Stages of Sleep

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Stages of Sleep
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Definitions

• Electroencephalograph An instrument that uses
  electrodes placed on the scalp to measure and
  record the brains electrical activity.
• EEG The graphic record of brain activity
  produced by an electroencephalograph.
• REM Sleep Type of sleep during which rapid eye
  movements (REM) and dreaming usually occur and
  voluntary muscle activity is suppressed also
  called active sleep or paradoxical sleep.
• NREM Sleep Quiet, typically dreamless sleep in
  which rapid eye movements are absent divided
  into four stages also called quiet sleep.

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Definitions cont

• Beta Brain Waves Brain-wave pattern associated
  with alert wakefulness.
• Alpha Brain Waves Brain-wave pattern
  associated with relaxed wakefulness and
  drowsiness.
• Hypnagogic Hallucinations Vivid sensory
  phenomena that occur during the onset of sleep.
• Sleep Spindles Short bursts of brain activity
  that characterize stage 2 NREM sleep.
• K Complex Single but large high-voltage spike
  of brain activity that characterizes stage 2 NREM
  sleep.
• Sleep Paralysis A temporary condition in which
  a person is unable to move upon awakening in the
  morning or during the night.

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Stages of Sleep

• Stage 1 NREM Lasts only a few minutes.
  Transitional stage during which you gradually
  disengage from the sensations of the surrounding
  world. You can quickly regain conscious
  alertness if needed.
• Stage 2 NREM Onset of true sleep and is defined
  by the appearance of sleep spindles and K
  complexes.

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Stages of Sleep cont

• Stage 3 and Stage 4 NREM Both stages are defined
  by the amount of delta brain-wave activity
  (larger, slower brain waves than the alpha and
  beta brain waves). It is also called slow-wave
  sleep. Stage 3 begins when delta waves represent
  more than 20 of brain activity. When delta
  brain waves exceed 50, it is considered stage 4
  NREM. In stage 4 NREM, heart rate, blood
  pressure and breathing rate drop to its lowest
  levels. Some people who sleepwalk will typically
  do so during this stage. It is possible to answer
  a phone or carry on a conversation for a few
  minutes without fully waking up or remembering it
  the next morning.
• REM Sleep Dreams will usually occur during this
  stage the brain becomes more active and
  generates smaller and faster brain waves. The
  sleepers eyes dark back and forth behind closed
  eyelids (Rapid Eye Movements). Muscles twitches
  occur. Sexual arousal may occur. This stage is
  very brief.

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• Graph taken from the following website
  http//www.helpguide.org/life/sleeping.htmj