive modeling: combining biophysical models with innovative experiments to move the circadian clock field forward". Journal of Biological Rhythms 22 (3): 200–10. doi:10.1177/0748730407301823.^ Pregnancy and postpartum depressions affect the body clock Researchers have also noted a strong connection between circadian rhythms and pregnancy related depressions.
    • Circadian Rhythms and Circadian Rhythm Disorders treated with Light Therapy 10 February 2010 13:27 UTC www.lighttherapy.com.au [Source type: Academic]
    • Circadian Rhythm CRD > ADS SHOP, Anxiety Depression Solutions, SAD, Insomnia, Sleep Disorder, Depression.SAD, Depression, Insomnia, SAD, S.A.D, Lightbox, Light, Lightboxes, Lamp, S.A.D Lamps, Daylight Alarm Clock, Anxiety, Seasonal Affective Disorder, Winter Blues 10 February 2010 13:27 UTC www.anxiety-depression-solutions.co.uk [Source type: FILTERED WITH BAYES]

    ^ These issues also include the question of what role alcohol may play in the disruption of normal circadian rhythms and the biological clock.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    ^ Every scientific field has its specific terminology; the scientific area of biological rhythms and sleep is no exception.
    • Overview of Circadian Rhythms 10 February 2010 13:27 UTC pubs.niaaa.nih.gov [Source type: Academic]

    PMID 17517910.
     
  • Rodrigo G, Carrera J, Jaramillo A (2007). "Evolutionary mechanisms of circadian clocks". Central European Journal of Biology 2 (2): 233–253. doi:10.2478/s11535-007-0016-z. 
  • Lighting Research Center, Light & Health Program

Simple English

A circadian rhythm is a rhythm that repeats about every 24 hours. Plants and animals have these built-in cycles which allow them to flower at the right time, sleep at the right time etc. The word "circadian" comes from the Latin circa, "around", and diem or dies, "day", meaning "about a day." The study of biological time-keeping rhythms such as daily, tidal, weekly, seasonal, and annual rhythms, is called chronobiology.

Circadian rhythms are "built-in" so that, without time signals from the environment, they keep time at the rate of about 24-hour periods. When kept in total darkness, plants and animals continue to behave by the built-in period which is about 24 hours. The rhythms are also affected and re-set by time signals such as daylight and the length of the day and the night. It is important that the rhythms be re-set regularly to the natural light/dark cycle. Adult humans of all ages have a circadian rhythm which averages 24 hours and 11 minutes.

The circadian rhythms, also called the "biological clock" or the "body clock", of humans and other animals, regulate many bodily functions including feeding, sleeping, body temperature and hormone production.

The primary body clock in humans and other mammals is located in the suprachiasmatic nucleus (or nuclei) (SCN), a pair of groups of cells in the hypothalamus in the brain. Destruction of the SCN results in the complete absence of a regular sleep/wake rhythm. The SCN receives information about light through the eyes and directs the pineal gland to release the hormone melatonin at night.

Some people have circadian rhythm sleep disorders which cause them to sleep much too early (Advanced sleep-phase syndrome, ASPS), much too late (Delayed sleep-phase syndrome, DSPS) or in several bouts throughout the day and night (Irregular sleep-wake disorder).


Citable sentences

Up to date as of December 29, 2010

Here are sentences from other pages on Circadian rhythm, which are similar to those in the above article.








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