Infradian and Ultradian Rhythms

    Cards (9)

    • infradian rhythms
      rhythms that have a duration of over 24 hours, and may be weekly, monthly, or even annually
    • ultradian rhythms
      rhythms that last less than 24 hours
    • 2 examples of infradian rhythms
      • the menstrual cycle
      • seasonal affective disorder (SAD)
    • what happens during the menstrual cycle
      • lasts around 28 days and releases oestrogen- causes uterus lining to build up
      • the luteinising hormone causes egg to be released
      • then progesterone released to thicken womb lining
      • if pregnancy doesn't occur egg is absorbed and womb lining breaks down- menstrual flow
    • Seasonal Affective Disorder (SAD) 

      a seasonal variation in mood with some people becoming severely depressed during winter months - melatonin is secreted from the pineal gland and has an affect on serotonin and mood
    • 2 examples of ultradian rhythms
      • sleep cycle (every 90 minutes)
      • the basic rest activity cycle (BRAC)
    • 5 stages of sleep
      first 4 stages= NREM (non-rapid eye movement)
      1 and 2-> light sleep
      3 and 4-> deep sleep
      last stage= REM (rapid eye movement)-> when dreaming occurs. brain activity speeds up significantly
    • the basic rest activity cycle
      a 90-minute rhythm cycle characterised by a period of alertness followed by a spell of fatigue. this occurs every 90 minutes throughout the day
    • evidence for the influence of exogenous factors on our menstrual cycle: Stern and Mclintock (1998)
      • aimed to investigate whether women's cycles would synchronise as a result of the influence of female pheromones
      • they took a group of women who had irregular periods and gathered a sample of pheromones from 9 of the women by using cotton pads and placing under their arms for 8 hours
      • these were then frozen and wiped under the noses of 20 other women
      • it was found that 68% of the women experienced changes to their cycles which were more in sync with their pheromone donor