Circadian Rhythms

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The Circadian Rhythms
What is a Circadian Rhythm?
They are rhythms last for approximately 24 hours i.e. a day. The 2 best examples:
sleepwake cycle and body temperature cycle
The Sleep Wake cycle
You might think we sleep at regular times because of the daylight (being sleepy when it's dark
and awake when its light) or because we know what time of day it is.
These are all external cues that are importing in guiding the sleepwake cycle however
there's also an internal circadian clock that's free running and lasts 2425 hours. The cycle
doesn't just work on its own as Exogenous Zeitgebers also affect it.
There are studies that show that Circadian rhythms persist when people are isolated from
these Exogenous Zeitgebers and showed the importance of these external cues as the
endogenous clock wasn't completely accurate and varied from day to day.

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This shows that the sleepwake cycle rests at approximately 24 hours when
there aren't any external cues
Aschoff and Wever
Put participants in a WWII bunker where they had no social or environmental cues
Most participants had 2425 hour circadian rhythms but other had as long as 29 hour
sleepwake cycles
This shows that without external cues the sleep wake cycle rests on average
between 24 and 25 hours…read more

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Core Body Temperature cycle
Another example of a circadian rhythm is the core body temperature cycle.
Lowest body temperature: 36 degrees at 4:30 am
Highest body temperature: 38 degrees at 6 pm
There is also a temperature dip after lunch ­ i.e.…read more

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