Circadian rhythms 16 marker
The circadian rhythms are a biological rhythm which is subjected to a 24-hour cycle, for
example the sleep wake cycle or the core body temperature cycle. The circadian rhythm is
influenced by internal body clocks (endogenous pacemakers) and external influences
(exogenous zeitgebers) such as light and is governed by the suprachiasmatic nucleus (SCN)
which then effects the release of different amounts of melatonin from the pineal gland to
control the sleep wake cycle.
Research by Siffre 1972 investigated the effect of removing of the exogenous zeitgeber light
on the circadian rhythms of the sleep wake cycle, by spending 6 months in a cave. His cycle
turned out to be more like 24 hrs 30 mins due to only being influenced by his internal body
clock. This shows that a free running circadian rhythm based on the internal body clock is
longer than 24 hrs but as a society we use exogenous zeitgebers to control it to 24 hrs,
showing it can still function without them.
One limitation of circadian rhythms is that individual differences occur based on your age. In
isolation studies in support (Siffre 1972) only one age is covered so this doesn’t measure the
effect that exogenous zeitgebers have or don’t have on a wide variety of ages. As different
ages may have different circadian rhythms so this research cannot be generalised to
everyone as with age endogenous pacemakers run much slower. Decreasing validity of
Siffres experiment in support for circadian rhythms.
Another limitation of Siffres research on circadian rhythms is that he still used artificial light.
Which research by Czseisler 1999 found that artificial light can drastically create shifts in
circadian rhythms by up to 6 hours. Meaning Siffre could have altered is own rhythms by
signalling it with artificial light. His circadian rhythms may not be as accurate as once
thought and instead a product of artificial light decreasing the validity of the study.
Another weakness of Siffres research is that he only accounts for biological influences on the
circadian rhythm. When in fact there must also be nurture influences a sin real life both
nature and nurture interact and work together. This decreases the validity of the study
because it only misses out an influence that may occur on circadian rhythms such as social
cues and nurture related infleunces.
The circadian rhythms are a biological rhythm which is subjected to a 24-hour cycle, for
example the sleep wake cycle or the core body temperature cycle. The circadian rhythm is
influenced by internal body clocks (endogenous pacemakers) and external influences
(exogenous zeitgebers) such as light and is governed by the suprachiasmatic nucleus (SCN)
which then effects the release of different amounts of melatonin from the pineal gland to
control the sleep wake cycle.
Research by Siffre 1972 investigated the effect of removing of the exogenous zeitgeber light
on the circadian rhythms of the sleep wake cycle, by spending 6 months in a cave. His cycle
turned out to be more like 24 hrs 30 mins due to only being influenced by his internal body
clock. This shows that a free running circadian rhythm based on the internal body clock is
longer than 24 hrs but as a society we use exogenous zeitgebers to control it to 24 hrs,
showing it can still function without them.
One limitation of circadian rhythms is that individual differences occur based on your age. In
isolation studies in support (Siffre 1972) only one age is covered so this doesn’t measure the
effect that exogenous zeitgebers have or don’t have on a wide variety of ages. As different
ages may have different circadian rhythms so this research cannot be generalised to
everyone as with age endogenous pacemakers run much slower. Decreasing validity of
Siffres experiment in support for circadian rhythms.
Another limitation of Siffres research on circadian rhythms is that he still used artificial light.
Which research by Czseisler 1999 found that artificial light can drastically create shifts in
circadian rhythms by up to 6 hours. Meaning Siffre could have altered is own rhythms by
signalling it with artificial light. His circadian rhythms may not be as accurate as once
thought and instead a product of artificial light decreasing the validity of the study.
Another weakness of Siffres research is that he only accounts for biological influences on the
circadian rhythm. When in fact there must also be nurture influences a sin real life both
nature and nurture interact and work together. This decreases the validity of the study
because it only misses out an influence that may occur on circadian rhythms such as social
cues and nurture related infleunces.
