Infradian rhythms

• What are infradian rhythms?

  Biological rhythm with a frequency of less than one cycle in 24 hours
• What are two examples of infradian rhythms?

  Menstruation and Seasonal Affective Disorder
• What is the menstrual cycle governed by?

  Monthly changes in hormone levels regulating ovulation
• What is the typical length of the menstrual cycle?

  28 days
• What happens during each menstrual cycle?

  Oestrogen causes ovary to develop an egg and release it
• What happens after ovulation?

  Progesterone helps womb lining grow thicker
• What do Stern and McClintock suggest the menstrual cycle is influenced by?

  Exogenous factors
• Who suggests the menstrual cycle is influenced by exogenous factors?

  Stern and McClintock
• What type of system is the menstrual cycle?

  Endogenous
• How many women did Stern and McClintock study?

  29
• What did Stern McClintock study?

  Women with irregular periods
• What was the procedure in Stern and McClintock's study?

  Pheromones gathered from nine women and rubbed on upper lip of other participants
• What did Stern and McClintock find?

  68% women experienced changes bringing them closer to their 'odour donor'
• What is Seasonal Affective Disorder?

  Seasonal depressive disorder
• What are the main symptoms of SAD?

  Low mood, lack of activity and interest in life
• What particular type of infradian rhythm is SAD?

  Circannual
• Why is SAD a circannual rhythm?

  Yearly cycle
• Why can SAD also be classed as a circadian rhythm?

  May be due to disruption of sleep/wake cycle
• What hormone have psychologists suggested causes SAD?

  Melatonin
• What does SAD stand for?

  Seasonal affective disorder
• What gland secretes melatonin?

  Pineal gland
• When does the pineal gland secrete melatonin?

  Night until dawn
• What does the lack of light in the morning in winter mean for the secretion of melatonin?

  Process continues longer
• What affect does the secretion of melatonin lasting longer have?

  Affects production of serotonin