chapter 5 section 2: the rhythms of sleep. why do we sleep? the exact function is still uncertain....
TRANSCRIPT
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Chapter 5 Section 2: The Rhythms of Sleep
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Why Do We sleep?
• The exact function is still uncertain.• Sleep appears to provide a time for
rejuvenation and repairs.–Eliminate waste products from muscles,
repair cells, strengthen the immune system, & recover abilities lost during the day
• When we do not sleep, our bodies operate abnormally and we lose mental function
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• Sleep deprivation for 4 or more days becomes uncomfortable & soon unbearable–Can lead to infection & death
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• Necessary for normal mental functioning–In chronic sleep deprivation, high
levels of cortisol may damage or impair the brain cells that are necessary for learning & memory–May even begin to have hallucinations
& delusions
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Sleep Disorders
• At least 40 million Americans suffer from chronic, long-term sleep disorders each year• These disorders interfere with work,
driving, & social activities
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• Insomnia- difficulty falling or staying asleep–Resulting from worry & anxiety, hot
flashes, arthritis• Sleep apnea- caused from blockage of
air passages to failure of the brain to control respiration correctly–Can lead to high blood pressure &
irregular heartbeat
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Sleep walking
• Characterized by walking or some activity while sleeping• REM disorder• Difficult to wake during an episode• Can be caused by fatigue,stress, or anxiety
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• Narcolepsy- daytime attacks of sleepiness lasting 5 to 30 minutes
• Causes of sleepiness–Staying up late & not allowing
for enough sleep
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Nightmares
• Stressful things that happen during the day can turn dreams into nightmares.• Nightmares may be a way to relieve
the pressures of the day.
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How much sleep do I need?
• Infants- 16 hours• Teenagers- 9 hours• Adults- 7-8 hours–Some can function on 5 others
need 10
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• When people are sleepy, traffic & work accidents are more likely
• 2/3 of Americans get fewer than the recommended 8 hours–Lack of sleep has been linked to lower
grades
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The Realms of Sleep
• Until the early 1950s, little was known about the physiology of sleep. • Then a breakthrough occurred in the lab of
physiologist Nathaniel Kleitman, who identified REM sleep.• The research led to our understanding of
the stages of sleep.
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• Cycle that recurs every 90 minutes–REM average 20 minutes
• Cycle–Alpha waves- regular, slow rhythm & a
high amplitude, eventually slow down & you drift off
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Sleep Sleep StagesStages
Physiological/Physiological/
Psychological ChangesPsychological ChangesAwake, Awake, but but DrowsyDrowsy
Body is relaxedBody is relaxed
Stage 1Stage 1
(5%)(5%)Heart rate slower, light Heart rate slower, light sleep (1 & 2 last 30 min)sleep (1 & 2 last 30 min)
Stage 2Stage 2
(44-55%)(44-55%)Person may talk in their Person may talk in their sleepsleep
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Stages of SleepStage 1. Your brain waves
become small and irregular, & you feel yourself drifting on the edge of consciousness, in a state of light sleep.
If awakened, you may recall fantasies or a few visual images.
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Stage 2. Your brain emits
occasional short bursts of rapid, high-peaking waves called sleep spindles.
Minor noises probably won't disturb you.
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Stage 3Stage 3 Deep sleep, somewhat Deep sleep, somewhat difficult to awakendifficult to awaken
Stage 4Stage 4
(15-(15-23%)23%)
Considerable movement, Considerable movement, most difficult to awakenmost difficult to awaken
REMREM
(20-(20-25%)25%)
90 min. into sleep cycle, 90 min. into sleep cycle, return to stage 1 & begin return to stage 1 & begin REM sleep; appear REM sleep; appear paralyzed, recall dreams paralyzed, recall dreams when awakenedwhen awakened
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Stage 3. In addition to the waves
characteristic of Stage 2, your brain occasionally emits delta waves, very slow waves with very high peaks.
Your breathing & pulse have slowed down, your muscles are relaxed, & you are hard to arouse.
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Stage 4. Delta waves have
taken over, & you are in deep sleep.
It will probably take vigorous shaking or a loud noise to awaken you.
If you talk or walk in your sleep, this is when you are likely to do so.
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• Sequence takes about 30-45 minutes & then goes in reverse–About 70-90 minutes into sleep in stage 1,
brain emits long bursts of rapid irregular waves, heart rate increases, blood pressure rises, & breathing becomes faster & irregular• Twitches may occur in your face &
fingers, skeletal muscles go limp (REM)
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• Most likely to dream• REM & non-REM sleep continue to
alternate throughout the night with stages 3 & 4 becoming shorter & tend to disappear–Varies from person to person