1. Definition: a
natural and
periodic state of
rest during which
consciousness of
the world is
suspended.
2. The theories described to explain the purpose of
sleep are:
Restoration theory proposes that sleep serves to
restore energy to our bodies after the physical and
emotional fatigue that occurs during wakefulness.
Survival theory proposes that sleep evolved as a
means of hiding during the night to avoid
exposure to predators and other dangers in the
dark, and to conserve energy for daytime activities.
Animals that are less susceptible to predators and
require less time to forage for food, such as cats,
tend to sleep for longer periods of time than
animals that need more time for foraging and are
more likely to be exposed to predators, such as
horses .
3. The stages of sleep are:
Non-Rapid Eye Movement Sleep which has Stages 1
to 4 and
Rapid Eye Movement Sleep.
Stage I – “Just Drifting” Stage
Last approximately 10 minutes
Pulse rate slows more
Muscles relax
Breathing becomes uneven
Brain waves grow irregular
4. Stage II
Brain waves shift from low amplitude/high
frequency to high amplitude/low frequency
Eyes roll from side-to-side
Lasts 30 minutes
Stage III
Delta wave patterns sweep through the brain
Stage IV
Deepest sleep – difficult to awaken a sleeper.
If awakened by a loud noise, the sleeper will be
disoriented.
Talking out loud, sleepwalking, bed wetting occur
here and leave no trace on the memory.
5. REM Sleep – Rapid Eye Movement or Active Sleep
Pulse rate and breathing become irregular
Levels of adrenal and sexual hormones increase
in blood – as if involved in an emotionally and
physically demanding activity.
Large muscles in arms become paralyzed.
Brain waves look as if you’re awake.
Dreaming occurs here.
Lasts for 15-45 minutes.
When completed you go through the stages
again – each complete cycle lasts for about 90
minutes.
6. Electroencephalogram (EEG): In the
1920s, German psychiatrist Hans Berger
was the first to discover that the human
brain has continuous electrical activity.
He invented the electroencephalograph, a
machine that records the patterns of this
electrical activity, without having to open a
person’s skull. The brain’s electric
currents, or brainwaves, were produced as
line tracings on strips of paper.
7. Berger noticed that the record, or
electroencephalogram (EEG), changed
according to the functional status of the
brain—for example, whether a person was
awake or asleep.
8. Electrodes are placed beneath the chin to
measure the electrical activity of the jaw
muscles. The record that results is known as
the electromyogram (EMG).
The EMG is recorded under the chin because
the activity of the jaw muscles shows
dramatic changes during sleep. EMG
recordings also differ depending on the stage
of sleep a person is experiencing.
9. A third technique used during sleep research
is the electro-oculogram (EOG).
An electrode on the skin near each eye
measures electrical changes associated with
spontaneous eye movement activity during
sleep.
The eyeball is like a small battery—as it
rotates, a change in voltage is recorded by
each electrode. This variation in voltage is
known as the EOG—a graph showing the
pattern of eye movement activity.
11. Sleep deprivation refers to not getting
adequate sleep.
Psychological and physical effects
Many studies have shown that sleep
deprivation affects performance on
cognitive tasks, such as a memory test or
learning task, because of a reduction in
concentration, motivation and attention.
These negative effects can be reversed if
the participants are motivated by the
researcher to perform to the best of their
ability.
12. Studies have revealed the most common
effect of partial sleep deprivation are
extreme weariness, increased sleepiness or
drowsiness, irritability, hand
tremors,anxiety, lapses in attention and a
feeling of pressure around the head.
The implications of increased drowsiness
and lapses in attention are serious when
performing tasks that require us to be
alert, such as bathing a newborn baby,
driving a bus or controlling air traffic. In
these circumstances, a lapse in attention
may be very costly.
