Entrainment (chronobiology)

Under entrainment is understood in the Chronobiology the synchronization of the internal clock with recurring environmental factors, the so-called timers. The most important timing for circadian rhythms is the alternation of day and night. Other external timer can be, for example, tides, temperature, or social interaction.

The resulting patterns are not a direct response to the environment changes, so it differs from simple stimulus- response patterns. If this is the case, it is called masking. Here, the stimulus does have a direct effect on the rhythm, but not to the internal clock. The environmental factor that affects the phase of the circadian rhythms, the timer is called. To speak of entrainment by a timer, four criteria must be met:

  • The Circadian rhythm must run free when switching OFF of the timer.
  • While the rhythm is exposed to the timer, the period of free-running rhythm of the timer must be the same ( control period).
  • It must have a fixed phase relation between timer and the perceived rhythm arise (possibly anticipation).
  • When omitting the timer of the free-running rhythm must show a phase of the phase joins that had the rhythm, as the timer was still present.

Chart 1 shows the activity of a diurnal animal recorded over 20 days. This form of representation is called in chronobiology actogram.

On the x -axis shows the time of day in hours, from left (0 Clock ) is applied to the right ( clock 24 ), on the y- axis represents the duration of the experiment in days from top to bottom. In this case, the observation begins on the first day around 0 clock at night and ends on the twentieth day by 24 clock.

The animal was observed during the first days (A ) in a light-dark cycle (lights In 6 clock / light 18 clock = LD12/12 ), the following days ( B) in constant darkness (DD) and the last days (C ) again held in LD 12/12. The black bars indicate the activity of the animal.

In period A, the animal is synchronized with the timing light, so entrainiert '.

In period B, the timer light removed and kept the animal in continuous darkness. A freewheeling adjusts with a circadian period shorter than 24 hours. That is, the animal begins its activity every day a little earlier (but not arbitrary).

In period C, the timer is activated again, and the animal is light again entrainiert within two days ' - that is in synchronization with the timer.

  • Chronobiology
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