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Summary biological rhythms - infradian and ultradian
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notes on biological rhythms for biopsych for aqa a level psychology
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Biological rhythms: Ultradian and InfaradianInfaradian rhythms (less than one cycle in 24 hours)
- The female menstrual cycle is an infaradian rhythm, it takes about 28 days.
- Rising levels of oestrogen cause the ovary to develop an egg and release it (ovulation)
- After ovulation progesterone helps to thicken the womb lining to prepare the womb for
pregnancy
- If pregnancy doesn’t occur the egg is absorbed into the body, the womb lining comes
away causing the menstrual flow (actual bleeding)
Stern and McClintock
- Studied 29 women with irregular periods.
- Pheromones were taken from some at different stages of their cycles, via a cotton pad
under the armpits.
- They were then rubbed on the upper lips of the rest of the women.
- 68% of women experienced changes in their cycles which brought them closer to the
cycle of the ‘odour donor’.
Seasonal affective disorder (SAD) is a depressive disorder (causing low mood, lack of
activity) with a seasonal pattern.
- called the winter blues as symptoms are triggered when hours of daylight become
shorter.
- During the night melatonin is secreted from the pineal gland, in winter secretion goes on
for longer. Causing low serotonin which is linked to depressive symptoms.
- Particular type of Infaradian rhythm called a circannual rhythm as it has a yearly cycle.
- Can also be classed as a circadian rhythm because the experience of SAD could be due to
disruption of sleep/wake cycle with prolonged periods of daily darkness in winter.
Ultradian rhythms (more than one cycle in 24 hours)
- Stages of sleep are an ultradian rhythm.
- Sleep patterns occur in 90-minute periods, divided into 5 stages each characterised by a
different level of brainwaves using an ECG.
5 stages of sleep:
Stages 1 and 2 – represent ‘sleep escalator’ where participant can easily be awoken.
(High frequency brain waves and short amplitude) alpha waves
Stages 3 and 4 – it’s difficult to wake someone up at this point. (Lower frequency brain
waves and higher amplitude) delta waves
Stage 5 (REM sleep) – associated with dreaming and rapid eye movement, correlates
with dreaming phase. theta waves
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