Chapter 5 Section 2: The Rhythms of Sleep. Why Do We sleep? The exact function is still uncertain....

Chapter 5 Section 2: The Rhythms of Sleep

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

• Sleep deprivation for 4 or more days becomes uncomfortable & soon unbearable–Can lead to infection & death

• 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

Sleep Disorders

• At least 40 million Americans suffer from chronic, long-term sleep disorders each year• These disorders interfere with work,

driving, & social activities

• 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

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

• Narcolepsy- daytime attacks of sleepiness lasting 5 to 30 minutes

• Causes of sleepiness–Staying up late & not allowing

for enough sleep

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.

How much sleep do I need?

• Infants- 16 hours• Teenagers- 9 hours• Adults- 7-8 hours–Some can function on 5 others

need 10

• 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

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.

• 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

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

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.

Stage 2. Your brain emits

occasional short bursts of rapid, high-peaking waves called sleep spindles.

Minor noises probably won't disturb you.

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

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.

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.

• 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)

• 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