endogenous pacemakers + exogenous Zeitgebers

Question 1

endogenous pacemakers

Answer 1

-internal body clock that regulates many of r biological rhytms
-scn interacts w/ EZ to regulate sleeo/wake cycle
-eg SCN suprachiasmatic nuclei
-communicates in pineal gland+ instructs secretion of melatonin
-animal studies: decoursey+ ralph et al

Question 2

decoursey et al
(2000)

Answer 2

-Destroyed the SCN connections in 30 chipmunks
-Chipmunks were returned to their natural habitat and observed for 80 days
-By the end of the 80 days, the sleep-wake cycle disappeared
-Most of them had been killed by predators

Question 3

Ralph et al (1990)

Answer 3

-Bred ‘mutant’ hamsters with a sleep-wake cycle of 20 hours (rather than 24ish)
-Took their SCN cells and transplanted them into the brains of ‘normal’ hamsters with a normal sleep-wake cycle
-The sleep-wake cycles of the ‘normal’ hamsters adapted to the cycle of the mutants

Question 4

ao3

limiations of EP

Answer 4

-animal studies: generalisability, humans more complex + affected by enviromental factors, ethical issues:consent
-Extensive research into the SCN may mean that other internal influences are overlooked
-The effect of endogenous pacemakers cannot be studied in isolation
-

Question 5

exogenous zeitgebers

Answer 5

-External factors that affect or entrain our biological rhythms
-A key example is light
-Other examples include factors such as social cues

Question 6

EZ

Campbell and Murphy (1998)

Answer 6

-light enters the eyes, then the information carries down the optic nerve to the suprachiasmatic nuclei
-15 participants were woken at various times and a light pad was shone on the back of their knees
-The researchers managed to deviate the participant’s regular sleep wake cycles

Question 7

social cues

Answer 7

-Newborn babies have a random sleep-wake cycle
-At 6 weeks, their circadian rhythms begin
-By 16 weeks, their rhythms have been entrained by schedules imposed by parents
-Research on jet lag also suggests that adapting to the local mealtimes etc is effective

Question 8

ao3 EZ

limitations

Answer 8

-Exogenous zeitgebers do not have the same effect in all environments
-A lot of what we know about exogenous zeitgebers comes from case studies