PSYA3 Infradian and ultradian rhythms

HideShow resource information
View mindmap
  • Infradian + Ultradian rhythms
    • Infradian rhythms
      • A01
        • Infradian rhythms last more than 24 hours such as the menstrual cycle, the cycle is controlled by the hormone oestrogen and progesterone.
        • It is an endogenous rhythm but similar to the sleep/wake cycle it can be affected by external cues. Such as, a woman spent 3 months in a cave and developed a shortening to her cycle.
          • Russell found that pheromones, a biochemical substance that acts like a hormone but is released into the air can synchronise women's cycles.
        • Infradian rhythms don't have to be monthly, they can occur once a year. People with SAD become depressed in the winter and recover during the summer.
          • The cause of this is that melatonin and serotonin are secreted when it's dark. The more darkness, the more melatonin and more melatonin means less serotonin and low levels of serotonin is associated with depression.
        • SAD has been explained in terms of being a natural outcome of infradian rhythms, but it could be a consequence of disturbed circadian rhythms. In the UK, as seasons change from summer to winter, circadian rhythms may be thrown out of phase.
          • People get up at the same time, but go to sleep earlier as it's dark meaning that the biological system gets the impression that time is shifting. Therefore, SAD may not be an outcome of infradian rhythms.
      • A02
        • There is research into the claim that menstrual cycle can be controlled by exogenous cues.
          • Russell took sweat from the upper lip of a group of girls and placed it on the lip of another group of girls. He found that, although they were kept separate, their cycles synchronised with their individual odour donor suggesting that the menstrual cycle can be affected by pheromones.
        • The menstrual cycle may have consequences (PMS) affects the women the week before menstruation begins and includes symptoms such as acne, depression and headaches.
          • Previously PMS was dismissed as being only physiological, but we now know it is also psychological.
            • Dilton found that PMS is associated with increase in accidents, lower academic achievement, suicide and crime suggesting that there are consequences of this infradian rhythm thus research has led to PMS being used as a criminal defence.
      • Research into SAD has lead to real world applications as it has led to photo therapy which is the use of strong lights in the evening and early morning to change melatonin levels.
    • Ultradian rhythms
      • A01
        • An ultradian rhythms are those that lasts for less than 24 hours. It is related to the brain and body size.
          • The smaller the animal, the more rapid the cycle, an example of this is the sleep stages as we spend 25% of our lifetime sleeping.
        • There are five stages of sleep, the first 4 are NREM sleep and the last stage is REM. Stage one and two are light sleep where we are easy woken and there is a decrease in heart rate. Stage three and four consist of long beta-waves as sleep deepens and is is hard to wake someone in this stage. In stage 5 (REM the body is paralysed to prevent acting out dreams.
      • A02
        • An issue with research into REM sleep is that it is dream sleep. Dement + Kletmen were the first to demonstrate the link as they woke participants at the time their brain waves were characteristics of REM sleep and found participants were highly likely to report dreaming.
          • However, they also found that dreams also occurred outside REM sleep, and when they were woken in REM sleep, they weren't always dreaming.
        • The importance of the REM / dream link is that it provides a way to identify when someone is dreaming therefore might provide theorists a way of explaining dreams.
          • Mccarley suggested that dreams are a psychological read out of random electrical signals. However, such theories are based on assumption that REM sleep is dream sleep therefore research based on this assumption may lack validity.
        • Another issue is that a lot of the research has been done using sleep labs which is not real so it makes the studies unrealistic.


No comments have yet been made

Similar Psychology resources:

See all Psychology resources »See all bio rhythms resources »