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A2 PSYCHOLOGY

AQA
Biological rhythms




PSYA3

BIOLOGICAL RHYTHMS

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Circadian Rhythms
1. THE MAIN Circadian rhythm is the sleep-wake cycle = lasts 24 hours.
Endogenous pacemakers (internal clocks) and exogenous zeitgebers (external time givers) are
both involved.

For example light, as an exogenous zeitgeber tells us when to go to bed and when
to wake up. The presence/absence of…

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A02


Folkard et al - read stories to children aged 12-13 years old at either 9am or 3pm
= the afternoon group (highest core body temp) retained more information - 8% more than the
morning group

THEREFORE ... long-term recall is best when body temp is at its highest

Gupta…

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ULTRADIAN RHYTHMS
An ultradian rhythm lasts for less than 24 hours and one example of this is sleep stages.

Awake = Beta waves


- LOW AMPLITUDE
- HIGH FREQUENCY


Stage 1 = Alpha waves

- GREATER
AMPLITUDE
- HEART RATE
SLOWS

Start to relax = slower + more regular brain…

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REM sleep is also known as the paradoxical sleep as the brain and eyes are active
but the body is paralysed


An issue with REM sleep is the assumption that it its dreaming sleep...




Dement and Kleitman = support of stages of sleep and
dreaming in REM

Woke participants up…

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Infradian rhythm- Infradian rhythms last longer than 24 hours
Monthly cycle
The human female menstrual cycle is the most well known infradian rhythm
= regulates ovulation.
The menstrual cycle = involves fluctuating hormone levels of progesterone and
oestrogen. Progesterone causes an increase in the blood in the lining of the…

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such rhythms further.

SEASONAL AFFECTIVE DISORDER (SAD)
Become depressed during the winter months and recover
during the summer

WINTER = LESS DAYLIGHT

MELATONIN + SEROTONIN ARE SECRETED
WHEN ITS DARK




more
darkness =
more
melatonin
more
melatonin = less
serotonin

less serotonin
= depression


Understanding the role of darkness in…

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ENDOGENOUS PACEMAKERS
= internally managed clocks which coordinate biological processes such as the circadian
sleep-wake cycle

The main endogenous pacemaker is the suprachiasmatic
Endogenous nucleus which lies on the hypothalamus
pacemakers interact
with exogenous The SCN obtains information about light from the
eye via the optic nerve
zeitgebers, such as…

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A02

Research support
Morgan transplanted the SCN of `mutant' hamsters who had been trained to have 20
hour circadian rhythms, into norma hamsters who in turn adopted the same 20 hour
rhythms.

However there are 2 main issues with conducting animal research.
1.The first ethical issue is harm
2.The second…

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DISRUPTION OF BIOLOGICAL RHYTHMS

Shift lag
When people change to a different shift, their bodily processes are in a
state of desynchronisation. This is because shift workers have to
reverse their natural circadian rhythms and adjust their sleep-wake
cycle without the aid of zeitgebers such as light and social cues.…

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