Discuss research into circadian rhythms. Refer to evidence in your answer.
[16 marks]
Biological rhythms are distinct patterns of changes in body activity that
conforms to cyclical time periods. Biological rhythms are influenced by
endogenous pacemakers, also known as internal body clocks as well as
exogenous pacemakers, which are external changes to the environment.
Circadian rhythm is a type of biological rhythm which is a 24- hour cycle
that regulates a number of body processes such as sleep/ wake cycle and
changes in the core body temperature.
Moreover, the ‘natural’ sleep/wake cycle may be slightly longer than 24
hours but that it is entrained by exogenous zeitgebers associated with our
24- hours day such as the number of daylight hours, typical meal times,
and family routines. We shouldn’t overestimate the influence of
environmental cues on our internal biological clock, and the existence of a
strong free-running circadian rhythm that cannot easily be overridden by
changes in the external environment. Lastly, we feel drowsy at night and
alert during the day, and this demonstrates the importance of daylight, an
important exogenous zeitgeber on our sleep/wake cycle.
The cave study conducted by Michael Siffre supports circadian rhythm.
Siffre spent two months in the caves of the southern Alps deprived of light
and sound, determining that his circadian rhythm remained between 24-25
hours. Further research support by Wever and Aschoff had a group of participants live in a
WWII bunker for four weeks and found that the sleep/wake cycle lasted just under 25hours
concluding that exogenous zeitgebers (light hours’/meal times) may have an impact
mediating the cycle. However other research by Folkard set participants sleep and wake
times that initially fit with a 24-hour day, but then unknown to the participants sped up the
clock so the cycle only lasted 22 hours. This had a significant impact on the participants who
were affected by the change from the set 24-25 hours. This therefore suggests that the
body’s internal clock is set 24-25 hours in the absence of external cues, and is intolerant of
any major alterations to sleep and wake cycles, through processes such as shift work and jet
lag.
To contradict, Siffre's study is a case study and therefore the limitation is that it can't
be generalisable. The Siffre study was only on one individual, and the Folkard, Wever and
Aschoff studies were conducted on only a handful of people, and therefore it is impossible
to generalise these results to whole populations of people, as there may be some individual
differences in the research sample that makes these participants respond the changes the
sleep/wake cycle in atypical ways. For example, Siffre noted that when he went into the
cave at 60yr his body responded very differently, with his body clock following more of a
48hr cycle. And Czeisler has found evidence that cycles can vary by as much as 13-65 hours.
This suggests that results cannot be generalised from these small samples onto everyone, as
factors such as age and gender may have significant impacts on our circadian rhythms.
[16 marks]
Biological rhythms are distinct patterns of changes in body activity that
conforms to cyclical time periods. Biological rhythms are influenced by
endogenous pacemakers, also known as internal body clocks as well as
exogenous pacemakers, which are external changes to the environment.
Circadian rhythm is a type of biological rhythm which is a 24- hour cycle
that regulates a number of body processes such as sleep/ wake cycle and
changes in the core body temperature.
Moreover, the ‘natural’ sleep/wake cycle may be slightly longer than 24
hours but that it is entrained by exogenous zeitgebers associated with our
24- hours day such as the number of daylight hours, typical meal times,
and family routines. We shouldn’t overestimate the influence of
environmental cues on our internal biological clock, and the existence of a
strong free-running circadian rhythm that cannot easily be overridden by
changes in the external environment. Lastly, we feel drowsy at night and
alert during the day, and this demonstrates the importance of daylight, an
important exogenous zeitgeber on our sleep/wake cycle.
The cave study conducted by Michael Siffre supports circadian rhythm.
Siffre spent two months in the caves of the southern Alps deprived of light
and sound, determining that his circadian rhythm remained between 24-25
hours. Further research support by Wever and Aschoff had a group of participants live in a
WWII bunker for four weeks and found that the sleep/wake cycle lasted just under 25hours
concluding that exogenous zeitgebers (light hours’/meal times) may have an impact
mediating the cycle. However other research by Folkard set participants sleep and wake
times that initially fit with a 24-hour day, but then unknown to the participants sped up the
clock so the cycle only lasted 22 hours. This had a significant impact on the participants who
were affected by the change from the set 24-25 hours. This therefore suggests that the
body’s internal clock is set 24-25 hours in the absence of external cues, and is intolerant of
any major alterations to sleep and wake cycles, through processes such as shift work and jet
lag.
To contradict, Siffre's study is a case study and therefore the limitation is that it can't
be generalisable. The Siffre study was only on one individual, and the Folkard, Wever and
Aschoff studies were conducted on only a handful of people, and therefore it is impossible
to generalise these results to whole populations of people, as there may be some individual
differences in the research sample that makes these participants respond the changes the
sleep/wake cycle in atypical ways. For example, Siffre noted that when he went into the
cave at 60yr his body responded very differently, with his body clock following more of a
48hr cycle. And Czeisler has found evidence that cycles can vary by as much as 13-65 hours.
This suggests that results cannot be generalised from these small samples onto everyone, as
factors such as age and gender may have significant impacts on our circadian rhythms.
