Environmental stimulus perception and control of circadian clocks

Circadian rhythms are influenced by light signals transmitted to the suprachiasmatic nucleus (SCN) in mammals.

• The SCN serves as the master clock in mammals, coordinating central and peripheral circadian rhythms.
• Light is the primary synchroniser for circadian rhythms, primarily detected by specialized retinal cells.
• Photoreception involves a novel opsin called melanopsin, with potential contributions from cryptochromes.
• In contrast to mammals, some peripheral tissues in flies and fish have direct light-sensing capabilities.
• Certain peripheral clocks in mammals may be regulated independently of the SCN through food restriction during the light period.

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