endogenous pacemakers and exogenous zeitgebers Flashcards
what is the SCN?
the suprachiasmatic nucleus
where is the SCN?
a small bundle of nerves located in the hypothalamus in each hemisphere just above the optic chiasm so can receive information directly from it, so we can adjust eve when asleep
why is the SCN important?
one of the primary endogenous pacemakers in mammalian species and influential in maintaining the sleep/wake cycle
describe Decoursey et al’s study
destroyed the SCN connections in the brains of 30 chipmunks who were then returned to their natural habitat an observed for 30 days
what are the findings of Decoursey et al’s study?
the sleep/wake cycle in the chipmunks disappeared cusing a significant proportion to be killed by preditors
describe Ralph et al’s study
bred mutant hamsters with 20-hour sleep/wake cycles the transplanted the scn cells from fetal tissue of the mutant hampsters into normal hamsters
what are the findings of Ralph et al’s study?
the hamsters deflected to a 20-hour cycle emphasising the role of the SCN in establishing and maintaining the sleep/wake cycle
where does the SCN pass information to?
the pineal gland which produces melatonin at night
what does light reset?
the body’s SCN
what des light indirectly influence?
hormone secretion and circulation in the blood
describe Campbell and Murphy’s study
15 ppt woken at various times in the night had a light pad shone on the back of their knees but not to their eyes
what did Campbell and Murphy aim to demonstrate?
that light may be detected by skin receptor sites on the body even when the same information is not given to the eyes
what were the results of Campbell and Murphy’s study?
the sleep cycle deviated by up to 33 hours
when approximately do circadian cycles begin?
6 weeks of age
whe re most babies entrained?
16 weeks likely influenced by their parents imposed schedules (meal and bedtimes)
what is the application of understanding social cues and exogenous zeitgebers?
adapting to local time zones by adapting to their sleeping and eating times
what are peripheral oscillators?
the many organs and cells that have their own independent circadian rhythms but are also healivy influenced by the SCN
where are Peripheral oscillators found?
the adrenal glands, oesophagus, lungs, liver, pancreas, spleen, skin, thymus
Describe Damiola et al’s study and results?
demonstrate how changing feeding patterns in mice can alter the circadian rhythms of cells in the liver by up to 12 hours while not effecting the SCN
what are the ethical problems of the animal studies?
animals exposed to the risk of significant harm when released back into their natural habitat and somewhere killed
describe the case study of Miles et al and how it is applied
a young man blind from birth had a circadian rhythm of 24.9 hours and despite exposure to social cues it could not be adjusted and he had to be sedated at night and stimulated in the mornings to ft into a 24-hour world. this means the influence of exogenous zeitgebers may be overestimated
give a real-world example which demonstrates the influence of exogenous zeitgebers may be overestimated
people who live in the arctic regions show normal sleep patterns despite prolonged periods of exposure to light
what are the methodological issues with Campbell and Murphy’s study?
- hasn’t been replicated
- confounding variables (light reaching eyes)
what are the practical applications of the effect of exogenous zeitgebers on the sleep/wake cycle and studies into the SCN?
- treating sleep disorders
- understanding the effect of a damaged SCN
what is an interactionist system?
in real-life pacemakers, and zeitgebers interact so it doesn’t make sense to separate them
