The Menstrual Cycle: Infradian Rhythm

• What is the role of circadian rhythm in humans?

  It regulates the sleep-wake cycle
• How does the circadian rhythm relate to the sun?

  It is influenced by the light from the sun
• What does the term 'infradian' mean?

  Below the frequency of once a day
• What does 'ultradian' mean in biological rhythms?

  More frequent than once every 24 hours
• What is the menstrual cycle's average duration?

  28 days
• What biological changes occur during the menstrual cycle?

  Egg release and womb lining changes
• Which hormones regulate the menstrual cycle?

  Estrogen and progesterone
• What is the role of endogenous pacemakers in the menstrual cycle?

  They keep biological processes on time
• How did McClintock's research contribute to understanding menstrual synchronization?

  It showed women synchronized cycles in dorms
• What did Russell's research in 1980 suggest about menstrual synchronization?

  It could be due to shared pheromones
• What did Stern's 1998 study find about menstrual cycles?

  Pheromones affected cycle length in women
• What is a criticism of the pheromone synchronization theory?

  Many studies failed to replicate findings
• What did Trevethan's 1993 study reveal about menstrual synchronization?

  Lesbian couples did not synchronize cycles
• What evolutionary advantage is proposed for menstrual synchronization?

  It prevents one male from dominating reproduction
• What is a conflicting argument against menstrual synchronization as an evolutionary advantage?

  Women may compete for the best genes
• What historical belief is associated with menstrual cycles?

  They were thought to be controlled by the moon
• What did the study of 1.5 million women find about menstrual cycles and the moon?

  No link between cycles and moon phases
• Why is the correlation between menstrual cycles and the moon considered correlation, not causation?

  There is no direct cause-effect relationship
• What are the types of biological rhythms based on frequency?

  • Circadian: around a day
  • Infradian: less than once a day
  • Ultradian: more than once a day
• What are the biological aspects of the menstrual cycle?

  • Egg release
  • Thickening of womb lining
  • Loosening of womb lining during menstruation
• What are the strengths and weaknesses of the pheromone synchronization theory?

  Strengths:

  • Some studies support synchronization
  • Suggests external cues influence cycles

  
  

  Weaknesses:

  • Many studies fail to replicate findings
  • Variability in cycles may explain results
• What is the significance of the menstrual cycle in psychology?

  • It reflects biological rhythms in humans
  • It is a key area of research in female fertility