Biological rhythms - Circadian rhythms

what are biological rhythms

distinct patterns of changes in body activity that conform to cyclical time periods

influenced by internal body clocks asw as external changes to the environment 

what are circadian rhythms

biological rhythms on a 24 hour clock which regulate a number of bodily processes for example sleep wake cycle

what is the sleep wake cycle

• demonstrates the effect of daylight on our sleep wake cycle

• also governed by the suprachiasmatic nucleus which provides info from the eye about light

what was Siffre’s cave study

• spent 2 months in a cave to study the effects of how own biological rhythms

• his biological rhythm extended to just about 24 hours

• he continued to fall asleep regularly even without light and dark

what was Aschoff and Weaver’s study

• group of Ps spent 4 weeks in a world war 2 bunker

• all but 1 P had circadian rhythms of 24 to 25 hours

• suggests the natural sleep wake cycle may be more than the ‘entrained’ 24 hour cycle made by exogenous zeitgebers

what was Folkard et al.’s study

• a group of 12 lived in a cave for 3 weeks 

• they went to sleep when the clock said 11:45 and rose when is said 7:45 

• they gradually sped up the clock so the ‘24 hour day’ was actually only 22 hours 

• only 1 participant was able to comfortably adjust 

• suggests circadian rhythms cannot be easily overrun by exogenous zeitgebers 

strength - shift work

• circadian rhythms provide understanding of the consequences of when it is disrupted

• night workers experience a period of reduced concentration around 6am leading to increased mistakes

• shift work is also 3x more likely to cause heart disease

counterpoint to shift work - correlational methods

• may be difficult to establish if desynchronisation is a cause of negative effects

• Solomon (1993) concluded high divorce rates in shift workers may be due to lack of sleep and other influences e.g. missing family events

• suggests research is too heavily reliant on the effects of circadian rhythms on other aspects of every day life

strength - medical treatments

• used in chronotheraputics

• e.g aspirin is best taken last thing at night because heart attacks are most common in the morning therefore the timing of circadian rhythms matter

• shows circadian rhythms can improve the effectiveness of medical treatments

limitation - individual differences

• research e.g. aschoff and wever is based on small samples

• Czeisler found sleep wake cycles varied from 13 to 65 hours

• Duffy et al. found some prefer waking and going to sleep early and others prefer the opposite

• means its difficult to use research to analyse anything other than averages which may be meaningless

strength - campaigns for shifting start of school day

• hormonal shifts in teenagers mean getting up early is more difficult

• research shows shifting the school day a couple hours later will be better for teenagers as they wont be sleepy at the start of the day which will improve academic performance

• however will disrupt day for parents