biological rhythms : circadian rhythms Flashcards
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
