circadian, infradian and ultradian rhythms

• Circadian - a rhythm that repeats itself approximately every 24 hour
• Infradian - a rhythm, that repeats itself less than 24h
• Ultradian - a rhythm, that occurs more than 24h
• Internal (endogenous) factors e.g our internal body clocks
• External (exogenous) factors e.g light
• Endogenous and exogenous factors interact to influence our biological rhythms, particularly our

  circadian cycle
• Disruption to our biological rhythms e.g jet lag can have serious consequences on our health

  and cognitive performance.
• Infradian rhythm

  It was always assumed that the approx. 28 day menstrual cycle was controlled by the body's

  internal biological clock. However, research has found that external factors also have an

  influence ( Sabbagh and Barnard)
• Sabbagh and Barnard found that when women live together their menstrual cycles often

  synchronise
• Research using EEG’s has identified 5 stages of sleep. It suggests that these changes occur over 90 minutes which is about 4-6 cycles a night
• Stage 1 (NREM sleep) only occurs in the first cycle as you drift off to sleep
• Stage 2 (NREM sleep) is the first proper stage of sleep and consists of theta and delta waves
• Stage 3 (NREM sleep) is transitional and you fall into a deeper sleep
• Stage 4 where the brain is least active and in its deepest sleep.
• Stage 5 which is REM sleep. The brain is most active in REM sleep and this is where most dreaming occurs; muscles are paralysed in REM sleep, possibly to stop you acting out your dreams.
• (+) NREM sleep is thought to be for physiological restoration and REM sleep is thought to be for psychological restoration
• research has found that infants have a lot more REM sleep than adults, which suggests that its function is linked with psychological restoration e.g brain development, learning and restoring
• Most of the evidence for changes in sleep patterns comes from laboratory research using EEG recordings. These recordings are obtained by attaching electrodes to participants; this creates an unfamiliar sleeping environment for the participants which may disrupt their usual sleep patterns and affect the validity of the results.
• with eeg attached to head= However, empson suggests that after the first night participants adjust to the conditions and sleep becomes representative of usual patterns.