biological rhythms

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Psychology: Biological Rhythms



·         Circadian Rhythm: A biological rhythm that takes place over 24 hours, such as sleep/wake cycle.


·         Infidelity Rhythm: Rhythm that last more than one day and a cycle that occurs less often, for example menstrual cycle 28 days.


·         Ultradian Rhythm: Rhythm cycle that occurs more than once in 24 hours, for example sleep stages – 90 minutes cycle.  



Control of Circadian Rhythm:


·         Endogenous Pacemaker: Internal control mechanisms, i.e. Suprachiasmatic nucleus and pineal gland.


·         Exogenous Zeitgebers: Extent control mechanisms, i.e. light.




Process of melatonin release:


  1. Light enters the eye even when shut.
  2. Information sent via neural pathways to SCN.
  3. SCN located in hypothalamus.
  4. Information sent via neural pathways to Pineal gland.
  5. Pineal gland is located deep within the Brain.
  6. Low light information from SCN triggers pineal gland


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