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Biological rhythms
Infradian and ultradian rhythms
Infradian rhythms
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Created by
Billy Dudden
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A Level > Psychology > Biopsychology > Biological rhythms > Infradian and ultradian rhythms > Infradian rhythms
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What are infradian rhythms?
Biological rhythms with a
frequency
of
less
than one in
24 hours
E.g.
menstrual cycle
Menstrual cycle
Time between first day of
period
and day before next
Regulated by
hormones
-
oestrogen
and
progesterone
Typical cycle is
28
days (can range from
24
-
35
)
Increase in
oestrogen
during first half - triggers ovary to develop and release
egg
Increase in
progesterone
during second half, thickening of
womb lining
preparing for
implantation
of egg
If not pregnant, egg is absorbed,
progesterone
and
oestrogen
levels drop and lining
sheds
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