A01

• What are infradian rhythms?

  Rhythms that have a duration of over 24 hours, and may be weekly, monthly or even annually
• What are ultradian rhythms?

  Rhythms that last less than 24 hours
• What are 2 examples of infradian rhythms?

  1. The menstrual cycle

  2. Seasonal affective disorder (SAD)
• What are 2 examples of ultradian rhythms?

  1. Sleep cycle

  2. The Basic Rest Activity Cycle (BRAC)
• What is Seasonal Affective Disorder (SAD)?


  A seasonal variation in mood with some people becoming severely depressed during winter months
• How does melatonin trigger SAD?

  - During winter, lack of light in morning means more melatonin, which affects production of serotonin = depressive symptoms
• Describe what happens during the menstrual cycle

  - Lasts around 28 days and releases oestrogen - causing egg to be released

  - Then progesterone released to thicken womb lining

  - If pregnancy doesn't occur egg is absorbed and womb lining breaks down - menstrual flow
• How many stages of sleep are there?

  5
• Describe the stages of sleep

  - First 4 stages = REM (rapid eye movement) -> 1 and 2 = light sleep and 3 and 4 = deep sleep

  - Last stage = NREM (non-rapid eye movement)
• What is the basic rest activity cycle?

  - A 90-minute rhythm cycle characterised by a period of alertness followed by a spell of fatigue

  - This occurs every 90-minutes throughout the day