Zeitgeber is any exogenous (external) cue that synchronizes an organism's endogenous (internal) time-keeping system (clock) to the earth's 24-hour light/dark cycle. The strongest zeitgeber, for both plants and animals, is light. Non-photic zeitgebers include temperature, social interactions, pharmacological manipulation, exercise, and eating/drinking patterns. To maintain clock-environment synchrony, zeitgebers induce changes in the concentrations of the molecular components of the clock to levels consistent with the appropriate stage in the 24-hour cycle, a process termed entrainment

Entrainment (chronobiology)

Entrainment, within the study of chronobiology, occurs when rhythmic physiological or behavioral events match their period and phase to that of an environmental oscillation. A common example is the entrainment of circadian rhythms to the daily light–dark cycle, which ultimately is determined by...

.

The German term zeitgeber came into the English language when Jürgen Aschoff

Jürgen Aschoff

Jürgen Walther Ludwig Aschoff was a German physician, biologist and behavioral physiologist. Together with Erwin Bünning and Colin Pittendrigh, he is considered to be a co-founder of the field of chronobiology.-Life:...

, one of the founders of the field of chronobiology

Chronobiology

Chronobiology is a field of biology that examines periodic phenomena in living organisms and their adaptation to solar- and lunar-related rhythms. These cycles are known as biological rhythms. Chronobiology comes from the ancient Greek χρόνος , and biology, which pertains to the study, or science,...

, used it in the 1960s. It is now in common use in the scientific literature in this field.

See also

• Phase response curve
  Phase response curve
  A phase response curve illustrates the transient change in the cycle period of an oscillation induced by a perturbation as a function of the phase at which it is received...
  
  
• Circadian rhythm
  Circadian rhythm
  A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...
  
  
• Infradian rhythm
  Infradian rhythm
  An infradian rhythm is a rhythm with a period longer than the period of a circadian rhythm, i.e. with a frequency less than one cycle in 28 hours, such as menstruation, breeding, tidal or seasonal rhythms...
  
  
• Ultradian
  Ultradian
  Ultradian rhythms are recurrent periods or cycles repeated throughout a 24-hour circadian day. In contrast, infradian rhythms, such as the human menstrual cycle, have periods longer than a day....
  
  
• Melatonin
  Melatonin
  Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes...
  
  
• Suprachiasmatic nucleus
  Suprachiasmatic nucleus
  The suprachiasmatic nucleus or nuclei, abbreviated SCN, is a tiny region on the brain's midline, situated directly above the optic chiasm. It is responsible for controlling circadian rhythms...
  
  or nuclei (SCN)

Literature

• Aschoff J (1965) The phase-angle difference in circadian periodicity.In "Circadian Clocks" (J. Aschoff, ed.). North Holland Press, Amsterdam, p. 262–278.