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Circadian Rhythms - Coggle Diagram
Circadian Rhythms
What is it?
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Photoentrainmanet
- Process by which light sets body clock to the correct time.
- Light proves primary input into the circadian system.
Mammals
- Light sensitive cells in eyes act as brightness detectors.
- Send messages about environmental light levels to the SCN.
- SCN then uses this information to coordinate the circadian system.
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Micheal Siffre 1975
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Procedure
- Spent six months underground ina cave in Texas, in dim light.
- He had no cues as to the time of day.
- He had food, water, exercise equipment and books.
- He had a telephone link to the outside world which was staffed at all times.
- Siffre was worked up via a computer and video so that his bodily functions could be monitored all of the time.
Findings
- Siffre’s bodily rhythms were erratic at first - went into a state of internal desynchronisation.
- It sooner settled down.
- He adopted a daily cycle that he established that seemed to run around 25 hours.
Conclusion
The pattern of sleep and wake reamins even when there are no external cues. It appears that th natural length of thr Circadian cycle is 25 hours.
Sleep wake cycle
- Circaduan rhythm dictates when we should be asleep and awake.
- External signals —-} light and dark.
- Time of day —-} strongest sleep drive usually occurs in two ‘dips’ between 2-4am and 1-3pm - post launch.
- Sleepness varies depending on amount of sleep we have had.
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Summary
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Homeostatic system —-} makes us sleepier as time does on throughout waking period regardless of day or night.
Circadian clock is = free running which means it maintains the cycle of around 24 hours regardless of external use. It is intolerant of any major alternation in sleep and wake schedules like being jet lagged or have overnight shifts…. Because it causes biological clock to become out of balance.
Other circadian Rhythm
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Hormone production
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Light amounts
Dark
Peak melatonin production, individual more likely to sleep.
Light
Production drops, more like to stay awake.