Ultradian & Infradian Rhythms

• How long does the female menstrual cycle typically take?

  28 days on average
• What happens during Stage 1 of the menstrual cycle?

  Ovulation occurs with high oestrogen levels
• What occurs during Stage 2 of the menstrual cycle?

  Implantation occurs with high progesterone levels
• What influences the menstrual cycle despite being endogenous?

  Exogenous factors like pheromones
• What effect do pheromones from another woman have on a woman's menstrual cycle?

  They can sync her cycle with another woman
• What is the evolutionary basis for menstrual synchrony?

  • Distant ancestors may have synced cycles
  • Increased survival rate of children
  • Requirement of breast milk for infants
  • Synchronization is an adaptive strategy
• What are the methodological limitations of the pheromone experiment?

  • Many confounding variables exist
  • Factors like diet and behavior affect results
  • Cannot definitively attribute synchrony to pheromones
• What are the three biological rhythms in our body?

  Circadian, infradian, ultradian rhythms
• What is a circadian rhythm?

  A cycle that occurs in a 24-hour cycle
• How often does the sleep cycle repeat?

  Every 90 minutes
• What happens during stages 1 and 2 of the sleep cycle?

  Light sleep with slow brainwaves
• What characterizes stages 3 and 4 of the sleep cycle?

  Deep sleep with delta waves
• What occurs during Stage 5 of the sleep cycle?

  REM sleep with body paralysis
• What have sleep scientists discovered about the sleep-wake cycle and age?

  • Sleep-wake cycle length decreases with age
  • Growth hormones are produced during sleep
  • Shorter cycles lead to sleep deficit
• What are individual differences in the sleep-wake cycle?

  • Significant differences in sleep effects
  • Especially in stages 3 and 4
  • Biologically dictated variations
• Why is it difficult to define a normal sleep cycle?

  Due to individual differences in sleep stages