Psya3 - Biological Rhythms and Sleep, Relationships and Aggression Notes

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Biological rhythms and Sleep

Circadian rhythms
Those which complete a cycle in a 24 hour period such as the sleep-wake cycle, heart rate or metabolism.

Temporal isolation studies demonstrate that the cycle persists despite the absence of light. Siffre spent long
periods in a cave with no exogenous zeitgebers. Found…

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Ultradian rhythms
Those which occur more than once in a 24 hour period, for example the sleep cycle which repeats approximately
four times per night. The stages of sleep repeat roughly every 90 minutes while asleep.

Another example of an ultradian rhythm is the basic rest-activity cycle: this cycle shows…

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Infradian rhythms
Those which occur over a period greater than 24 hours, such as the menstrual cycle and seasonal affective

Seasonal affective disorder is where low light levels stimulate melatonin production and decrease serotonin
production. Terman et al. (1998) researched 124 participants with SAD; 85 were exposed to a…

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Endogenous pacemakers
Internal factors which are able to regulate biological rhythms.

To study these, Siffre (1962) spent 61 days in a cave in low light conditions. During this period, his body clock
extended to a 24.5 hour day and when he emerged he believed it was 28 days earlier than…

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Exogenous Zeitgebers
External time cues to help regulate biological rhythms and synchronise them. Endogenous pacemakers and
exogenous zeitgebers need to work together in order to co-ordinate the behaviours they regulate with the external
environment (entrainment).
Light entrains the free-running biological rhythm. This affects the SCN and other peripheral oscillators. Campbell…

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Disruption of rhythms

Jet lag is caused by the body's internal clock being out of sync with external cues and has symptoms including
fatigue, insomnia, anxiety and dehydration.

Schwartz et al. (1995) studied the performance and reaction times of baseball teams flying from the East to West
coast of America…

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reported nine months later.. This study had tangible real life benefits and applications.

Boivin et al. (1996) put 31 male participants on an inverted sleep pattern for three days. After waking on each day
they were subjected to one of the following conditions: very bright light, bright light, ordinary room…

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Evolutionary Theory of Sleep
The evolutionary theory proposed by Meddis states that due to poor vision in low light, sleep has an evolutionary
advantage to humans because it keeps the species safe at night; and therefore more likely to survive to pass on
genes. This theory also takes into account…

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Supporters of the theory say it considers the whole animal when looking at the causes because a large
number of factors are accounted for, such as foraging requirements and energy conservation. Therefore it
looks at the animal as a whole.
Research Methods: correlational research is often used. Can't establish…

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antidepressants spend less time in REM sleep, but when the treatment is stopped, there is no REM rebound.
Naturally, it has been suggested that the antidepressants (which are known to increase serotonin and dopamine
levels) are providing what REM sleep would otherwise provide.

Horne and Millard (1985) found that even…


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