Chronobiology

Chronobiology is a field of biology that examines time-relatedphenomena in living organisms. These cycles are important in many essential biological processes that occur in a "scheduled"fashion, such as eating, sleeping, mating, hibernating, migration, and cellular regeneration.

The most important rhythm in chronobiology is the circadianrhythm , which refers to the 24-hour daily biological cycle; however, many other important cycles are also studied,including:

• Infradian rhythms ,which are long-term cycles, such as the annual migration or reproduction cycles found in certain animals or the monthly menstrual cycle of human females.
• Ultradian rhythms ,which are short cycles, such as the 90-minute REM cycle insleep or the 3 hour cycle of growth hormone production. The haveperiods of less than 24 hours.
• Tidal rhythms , commonlyobserved in marine life, which follow the (roughly) 12-hour transition from high to low tide and back.

Related to, but not part of, chronobiology is the unsubstantiated theory of biorhythms , which are said to be a set of cyclic variations in human behaviour. The theory's basis lies inphysiological and emotional cycles. Some people consider it pseudoscience and others protoscience .

External link

• The University of Virginia offers an online tutorial on chronobiology.