Biological rhythms

• All living organisms have biological rhythms
• what are biological rhythms governed by?

  endogeneous pacemakers and exogeneous zieterbergs
• what is an exogenous zeiterberg?

  they are external cues
• what is a circadian rhythm?

  a biological rhythm that lasts 24hrs
• what is an example of a circadian rhythm?

  sleep-wake cycle
• what is an endogenous pacemaker?

  internal mechanisms that govern biological rhythms
• what is a type of endogenous pacemaker?

  SCN, the master clock
• what does the SCN do?

  receives information about light via the optic nerve which causes an increase of melatonin at night
• what is an exogenous zietgeber?

  environmental cues that are responsible for resetting the biological clock of an organisms
• what is an ultradian rhythm?

  Biological rhythms that occurs more than one cycle in 24hrs
• what is an infradian rhythm?

  biological rhythms that occurs less than one cycle 24 hours
• What type of rhythm is the menstrual cycle?

  Infradian rhythm
• What did stern and Mclintok study?

  Studied 24 women who had irregular periods and samples of pheromones were taken from 9 of the women at different stages of the menstrual cycle. Found that 68% of women experienced changes to their cycle which caused them to be closer to the other person whose odor they had on them
• what is seasonal affective disorder?


  where seasonal patterns affect someone’s mental health
• what are some symptoms of seasonal affective disorder?

  low mood, general lack of activity
• what type of rhythm is season affective disorder?

  Infradian rhythm
• a strengoth of infradian rhythis is that there is supporting evidence from Reinberg that shows after women stayed in a cave for 3 months their menstrual cycle had shortened. this suggests that a lack of light in the cave had affected their menstrual cycle.
• what is an example of an ultradian rhythm?

  human sleep pattern
• what is stage one of human sleep pattern

  light sleep, alpha waves slowly turn into theta waves
• what is stage 2 of the human sleep pattern?

  deep sleep, associated with delta waves
• what is stage 5 of the human sleep pattern?

  REM sleep, body is paralysed, desynchronised brain waves
• what is a strength of ultradian rhythms

  a Case study when a man stayed awake for 264 hours after this he then slept for 15 hours. over several nights he recovered only 25% of his lost sleep. recovered 70% of stage 4 sleep and 50% of REM sleep. these results show the large degree of flexibility in terms of the different stages within the sleep cycle and then variable nature of ultradian rhythms
• what is a limitation of ultradian rhythms?

  there are individual differences because some of the studies were done as case studies it means that they are ideographic. therefore, due to their small sample size they cannot be generalise to everyone and therefore might not be able to be used as an accurate explaination. this means that there may be other external factor that affect ultradian rhythms
• a strenght of ultradian rhythms is there is real life application

  this is because it shows the damage between too much or too little sleep. this means that these results can be used on a medical basis to benefit the medical field. therefore this means that it has medic credibility and is used to help people everyday.