The document discusses the characteristics and patterns of sleep. It describes the stages of non-REM (NREM) sleep including stages 1-4, as well as REM sleep. NREM sleep makes up about 80% of total sleep and involves light to deep unconscious sleep, while REM sleep involves vivid dreaming. Sleep cycles through NREM and REM stages about every 90 minutes. Theories on why we sleep include survival theories that sleep conserves energy and restorative theories that sleep enhances functions like memory, growth, and repair of the body. However, both types of theories have limitations in fully explaining sleep.

1. Lesson 3: Characteristics and Patterns of Sleep

2. http://www.youtube.com/watch?v=t27suXgfi8w
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3. Characteristics of Sleep

4. NREM Sleep Non-rapid eye movement sleep
NREM sleep includes those stages not associated with rapid
eye movements. Adults spend approximately 80 percent of
their nights sleep in NREM, and typically the first half of the
night has more NREM sleep than the second half.
NREM is essential to the physical growth and repair of the
body. Research has found the amount of NREM increases after
vigorous exercise (Vein et al., 1991).
NREM is dream free about 90% of the time, dreams tend to be
more short lived and fragmented than those in REM.

5. NREM Stage 1
~Theta waves, which are of lower frequency and higher amplitude than
alpha waves, appear and start to replace alpha waves.
~Despite the fact that various wave types are shown in this stage, theta
waves define Stage 1 NREM sleep.
~In stage one of sleep, breathing becomes irregular, muscles relax, and
hypnogogic jerks often occur.
~Stage 1 lasts for approximately 5 min but this can vary.

6. NREM Stage 2
~In this stage there is a prevalence of theta-wave activity.
~ As sleep deepens EEG recordings begin to pick up unique brain wave
features that are characteristic of stage 2 sleep. Theses include
• Sleep spindles – brief bursts of higher frequency brain waves
• K complexes – single sharp bursts (rise then fall) in amplitude (and
lower frequency).
• Body temperature decreases
• Breathing and heart rate decrease
• ~Stage 2 sleep lasts for approximately 20 min

7. NREM Stage 3
~Delta waves begin to appear which are
large and slow.
~Stage 3 is a transitional stage and
lasts for approximately 10 min.

8. NREM Stage 4
~Brain waves become almost pure delta waves
~Regular (slow) heartbeat, slow (rhythmic) respiration &
little muscle activity
~ Lasts for approximately 30 min
~Very hard to awaken a sleeper from Stage 4 sleep.

9. REM ~ Rapid Eye Movement
~REM sleep is strongly associated with dreaming. About 85% of the time a person is
awakened from REM sleep they report vivid dreams.
~ The brain wave pattern associated with REM sleep is irregular, consisting of low-
amplitude, relatively high-frequency beta waves, like those produced during alert
wakefulness.
~On average REM sleep totals about 90 min per night. The amount of REM sleep
tends increases with stress in an individuals life.
~REM sleep is sometimes called paradoxical sleep, as aspects of REM sleep appear to
contradict each other. The brain wave pattern is very much like those produced during
alert wakefulness. The bodies internal functioning is more active during REM sleep
than during NREM sleep, the heart beats faster, breathing is more rapid and
irregular, and genitals become aroused. On the other hand, the sleeper is totally
relaxed; most of the skeletal muscles are totally relaxed (to the point of paralysis).

10. Patterns of Sleep
An adult sleeps for approximately 8 hrs per night progressing through cycles of about 1.5
hours. Periods of deep sleep (NREM4) occur earlier in the night, and periods of REM sleep occur,
on average every 90 minutes.
Adults experience a total of 1-2 hours REM sleep a night, in 4-5 sessions, each progressing in
length.
The period of total REM sleep lessons as individuals get older. A newborn spends approximately
50% of total time in REM sleep compared to an adult who spends approximately 20% of their
time in REM sleep.

11. WHY DO WE SLEEP?

12. Survival Theories
Focuses on when and why different species sleep
Sleep depends on the need to find food
Sleep depends on an animal’s vulnerability to predators
Sleep conserves energy

13. Limitations of Survival Theories
Survival theories state that sleeping offers security from
predators, however the loss of awareness while asleep
contradicts this statement.
Survival theories fail to explain why we MUST sleep

14. Restorative Theories
Focuses on why sleep is important
Sleep enhances mood
Sleep repairs and replenishes the body and
prepares it for action the next day
The neurotransmitters adenosine (energy),
norepinephrine (alertness)
Metabolism
Growth hormones
Immunity to disease
Consolidates memories

15. Limitations of Restorative Theories
The body does not completely “rest” during sleep (REM)
as assumed by restorative theories
Lack of physical activity does not reduce the amount
of sleep needed