BIOLOGICAL RHYTHMS

• RHYTHM 


   physiological pattern of changes within the body, which repeats itself on a regular basis.
• CIRCADIAN

  a rhythm that repeats itself approximately every 24 hours 58 e.g sleep-wake cycle (8 hrs asleep, 16 hrs awake)
• INFRARADIAN 


  a rhythm, that repeats itself less than once every day E.g the monthly menstrual cycle (PROCESS)
• ULTRARADIAN 


  a rhythm, that occurs more than once a day E.g the stages within sleep (90 minute cycles)
• ENDOGENOUS (INTERNAL FACTORS)


  e.g our internal body clocks
• EXOGENOUS (EXTERNAL FACTORS)


  e.g light 
• ENDOGENOUS AND EXOGENOUS 


  factors interact to influence our biological rhythms, particularly our circadian cycle. Disruption to our biological rhythms e.g jet lag can have serious consequences on our health and cognitive performance. Infradian rhythm It was always assumed that the approx. 28 day menstrual cycle was controlled by the body's internal biological clock. However, research has found that external factors also have an influence
• EEGS - 5 STAGES OF SLEEP 


  Stages 1-4 are NREM sleep and stage 5 is REM sleep. 

  It suggests that these changes occur over 90 minutes which is about 4-6 cycles a night i.e 6-9 hours of sleep 
• STAGE 1 


   (NREM sleep) only occurs in the first cycle as you drift off to sleep 
• STAGE 2 


   (NREM sleep) is the first proper stage of sleep and consists of theta and delta waves 
• STAGE 3 


  (NREM sleep) is transitional and you fall into a deeper sleep
• STAGE 4 


  where the brain is least active and in its deepest sleep. The cycle descends the sleep staircase back to stages 3 then 2
• STAGE 5 


   which is REM sleep. The brain is most active in REM sleep and this is where most dreaming occurs; muscles are paralysed in REM sleep, possibly to stop you acting out your dreams
• (+) INFRARADIAN 


  PENTON VOAK ET AL

  women generally expressed a preference for ‘slightly feminised’ male faces when picking a partner for a long term relationship. However, when in the ovulatory phase of their menstrual cycle =, women showed a preference for more masculine faces. This suggests that human mate choice varies across the menstrual cycle, an infradian rhythm, with different preferences at different stages of the cycle. 
• (-) INFRARADIAN 


  is that the effects of pheromones on behaviour is derived from animal studies.  Human behaviour is controlled more by conscious and cognitive factors.  Also, animals may be tested in artificial conditions, so findings may be invalid.  This suggests that care needs to be taken when generalising to humans as the attraction and sexual selection made might be less governed by pheromones than it is in animals.   
• (-) INFRARADIAN 


  Validity of the evolutionary perspective has been questioned by SCHANK (2004) - Synchronisation within social groups would provide too much competition for the highest quality males (reducing fitness of offspring), also put a strain on resources.  The avoidance of synchrony would be more adaptive.
• (+) CIRCADIAN 


   support the role free running come from *Siffre (1962).  He spent two months in a cave in the Alps, deprived of exposure to natural light and sound, but access to food and drink.  He later spent six months in a Texan cave.  In each case, his biological rhythm settled down to one just beyond the usual 24 hours.  These results suggest that with the absence of exogenous zeitgebers, the endogenous pacemakers can regulate circadian rhythms, but not accurately.
• (+) CIRCADIAN - real word application

  chronotherapeutics - the study of how timing affects drug treatments. The specific time that patients take their medication is very important. right concentration of a drug is released in the target area of the body at the time that the drug is most needed. EG the risk of heart attack is greatest during the early morning hours after awakening. = chronotherapeutic medications can be administered before the person goes to sleep at 10 pm, but the actual drug is not released until the vulnerable period of 6 am to noon (Evans and Marain, 1996).
• (-) CIRCADION - INDIVIDUAL DIFFERENCES

  DUFFY ET AL =

   found that some people display a natural preference for going to bed early to bed, early to rise (10pm to 6am).  Morning people (lark) or evening people (owl) - late to bed, late to rise (1am to 10am).  Individuals appear to be innately different in terms of when circadian rhythms peak.
• (-) CIRCADIAN


  BUHR ET AL =

  temperature actually controls our body clock rather than light. Although light may be the trigger, the SCN transforms information about light levels into neural messages that set the body's temperature. Body temperature fluctuates on a 24-hour circadian rhythm and even small changes in body temperature can send a powerful signal to our body clocks.
• (-) CIRCADIAN 


  BUHR ET AL =

  Buhr et al. found that these fluctuations in temperature set the timing of cells in the body, and therefore cause tissues and organs to become active or inactive. This suggests that temperature may be more important than light in setting circadian rhythms.
• (+) ULTRARADIAN 


  DEMENT + KLEITMAN =

  Brainwave activity was recorded on an EEG and the effects of caffeine and alcohol were controlled.  It was found that 90% of participants awakened during REM sleep reported dreaming, compared with only 7% awoken during NREM sleep.  This suggests that REM activity during sleep was highly correlated with the experience of dreaming and brain activity varied according to how vivid the dreams were.
• (-) ULTRARADIAN - INDIVIDUAL DIFFERENCE (biologically determined)


  TUCKER ET AL =

  over 11 days + nights in a controlled laboratory environment. The researchers assessed sleep duration, time to fall asleep and the amount of time in each sleep stage. = large individual differences in each of these characteristics, which showed up consistently across 8 nights. For deep sleep (stages 3 and 4), the individual differences were particularly significant. This meant that differences between participants were not driven by circumstances, but were at least particularly biologically determined.  
• (+) ULTRARADIAN - supportive evidence

  ERICSSON ET AL =

  violinists performed best when they practised for three sessions a day, lasting no longer than 90 minutes. This supported Kleitman's claim that fatigue was a characteristic of the end of the BRAC cycle. Ericsson’s analysis also indicated that the violists frequently napped to recover from practice, with the very best violists napping more than their teachers. 
• (-) ULTRARADIAN


  Age-related changes in sleep. 

  Sleep scientists have observed that SWS reduces with age, therefore growth hormones are reduced in older people, which explains issues in old age such as reduced alertness (Eve van Cauter et al, 2000).