Sleep and Biological rhythms

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  • Created by: Maddie
  • Created on: 05-11-13 17:32
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  • Sleep and Biological rhythms
    • Rhythms of sleep
      • Circadian rhythms
        • Michel Siffre and the cave study
        • Average sleep wake cycle lasts 24.9 hours
        • Core body temperature
          • Highest: about 6pm
          • Lowest: about 4.30am
        • Hormones
          • Melatonin and the growth hormone peak at 12pm
          • Cortisol is lowest at 12pm and highest at 6pm
      • Ultradian Rhythms
        • Sleep stages
          • NREM
            • Stages 1-4 exc REM
              • Stage 1
                • Theta Waves
                  • Increased wave frequency with bursts of activity
              • Stage 2
                • Theta Waves
                  • Increased wave frequency with bursts of activity
              • Stage 3
                • Delta Waves
                  • Stage 4
                  • Slow Wave Sleep (SWS) with a decreased wave frequency
                    • Growth hormone produced in these stages
              • Stage 4
          • REM
            • Body paralysis occurs in this stage
          • One full sleep cycle is repeated about 5 times in the night
        • Basic Rest-Activity Cycle (BRAC)
          • The 90 minute sleep cycle is continuous throughout the day
      • Infradian rhythms
        • A monthly cycle ie the menstrual cycle
        • Can occur yearly
          • Seasonal Affective Disorder (SAD)
    • Endogenous Pacemakers and Exogenous Zeitgebers
      • Endogenous Pacemakers
        • The SCN in the hypothalamus observes light and wakes us up (the internal body clock)
        • The pineal gland in the SCN sends signals to release melatonin at night (which makes us tired) and reduces it to wake us up
      • Exogenous Zeitgebers
        • Light
        • Social Cues
        • Temperature
    • Disrupting biological rhythms
      • Shift Work
        • Night workers experience a 'circadian trough' of decreased alertness
          • Boivin et al
        • Night workers lose 2 hours of sleep with REM being affected the most
          • Tilley and Wilkinson
        • Individuals working more than 15 years are more likely to develop organ disease
          • Knuttson et al
      • Jet lag
        • It takes a day to adjust to each hour in time change
          • Winter et al
        • US baseball results- Recht et al
          • East to West (Phase Delay) won 44%
          • West to East (Phase Advance) won 37%
    • Nature of sleep and lifespan changes
      • Within infancy a circadian rhythm is established in about 6 months
      • In childhood more REM sleep occurs
      • At old age it becomes difficult to remain asleep
    • Restoration Theory
      • SWS is when growth hormone is secreted- cell repairing
      • REM Sleep
        • A suggested link between REM sleep and neural growth
          • Siegel et al
        • Neurotransmitter activity may be affected by REM sleep
          • Sleep allows for a break in neurotransmitter activity
            • Siegel and Rogawski
        • There's a suggestion that during REM sleep, unwanted memories are discarded
          • Crick and Mitchison
      • Total Sleep deprivation
        • Peter Tripp
          • Hallucinations, paranoia, decline in body temperature, unpleasant behaviour
        • Randy Gardner
          • Hallucinations, paranoia, decline in body temperature, unpleasant behaviour
    • Evolutionary explanation
      • Energy is conserved during sleep
      • As carnivores we can afford to save energy sleeping
      • We could've slept for predatory avoidence
      • Meddis proposed that sleep was to 'waste time'
    • Insomnia
      • Primary
        • Where the insomnia occurs on its own with no known cause
      • Secondary
        • Where a single, underlying cause is the problem not the insmonia itself (medical, psychiatric, etc)
      • Risk factors
        • Age and gender- Older people and women are more prone
        • Parasomnias i.e sleep apnoea can affect sleep
    • Explanations for other sleep disorders
      • Narcolepsy
        • Feeling continuously sleepy and having cataplexy
          • REM- A lack of it in night-time sleep and it intrudes in day-time sleep
        • Neurotransmitters- Hypocretin maintains wakefulness, when disrupted narcolepsy can be caused
      • Sleep Walking
        • Incomplete arousal
          • It looks as if the person is awake on an EEG, with a mixture of delta waves (sleep state) and beta waves (awake state)- the brain is neither awake nor asleep
        • Various Factors
          • Plazzi et al found that external factors i.e sleep deprivation or alcohol increase the likelihood of sleep walking
        • Why children?
          • Children have more SWS than adults. Oliverio suggested that the system that inhibits motor activity may not be sufficiently developed

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