Infradian rhythms Flashcards
(10 cards)
What is an infradian rhythm?
Type of biological rhythm with a frequency of less than one cycle in 24 hours
What is the menstrual cycle?
Monthly changes in hormone levels which regulate ovulation
Cycle - time between the first day of a womans period, when womans womb lining is shed, to day before her next period.
Approximately 28 days to complete
Rising levels of the hormone oestrogen can cause ovary to develop an egg and release it (ovulation)
After
Hormone progesterone helps the womb lining to grow thicker
Readying womb for pregnancy
If pregnancy does not occur egg is absorbed into the body, womb lining comes away and leaves the body (menstrual flow)
What did Stern and McClintock try and demonstrate?
Demonstrated how menstrual cycles may synchronise as a result of the influence of pheromones
What was Stern and McClintocks study?
29 women
History of irregular periods
Samples of pheromones gathers from 9 of the women at different stages if their menstrual cycles
Via cotton pad placed in their armpit
Pads were worn for at least 8 hours to ensure pheromones were picked up
Pads were treated with alcohol and frozen
To be rubbed on upper lip of other participants
Day 1 - pads from the start of menstrual cycle were applied to all 20 women
Day 2 - given a pad from the second day of their cycle and so on
What did Stern and McClintock find?
Found 68% of women experienced changes to their cycle which brought them closer to the cycle of their odour donor
What is seasonal affective disorder (SAD)?
Depressive disorder
Seasonal pattern of onset, described and diagnosed as a mental disorder in DSM-5
Persistent low moods, general lack of activity and interest in life
Triggered during winter months when number of daylight hours become shorter
Circannual rhythm - yearly cycle
How could SAD also be classed as a circadian rhythm?
Disruption of the sleep/wake cycle and this can be attributed to prolonged periods of daily darkness during winter
How does SAD work?
Hormone - melatonin is implicated
During night - pineal gland secretes melatonin until dawn when there is an increase in light
Winter - lack of light in morning means secretion process continues for longer
Thought to have a knock on effect in the production of serotonin in the brain
Chemical that has been linked to the onset of depressive symptoms
What is a strength of infradian rhythms?
Mentrual synchrony
Explained by natural selection
Synchronisation - thought to have evolutionary value
Advantageous for women to menstruate together and become pregnant at same time
Social group - allow babies who lost their mothers during or after childbirth to have access to breastmilk
Improving chances of survival
Suggesting synchronisation is an adaptive strategy
What is a negative of infradian rhythms?
Methodological limitations
Many factors that may effect change in menstrual cycle
Eg. stress, diet, exercise
Confounding variables
Any supposed patter of synchronisation is no more than would have been expected to occur by chance
May explain why other studies have failed to replicate this finding
Suggesting menstrual synchrony studies are flawed
