PSYA3 Sleep

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Biological Rhythms: The Circadian Rhythm
Rhythms that last about 24 hours. the two bestknown circadian rhythms are the sleepwake cycle and the
body temperature cycle.
SleepWake Cycle
Endogenous pacemakers
The sleepwake cycle is controlled by an endogenous pacemakers (internal body clock). It tells our body
when to feel sleepy and when to feel awake. Our SCN is our main endogenous pacemaker.
(+) (Michael Siffre, 1975) when no there were no zeitgebers, a freerunning was little more than 24hours.
(+) (Aschoff and Wever, 1976) in a WW2 bunker in the absense of time cues, people displayed rhythms
between 24 and 25 hours.
() Not isolated from artificial light.
Individual differences: Cycle length different peoples cycles can vary from 13 65 hours.
Cycle onset individuals appear to be innately different in terms of when their
circadian rhythm reaches its peak. I.e. morning people rise early and go to bed late, whereas evening people
wake and go to bed later.
Determinism: It is a biological approach. It proposes that it can be explained in terms of brain structures
and hormonal activity. However, human behaviour is more complex than this.
Exogenous zeitgebers
They are external cues that fine tune our rhythms in order to remain in time with the external world which
fluctuates in its rhythms.
Light is the dominant zeitgeber in humans. It can reset our main pacemaker, the SCN, but can also reset
other oscillators such as the protein clock.
Our daily rhythm appears to be entrained by social convention, not internal biology. All parts of the body
produce their own oscillating rhythms and some of these are not primarily reset by light.
(+) (Campbell and Murphy, 1998) If you shine light on the back of participants knees this shifted their
circadian rhythm.
() (Folkard et al., 1985) when isolated from other time cues and all participants went to bed and wake up
when the clock indicated a certain time, which was sped up, the volunteers cycles no longer matched the
Realworld applications: Chronotherapeutics the study of how timing effects drug treatments. I.e. taking
aspirin to treat heart attacks. This is most effective at around 11pm which allows the aspiring to peak in the
bloodstream. This is because they normally occur in the early morning.
Core body temperature
One of the best indicators of the circadian rhythm. It is lowest at about 4.30 am and highest around 6pm.
There is a slight trough after lunch which occurs even when people have not eaten.
The temperature dip is a bidaily rhythm, which is an example of an ultradian rhythm.
(+) (Folkard et al., 1977) when children were read stories either in the AM or PM, they had greater recall
and comprehension in the PM.
(+) (Gupta, 1991) performance on IQ tests were best at 7pm compared to 9am or 2pm. Suggesting that
higher cognitive ability was linked with a higher core body temperature.
(+) (Geisbrecht et al., 1993) when CBT was lowered, by placing participants in cold water, cognitive
performance was worse on some tasks.
A reallife application: Deciding on the best time to study. You are most alert in the morning and early
evening, so those are the best times to work.
Follow a circadian rhythm. Cortisol is at its lowest around midnight and peaks around 6am. It is produced
when we are stressed but is also related to making us alert when we wake up.
Melatonin and growth hormone also have a clear circadian rhythm both peaking around midnight.

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Ultradian and Infradian Rhythms
Ultradian Rhythms
The sleep staircase
There are 5 stages of sleep. The first 4 are NREM and the fifth is REM.
1) Light, 45% of total, occasional muscle twitching. Muscle activity slows, Alpha waves.
2) 4555% of total, Theta waves, greater amplitude, sleep spindles.
3) 46% of total, slow Delta waves, deep sleep begins, SWS.
4) 1215% of total, slow rhythmic breathing, very deep, repair work takes place, growth hormones
released, slow Delta waves, SWS.…read more

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Can be controlled by exogenous cues: (Russell et al., 1980) when sweat from one group of women was
rubbed on the upper lip of the second group, their menstrual cycles synchronised with their individual donor.
Suggesting synchronisation of menstrual cycles can be effected by pheromones.
Reallife application: Consequences of the menstrual cycle PMS can cause acne, anxiety, fatigue,
headaches, insomnia, water retention, mood swings and aggression. It used to be considered a psychological
problem.…read more

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SCN's disconnected were compared to 2 other groups of chipmunks 24 surgical controls and 20 intact
controls. 80 days later signiicantly more of the SCNlesioned chipmunks had been killed by weasels.
Presumably because they remained awake in their burrows and the weasels could here them.
Research into the pineal gland provides further support for an interaction between internal body clocks and
external cues.
As darkness falls, the lightsensitive pineal gland releases melatonin, which stimulates the release of
serotonin.…read more

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Disrupting Biorhythms
Shift Work
Decreased alertness
(Boivin et al., 1996) Nightworkers often experience a circadian 'trough' of decreased alertness during their
shifts. This occurs between midnight and 4am when CBT is lowest.
Sleep deprivation is another explanation for decreased alertness. Shift workers often experience sleep
deprivation because when they finish work it is daytime and there are other interruptions and daylight reduces
the quality of sleep.
Daytime sleep is typically between 1 and 2 hours shorter than a nocturnal sleep period REM is particularly
affected.…read more

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Reallife application: melatonin is a natural hormone that induces sleep and has been put forward as a
'miracle' cure.
(Herxheimer and Petrie, 2001) where melatonin was taken near bedtime it was remarkably effective.
Reallife application: social customs can help entrain biological rhythms i.e. when travelling it helps to eat
at the right time and sleep when the clock says to. (Fuller et al., 2008) fasting followed by eating on the new
time schedule should help entrain biological rhythms.…read more

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Individuals sleep for an average of 910 hours per night. The amount of REM sleep is less than in childhood.
Circadian rhythms also change so that teenagers feel more awake later at night and have more difficulty getting
up early (a delayed sleep phase).
(+) Hormones are generally released at night and so sleep patterns are disturbed leading to sleep
(+) (Crowley et al., 2003) hormonal changes can also explain the upset circadian clock this is described
as the delayed sleep phase syndrome.…read more

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Case studies: The study of sleep deprivation is generally restricted to case studies. The main problem
therefore is that the participants are likely to be unique. I.e. someone who has difficulty sleeping is less likely
to volunteer for studies, and people who do volunteer are probably highly motivated to try to cope well with sleep
Nonhuman animal studies
Suggest that sleep deprivation may have fatal consequences
(+) (Rechtschaffen et al.…read more

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Warmblooded animals use energy to maintain temperature. This is especially true for small animals with a
high metabolic rate.
(+) (Zepelin and Rechtschaffen, 1974) smaller animals, with a higher metabolic rate slept more than larger
() (Capellini et al., 2008) there was a negative correlation between metabolic rate and sleep, which doesn't
support the energy conservation hypothesis.
() The methods used were not standardised and therefore comparisons between species are meaningless.…read more

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Explanations of Insomnia
May involve trouble falling asleep (initial), trouble remaining asleep (middle), or waking up too early (terminal).
It is transient, intermittent, or chronic.
Primary insomnia
Where insomnia simply occurs on its own, for more than a month.
It is the persons primary problem.
It may be that they have bad sleep habits or sometimes insomnia may have had an identifiable cause
which has now disappeared but insomnia persists because of an expectation of sleep difficulty.
(+) (Watson et al.…read more


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