infradian rhythms

• What are infradian rhythms?

  Biological cycles lasting longer than 24 hours.
• What is an example of an infradian rhythm?

  The menstrual cycle.
• How long is the average menstrual cycle?

  28 days.
• What regulates the menstrual cycle?

  Hormone secretions from the ovaries, specifically oestrogen and progesterone.
• How did the understanding of menstrual cycle regulation evolve?

  Initially thought to be controlled solely by the hypothalamus, but now known to be influenced by external cues as well.
• What is PMS?

  A condition occurring before menstruation characterized by irritability and stress.
• What are common symptoms of PMS?


  Irritability, stress, poor concentration, and loss of appetite.
• What is Seasonal Affective Disorder (SAD)?

  A form of depression experienced during the winter months due to reduced daylight.
• How does reduced daylight affect serotonin levels in SAD?

  Less light increases melatonin production, lowering serotonin levels.
• What happens to the symptoms of SAD in summer?


  The rhythm recovers, and symptoms typically improve.
• What are annual rhythms?

  Biological rhythms occurring once a year.
• What is an example of an annual rhythm related to health?

  Increased heart attacks and deaths in winter months.
• What does the increase in heart attacks in January suggest?

  There is an annual cycle to mortality.
• What was the duration of the woman's menstrual cycle after spending 3 months in a cave without natural light according to Reinberg (1967)?


  25.7 days
• What do the findings of Reinberg (1967) suggest about infradian rhythms?


  They are influenced by exogenous zeitgebers like light
• What are the limitations of Reinberg's study regarding ecological validity?


  The study has low ecological validity and confounding variables may have affected results
• What did Russell et al. & McClintock find regarding menstrual cycles?


  Applying underarm sweat to women's upper lips synchronized menstrual cycles
• What implication do the findings of Russell et al. & McClintock have about pheromones?


  Pheromones act as exogenous zeitgebers
• What is a potential criticism of the findings on menstrual synchrony by Russell et al. & McClintock?


  Menstrual synchrony might be random and cycles vary
• What evolutionary advantage did Turke suggest regarding synchronized periods?


  It allowed women to share child-caring duties
• What is a limitation of Turke's evolutionary explanation for synchronized periods?


  The theory is speculative and lacks empirical support
• What causes Seasonal Affective Disorder (SAD)?


  Reduced daylight increases melatonin production and lowers serotonin
• What are the depressive symptoms associated with SAD?


  They are caused by increased melatonin and decreased serotonin
• What treatment has been effective for SAD?


  Phototherapy (exposure to bright light)
• What is a concern regarding the efficacy of phototherapy for SAD?


  Placebo effects show a 32% improvement
• How does Rosenzweig et al. link SAD to infradian rhythms?


  They suggest darkness triggers melatonin
• What alternative explanation is provided for SAD related to circadian rhythms?


  SAD might be caused by a disrupted circadian rhythm due to seasonal time shifts
• What are the key findings and implications of Reinberg's study on infradian rhythms?


  • Woman spent 3 months in a cave without natural light
  • Menstrual cycle shortened to 25.7 days
  • Suggests infradian rhythms are influenced by exogenous zeitgebers like light
  • Study has low ecological validity and confounding variables may have affected results
• What are the findings and criticisms of Russell et al. & McClintock's research on menstrual synchrony?


  • Applying underarm sweat synchronized menstrual cycles
  • Implies pheromones act as exogenous zeitgebers
  • Criticism: menstrual synchrony might be random and cycles vary
• What is the evolutionary explanation for synchronized menstrual cycles proposed by Turke?


  • Synchronized periods allow women to share child-caring duties
  • The theory is speculative and lacks empirical support
• What is Seasonal Affective Disorder (SAD) and its treatment?


  • Caused by reduced daylight, increasing melatonin and lowering serotonin
  • Treatments include phototherapy (bright light exposure)
  • Placebo effects raise questions about efficacy
• How is SAD linked to circadian rhythms?


  • Darkness triggers melatonin production
  • SAD may also result from disrupted circadian rhythms due to seasonal time shifts