biological rhythms : circadian rhythms Flashcards
(17 cards)
What are biological rhythms?
Patterns of changes in the body activity that conforms to cyclical periods which are influenced by internal factors (endogenous pacemakers) and external factors ( exogenous zeitgebers)
What is a circadian rhythm?
A biological rhythm that is subject to a 24 hour cycle and regulates a number of bodily processes
What is an example of a circadian rhythm?
Sleep/wake cycle
What research did Siffre do into the sleep/wake cycle?
- spent several periods of time underground to study his biological rhythms which led him to being deprived from natural light and sound
- he spent 2 months in a cave in the Southern Alps in which he came out the cave September 1862 believing it was August
- he also spent 6 months in a texan cave
- he found that his ‘free running’ biological rhythm settled down to a 25 hour cycle
- however , as he fell asleep at regular hours he may have had some light exposure which may have affected sleep
- this was only done on him as a participant which may not be reliable
What research did Aschoff & Wever (1976) do into the sleep/wake cycle?
- had ppts spend 4 weeks in a WW1 bunker where they were deprived of natural light
- all but one displayed a circadian rhythm between 24 & 25 hours
- however one had a 29 hour cycle
What did Aschoff & Wever research suggest?
the ‘natural’ sleep/wake cycle may be slightly longer than 24 hours but it is influenced by exogenous zeitgebers
What research did Folkard et al (1985) do?
- studied a group of people who lived in a cave for 3 weeks who went to bed and 11:45pm and got up at 7:45am
- during the study the clock was put forward (thought that a 24 hour day only lasted 22 hours)
- only one of the ppts could comfortably adjust to the new regime
What does the research done by Folkard et al (1985) suggest?
the existence of a strong ‘free running’ circadian rhythm that can’t be easily be overriden by changes in the external environment
How is practical application to shift work a strength of circadian rhythms?
- disruption of circadian rhythms is called desynchronisation which has negative consequences for people who work night shifts ( research into this increases our understanding)
- night shift workers have a period of reduced concentration at 6am which is when mistakes and accident are most likely to happen
- there’s a link between shift work & poor health (Knutsson (2003) )
- above may have real world economic complications for how to manage worker productivity
What research did Knutsson (2003) into links between shift work & poor health?
shift workers are more likely to develop heart disease which could be due to the stress of having to adjust to different sleep/wake patterns and poor quality sleep during the day
How is practical application to drug treatment a strength of circadian rhythms?
- circadian rhythms coordinate some the body’s processes ( heart rate , digestion etc) which rise and fall during the day and has led to the field of chronotheraputic
- how medical treatments can be given in a way that corresponds with biological rhythms
- aspirin is a treatment for heart attacks that is most effective when taken at night
- heart attacks are most likely to happen first thing in the morning
- proves that circadian rhythm research can help increase the effectiveness of drug treatments
how is shifting the school day a strength of circadian rhythms?
- researchers suggest that the school day should start a couple of hours later to fit in with the teenage chronotype
- due to hormonal shifts in teenagers it makes it difficult to sleep meaning they are tired in the morning
- evidence of better academic and behavioural performance when lessons start later in the day , including reduced dependance on caffeine
How is individual differences a weakness to circadian rhythms?
- generalisations are difficult to make since we are all different
- Siffre’s study was just about himself
- Aschoff & Wever study was conducted on a small sample
- these people may not represent the population and therefore it lacks population validity
- sleep/wake cycles may vary from person to person
- 1999 Siffre carried out research on himself at the age of 60
- reported his internal clock was much slower than when he conducted similar studies as a young man
- shows that research data is difficult to generalise due to individual differences
How is practical application to shift work a weakness to circadian rhythms?
- studies looking at shift work uses correlation which means we can’t day that desynchronisation caused the negative effects (other factor can be involved)
- eg. high divorce rates in shift workers due to the strain of deprived sleep and missing out on important family events
- shows that it may no be desynchronisation causing negative effects but environmental factors
What did the Czeisler et al (1999) research suggest?
the sleep/wake cycle can have the variety can be between 13 & 65 hours
What did the Duffy et al (2001) research highlight?
that some people prefer to go to bed early and wake up early (larks) & others prefer to stay up late (owls)
How is shifting the school day a weakness of circadian rhythms?
- the shift in the school day could be disruptive
- some critics say this wouldn’t reduce sleep deprivation it would just make teenagers stay up later and still be tired
