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Biological Rhythms & Sleep

Biological Rhythms: circadian, infradian & ultradian.

Endogenous Pacemakers & Exogenous Zeitgebers

The Disruption of Biorhythms: jet lag & shift work.

The nature of Sleep & Life Span Changes: sleep stages & the changes of the sleep

Functions of Sleep: restoration theory & evolutionary theory.


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Biological Rhythms-AO1
Circadian Infradian Ultradian
A circadian rhythm lasts for 24 An infradian rhythm lasts for more An ultradian rhythm lasts for less
hours. An example of this is the than 24 hours but less than a than 24 hours. An example of this
sleep-wake cycle. year. An example of…

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cause chronic depression. with age and this does
Miles et al: blind people show the Eastman treated patients with not take that matter into
same pattern as sighted people bright light or a placebo and found account.
therefore it must be due to an that those treated with a bright…

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Endogenous Pacemakers:-
The Suprachiasmatic nucleus (SCN) is an endogenous pacemaker. The SCN is a cluster of nerve cells in the
hypothalamus. It receives information about light as it is located above the optic chiasma (even when our
eyes are closed). Stephan & Zucker found that when the SCN is lesioned,…

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How do we disrupt our biological rhythm?

Usually exogenous zeitgebers change gradually allowing us time to adjust however a rapid change disrupts
co-ordination between endogenous pacemakers and exogenous zeitgebers. This consequently means we
are not always able to function properly. A lack of synchrony within the environment might lead to…

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1. Real life applications: Czeisler et al studies shift workers in a factory. They found high illness rates,
sleep disorders and elevated levels of stress suggesting that their body clocks were out of sync. The
researchers suggested they move to a phase delay system of rotating shifts to reduce negative…

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Sleep and the lifespan:-

Infancy: babies sleep for about 16 hours a day but not continuously. They wake up every hour or so
and the cycle is shorter than an adults. They experience two types of sleep: active and quiet which
are versions of REM and SWS. Approximately half is…

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Theories of Sleep
Evolutionary (Ecological) Theory:-
Sleep is adaptive. It exists to promote survival and reproduction. Any behaviour or characteristics that
increase likelihood of survival and reproduction will be naturally selected and will survive as the animal
evolves. Each animal adapts their sleep pattern to their environment (ecological niche) for…

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Shapiro et al: runners of the marathon slept more the following days and NREM sleep increased

Dement: DJ wakethon for charity. Stayed awake for 201 hours (8days). 3 days in he became abusive.
5 days in he developed hallucinations. By the end of the wakethon his body temperature…

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Disorders of Sleep
Insomnia may relate to difficulties in going to sleep and/or staying asleep and may occur transiently,
intermittently or chronically (more than once a month).

Insomnia and its cause can be grouped into primary and secondary:

PRIMARY INSOMNIA: defined by DSM as a problem with no known…




Wow, really useful, thank you! 

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