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Summary Infradian and ultradian rhythms
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AQA A level psychology Detailed Cornell style notes of Infradian and Ultradian rhythms
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INFRADIAN AND ULTRADIAN RYTHMSInfradian Rhythms
Infradian rhythm Infradian rhythm: a type of biological rhythm with a frequency of less than one
cycle in 24 hours, such as menstruation and seasonal affective disorder
The menstrual cycle
• The menstrual cycle, an example of Infradian rhythm, is governed by
monthly changes in hormone levels which regulate ovulation
• The cycle refers to the time between the first day of a woman's period,
when the womb lining is shed, to the day before her next period
• The typical cycle takes approximately 28 days to complete(though
anywhere between 24-35 days is generally considered normal)
Oestrogen • During each cycle, rising levels of the hormone oestrogen cause the
ovary to develop an egg and release it(ovulation)
• After ovulation, the hormone progesterone helps the womb lining to
grow thicker, readying the womb for pregnancy
• If pregnancy does not occur, the eff is absorbed into the body, the
womb lining comes away and leaves the body(the menstrual flow)
Synchronising the menstrual cycle
Exogenous • Although the menstrual cycle is an endogenous system, evidence
suggests that it may be influenced by exogenous factors, such as the
cycles of other women
• A study by Kathleen Stern and Martha McClintock(1998) demonstrated
how menstrual cycles may synchronise as a result of the influence of
pheromones
Pheromones • Stern and McClintock studied 29 women at different stages of their
menstrual cycles, via a cotton pad placed in their armpit
• The pads were worn for at least 8 hours to ensure that pheromones
were picked up
• The pads were treated with alcohol and frozen, to be rubbed on the.
Upper lip of the other participant
• On day one, pada from the start of the menstrual cycle were applied to
all 20 women, on day two they were all given a pad from the second
day of the cycle, and so on
• Stern and McClintock found that 68% of women experienced changes
to their cycle which brought them closer to the cycle of their 'odour
Seasonal donor'.
affective
disorder(SAD) Seasonal affective disorder
• Seasonal affective disorder(SAD) is a depressive disorder which has a
DSM-5 seasonal pattern of onset. And is described and diagnosed as a mental
disorder in DSM-5
Depression • As with other forms of depression, the main symptoms of SAD are
persistent low mood alongside a general lack of activist and interest in
Circannual life
rhythm • SAD often referred to as the winter blues as the symptoms are triggered
during the winter months when the number of daylight hours becomes
shorter
Hormone • SAD is a particular type of Infradian rhythm called a circannual rhythm
melatonin as it is subject to a yearly cycle
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