Biopsychology: Endogenous Pacemakers and Exogenous Zeitgebers Flashcards
what’s an endogenous pacemakers?
internla body clocks that regulate many of our biological rhythms such as the influence of the superchiasmatic nucleus on the sleep wake cycle.
what’s the suprachiasmatic nucleus?
the SCN is a bundle of nerve cells lcoated in the hypothamalus. it’s influential in maintaining the sleep/wake cycle. nerve fibres connected to the eye cross in the optic chiasm on the way to the cerbral cortex.
what’s Decoursey’s animal studies?
she destroyed the SCN connections in the brain of 30 chipmunks who were returned to their natural habitat and observed for 80 days. the sleep/wake cycle dissappeared and by the end of the study, a significant proportion of them had be killed by predators.
what’s Ralph’s animal studies?
he bred mutant hamsters with a 20 hour sleep/wake cycle. when the SCN cells of the mutant hamsters were transplanted into the brain of normal hamsters, the cycles of the second group defaulted to 20 hours.
what’s the role of melatonin in the sleep/wake cycle?
the SCN passes information on day length and light that it receives to the pineal glands, which produces melatonin at nights.
what’s an exogenous zeitgebers?
external cues that may affect or entrain our biological rhythms such as the influence of light on the sleep/wake cycle.
what’s Campbell and Murphy’s study on light as an exogenous zeitgebers?
they demonstrated that light may be detected by skin receptor sites on the body even when the same information is not received by the eyes. 15 participants were woken up at various times and a light was shone on the back of their knees. the researcher managed to produce a deviation in the participant’s usual sleep/wake cycle, suggest light is a powerful zeitgebers.
what’s the ethics in animal studies? (A03)
in Decoursey’s study, the animals were exposed to considerable harm and subsequent risk when they were returned to their natural habitat. whatever we learn from the investigations such as these justifies the aversive procedures involved.
how is the influence of exogenous zeitgebers overstated? (A03)
Miles recounted the story of a young man, blind at birth, with the circadian rhythm of 24.9 hours. despite exposure to social cues, his sleep/wake cycle couldn’t be adjusted and had to take sedatives at night and stimulants in the morning to keep pace with the 24 hour world. similarly studies of individuals who lived in the arctic region shows normal sleep patterns despite the prolonged exposure to light. both these examples suggest exogenous zeitgebers have little bearing on our internal rhythms.
research showed there are numerous circadian rhythms in many organs and cells. although these peripheral clocks are highly influenced by the actions of the SCN, they can act independently. Damiola demonstrated how changing feeding patterns in mice could alter circadian rhythms of cells in the liver by up to 12 hours while the rhythm of the SCN is unaffected. this shows there may be other more complex influences.
