Infradian and Ultradian Rhythms

Ultradian Rhythms

• Sleep Stages
• Daily cycles of wakefulness and sleep follow a circadian rhythm, within the sleep portion, a cycle called an ultradian rhythm exists.
• These are the five stages of sleep; the first four are called NREM sleep and the last is REM.
• One sleep cycle goes through all 5 stages and lasts 90 minutes.
• Stages 1 and 2 are light sleep; characterised by a change in the electrical activity of the brain.
• The awake brain produces a pattern called a beta wave. 
• As you are more relaxed the brain waves become slower and more regular and have a greater amplitude. This is an alpha wave.
• As you go to sleep they slow down further which is a theta wave.
• Stages 3 and 4 are characterised by even slower delta waves. These are called SWS.
• In SWS, most of the bodys physiological repair work happens and biochemical processes take place such as production of growth hormones.
• Each sleep cycle is about 60 minutes in early infancy, increasing to 90 minutes during adolescence.
• Basic Rest-Activity Cycle
• The 90 minute cycle is located within a 24 hour circadian cycle, would make sense to find this 90 minute clock was ticking throughout the day.
• It is called the basic rest activity cycle.
• Eating and drinking behaviour in a group of psychiatric patients over 6 hours was observed.

Infradian Rhythms

• Monthly Cycles
• Female menstrual cycle is an obvious infradian rhyth,s
• Fucntion of the menstrual cycle is to regulate ovulation.
• Pituitary gland releases FSH…