Biological Rhythms

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  • Biological Rhythms
    • Circadian Rhythms
      • Approx. 24 Hours
      • Sleep-Wake Cycle
        • Internal Body Clock (24-25 Hours)
        • Controlled by internal factors such as:
          • SCN
          • Pineal Gland
            • Releases Melatonin
        • Siffre
          • Spent several extended periods underground to study effects on CR
        • Aschoff & Weaver
          • 24 P's spent 4 weeks in a WWII Bunker
        • Folkard et al (1985)
          • 12 people lived in a dark cave for 3 weeks
    • Infradian Rhythms
      • 24+ Hours
      • Menstrual Cycle
        • Approx. 28 days for Cycle to complete
        • Stern & McClintock (1998)
          • 29 women with irregular periods
            • Pheromones collected from 9 of the women at diff stages (from armpit)
              • Rest collected from upper lip
                • 68% experienced changes to Cycle
      • SAD
        • Yearly cycle
          • Depressed in winter, recover in summer
            • Darkness = more Melatonin
              • More Melatonin = Less Serotonin
                • Low levels of Serotonin linked with depression
    • Ultradian Rhythms
      • >24 Hours
        • Usually 90 minute cycles
      • Stages of sleep
        • REM
          • Associated with dreaming
          • Recovery of the brain
          • Brain is active
            • Body is paralysed
        • NREM
          • Recovery of the body
          • 1&2
            • Light sleep
              • Brain wave patterns slow down
          • 3&4
            • Deep sleep
              • Slow Wave Sleep
                • Growth hormone is released
                  • Harder to wake someone
        • Each stage is different and defined by diff patterns in the brain
    • Endogenous Pacemakers
      • Inherited mechanisms important for regulation of bio Rhythms
        • SCN
          • Pair of tiny clusters of nerve cells
            • One half in left hemisphere in brain and one in right
              • Just above where each optic nerve crosses over
                • SCN obtains info on light from optic nerve even when eyes are shut
          • Ventral
            • Relatively quickly reset by external cues
          • Dorsal
            • Less affected by light
        • Pineal Gland
          • Located bottom of hypothalamus at base of brain
            • Receives signal from SCN and releases Melatonin in relation to fading light
              • Melatonin - Body's natural sedative
                • M produced from Serotonin
                  • M reduces CNS activity, leads to feeling tired
                    • Light - production of Melatonin in the Gland is stopped.
      • Main pacemaker found in hypothalamus
        • Biological clock
    • Exogenous Zeitgebers
      • External events that help control biological rhythms
        • Sleep-Wake controlled by interaction of internal and external factors
          • Light
            • Main Zeitgebers in humans
              • Reset SCN and exposure to bright light suppresses Melatonin production
            • Campbell & Murphy
              • Found they could entrain bio Rhythms by exposing P to light shone through back of knees
            • Boivin et al
              • Artificial light does have an affect
                • Bright light is better for resetting CR
      • Social Cues
        • Important Zeitgebers for human CR

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