Lecture notes Biopsychology - Biological Rhythms_ Infradian and Ultradian Rhythms
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Course
Biopsychology
Institution
AQA
Breakdown information and notes on Biological Rhythms_ Infradian and Ultradian Rhythms
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Biological Rhythms: Infradian and Ultradian Rhythms
KEY TERMS:
- INFRADIAN RHYTHMS - type of biological rhythms with a frequency of less than one cycle
in 24 hours, such as menstruation and seasonal affective disorder
- ULTRADIAN RHYTHMS - type of biological rhythms with a frequency of more that one cycle
in 24 hours such as the stages of sleep
INFRADIAN RHYTHMS:
THE MENSTRUAL CYCLE -
- Female menstrual cycle is an example of infradian rhythm which is governed by monthly
changes in hormone levels which regulate ovulation
- Cycle refers to the time between the first day of a women’s period when womb lining is shed
to the day before her next period
- Typical cycle approx is 28 days to complete but between 24-35 days is considered normal.
- In each cycle - hormone oestrogen level rises causing ovary to develop an egg releasing it
(ovulation)
- After ovulation the hormone progesterone helps womb lining to grow thicker ready for body
for pregnancy
- If pregnancy don’t occur, egg is absorbed into body, womb lining comes away and leaves the
body (menstrual flow)
RESEARCH STUDY -
- Menstrual cycle is endogenous system but evidence show that is can be influenced by
exogenous factors e.g. cycle of other women
- Kathleen Stern and Martha McClintock (1998) demonstrated how menstrual cycles may
synchronise as a result of the influence of female pheromones
- McClintock involved 29 women with a history of irregular periods. Samples of pheromones
were gathered from 9 of the women at different stages of their menstrual cycle via cotton pad
placed in their armpit
- Pads were worn for at least 8 hrs so pheromones can be picked up
- Pads were treated with alcohol and frozen. Then rubbed on upper lip of the other
participants
- Day one - pads from the start of the menstrual cycle were applied to all 20 women
- Day 2 - all given a pad from the second day and so on
- McClintock found 68% women experienced changes to their cycle which brought them
closer to the cycle of their 2odour donor”
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