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Chapter 11

Sleep and Waking

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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.

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Adjustments to Phase Delays Are Easier than Phase Advances

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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Protein Fluctuations and Fruit Fly Circadian Rhythms

Proteins:- per- tim- Clock

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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.

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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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Sleep Patterns Across the Lifespan

REM sleep is more prevalent in infancy. Aging is associated with drops in overall sleep

and proportion of SWS.