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Sleep Deprivation Trivia
Peter Tripp stayed awake for 201 hours in 1959. Guinness Book of Records record is 18 days, 21
hours, 40 minutes.
Sleep deprivation implicated in Three Mile Island, Exxon Valdez, Challenger and Bhopal disasters.
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Examples of Biological Rhythms Seasonal migrations
Mating seasons
Menstruation
Circadian rhythms: Daily rhythms “Circa” means around, “dia” means day
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Zeitgebers: External Cues Help Set Circadian Rhythms “Zeit” means time in German. “Gebers” means givers.
Internal clocks interact with zeitgebers. Light is an important human zeitgeber. Human “free-running” cycle is about 25
hours. Blind individuals and sailors serving on
submarines may experience sleep problems.
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Individual Variations
“Larks” are morning people.
“Owls” are night people.
Many people are in between these extremes.
Most adolescents are temporarily owls.
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Results of Disruptions in Sleep Cycles More errors occur on evening and night
shifts. Shift workers average 1.5 hours less sleep,
and are more prone to sleep-related illnesses and psychological disorders.
Jet lag Symptoms: fatigue, irritability Conflict between internal biological clock
and external zeitgebers in new surroundings Adjustment to jet lag requires about 1 day
per time zone crossed.
Daylight Savings Requires Adjustment, Too April shift is a phase advance.
analogous to eastward travel 7% increase in traffic accidents
October shift is a phase delay. analogous to westward travel 7% decrease in traffic accidents
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The Suprachiasmatic Nucleus in the Body’s Master Internal Clock
“supra” – above (above optic chiasm)
SCN is near: Hypothalamus Flow of visual info
Retinohypothalamic pathway Axons from eyes going
to hypothalamus Provides light info to
hypothalamus to maintain circadian rhythms
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SCN Activity and Light/Dark Cycles
The SCN is active during the day in both diurnal and nocturnal animals.
The SCN tells the animal whether it’s day or night, but not how to behave.
Transplants of SCN establish donor rhythms in recipient animals.
The SCN tells an animal the difference between night and day, not whether it’s time to sleep or be awake.
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Origin of the Internal Clock
Oscillations of protein production and degradation serves as the “ticking” of the internal clock (takes about 24 hours).
Light may participate in the triggering of some of these protein fluctuations.
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The Biochemistry of Circadian Rhythms
Cortisol release is highest in
the morning and drops during the day.
Glutamate Released by the
retinohypothalamic tract during light
Melatonin released only at night
(by the retina and the pineal gland).
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Seasonal Affective Disorder (SAD) Depression related to the season:
1.4% of Florida residents experience SAD. 9.7% of New Hampshire residents experience
SAD. Icelanders may enjoy some genetic immunity.
Serotonin levels normally drop in late fall through winter—people with SAD may experience too much of a drop.
Light therapy uses lights of 2500 lux (normal indoor light is about 100 lux, sunlight is about 10,000 lux).
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Evaluating Sleep and Wakefulness
Electroencephalogram (EEG) Evaluation of muscle tone Evaluation of eye movement
© Lester Lefkowitz/CORBIS
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Stages of Waking and Sleeping
Wakefulness is characterized by relatively desynchronized alpha and beta waves.
Slow-wave sleep (SWS) is characterized by relatively synchronized theta and delta waves.
90–120 minute cycles characterize both sleep and wakefulness.
Ultradian cycles
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EEG During Wakefulness and Sleep
Awake – alpha and beta waves
Rapid-eye-movement sleep (REM) - active EEG, eye movements and muscular paralysis
Stage 2 - Sleep spindles and K complexes
Stages 3 and 4 - larger percentages of delta waves.
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Sleep Patterns in a Typical Night
The first 4 hours contain more SWS, especially Stages 3 and 4.
The second 4 hours contain more REM.
REM episodes occur approximately every 90–120 minutes.
Copyright © Houghton Mifflin Company. All rights reserved.
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Brain Activity in Wakefulness, SWS and REM
REM vs. waking (top): primary visual cortex equally
active limbic system more active during
REM
REM vs. SWS (lower): most of the brain is more
active during REM than during SWS
primary visual cortex is more active during SWS
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