endogenous pacemakers and exogenous zeitgebers

Question 1

endogenous pacemakers

Answer 1

internal bodyclocks that regulate many of our biological rhythms

Question 2

the suprachiasmatic nucleus (SCN)

Answer 2

• located in the hypothalamus in both hemispheres
• lies just above the optic chiasm and receives information about light from this structure
• this continues even when our eyes are closed which enables the biological clock to adjust to changing patterns of daylight

Question 3

animal studies and the SCN

Answer 3

• DeCoursey destroyed the SCN connections in 30 chipmunks who were then returned to their natural habitat and observed for 80 days
• the sleep/wake cycle of the chipmunks disappeared and by the end of the study a significant amount of them had been killed by predators (because they were vulnerable from being awake when they should have been sleeping)
• emphasises the role of the SCN in maintaining the sleep/wake cycle

Question 4

exogenous zeitgebers

Answer 4

external cues that may affect or entrain our biological rhythms

Question 5

light

Answer 5

• a key zeitgeber in humans in regulating the sleep/wake cycle
• Campbell and Murphy demonstrated that light may be detected by skin receptor sites even without being identified by the eyes
• 15 pps were woken at various times and a light was shone on the back of their knees
• the researchers managed to produce a deviation in the pps usual sleep/wake cycle by up to 3 hours
• shows power of exogenous zeitgebers

Question 6

social cues

Answer 6

• at about 6 weeks of age the circadian rhythms begin and by 16 weeks most babies are entrained
• the schedules imposed by parents are likely to be a key influence including mealtimes and bedtimes

Question 7

evaluation: ethics in animal studies

Answer 7

• there’s not only difficulty generalising the findings from animals to humans but the animals were placed under considerable harm when placed back in their natural habitat
• debate between whether the findings of the research were worth putting animals under harm

Question 8

evaluation: influence of exogenous zeitgebers may be overstated

Answer 8

• blind from birth man had a circadian rhythm of 24.9 hours
• despite being exposed to social cues, his sleep/wake cycle could not be adjusted and he had to resort to using sedatives at night and stimulants in the morning to keep at pace with the 24 hour world
• there are occasions were exogenous zeitgebers have little influence on internal rhythms

Question 9

evaluation: methodological issues in studies

Answer 9

• Campbell and Murphy’s study is yet to be replicated
• other psychologists have been critical of the manner of the study, claiming that there could have been some light exposure which is a major confounding variable