Exogenous Zeitgebers Flashcards
What are exogenous zeitgebers?
External factors affecting biological rhythms
What is the importance of exogenous zeitgebers?
Biological rhythms need to be fine-tuned by external cues to remain in time with the external world which fluctuates in its rhythms
What is entrainment?
The process of resetting biological clocks with exogenous zeitgebers
What is the opposite of entrainment?
Free-running
What is free-running?
When biological clock operates in the absence of any exogenous zeitgebers
What is the main/dominant exogenous zeitgebers?
Light
Why is light such an important exogenous zeitgebers?
It can reset the main endogenous pacemaker and also other oscillators throughout the body, e.g. some proteins are light-sensitive
Name 2 other exogenous zeitgebers
1) Social customs
2) Temperature
How is social customs an exogenous zeitgeber?
We eat at socially determined meal times and go to bed and wake up at times designated as appropriate for our age
How is temperature an exogenous zeitgeber?
Research suggests daily changes in body temperature are governed by their own circadian rhythm and these temperature changes entrain other circadian rhythms
Name 2 studies for exogenous zeitgebers
1) Miles (1977)
2) Luce & Segal Arctic Circle study (1966)
Outline Miles (1977)
Totally blind man had a circadian rhythm of 24.9 hours and had to use stimulants and sedatives to adjust the rhythm to 24 hours
What does Miles (1977) show?
Suggests that light is the main exogenous zeitgeber
Outline Luce & Segal Arctic Circle study (1966)
Those who live within the Arctic Circle sleep on average 7 hours despite the sun never setting in the summer
What does Luce & Segal Arctic Circle study (1966) show?
Suggests that light is not the only exogenous zeitgeber and the biological clock is not only influenced by light, thus it was suggested other exogenous zeitgebers like social customs and psychological factors also have an effect
