Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 1998 Dec;317(7174):1704-7.
doi: 10.1136/bmj.317.7174.1704.

The brain, circadian rhythms, and clock genes

M Hastings  1
Affiliations
Review

The brain, circadian rhythms, and clock genes

M Hastings. BMJ. 1998 Dec.
No abstract available

PubMed Disclaimer

Figures

Figure 1
Figure 1
Most aspects of physiology and behaviour are governed by a central clock mechanism in the hypothalamus. The clock acts on neural and endocrine pathways to regulate individual circadian rhythms so that internal state varies predictably over 24 hours. This enables adaption to daily and seasonal environment and enhances efficiency by separating anabolic and catabolic processes in time
Figure 2
Figure 2
Circadian clock molecules in drosophila. Early cycle: Expression of the clock genes period (per) and timeless (tim) is stimulated by the factors Bmal and Clock (blue/green circles). As cytoplasmic concentrations of per mRNA increase, Period protein (Per) is produced (red circles). Initially it is unstable and degraded. Mid-cycle: As the concentrations of Per and Timeless (Tim) proteins increase, the proteins form heterodimers (red and grey clusters), which enter the nucleus and suppress the expression of per and tim genes. Late cycle: Transcription of the genes is halted. With time Per and Tim proteins are inactivated, and without mRNA no new proteins can be produced. Consequently, Bmal and Clock are able to exert their stimulatory actions and the cycle begins again after about 24 hours
Figure
Figure
Scanning electron micrograph of a mutant fruit fly with leg antennae
See this image and copyright information in PMC

References

    1. Aschoff J. Handbook of behavioural neurobiology. Vol 4. Biological rhythms. New York: Plenum; 1981.
    1. Pittendrigh CS. Temporal organisation: reflections of a Darwinian clock-watcher. Annu Rev Physiol. 1993;55:16–54. - PubMed
    1. Hastings MH. Central clocking. Trends Neurosci. 1997;20:459–464. - PubMed
    1. Klein DC, Moore RY, Reppert SM. Suprachiasmatic nucleus: the mind’s clock. New York: Oxford University Press; 1991.
    1. Welsh DK, Logothetis DE, Meister M, Reppert SM. Individual neurons dissociated from rat suprachiasmatic nucleus express independently phased circadian firing rhythms. Neuron. 1995;14:697–706. - PubMed