Ultradian & infradian rhythms

• How do we measure the sleep-wake cycle for ultradian rhythms under 24 hours?

  through EEGs, roughly 90-100 mins in length
• how many cycles are there every night when measuring the sleep-wake cycle under 24 hours?

  5
• what is stage one of measuring Ultradian sleep wake cycle?

  • NREM: light sleep, muscle activity slows (twitching)
• what is the second stage in measuring the sleep-wake cycle in under 24 hours?

  • NREM: breathing & heart rate slows
• what is the third stage in measuring the sleep-wake cycle in under 24 hours?

  NREM: deep sleep begins
• what is the fourth stage in measuring the sleep-wake cycle in under 24 hours?

  NREM: very deep sleep, limited muscle activity
• what is the fifth stage in measuring the sleep-wake cycle in under 24 hours?

  REM: bran activity resembles that when awake. Muscle paralysis happens to stop activity when acting out a dream
• what is the basic rest activity cycle (under 24 hours)?

  not as obvious as the sleep cycle but 90-100 cycles occur during the awake period - progressively form a state of alternes to fatigue. Endogeneous and Exogeneus pacemakers work together to keep us in time
• Strength of Ultradian rhythms (under 24 hours)

  • Ericsson found elite violinists limited their practice to no more than 90 mins at a time and napped frequently to recover from practice sessions - common amongst athletes, chess players and writers
• weakness - under 24 hours Ultradian

  • Sleep differences may be biologically determined
• weakness - ultradian

  • Tucker reared large differences in sleep duration, time to fall asleep and time spent in each skeep stage of ppts spending 11 nights in a controlled lab
• weakness - ultradian

  • low ecological validity testing sleep stages in a lab with EEG - not like real life
• Infradian rhythms (over 24 hours)

  • Woman’s reproductive cycle lasts about 1 month. regulated by hormones which promote ovulation or stimulates the uterus for fertilisation
  • ovulation occurs roughly half way through the menstrual cycle when oestrogen levels peak
  • after this, Progesterone levels increase in preparation for the possible implantation
• seasonal affective disorder -

  Seasonal variations in mood, during the winter months where there are longer hours of darkness, which increases our melatonin. This has a knock on effect of serotonin level (leads to depression)
• strength of infradian rhythms

  • Russell, daily rubbed underarm sweat from one group of women on to the upper lip of a different group of women that were separated. 68% of their menstrual cycles synchronised. Pheromones (Exogeneous) of others have an effect on us
• real world application for infradian rhythms

  • Light therapy has been created based on research into rhythms. It has an 80% success, useful in the short term
• Weakness of infradian rhythms

  • Turke - Believed there to be an evolutionary significance to synchronised periods allowing women to live together to share child-caring duties