Psychology AQA A A2 Biological Rhythms and sleep

Quick overview of my notes for my A level Psychology exam, from AQA, Psychology A.

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Biological Rhythms
Endogenous pacemakers- internal body clocks, innate, e.g. hormones (melatonin), hunger.
Exogenous zeitgebers- environmental stimuli, external, e.g. light, alarm clock.
Length Example Research
Circadian Rhythms 24 hours Sleep/wake Siffre 1975; 6 months in cave with no
cycle, body natural light, absence of zeitgebers
temperature (light) pacemakers can still regulate
body, Siffre found average day of 25
hours. SCN is internal body clock,
synchronised by light received by
retina of eye. Controls pineal gland
and the release of melatonin.
(endogenous) Melatonin is hormone,
makes us sleepy, released by pineal
gland, and light reduces the levels,
whilst darkness increases it.
Circannual About a year Hibernation, Penngelly and Fisher 1978; squirrels in
Rhythms migration controlled environment, hibernated
when expected to, suggests that light
and temperature contribute, but also
endogenous factors.
Infradian Rhythms More than 24 Menstrual cycle Reinberg 1967; pheromones
hours (hormone released into air, can
synchronise women's menstrual cycles
to one another) released into the air
can have an effect on synchronising a
group of women when repeated
exposure. Menstrual cycle controlled
by hormones, can be affected by
exogenous factors such as stress, diet
or drugs. SAD effects people in winter
and there is less light, sleep more,
Ultradian Rhythms Less than 24 Sleep stages Dement and Kleitman 1957; found
hours 70% of participants woken in REM
sleep report dreaming. Stage 1; light
sleep, alpha waves, relaxed muscles,
drowsiness. Stage 2; decrease in body
temp, heart rate slows, EEG slower,
20 mins, easily woken. Stage 3; deep
sleep begins, delta waves, snoring
may start. Stage 4, very deep sleep,
rhythmic breathing, limited muscle
activity, sleep walking/talking. REM;
brain waves speed up, dreaming

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Disruptions of biological rhythms
Edison's invention of the electric light in the late 19t century freed us from dependence on natural
light and candles. People were able to work and socialise longer throughout the night, and could
sleep when they liked.
Shift Work Jet Lag
Explanatio Working patterns which enable The dislocation between the body clock
n organisations to work around the and local zeitgebers (light, meal and work
clock.…read more

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Research Dement 1960; deprived subjects of Randy Gardner; 17 year old student, stayed
either REM or non-REM sleep, and awake for 11 days, effects were
compared effects of both. disorganised speech, blurred vision and
Deprivation of REM sleep was more paranoia.
severe and when allowed to sleep, Rechtschaffen et al 1983; rats on rotating
REM sleep doubled. plates above water.…read more

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Fatal effects
with the immune system which may lead shown in sleep deprivation studies
to death. Face validity, restoration as a confirm that sleep in needed for
theory makes sense. Restoration theories survival.
claim that a key function of sleep is
protein synthesis, the main constituents
of proteins are only freely available for 5
hours after eating, not during sleep.
Sleep Disorders
Dyssomnias- problems with the amount, quality or timing of sleep, e.g. insomnia or narcolepsy, and
often produce daytime tiredness.…read more


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