Sleep

• Features, functions and benefits of sleep


  • The four stages of sleep, including REM sleep
  • The sleep cycle
• There are four stages of sleep, with REM sleep forming a fifth part of the sleep cycle. These stages appear more than once throughout a night's sleep
• Brain activity


  Can be measured using an EEG electroencephalograph to characterise sleep stages
• The four stages of sleep


  1. Stage 1 (sleep onset)

  2. Stage 2 (late night stage)

  3. Stage 3 (deep sleep)

  4. Stage 4 (deep sleep)
• REM sleep


  Rapid eye movement sleep when dreaming occurs
• REM sleep


  • Incoming sensory information is blocked (sensory blockade)
  • Movement is prevented (movement inhibition)
  • Rapid, shallow and irregular breathing
  • Eyes jerking
  • Muscles paralysed
  • Heart rate and blood pressure rise
  • Dreaming can occur
• Key terms


  • REM sleep
  • Sleep cycles
  • NREM sleep
  • Sensory blockade
  • Neuron
  • Movement inhibition
• About 20 per cent of our sleep is REM sleep, though for infants REM sleep accounts for nearly 50 per cent of their sleep
• REM sleep stimulates learning and is associated with an increase of protein, so it is important
• Some participants did not report dreaming when woken up from REM sleep and some reported dreaming in NREM sleep, so this is not an easy area to study or draw conclusions about
• The sleep cycle


  • Stage 1
  • Stage 2
  • Stage 3
  • Stage 4
  • REM
• Sleep deprivation


  Not having enough sleep, this can affect physical functioning such as weight and brain functioning
• Adults tend to need about 7 or 8 hours of sleep, while teenagers need about 9 hours
• It is possible for people to catch up on sleep after being deprived of it
• People often find that over the age of 65 deep sleep steps, probably because of age or medication. People fall asleep during the day, or immediately when they go to bed, this suggests that they are sleep deprived
• Sleep deprivation means a person will not function as well at a high level, which can affect driving and work tasks. Animal studies suggest that sleep is needed for survival
• Our brain chemistry is affected when we have too little sleep and sleep is thought to help neurons repair themselves. Deep sleep can also help prevent the breakdown of proteins
• Internal and external influences on sleep


  • Bodily rhythms and sleep, including circadian and ultradian rhythms
  • Hormones, including the pineal gland and melatonin
  • Zeitgebers, including light, relating to the sleep-wake cycle
• Circadian rhythms


  Biological internal rhythms that have a daily (24 hour) cycle, such as the sleep-wake cycle
• Ultradian rhythms


  Rhythms that occur in a period of less than 24 hours, such as a sleep cycle
• Sleep-wake cycle


  A circadian daily rhythm generally triggered by the day-night cycle
• Jet lag affects the sleep-wake cycle and happens when we cross time zones. Shift work also affects the sleep-wake cycle
• Suprachiasmatic nuclei (SCN)


  Control circadian rhythms and are set by external triggers such as sunlight and other clues to time
• Hormones


  Chemical messengers taking messages through the bloodstream
• Melatonin


  A hormone involved in setting circadian rhythms including the sleep-wake cycle and blood pressure
• Pineal gland


  A small endocrine gland that produces melatonin
• Endogenous


  Internal biological clock that keeps biological rhythms synchronised
• Exogenous


  External cues in the environment that affect our biological clock
• Zeitgebers


  External cues that synchronise our biological rhythms, for example, to a 24-hour clock
• The main zeitgeber is light. Light comes into our eyes and light sensitive cells in the retina of the eye let the internal body clock know whether it is day or night
• Entrainment


  When biological rhythms are matched to their environmental triggers, such as circadian rhythms being set in response to external (light) cues
• Ava works shifts and cannot understand why she cannot sleep during the day

  Using understanding of the sleep-wake cycle, explain why she is having problems sleeping
• Strengths and weaknesses of the internal influences on sleep explanation


  • Strengths
  • Weaknesses
• Strengths and weaknesses of the external influences on sleep explanation

  • Strengths
  • Weaknesses
• Received must be complex
• 1. Gunderson et al (2015)

  Confirm that the pineal hormone melatonin is important for controlling sleep
• Study using rats


  1. Early sleep deprivation (ESD) led to reduction in melatonin levels

  2. Researchers suggested giving children melatonin supplements to prevent this reduction
• People with NLP blindness might perceive light and colours
• Ralph Mistiberger and Debra Skene (2004) agree that light is the main way bodily rhythms are synchronised to an individual's day and night times
• Social stimuli, such as exercise, are also cues to time