User Tools

    To create and edit articles, please register and log-in

Main Menu

Main menu
Click categories to expand

A-Z listingplugin-autotooltip__plain plugin-autotooltip_bigA-Z listing

This is an alphabetical index of all content pages.

Other categories



Also see

Importance Ratings
Curator's rationale

Wikenigma supports:

Feeds etc
rss / xml feed
sitemap file
A-Z listing (archived)

Auto-Translate Site
Indexed under : Life Sciences / Human Body

Wikenigma - an Encyclopedia of Unknowns Wikenigma - an Encyclopedia of the Unknown

Core Clock

In humans, mammals, fish, insects, and very many other organisms, the 'Core Clock' which regulates variations in body functions is set to (approximately) 24 hours. This is the so-called Circadian Rhythm. - which in many organisms, is synchronised via daylight.

The clock is regulated via a brain area known as the Suprachiasmatic nucleus (SCN). Neurons in the SCN fire action potentials in a 24-hour rhythm. At mid-day, the firing rate reaches a maximum, and, during the night, it falls again.

Although the SCN has been extensively studied, and the majority of its internal processes are now well understood, fundamental questions still remain. Notably, how the gene expression cycle connects to the SCN's neural firing, and how the neurons in the SCN remain in synch.

[…] whereas the core circadian oscillatory mechanism was obscure only a decade ago, we now have a standard model for the innermost clockworks. Much remains to be determined. What are the requirements for being part of the core mechanistic loop? Because cellular redox state can influence Clock:Bmal1 DNA binding and is likely influenced by clock-controlled phenomena such as electrical activity, is redox potential in or out of the loop? The cell biology of core clock components, particularly regulation of their nuclear export and entry, remains poorly understood. We also do not understand why clock mechanisms have retained (at least) two interconnected loops. What advantages does this confer over a single-loop system? As more detail of the innermost clock’s working is discerned, a major challenge to the field has become stepping back out of the loops and determining how these core oscillations are translated into a temporal program for the whole organism.“

Source : CircadianRhythms:In the Loop at Last Science 6 June 2003 Vol. 300

For examples of current research on the core circadian clock, see the publications of the Partch Lab (archived) at the University of California Santa Cruz, Teams at the lab have recently managed to create an 'in vitrio' simulation of the the bio-clock of some bacteria (ref.) , which involves just 3 proteins, forming a biochemical 'oscillator.'

The intimate coupling between oscillator and input-output components blurs their distinction, although the extent to which this coupling can be generalized to eukaryotic clocks remains an open question.”
Source : Science Vol. 374, No. 6564

Circannual rhythm

In addition to the 'daily' clock, many organisms - from bacteria to mammals - also have a 'yearly' clock known as the Circannual Rhythm.

For example, many mammals moult their fur at certain times of year, or go into hibernation. Various experiments, in which mammals and birds have been kept in artificial indoor environments (i.e. without access to changes in sunlight and temperature etc) have shown that they can still maintain their annual cycle.

The implication is that the organisms have an internal ' clock' of some kind which runs over long timescales of a year or more.

The location of the physical circannual timer in organisms and how it works are almost entirely unknown.

See: Wikipedia

Also see Time Awarenessplugin-autotooltip__plain plugin-autotooltip_bigTime Awareness

"Anticipating events that will happen in the future is among the most important functions the brain performs. Indeed, it has been increasingly stressed that learning and memory are prospective brain functions; that is, they are only adaptive to the exte…
and Rhythm perceptionplugin-autotooltip__plain plugin-autotooltip_bigRhythm perception

Humans (and some other animals) have a sense of 'rhythm', i.e. the ability to detect and react with 'beats' in musical compositions. Professional drummers and percussionists can 'beat time' with accuracies of just a few milliseconds per beat (ref.

Importance Rating

    Share this page :

Dear reader : Do you have any suggestions for the site's content?

Ideas for new topics, and suggested additions / corrections for old ones, are always welcome.

If you have skills or interests in a particular field, and have suggestions for Wikenigma, get in touch !

Or, if you'd like to become a regular contributor . . . request a login password. Registered users can edit the entire content of the site, and also create new pages.

( The 'Notes for contributors' section in the main menu has further information and guidelines etc.)

Automatic Translation

You are currently viewing an auto-translated version of Wikenigma

Please be aware that no automatic translation engines are 100% accurate, and so the auto-translated content will very probably feature errors and omissions.

Nevertheless, Wikenigma hopes that the translated content will help to attract a wider global audience.

Show another (random) article