Circadian rhythms

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    Cards (10)

    • Biological rhythms and circadian rhythms
      • Biological rhythms - patterns of change in the body that conform to cyclical time periods, they are influenced by biological body clocks and external changes to the environment
      • Circadian rhythms - rhythms that last around 24 hours e.g. sleep/wake cycle and body temp
    • The suprachiasmatic nucleus (SCN)

      • Our circadian rhythms are driven by our body clocks, found in all cells, synchronised by master circadian pacemaker - suprachiasmatic nuclei, found in hypothalamus
      • Must be constantly reset so our bodies are in synch with outside world
      • Light is primary input, setting body clock to correct time Is 'photoentrainment'
    • Sleep/wake cycle
      • SCN lies above optic chiasm - provides info from light-sensitive cells to coordinate the activity of the entire circadian system
      • Most familiar is sleep/wake system - drowsy at night and alert in day, demonstrates the effect of daylight on the sleep/wake cycle
    • Siffre's research
      • Spent extended periods in a cave to study the effects on his biological rhythms, deprived of exposure to natural light and sound
      • Resurfaced mid-September - believed it to be August
      • 6-month cave study - Texan cave
      • His free-running biological rhythm came to 25 hours - continued to fall asleep and wake up on a regular cycle
      • Our natural cycle is closer to 25 hours but is entrained by EZs
    • Ashoff and Weber's research
      • 4 weeks in WW2 bunker
      • Circaidan rhythm between 24 and 25 hours
      • Longer than expected
    • Folkard's research
      • Cave study - 3 weeks
      • Go to bed at 11:45, wake at 7:45
      • Eventually sped up clock to 22 22-hour day - only one participant could comfortably adjust
      • Kept with natural body clock of their circadian sleep/wake cycle
      • Strong-freerunning circadian rhythms can't be overridden by EZs