infradian + ultradian rhythms

• infradian rhythm:

  • more than 24 hours
• ultradian rhythm:

  • less than 24 hours
• menstrual cycle:

  • day 1-4 : menstruation
  • day 4-14: build up of uterus lining, egg released, oestrogen levels increase
  • day 14-28: lining maintained, oestrogen decreases, progesterone increases
  • day 28 : lining breaks down
• synchronising menstrual cycle:

  • endogenous system, exogenous factors can influence
• Stern + McClintock:

  • 29 women with irregular periods
  • samples of pheromones gathered from9 at different stages of cycle (cotton pad on armpit)
  • treated, frozen, rubbed on upper lip of other person on each day of cycle
  • 68% experienced changes - close to odour donor
• seasonal affective disorder (SAD):

  • depressive disorder with seasonal pattern (circannual rhythm)
  • symptoms triggered during winter months - decrease of daylight hours)
  • lack of light in morning, melatonin secreted for longer, knock on effect on serotonin
• stages of sleep:

  • ultradian rhythm
  • 5 stages span 90 minutes
  • characterised by different levels of brainwave activity (monitored through EEGs)
• stage 1-3 of sleep:

  • 1: light sleep (some muscle activity) - alpha waves
  • 2: breathing + heart rate decrease, slight decrease in body temperature -alpha waves
  • 3: deep sleep - delta waves
• stage 4-5 of sleep:

  • 4: very deep sleep (rhythmic breathing + limited muscle activity) - delta waves
  • 5: rapid eye movement REM - brainwaves speed up and dreaming occurs
• REM:

  • makes sense of info - connections between stored + newly stored info
  • helps us deal with emotions (sleep therapy through dreaming) - some parts are more active when sleeping e.g amygdala 30% more active
• NREM:

  • fact based memory, maintains memories + salvages those lost night before
  • renews ability to learn new info - clears hippocampus
  • deep sleep allows storage + ability to recall info + restocking immune system
• EVALUATION: evolutionary basis

  • synchronisation of menstrual cycle - female ancestors become pregnant at same time - allows orphan babies to access milk
  • Penton-voak et al - mate choices vary, women prefer feminised male features for long term partner, ovulation = more masculine
  • sexual behaviour is influenced by infradian rhythms - adaptive strat
• EVALUATION: synchronisation - methodological issues

  • many factors menstrual cycle e.g stress, diet - may act as CVs, pattern of synchrony is no more than would be expected by chance
  • explains why studies cant replicate findings
  • menstrual synch studies are flawed
• EVALUATION: role of melatonin in SAD

  • Terman - rate of SAD more common in north countries - winter nights are longer
  • led to practical application (light therapy) - effective in decreasing effects of SAD in 80% of users
  • knowing possible causes of SAD leads to treatment of sufferers
• EVALUATION: evidence for REM sleep stage

  • Dement + Kleitman - monitored sleep patterns of 9 people on EEGS, EVS e.g caffeine + alcohol controlled
  • REM activity highly correlated to experience of dreaming - activity varied on how vivid dreams were + people woken during dreaming could recall dreams
  • replications found similar findings - reliable research that REM is important to sleep cycle
• EVALUATION: individual differences - variations in ultradian rhythms

  • Tucker et al - studied participants over 11 consecutive days and nights- found differences in duration of sleep stages (3+4)
  • suggests differences are likely to be biologically determined
  • difficult to describe normal sleep in a meaningful way + generalise findings - limits external validity