biological rhythms



(Circadian, Infradian and Ultradian)

Circadian Rhythms

  • follow a 24 hr cycle
  • e.g sleep-wake cycle
  • HR, metabolic rate, BR and body temp all reach max values in late afternoon and min values in early hours of the morning.
  • if we reverse our sleep-waking pattern these rhythms persist indicating that human bodies are evolved for activity in the day and rest at night
  • to disrupt the circadian cycle is physiologically stressful and psychologically harmful.

Infradian Rhythms

  • occur less than once a day 


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