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  • Created by: ava.scott
  • Created on: 11-03-15 23:59
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  • BIORHYTHMS: Cicardian
    • AO1
      • CONTROL
          • The suprachiasmatic nucelus
            • small group of cells above the nucleus
            • just abive the optic chaism and connects the retina of the eye to the SCN.
              • Allowing light to influence the activity of the SCN.
            • The cells in the SCN produce a protein for hours until the level inhibits further production, again for hours.
              • this rhythm activates the pineal gland which releases melatonin.
                • melatonin is released at night in the dark. So light must inhibit the protein production, and therefore melatonin.
          • e.g. light and dark
          • Light is the dominant cue for cicardian rhythms
          • Light sensitive cells in the retina tell the brain whether it is day or night ad adjusts sleep patterns.
          • when the sleep wake cycle has to adjust to new cues, this is called ENTRAINMENT.
        • sleep-wake cycle exists without light, but is influenced by exogenous zeitgebers too.
    • IDA
      • Biological approach- good
        • easy to test empirically and objectively.
        • practical apps.
        • can understand mechanisms clearly.
      • biological approach- bad
        • doesnt explain cultural variations: the spanish and other Mediterranean countries have a nap at midday, when the sun is brightest--- therefore melatonin should be low?
        • doesnt explain time changes: research by wehr and ekirch give evidence for two sleeps and a mid-night wakeful period.
      • morgan
        • removed the SCN's from hamsters, and found they had no sleep wake cycle. They then transplanted mutated SCN's into healthy masters and found they took on the mutated cycles.
        • Grounding: Supports the theory as it shows how significant the SCN and its activity is in the sleep patterns and behavior of hamsters. It also completely defines their sleep-wake cycle.
        • Evaluation: not humans, so not completely generalisable to people.
        • evaluation: ecologically invalid as being in a artificial setting may make the hamsters more or less influenced by their SCN.
        • Evaluation: highly controlled as hamsters were kept in a laboratory, so very few variables. this is good for the evidence and theory.
      • Shochat
        • kept 6 men in a sleep lap for 29 consecutive hours.
          • by taking their blood every 20 minutes, he found that melatonin release preceeded the sleep gate by 120 minutes.
          • made them go into a dark room for 7 minutes of every 20 minutes, to try and sleep.
        • Evaluation: small populational validity; men may take longer/shorter amount of time to respond to melatonin.
        • evaluation: artifical conditions may have made the participants more or less tired, therefore affecting the ecological and internal validity.
          • the dark room for 7 minutes may have made the effects of melatonin stronger or weaker, or caused it to be released sooner or later.
        • evaluation: very repeatable and empirical. blood analysis is not easy to create bias in.
        • Grounding: Supports the role of melatonin in drowsiness, as it preceeds the sleep gate. Therefore, it may play a role in making the sleep gate come around.
          • However, low ecological and populational validity means the research cannot be generalised freely.
        • also found that melatonin tablets helped insomniacs get to sleep, when taken 2 hours before.
      • Case studies
        • SIFFRE
          • Spent 2 months in a dark cave and found hat his natural cicardian rhythm lengthened to 25 hours.
          • Grounding: Supports that there is a sleep wake cycle that is endogenous and exists without light cues. However, the darkness had an effect of the cycle. Therefore, exogenous zeitgebers are influential. This supports the theory as there is an interaction between the two.
          • evaluation: low populational validity- only oneguy!
          • evaluation: many factors that change within the cage e.g. diet, social interaction, exercise.
          • evaluation: unappliable to real life.
          • developed a 24.9 hour sleep-wake cycle and needs to take stimulants and sedatives to sleep at normal times.
          • Grounding: supports role of both endogenous  and exogenous zeItgebers. without normal light as a exogenous zeitgeber, there was not a normal 24 hour cycle, so they are needed for synhronisation
            • evaluation: low populational validity- only oneguy!
      • Mariana Figueiro
        • Found that the use of an ipad or self-luminous screen suppressed melatonin by up to 22%.
        • Grounding: the new light from the device told the brain it was daylight, and they should tsay awake. Therefore it supports the role of light as an exogenous zeitgeber.
        • evaluation: many factors within the tablet- mental stimulation via games and rwading may also suppress melatonin.
        • evaluation: artificial environment leads to higher awareness of surroundings and less melatonin (tablets)
      • many practical applications
        • melatonin tablets
        • reducing screen time before bed
      • difficult to strudy as depriving people of light or sleep is unethical.
        • also time consuming as sleep patterns could be learnt, and this social influence leads to another factor in results.





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