infradian rhythms

• example of infradian rhythm?

  • menstrual cycle
• how long does 1 menstrual cycle take to complete?

  28 days
• how often does the menstrual cycle occur?

  once a month
• describe menstrual cycle?

  1. begins on 1st day of period - womb lining sheds
  2. during each cycle - hormone oestrogen increases causes ovary to develop egg & release it - ovulation
  3. after ovulation - hormone progesterone helps womb lining grow thicker to prepare body for pregnancy
  4. if not pregnant womb lining sheds & leaves body
• who researched into exogenous zeitgebers for menstrual cycle?

  mcclintock
• mcclintocks study?

  • 29 women with irregular periods
  • 9 women gave samples of pheromones from armpits at different times in cycle
  • pheromone samples sterilised & rubbed on lip of other p
  • 68% experienced changes to their cycle
  • made them closer to cycle of donor who they got pheromones from
• 2 X of infradian rhythms?

  1. evidence to contradict exogenous zeitgebers by yank & schank
  2. methodological issues
• 1 * of yank & schanks study?

  used natural experiment
• X evidence to contradict influence of e.z by yank & schank?

  • natural experiment - studied 186 chinese women living in uni halls over a year
  • found no evidence of womens cycles becoming synchronised
  • shows that mcclintocks findings not fully representative of all womens menstrual cycle
  • may be other factors other than pheromones that control this b.r
• X methodological issues for infradian rhythms?

  • many evs such as sleep/diet/exercise that can affect menstrual cycle
  • rarely controlled in studies such as mcclintocks
  • means other factors affecting timings of cycle
  • difficult to determine cause & effect between menstrual cycle & i.r
  • more controlled studies need to be conducted that control for diet/stress levels
• what is a biological rhythm?

  • pattern of change in body that occurs in cycles & repeats
  • can match daily, monthy, yearly cyclic changes in environment
  • different rhythms have cycles that last different amounts of time for them to complete & begin again