Exogenous Zeitgebers Flashcards
What are exogenous zeitgebers?
Environmental events that are responsible for resetting the biological clock
What are the two main exogenous zeitgebers?
- Social cues
- Light
What is entrainment?
Where the biological clock everyday has to reset itself slightly
What is light thought to be?
The dominant zeitgeber entraining the biological clock, the light levels change gradually everyday of the year and the body has to adjust
What do social cues help us do?
To entrain to the gradual changes in light levels, these are things that regulate our daily life; meal times at regular times, regular routines etc
What did Campbell and Murphy show?
You can change a person’s circadian rhythms by shining a light on the back of participants knees, they measured the pps levels of melatonin the blood before and after exposure
What was the conclusion of this study?
- External factors can change the sleep wake cycle
- Humans react the same as plants?
- Cannot be recreated
What did Miles study?
A man who has been blind from birth had a circadian rhythm of 24.9 hours, social cues did not help to entrain his body clock, the only way for him to cope was through the use of sedatives and stimulants
What was the conclusion of this study?
The body clock can change with external things but only to a certain extent
What did Kelly do?
Conducted a study on board a US nuclear submarine to see if the submariners can adapt to an 18 hour day
What did Kelly find?
The social cues (artificial lighting, meal times etc) were not powerful enough to shift the body’s natural endogenous rhythm
What is the conclusion of all of the studies?
Both endogenous and exogenous play a critical role in the biological and they work together not separately
