Endogenous pacemakers and exogenous zeitgebers STUDIES

Question 1

Morgan 1995 hamsters

Answer 1

Mutated hamsters to have circadian rhythms of 20 hours, then transplanted the SCN of these hamsters into new-born ones, there displayed circadian rhythms of 20 hours regardless of exogenous zeitgebers. This implies that the SCN is majorly responsible for the regulation of circadian rhythms.

Question 2

DeCoursey 2000 chipmunks

Answer 2

Removed SCNs from chipmunks. They were then more likely to be killed by weasels because they did not sleep. This implies that the SCN is incredibly important to survival and is a development of evolution, suggesting that exogenous zeitgebers only play a minor part in regulating the SCN

Question 3

Burgess 2003 jetlag

Answer 3

The effects of jetlag are counteracted with bright light as soon as a person wakes up. Pp’s exposed to continuous bright light shifted their circadian rhythms by 2 hours whereas those exposed to dim light only shifted by .6 hours

Question 4

Folkard 1996 temporal isolation

Answer 4

Student in temporal isolation had a shifted sleep cycle of 30 hours, with up to 16 hours a day, but her temperature cycle was still at 24 hours. This implies that core body temperature does not affect the circadian rhythms as much as other factors like the SCN and other exogenous zeitgebers.