The Menstrual Cycle

• What is the role of circadian rhythm in humans?

  It regulates the cycle of sleeping and waking.
• How does the circadian rhythm relate to the internal body clock?

  The circadian rhythm is governed by an internal body clock that responds to environmental cues like sunlight.
• What does the term "ultradian" refer to?

  It refers to rhythms that occur more than once every 24 hours.
• What does "infradian" mean in the context of biological rhythms?

  Infradian refers to rhythms that take longer than a day to complete.
• What is the most obvious infradian rhythm in humans?

  The menstrual cycle.
• What is the typical duration of the menstrual cycle?

  The menstrual cycle typically lasts 28 days.
• What biological changes occur during the menstrual cycle?

  Changes include egg release, womb lining thickening, and loosening during menstruation.
• Which hormones regulate the menstrual cycle?

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

  They act as an internal body clock regulating biological processes.
• How did McClintock's research contribute to understanding menstrual synchronization?

  It suggested that women living together may synchronize their cycles through social interactions.
• What did Russell's research in 1980 suggest about menstrual synchronization?

  It suggested synchronization could be due to women sharing pheromones.
• What was the method used in Stern's 1998 study on menstrual cycles?

  Women were given pads to wipe on their lips, which contained pheromones from other women.
• What were the findings of Stern's 1998 study?

  Women adjusted their menstrual cycles based on the pheromones of donor women.
• What is a criticism of the idea that pheromones influence menstrual synchronization?

  Many studies have failed to replicate the findings of synchronization.
• What did Trevathan's 1993 study find regarding cohabiting couples?

  Even cohabiting lesbian couples did not synchronize their menstrual cycles.
• What is the evolutionary argument regarding menstrual synchronization?

  Some argue it could prevent one male from dominating a group, promoting genetic diversity.
• What is the historical belief about menstrual cycles and the moon?

  Many believed menstrual cycles were controlled by the phases of the Moon.
• What did the study of 1.5 million women reveal about menstrual cycles and the moon?

  There was no link between menstrual frequency and the moon phases.
• What is the significance of the chimpanzee's menstrual cycle in this context?

  It shows that if synchronization had an evolutionary advantage, it should be evident in our closest relatives.
• How long is the average human woman's menstrual cycle?

  About 28 days.
• What is the correlation between menstrual cycles and evolutionary advantages?

  There is no clear evidence of a correlation between menstrual cycles and evolutionary advantages.
• What are the types of biological rhythms discussed in the study material?

  • Circadian rhythms: around a 24-hour cycle
  • Infradian rhythms: longer than a day (e.g., menstrual cycle)
  • Ultradian rhythms: more frequent than once a day
• What are the biological aspects of the menstrual cycle?

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

  • Many studies failed to replicate findings
  • Variability in menstrual cycle lengths can explain apparent synchronization
  • Evolutionary arguments are conflicting