PSYA3 Biological Rhythms & Sleep Notes

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  • Created on: 16-06-13 10:44
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24 Hour (Daily) cycles i.e. the sleep/ wake cycle, body temperature.
Sleep/ Wake cycle- Average of 7 to 8 hours sleep a day. This varies between person to person as it
depends upon individual differences such as age, where babies sleep a lot because of
development and elderly people sleep less.
-> Siffre- Body clock extended to a 25 hour day where he gained an hour of sleep daily. This
resulted in him losing a considerable number of days. This was due to the absence of daylight.
Daylight is an Exogenous Zietgeber that influences the Endogenous Pacemaker, i.e. the
Suprachiasmatic Nucleus.
o Damage to SCN in rats influenced circadian rhythms such as drinking and wheel-running.
o Isolated SCN tissue continued to exhibit circadian rhythms.
o SCN transplants caused rats to exhibit a circadian length that was similar to that of the
Blindfolded Squirrel Monkey's cycles became free-running but they only varied by a few minutes.
Siffre study was a case study so it lacks ecological validity as it cannot be generalised to the
entire population-> Results have been confirmed by other studies however.
Individual who was blind from birth had trouble getting to sleep and waking up due to the fact that
his circadian cycle had extended to 24.9 hours.
Folkard- Reported a woman who had been isolated from zeitgebers and her circadian rhythm had
extended to a 30-hour period-> was asked to play bagpipes when she thought that it was the same
Longer than 24 Hour cycles i.e. menstrual cycle, hibernation, seasonal affective disorder.
->Snakes continued to stick to a natural cycle when skin shedding despite the altering light
levels but deer could be encouraged to grow and shed antlers.
Menstrual Cycle- The endogenous pacemaker is hormones being released from the Pineal gland.
The Zietgeber is thought to be pheromones which allow for women to sync their cycles, however
there is not much evidence for this.
-> Woman in cave showed shortened menstrual cycle but was still present even in the
absence of zeitgebers.
o Women living in uni accommodation and mother/ daughter living arrangements
encouraged syncing of the menstrual cycles.
Hibernation- Hormones influence the changes in metabolism, kidney and heart function.
Zeitgebers are the environmental changes i.e. harsher weather and shorter days indicate that
the animal should be in hibernation.
->Donated blood from hibernating squirrels caused hibernation in awake ones.
SAD- Melatonin, secreted by pineal gland, is the EP as levels increase during darkness. Light is the

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Exposure to light as a treatment significantly helped, however it did not work for
summer affected patients.
Yang & Schank- Chinese women living in university accommodation showed no synchronisation of
menstrual cycles.
Some SAD patients secrete melatonin normally.
Plasma from squirrels injected into a monkey bought on pre-hibernation like changes.
Shorter than a 24-Hour cycle i.e. REM and NREM sleep and Basic Rest Activity (BRAC)
Stages of sleep- 90 minute cycles. Slow wave sleep (stages 3 & 4) is part of NREM.…read more

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Shift Work- Outside of normal bodily hours and the body is not equipped to deal with it so there is
disruption. -> Police had 4 times as many accidents while working nights but this was improved
when shifts were changed.
->Kubo et al- Four times more likely to develop prostate cancer if working night shifts.
o US nurses risk of breast cancer increased when the years spent working nights
o Reduced levels of melatonin, increased hormones associated with cancer.…read more

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Paradoxical sleep occurs where the muscles become
Total sleep time generally decreases as the child matures with the child having 15 hours at birth
and decreasing to around 7 hours in adulthood.
REM sleep also decreases during ageing. A baby has the same amount of REM as it does NREM
and sleeps for 17 hours a day. This decreases to 13 hours after a year.
Amount of SWS also decreases during two periods: between 16-25 and 35-50 years.…read more

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IDASà Nature/ Nurture, Limited, Reductionist, Determinism, Cultural Bias
Growth and Repair Hypothesis (Oswald)- REM allows for the restoration of the nervous system
and NREM, especially SWS encourages repair by releasing growth hormone.
->Horne- Repair generally happens during REM and SWS sleep but could take place in optional
sleep and relaxed wakefulness as well.…read more

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High concordance rate for
MZ twins with insomnia and low rate in DZ twins.
o Personality Influences- Belief that insomniacs share similar personality traits.
->Kales et al- Tend to share how they handle stress and conflict by internalisation.
Harm avoidance is closely related to the type of brain activity associated with Insomnia.
Secondary Insomnia- The inability to get to sleep, caused by other disease processes or
interventions i.e. caused by pain from medication.…read more


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