Biopsych - Infradian Rhythms Flashcards
What are infradian rhythms
Biological rhythms that last more than 24 hours. o Weeks
o Months o Years
What is an example of an infraradian rhythm
The menstrual cycle
SAD
Explain the menstrual cycle
Monthly rhythm
The cycle refers to the time between the first day of a woman’s period, when the lining is shed, to the day before her next period.
Cycle varies - most commonly 28 days
During each cycle
Oestrogen levels rise
Cause ovary to release developed egg
-> known as ovulation
After ovulation - progesterone levels increase to help womb lining grow thicker , preparing for pregnancy
If pregnancy doesn’t occur - egg absorbed , womb lining comes away and leaves body —> menstrual flow
Outline McClintocks study
29 women with irregular periods
Pheromones gathered from 9 of women at different stages of menstruated cycle
Via cotton pad on armpit
Pads treated with alcohol and frozen - rubbed on upper lip of other participants
Pads from start of cycle applied on day 1
Day 2 pads applied from second day of cycle and so on
68% of women were brought closer to cycle of their odour donor
Influenced by exogenous factors
Explain Seasonal Affective Disorder (SAD)
Circannual rhythm - yearly cycle
depressive disorder which has a seasonal pattern of onset. The main symptoms of SAD are persistent low mood and a general lack of activity and interest in life.
Melatonin is involved.
In night pineal gland secretes melatonin until morning when there is an increase in light.
During winter the lack of light means the secretion process continues for longer.
knock-on effect on the production of serotonin which has been linked to depressive symptoms
Strength of infraradian rhythms (evolutionary value)
Menstrual cycle being synchronised - evolutionary value
advantageous for our female ancestors to menstruate together and become pregnant around the same time.
offspring could be cared for together
within a social group
increasing the offspring’s chances of survival.
evolutionary advantageous
What is a limitation of infraradian rhythms (questionable evolutionary perspective)
Schank - questions evolutionary perspective
Too many females cycling - increase competition for high quality males
As females want best genes for offspring
Competition leads to less high quality males - low genetic fitness of offspring
Avoidance of synchrony naturally selected
Questions how adaptive menstrual cycle is
What is another limitation of infraradian rhythms (methodology in research)
Been argued many factors may change a women’s menstrual cycle and act as confounding variable. In research
Eg stress + changes in diet
Supposed Pattern of synchronisation in mcClintock’s study could’ve been just due to chance
+ research involves small sample of women and self report on their cycle -> inaccurate
Study lacks internal validity
What is a strength of infraradian rhythms (practical application)
Research into SAD
Leads to Effective treatment for SAD
Phototherapy - light box stimulates strong light in morning and evening
Resets Melatonin levels
Relives symptoms of 60% of suffers
Research into infraradian rhythms - improved quality of life
