infadian rythms


Infadian Rhythms- biologcal clocks lasting more than 24 hours

Menstral cycle - monthly-function regulate ovulation by flucuation of hormones, pituity gland releases the hormones FSH and LH- stimulate a follical n one ovary to ripen an egg and also release oestrogen. once egg ripened- ruptured follical release progesterone- causes line of whomb to prepare for pregnancy. 2 weeks- not pregnant lining of womb shreds. orginally thought to be regulated by the hypothalumus an edogenous pacemaker- however evidence has shown edogenous zeitgebers play a part too.

Seasonal affective disorder- yearly- become drepressed in the winter months and recover during the summer. Suffers suffer from server symptoms of low moods and depression through seasonal changes, thought to be brought about through less light and increased melatonin production in the darkness by pineal gland. sertonin is also converted to melatonin causing low amount of sertonin which has been linked to chronic depression.

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AO2- Russel et al 1980

shows that the menstral cycle is influenced by exogenous zeitgebers

  • allocated 3 groups of women
  • 1- donar of sweat, 2. sweat and alchole rubbed on upper lip, 3- control group- alchole on lip
  • women kept seperate
  • results found that women from group two got syncronised cycles with donars of sweat

this shows menstral cycle is influenced by exogenous zeitgebers as they nfluence edogenous pacemakers

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AO2- reinburg

reported on a women who spent 3 months in a cave

  • menstral cycle went from 28 days to 25.7 days

which imples that infradian rhythms are influenced by exogenous zeitgebers such as light cues and required to remain syncronised


  • living in a cave has low ecologcal vlidity and is not representative of natural settings
  • results cannot be genralised nor can be concluded such changes were due to the absence of light as temperature, smell and noise could have also contributes in some form of exogenous zeitgebers
  • other confounding variables could not be rules out

case study- one individual- results may not have external validity and genralisation to the wider population due ti indivdual differences such as age and health

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premenstral sydrome

  • disorder that affects women a week before menstration
  • symptoms such as depression, mood swings and aggression

menstral cycle important to understand- shown that PMS is physological (caused by hormones) but has psychologcal effects.

Dalton- found that PMS was assosiated with an increase in accidents, suicides and crime

some cases PMS has been cited as 'mental disorder' to excuse behavours such as murder

  • ms english- drove car in married love after an argument and killed him. her defence team used PMS as a legal defence and she was placed on probation
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IDA- deterministic- PMS

however- makes it a deterministic explanation as it assumes women have no free will of their own or any control  over this mental disorder and therefore could not be held liable for their actions

  • opens a great debate as too how much free wll plays a role with PMS suffers could cite such for other aggressive acts devolving people responsibility for their actions.

also to classify PMS as a mental disorder is very reductionist and oversimplying the control women actually have in their actions.

  • Many psychologcal and cognitive factors have been shown to enable people to manage their emotions and have self-control
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AO2-alternative explanation

also explained in terms of being a natural outcome of infradian rythm, but alternativly it could be a consequence of distrupted circadium rhythms.

  • in the uk, as the seasons change from summer to winter, circadium rhythms may be thrown out of phase
  • people continue to get up the same time but go to bed earlier because it darker

this means that the biologcal system gets the impresssion that time is shifting and the result is similar to jet lag

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IDA- real world application

understanding the role of darkness in SAD has lead to successful therapies, most notably the Photothearpy.

  • this uses strong lights in the evening or mornings to change levels of melatonin and serotonin.
  • SAD suffers have reported that daily use of such light theorpies is enough to relieve from such feelings like depression and other symptoms

eastman et al- however found that placebo effects could also be at wokr simply a beliefe that the therapy will work.

  • one study found that 32% of participants reported improvments with the placebo alon which questions the effectivness
  • the problem could then be more psychological for some than others and other therapies maybe more suitable
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