Ultradian rhythm

• How long does an ultradian rhythm last?


  Shorter than 24 hours
• What cycle is part of the ultradian rhythms?


  Sleep cycle
• How many stages are in the sleep cycle and how many are REM and non REM?


  5 stages, 4 non REM and 1 REM
• What happens in stage 1 and how long is it?


  approx 15 mins.

  • person becomes relaxed.
  • state of drowsiness, a hypnogogic state where hallucinatory images can be experienced
• What happens in stage 2 and how long is it?


  approx 20 mins

  • EEG waves become slower and larger
  • K-complexes are also characteristics of this stage, this is the brains response to external stimuli
  • it is easy to be awakened at this stage
• What happens in stage 3 and how long is it?


  approx 15 mins

  • sleep deepens and brain waves slow down
• What happens in stage 4 and how long is it?


  approx 30 mins

  • deeper stage of sleep than any of the first 3 stages. known as slow-wave sleep (SWS)
  • it is also hard to wake someone up in this stage
  • growth hormones are secreted
  • sleep walking, sleep talking and night terrors can occur at this stage.
• What happens in stage 5 and how long is it?


  approx 10 mins in 1st cycle, builds up to an hour by the 5th cycle.

  • dreaming occurs here due to increased brain activity
  • body becomes paralyzed to stop us acting out our dreams
  • brain wave activity is the same to when we are awake