ULTRADIAN RHYTHMS

• What is an ultradian rhythm?

  A biological rhythm that lasts less than 24 hours, experience more than one cycle a day
• example of ultradian rhythm

  sleep cycle
• how many stages in the sleep cycle?

  4 take around 90 minutes to cycle through

  go through about 4-6 each night
• how is each sleep cycle stage characterised?

  by different levels of brain wave activity
• what are the stages of the sleep cycle?

  stage 1 to 2 - light sleep

  stage 3 - deep sleep

  stage 2 to 1 - light sleep

  REM
• what does light sleep involve?

  brain waves slightly slower than the awake state, gradually slower moving from stage 1 to 2

  may be easily woken
• what does deep sleep involve?

  slow wave sleep characterised by slow delta waves, difficult to wake someone
• what does REM sleep involve?

  rapid eye movement, fast jerky activity of the eyes. body paralysed yet brain activity speeds up

  alpha waves
• research support

  Dement and Kleitman conducted landmark lab experiment with 9 Ps which first discovered the link between REM sleep and dreaming.

  confounding variables such as caffeine and alcohol were controlled

  replications have shown similar finding
• differences in sleep are blamed on external factors

  nature vs nurture

  Tucker had Ps sleep in a lab for 11 days, each time they spent in each sleep stage varied even though the environment was kept constant. therefore individual differences are caused by nature not nurture
• real world application

  suggested that 90 min sleep cycle continues throughout the day, go through 90 mins of alertness followed by 20 minutes of fatigue

  could help in schools etc and breaks at jobs