In the sentence about chronobiology, "weekly rhythms" are mentioned. Incidentally, this sentence appears to have been copied verbatim from the comment above me by Jclerman. I was not aware of any examples of these (after all, a week is an artificial construct, although I'll grant it's possible that some natural rhythms might coincidentally last one week). Was "monthly rhythms" perhaps intended? Robin S 00:27, 15 July 2007 (UTC) reply

Weekly was, indeed, intended. See: "Sleep Research" (Brain Information Service/Brain Research Institute, UCLA), vol. 14, p.303 (1985): "SLEEP IS A DELIGHT ON SABBATH: CHRONOBIOLOGIC ORIGIN OF THE WEEK ?", by Juan-Carlos Lerman [a version with corrected typos is available by email to those who request it]. Jclerman 06:41, 15 July 2007 (UTC) reply

Thanks once again for sending me that paper. It made an interesting read and I look forward to researching more information about the phenomenon. Robin S 07:34, 15 July 2007 (UTC) reply

I just want to know when my circadian rythms are telling me to go to sleep, as the RTA ad in Australia has stopped playing and I forgot what the best time to go to sleep is. The reason I am wanting to know this is I have my HSC in 10 days and I want to know how to best study and not study when my circadian rhythms are telling me I should be sleeping. TeePee-20.7 11:37, 9 October 2007 (UTC) reply

quote:"if there were no sunlight, the behavior would not persist." this is strictly an opinion and should not be worded that way, it should say "the behavior would likely not persist" or simply be excluded from the article as an example, there are some in the world who do, in fact, wear sunglasses in the day - The blind for example. —Preceding unsigned comment added by 71.112.198.228 ( talk) 11:38, 6 May 2008 (UTC) reply

You're right, and that rather lame example has always bothered me, but I hadn't come up with a good example to replace it. I hope that my rewording of that section is satisfactory. -- Hordaland ( talk) 15:14, 6 May 2008 (UTC) reply

Doesn't the circadian behavior persist when entrained by other zeitgebers than light, such as feeding, social interactions, etc.? Jclerman ( talk) 16:25, 6 May 2008 (UTC) reply

Indeed, but does the present formulation preclude that? There seem to be some animals which are (exclusively?) entrained by some of these "other" cues. (I read recently that some bats in cave colonies never are exposed to light at all other than moon- and starlight. One or two individuals awaken and fly out to check the level of dusk; the others are signaled by them when it's dark.) There's perhaps some overemphasis on light these last decades as a reaction to earlier assumptions that humans were/are so very special that rules applicable to other mammals don't apply to us. -- Hordaland ( talk) 18:12, 6 May 2008 (UTC) reply

A rhythm cannot be considered endogenous before it has been tested in conditions without external periodic input.

• Does this mean that after testing (the system?), it doesn't matter what the results of the test are?

Jclerman ( talk) 16:21, 6 May 2008 (UTC) reply

Um. Changed before to unless. Does that solve the problem? -- Hordaland ( talk) 17:53, 6 May 2008 (UTC) reply

Concerning the page on circadian rhythms, there is an error in information. It is noted that the Citric Acid Cycle aka the Krebs Cycle is the continual breakdown of glycogen. This is completely false. To enter the krebs cycle, Glycolysis (the breakdown of glycogen/glucose) has to have a final product of pyruvate. Pyruvate must then be converted to Acetyl CoA and it is the Acetyl CoA that enters the Krebs Cycle. The Krebs cycle is a means of electron transport to the electron transport chain for rephosphorylation of ADP to ATP. —Preceding unsigned comment added by Dr. exphys ( talk • contribs) 12:58, 5 June 2008 (UTC) reply

Circadian Rhythm, Origin And Nature

Circadian Rhythm: Genes Are Organisms, Not Molecular Contraptions

A. "Molecular Basis And Regulation Of Circadian Rhythms In Plants"

http://www.eurekalert.org/pub_releases/2008-07/asop-pit062408.php

B. A mechanisms of energy absorption, by which archae genes became and function as active energy packages, i.e. became living organisms:

http://www.physorg.com/news115053032.html

C. Chromosomes coil more tightly during the day and relax at night.

http://www.physorg.com/news114872572.html

D. My elsewhere suggestions re the origin of Circadian Rhythm applies neatly in the above two cases. I posit that the mechanism involved in the absorption of energy by the archae genes is the mechanism of phasing of RNA-type olygomers into replicating primal Earth organisms, individual independent genes. This phasing from chemicals to living organisms was the genesis of Earth's biosphere.

Science will comprehend one day that genes are primal and genomes are evolved organisms.

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.

For the archaic genes, parents of all Earth's Life, direct sunlight was the only source of energy, and it was available to them at different times of the day in accordance with their location on Earth...

Dov Henis

http://blog.360.yahoo.com/blog-P81pQcU1dLBbHgtjQjxG_Q--?cq=1 Dov Henis ( talk) 06:24, 8 July 2008 (UTC) reply

• This text, which was inserted at the top of the article, appears to have been meant for the talk page. -- Hordaland ( talk) 06:39, 8 July 2008 (UTC) reply

Did you know that "24 hours" equivalent exists only in a very few languages of the world?

Lithuania: para (PARA') ( literal translation almost impossible** ) Russia: sutki (CY'TKU) ( literal translation impossible** ) Greece: Nychthemeron (literally night-day) Latin: Circadia (?)

• • Although Russians have a word "pora" ("pora idti" = "it's time to go") which means "time now to begin something" and Lithuanians (not related to Russians linguistically) have a word "pora" which means "a couple; a pair". If accent on PO:'RA then "a pair" but if PORA' then "a couple" (man and wife).

Any other language that you might know has similar word for 24hrs? It's curious that all these German, Italian, French languages don't have (as much as I know) a singular word for "daynight" including English! I suppose CIRCADIA is a Latin equivalent which has been created recently or is it an older word? —Preceding unsigned comment added by Audriust ( talk • contribs) 18:05, 13 July 2008 (UTC) reply

I don't think I've ever seen "circadia" used as a word (noun) before. Circadian is an adjective, coined a few decades ago. Circa means approximately and some form of die(s) means a day - as in 1 day + 1 night. And our endogenous circadian rhythms are approximate (averaging, among normal humans, 24 hr 11 min).

The Scandinavian languages do have a common (and useful), word, døgn or dygn, meaning 24 hours. -- Hordaland ( talk) 09:03, 6 September 2008 (UTC) reply

I was wondering if purposeful sleep deprivation as a form of torture should be added to the human health section, specifically the disruption portion. -- Thaddius ( talk) 04:42, 6 September 2008 (UTC) reply

There's a section, Torture, in the article Sleep deprivation. That's probably enough. Though keeping people in solitary with no daylight and purposefully mixing up lengths of days and times of meals has probably been tried, too. It wouldn't kill you, just drive you mad, I reckon. -- Hordaland ( talk) 09:22, 6 September 2008 (UTC) reply

Oh sweet. I was quite surprised that there was no mention here, but it makes sense that it'd be somewhere like sleep deprivation. Should just broaden my searches next time. -- Thaddius ( talk) 13:01, 8 September 2008 (UTC) reply

While looking up this article I saw two different citations of Czeisler's work that appear to contradict each other:

By recording the daily rhythms of hormones and body temperatures in 24 healthy young and old men and women over a one-month period, the researchers conclude that our internal clocks run on a daily cycle of 24 hours, 11 minutes.

"That’s slightly longer than 24 hours, but significantly shorter than past estimates of 25 hours," says Charles Czeisler, professor of medicine at the Harvard Medical School. "Researchers previously reported a range of 13 to 65 hours, with a median of 25 hours, 12 minutes. The variation between our subjects, with a 95 percent level of confidence, was no more than plus or minus 16 minutes, a remarkably small range."

June 15, 1999 [1]

Brain clocks vs. wall clocks

While checking the biological clocks of young, healthy subjects, Czeisler's team made what he calls, "an amazing observation." They knew that all people don't operate on the same clocklike 24-hour cycle, but the differences they found were startling. The 12 men and women in the Mars study, who were 22 to 33 years old, showed circadian periods ranging from 23 1/2 to 24 1/2 hours.

These natural differences cause some people to jump energetically out of bed in the morning, or to enjoy staying up late. Those with less than 24-hour brain rhythms tend to go to bed earlier and get up earlier. They are morning people. Those with a 24-hour-plus rhythm tend to stay up later. They are evening people. "Such individuals would have no trouble adjusting to a Martian day," Czeisler notes.

May 15, 2007 [2]

Couple of theories:

1. Outdated research in one
2. Badly cited
3. Referring to different biological mechanisms

I suspect the Czeisler's original publications will shed some light on this subject, looking for it...

-- Party on Aisle 7 ( talk) 20:48, 28 February 2009 (UTC) reply

What surprised me reading that 2nd article was this: Exposure to such bright light in the morning should also get evening people going faster in the morning. "We haven't tested this yet, but it should work in many cases," Czeisler says. It's hard to believe that he hasn't tested this yet; many others have. It's the standard treatment for Delayed sleep phase disorder, which, admittedly, is not within the normal range.

The contradiction you're pointing out must be between a circadian period for all normal human adults:

(1999) between 23h 55 min and 24h 27 min and

(2007) between 23h 30 min and 24h 30 min.

The first study is based on only 24 people, the 2nd on just twelve. Measurements may be more precise a decade later. There are also several ways of measuring the period: core body temperature rhythm, cortisol rhythm, onset / midpoint / offset of melatonin secretion, at least. So, IMO, that's not much of a contradiction.

See also: Chronotype. - Hordaland ( talk) 23:17, 28 February 2009 (UTC) reply

The comment(s) below were originally left at Talk:Circadian rhythm/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Last edited at 21:41, 28 April 2014 (UTC). Substituted at 20:19, 2 May 2016 (UTC)