Biological rhythms

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  • Created by: Danielle
  • Created on: 23-05-13 16:38
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  • Biological Rhythms
    • Ciradian rhythm
      • 24 hour cycle e.g. Sleep wake cycle and body temperature
      • Sleep wake cycle is controlled by endogenous pacemakers, are essentially internal body clocks & also controlled by external environmental cues, called exogenous zeitgebers e.g. light
        • Light comes in through eyes, this activates the SCN which controls the pineal gland, and releases melotonin which increases tiredness
      • Research - Siffre 7 months in a cave, found ciradian rhythm increased to 25 hours
        • Evaluation
          • Case study, not representative of whole population, therefore have difficulty generalising
          • Research support, Wever places participants in WW2 blunker, found sleep wake cycle still operates despite the lack of external cues. Therefore supporting the idea of endogenous pacemakers
          • Study has artifical setting, so lacks mondue realism and therefore, questions validity of study
      • Morgan - He removed the SCN from Hamsters, found that the cycle disappeared. So shows SCN does cause our body clock to change
        • Evaluation
          • Research support from Silver, carried out same experiment and found same results. Therefore high internal reliability
          • Biologically reductionistic,as even though hamster and humans have SCN hamsters are nocternal & humans are diernal. So issues with generalastion
          • High control over variables, as lab exp. So high internal reliability
    • Infradian rhythm
      • Cycles that last more than 24 hours like menstrual cycle
      • Menstrual cycle - is governed by hormones, an endogenous mechanism.It is governed by the female hormones oestragon & progestrone
        • McClintock - Looked at women living together i.e. nuns and boarding schools through diaries and questionnaires. Found that with women living together it made their menstrual cycles syrenised with each other. So external factors do affect the menstrual cycle
          • Evaluation
            • Case study, not representative of whole population, therefore have difficulty generalising
            • Why would women sychonise, maybe because of evolution, can share looking after.
            • Supports external factors do affect the cycle
      • Reinberg - Observed women in a cave for 3 months, with only dim lighting. Found menstrual cycle become shorter during, it took a further year for her cycle to return to normal. Suggeting that external cues can effect the endogenous rhythm of the menstrual cycle
        • Evaluation
          • Case study, not representative of whole population, therefore have difficulty generalising
          • Study has artifical setting, so lacks mondue realism and therefore, questions validity of study
          • Women may have suffered pschological harm as had no interaction for 3 months.
    • Ultradian rhythm
      • Cycles under 24 hours e.g. cycles within sleep, feeding/digestion
      • Jouvet - Tested the consequences of REM deprivaiton in cars. Placed an upturned flower-pot in a large tank of water. Cats had to sit on it. Found in NREM sleep they were able to remain sitting up, but with loss of muscle tone. In REM sleep they slipped into the water, as they woke up there heads began to nod. The cats died in the end.
        • Evaluation
          • Ethical issues, animals can't consent
          • Testing on animals, have different sleep paterns so biologically reductionistic
          • Lab study, high control over variables, therefore more internally relaible
      • Dement - Carried out a systematic study of REM & NREM. Some participants were deprived of REM sleep over a period of several days, whereas otehrs deprived of NREM sleep. In general effects of REM sleep deprivation were more severe, including increased aggression & poor concentration
        • Evaluation
          • Lab study, high control over variables, therefore more internally relaible
          • Study has artifical setting, so lacks mondue realism and therefore, questions validity of study
          • Small sample size, so not representative of whole population. Therefore, lacks external reliability
  • Study has artifical setting, so lacks mondue realism and therefore, questions validity of study

Comments

Liam

"Jouvet - Tested the consequences of REM deprivation in cars"... Sleepy cars?

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