Timer

This article deals with biological timers, for the technical meaning see Timers or Time Servers

In chronobiology, a timer is any external influence that can act as an exogenous component on the endogenous "internal clock" of a living being in such a way that its internal rhythms are synchronized with the environment . The most effective timer for plants and animals is light. In addition, ambient temperatures, noises, social interactions, physical activities, food consumption, alarm clocks or manipulation by pharmaceuticals also occur as timers.

Concept formation

The term Zeitgeber was coined in the early 1950s by Jürgen Aschoff , one of the pioneers in the field of chronobiology, and is best known for his contribution Zeitgeber der Tierischen Tagesperiodik , published in 1954 in the journal " Die Naturwissenschaften " :

“The synchronizing factors are called timers. Timers for the animal 24-hour period are all periodic environmental processes of a continuous or discontinuous nature that are coupled with the rotation of the earth and that are stimulating for the animal. "

- Jürgen Aschoff : Timer of the animal daily period. In: The natural sciences. February 1954, p. 55.

The German word was adopted as a loan word in the English technical language: English Zeitgeber .

Examples

Light is the most common and most effective biological timer for most living things. It synchronizes the "internal clock" of plants, animals and humans with the actual length of the day. As a result, circadian rhythms are set to the day-night cycle and daily rhythms are formed that regulate, for example, the opening of the flowers of plants or the sleep phase of animals.

The duration of the incidence of light - as the length of the clear day - also influences infradian rhythms in animals , which are expressed as annual rhythms, for example in bird migration , rutting season , hibernation and hibernation . In the case of plants, in addition to the ambient temperature, the daily incidence of light also plays an important role for flower formation , fruit ripening and leaf fall . Therefore, light can be used in greenhouses to influence the harvest time.

See also

• Photoperiodism
• light therapy

further reading

• J. Aschoff: The phase-angle difference in circadian periodicity. In: J. Aschoff (Ed.): Circadian Clocks. North Holland Press, Amsterdam 1965, pp. 262-278.

Notes and individual references

1. ↑ see Jürgen Aschoff: Zeitgeber der Tierischen Tagesperiodik. In: The natural sciences . 41. Vol. 3, 1954, pp. 49-56.