We have a 24-hour Sleep Rhythm
Some People are Most Awake in the Morning and Least Awake at Night
Some People are Most Awake at Night and Least Awake in the Morning
Which are You?
Biological Rhythms: cycles that our bodies
have.
Shorter than 1 day
Daily - Also called "Circadian Rhythms"
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Awakeness
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Body temperature
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Testosterone level in males (generally highest around 6 a.m., lowest around
6 pm.)
Monthly
Yearly
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Seasonal Affective Disorder Syndrome
Circadian Rhythms (24 hours) - How does our body know what time
it is?
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We have an internal clock that tells our body that it's morning, afternoon,
night.
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It runs on a 25 hour schedule if we're in sensory deprivation (no people
or other outside information).
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It gets set every day through entrainment: setting our internal clock through
information in the outside world.
Sources of entrainment - things in our environment that set our
internal clock
Daylight
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Suprachiasmatic Nucleus - in hypothalamus. In darkness, s.n. gives orders
to release melatonin to make us sleepy.
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In light, s.n. stops release of melatonin to make us awake.
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May be one cause of SADS - in winter s.n. can't get enough light.
Things that can interfere with the cycle:
Jet lag - our internal clock is wrong for our new environment
Shift work - especially with swing shifts, our clock is never accurate
no matter how much sleep we get.
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People who work nights perform worse than people who work days no matter
how much sleep they get.
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Working 4 nights and then having 3 nights off is worse than working 5 nights
and having 2 nights off - it gives our clock more of a chance to reset
itself to being awake during the day.
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The only way for night shifts not to harm performance is if person stays
up all night when not working too, to keep clock the same.
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Even this doesn't really work if we get any natural light.