12. • A hypnogram is a form of polysomnography; it is a
graph that represents the stages of sleep as a function
of time.
• It was developed as an easy way to present the
recordings of the brain wave activity from
an electroencephalogram (EEG) during a period of
sleep.
• It allows the different stages of sleep: rapid eye
movement sleep (REM) and non-rapid eye movement
13. • NREM sleep can be further classified into NREM
stage 1, 2 and 3.
• The previously considered 4th stage of NREM sleep
has been included within stage 3; this stage is also
called slow wave sleep (SWS) and is the deepest
stage of sleep.
• Each of the three NREM stages as well as the
period of REM sleep and the awake state can be
determined and displayed on a hypnogram
15. TYPES OF SLEEP
• There are two types of sleep:
1. Non Rapid Eye Movement Sleep ( NREM )
[Slow Wave Sleep- Dreamless].
2. Rapid eye movement Sleep ( REM )
[Dreamful].
• Both types alternate with each other.
• Surprisingly, they are as different from each other
as either is from waking
19. Normal Sleep Stages and Function
Vander et al. Consciousness and behavior. In: Human Physiology. 1990.
States Function
Active state of brain
functions in learning
and memory
Body’s rest and
metabolic restoration
Phasic eye movements
Loss of muscle tone
EEG neutral
Stage 3
Stage 4
(REM)
Stage 1
Stage 2
(NREM)
20. NREM Sleep
4 stages of NREM Sleep
• Stages 1 and 2
– Light sleep stages
• Stages 3 and 4
– Deep sleep or slow wave sleep stages
23. Sleep Architecture in young Adults
•Wakefulness in sleep, <5% of night
•Stage I 2 - 5%
Stage II 45 - 55%
Stage III 3 - 8%
Stage IV 10 - 15%
NREM 75 - 80%
•REM 20 - 25% in 4-6 episodes
27. Normal Physiology - Basics
• Non-REM Sleep
– Stage 1: very light, easy to arouse
– Stage 2: most of the night’s sleep
– Stage 3,4: slow wave, deeper sleep
• REM Sleep
– EEG similar to stage 1
– Low/absent muscle tone
– Dreaming occurs here
– Greatest cardiac and respiratory instability
28. SLEEP PHYSIOLOGY
•REM and non-REM sleep alternate
cyclically
•REM sleep:
- 20-30min every 90-120 min
- increases later in night
29. Normal Physiology - Basics
• Sleep Architecture
– REM latency is about 90 minutes (wide
variation)
• Very short in narcolepsy
– REM normally occurs every 90 to 120
minutes
– More stage 3,4 in first half of night, more
REM 2nd half
– Brief awakenings (30 sec) common, not
usually remembered
– Brief arousals (3 sec) are normal
31. Typical Nightly Sleep Stages
Hours of sleep
Minutes
of
Stage 4
and
REM
1 2 3 4 5 6 7 8
0
10
15
20
25
5
Decreasing
Stage 4
Increasing
REM
32.
33. Sleep Cycles
• Usually about 10-30
minutes to fall asleep
– <5 minutes indicates
excessive sleepiness
– >30 minutes due to
lack of sleepiness,
emotional stress,
environmental
disturbances,
medication, illness,
or pain
• Full sleep cycle:
– Stage one
– Stages 2-4
– Return to stage 3 then
stage 2
– From stage 2 comes
REM
– End of REM in the
conclusion of the first
cycle
• Normal night’s sleep =
4-6 cycles of sleep
34. Normal Sleep Cycle
• Normal sleep
cycle. The sleeper
progresses
through Stages 1,
2, 3, and 4;
followed by a
return to Stage 3
and 2.
• From Stage 2 the
sleeper moves
into REM sleep.
The end of REM
sleep ends the
first sleep cycle.
• From REM sleep,
the sleeper moves
back to Stage 2
and a new sleep
35. • In a normal night's sleep, a sleeper begins in
stage 1, moves down through the stages, to stage
4, then back up through the stages, with the
exception that stage 1 is replaced by REM, then
the sleeper goes back down through the stages
again.
• One cycle, from stage 1 to REM takes
approximately ninety minutes. This cycle is
repeated throughout the night, with the length of
REM periods increasing, and the length of delta
sleep decreasing, until during the last few cycles
there is no delta sleep at all.
47. Sleep Stages
• Sleep architecture follows a pattern of alternating
REM (rapid eye movement) and NREM (non-rapid
eye movement) sleep throughout a typical night in a
cycle that repeats itself about every 90 minutes.
1. NREM sleep (75-80% of sleep in healthy young
adults).
2. REM sleep (20-25% of sleep in healthy young
adults).
• These stages are defined by distinct
48. Quiet sleep
• Sleep specialists have called non-REM or quiet
sleep “an idling brain in a movable body.”
• During this phase, thinking and most physiological
activities slow down, but movement can still occur,
and a person often shifts position while sinking
into deeper stages of sleep
49. • When you are awake, billions of brain cells receive
and analyze sensory information, coordinate behavior,
and maintain bodily functions by sending electrical
impulses to one another. If you’re fully awake, the
EEG will record a messy, irregular scribble of activity.
• Once your eyes are closed and your nerve cells no
longer receive visual input, brain waves settle into a
steady and rhythmic pattern of about 10 cycles per
second. This is the alpha-wave pattern, characteristic
of calm, relaxed wakefulness.
• The transition to quiet sleep is a quick one that might
be likened to flipping a switch — that is, you are either
awake (switch on) or asleep (switch off)
Quiet sleep
50. • Non-REM sleep may be viewed as a period of
relative low brain activity during which the
regulatory capacity of the brain is actively
ongoing and in which body movements are
preserved
• Non-REM sleep is further divided into:
¯ Stage 1
- Stage 2
- Stage 3
- Stage 4
51. Stage 1 (Transition to sleep)
—Stage 1 sleep (2-5%) which occurs at the sleep-
wake transition and is often referred to as “light
sleep”
—Stage 1 lasts about five minutes.
—Eyes move slowly under the eyelids, muscle
activity slows down
—You are easily awakened.
—if awakened people say they weren’t asleep.
—E.E.G. findings: Alpha waves diminish and
Theta waves appear on EEG.
52. —In making the transition from wakefulness into light
sleep, you spend about five minutes in stage N1
sleep.
—On the EEG, the predominant brain waves slow to
four to seven cycles per second, a pattern called
theta waves.
—Body temperature begins to drop, muscles relax,
and eyes often move slowly from side to side.
—People in stage N1 sleep lose awareness of their
surroundings, but they are easily jarred awake.
—However, not everyone experiences stage N1 sleep
in the same way: if awakened, one person might
Stage 1 (Transition to sleep)
53. —Stage 2 sleep is the first stage of true sleep.
—lasts 10 to 25 minutes. you spend about half the
night (45-55) in stage 2 sleep.
—Stage 2 sleep is usually considered the initiation of
“true” sleep , This stage involves the following :
—Your eyes are still, and your heart rate and breathing
are regular slower than when awake , body
temperature drops
—The person experiences only light sleep.
—It is a little harder to awake the person.
Stage 2: Light Sleep
54. —In Stage 2 sleep , EEG tracings is characterized by
bursts of rhythmic rapid EEG activity called sleep
spindles (fluctuating episodes of fast activity) and
high amplitude slow wave spikes called K-
complexes
—Scientists think that K-complex, represents a sort of
built-in vigilance system that keeps you poised to
awaken if necessary.
—K-complexes can also be provoked by certain
sounds or other external or internal stimuli.
Stage 2 : Light Sleep
55. Deep Sleep
• Stage 3 sleep is usually combined with stage 4
sleep and usually constitutes 12-18% of sleep.
• During this stage, known as deep sleep or slow-
wave sleep, the brain becomes less responsive to
external stimuli, making it difficult to wake the
sleeper.
• Deep sleep seems to be a time for your body to
renew and repair itself.
56. Deep Sleep
• Typically during this stage:
1. Large, slow brain waves called delta waves
become a major feature on the EEG.
2. Breathing becomes more regular. Blood pressure
falls, and pulse rate slows to about 20% to 30%
below the waking rate.
3. Blood flow is directed less toward your brain.
4. At the beginning of this stage, the pituitary gland
releases a pulse of growth hormone that stimulates
tissue growth and muscle repair.
57. oStages 3 and 4 sleep which are otherwise
know as “deep” sleep, slow wave sleep, or
delta sleep and during which the highest
arousal threshold (most difficult to awaken)
also occurs.
oDelta sleep is generally considered the
most restorative stage of sleep
oThe deepest stage of sleep. Brain waves
are extremely slow. Blood flow is directed
away from the brain and towards the
muscles, restoring physical energy.
58. • Note: Most sleep during each night is of a slow
wave Lasts for 80=90 minutes.
• Dreams / night mare even occur.
• The difference is that the dreams in slow
wave sleep are not remembered but in REM,
dreams can be remembered.
Deep Sleep
59. • Normally, young people spend about 20% of their
sleep time in deep sleep lasting, but deep sleep is
nearly absent in most people over age 65.
• Someone whose deep sleep is restricted will wake
up feeling less refreshed.
• When a sleep-deprived person gets some sleep, he
or she will pass quickly through the lighter sleep
stages and spend a greater proportion of time in
deep sleep, suggesting that deep sleep fills an
essential role in a person’s optimal physical
functioning.
60. Stages 3 and 4
Deepest and most restorative sleep
Blood pressure drops
Breathing becomes slower
Muscles are relaxed
Blood supply to muscles increases
Tissue growth and repair occurs
Energy is restored
Hormones are released, such as: Growth
hormone, essential for growth and development,
including muscle development
Deep Sleep
61. PHYSIOLOGIC CHANGES DURING
NREM
AUTONOMIC NERVOUS SYSTEM
• Increased parasympathetic tone and decreased
sympathetic activity in NREM sleep.
GASTRIC FUNCTION: In NREM, failure of inhibition of
gastric secretion in 1st 2 hours of sleep; overall
decrease in gastric motility during sleep.
• Swallowing is suppressed in NREM, stage 3 with
prolonged gastric mucosa exposure to reflux.
• In NREM there is decrease in core body temperature
by due to vasodilatation, lowest at third sleep cycle.
ENDOCRINE: In NREM, growth hormone and prolactin
secretion is increased. In REM certicotropi-cortisol
rhythm is increased in the morning.
62. •Upon reaching stage 4 and after about 80 to 100 minutes of
total sleep time, sleep lightens, returns through stages 3 and 2
•REM sleep emerges, characterized by EEG patterns that
resemble beta waves of alert wakefulness
– Muscles most relaxed
– Rapid eye movements occur
– Dreams occur
•Four or five sleep cycles occur in a typical night’s sleep; less
time is spent in slow-wave, more is spent in REM
63. REM Sleep
(“brain on, body off”)
—Rapid eye movements
—Wakeful EEG pattern
—Increased cerebral blood flow
—Absent spinal reflexes
—Associated with dreaming
—REM sleep usually constitutes 20-25% of sleep
in 4 to 6 episodes.
64. REM ( RAPID EYE MOVEMENT) SLEEP,
PARADOXICAL SLEEP, DESYNCHRONIZED
SLEEP
• 5-30 minutes long, every 90
minutes;
• ↓ muscle tone;
• ↑ brain metabolism ( as much
as 20 % );
• Irregular heart and respiratory
rate;
• Rapid eye movements;
• Less restful, desynchronised;
• Associated with psychical
activities, such as dreaming.
65. REM ( RAPID EYE MOVEMENT) SLEEP,
PARADOXICAL SLEEP, DESYNCHRONIZED
SLEEP
Bouts of REM sleep last for 5 to 30 min & usually appear on
average every 90 minutes;
As the person becomes more rested during the night, the
durations of the REM bouts ↑
REM characteristics:
1. Active dreaming
2. The person is more difficult to arouse by sensory stimuli than during
the deep slow- wave sleep & people usually awaken spontaneously
during a REM episode;
3. Muscle tone is exceedingly depressed – strong inhibition of the
spinal muscle control areas;
4. Heart rate & respiratory rate become irregular;
5. Brain is ↑ active & brain waves are similar to those of wakefulness.
66. REM sleep is characterized by
• paralysis or nearly absent muscle tone (except for
control of breathing), Body becomes immobile and
relaxed, as muscles are turned off
• high levels of cortical activity that are associated
with dreaming, irregular respiration and heart rate,
and episodic bursts of phasic eye movements that
are the hallmark of REM sleep.
• First occurs about 90 minutes after falling asleep
and recurs about every 90 minutes, getting longer
later in the night
67. • REM sleep sets the stage for dreams. Our eyes are
scanning back and forth, but our skeletal muscles
are paralyzed, Skeletal muscle atonia during REM ,
perhaps to keep us from acting out our dreams.
• A typical night’s sleep consists of four or five
REM/non-REM cycles with occasional, brief
episodes of wakefulness.
• Most Stage 4 sleep occurs during the first two to
three hours of sleep. As morning approaches, REM
sleep occupies an increasing share of slumber.
REM sleep (Dream sleep)
68. Dreaming (REM) sleep
• Dreaming occurs during REM sleep, which has been
described as an “active brain in a paralyzed body.”
Here is what happens:
• Your brain races, thinking and dreaming, as your
eyes dart back and forth rapidly behind closed lids.
• Your body temperature rises. Your blood pressure
increases, and your heart rate and breathing speed
up to daytime levels.
69. • The sympathetic nervous system, which creates
the fight-or-flight response, is twice as active as
when you’re awake.
• Despite all this activity, your body hardly moves,
except for intermittent twitches; muscles not
needed for breathing or eye movement are quiet.
Dreaming (REM) sleep
70. • In REM, there is penile erection and clitoral
engorgement.
• They usually bear little relationship to dream
content and do not correlate with sensual
dreaming.
• The ability to obtain normal erection is used to
distinguish between physical and psychological
impotence.
71. • Non-REM and REM sleep alternate throughout the
night in cycles of about 90-110 minutes.
• Brief arousals normally followed by a rapid return
to sleep often occur at the end of each sleep cycle
(4-6 times per night).
• The relative proportion of REM and non-REM
sleep per cycle changes across the night, such
that slow wave sleep predominates in the first third
of the night and REM sleep in the last third.
72. • About three to five times a night, or about every 90
minutes, a sleeper enters REM sleep. The first such
episode usually lasts only for a few minutes, but
REM time increases progressively over the course
of the night. The final period of REM sleep may last
a half-hour.
• Normally, REM sleep makes up about 25% of total
sleep in young adults.
• If someone who has been deprived of REM sleep is
left undisturbed for a night, he or she enters this
stage earlier and spends a higher proportion of
sleep time in it — a phenomenon called REM
rebound.
73. REM Sleep
—Just as deep sleep renews the body, REM sleep
renews the mind.
—REM sleep plays a key role in learning and
memory.
—During REM sleep, your brain consolidates and
processes the information you have learned during
the day, forms neural connections that strengthen
memory, and replenish its supply of
neurotransmitters, including feel-good chemicals
such as serotonin and dopamine that boost your
mood during the day.
74. • During REM (dreaming) sleep, the body is
still, but the mind is racing.
• Time spent in REM sleep increases as the
night progresses.
• REM sleep restores the mind , It is important
for both learning and memory.
REM Sleep
77. Characteristics of REM &non-REM sleep
Sleep activity REM sleep Non-REM sleep
Eye movement Rapid Slow (drowsiness)
Body movement Muscle
twitches
Muscle relaxation
Vital signs Fluctuating Stable
Muscle tone decreased Some tone in postural muscle
Penile erection common Rare
Dreams Common Rare
EEG Low
voltage
Spindles, V-waves, K-
complexes, slow waves
Percentage-adults 20-25 75-80
Percentage-infants 50 50
78.
79. Sleep Cycle
• Movement from Stage 1 to Stage 4 and back to Stage
1
• REM Sleep substitutes for Stage 1 sleep during cycle
• Between 90-110 minutes to move through an entire
cycle
• Each night = 3 to 5 complete cycles
80. Sleep architecture
• During the night, a normal sleeper moves between
different sleep stages in a fairly predictable pattern,
alternating between quiet sleep (non-REM) and
dreaming sleep (REM). When these stages are
charted on a diagram, called a hypnogram , Sleep
experts call this pattern sleep architecture.
• In a young adult, normal sleep architecture usually
consists of four or five alternating non-REM and
REM periods. Most deep sleep occurs in the first
half of the night. As the night progresses, periods of
REM sleep get longer and alternate with stage N2
light sleep. Later in life, the sleep skyline will
change, with less deep sleep, more stage N1 sleep
drowsiness, and more awakenings.
81. •Sleep cycles emerge during prenatal development.
•Newborns sleep about 16 hours per day.
•By age 2, 75-minute sleep cycles are experienced.
•By age 5, typical 90-minute sleep cycles of alternating
REM and NREM sleep emerge.
•Deeper slow-wave sleep decreases with age.
•Time in REM sleep increases during childhood and
adolescence, remains stable throughout adulthood, and
decreases during late adulthood.
83. Human Sleep Exhibits Different Stages
• In a typical night of young adult sleep:
—Sleep time ranges from 7-8 hours.
—45-50% is stage 2 sleep, 20% is REM
sleep.
—Cycles last 90-110 minutes, but cycles
early in the night have more stage 3 and 4
SWS, and later cycles have more REM
sleep.
84. • At age 20, we spend an average of 7.5 hours a
night sleeping —with about 90 minutes each of
REM and deep sleep
• By the time we’re 60, we’re only sleeping 6.2
hours a night.
Our Sleep Patterns Change
across the Life Span
85. Our Sleep Patterns Change
across the Life Span
• Mammals sleep more during infancy than
in adulthood.
• Infant sleep is characterized by:
— Shorter sleep cycles
— More REM sleep – 50%, which may
provide essential stimulation to the
developing nervous system
86. Newborn and Infant Sleep
• Newborn sleep has 2 stages
50% “quiet or non-rapid eye movement (NREM)
sleep” and
50% “active or rapid eye movement (REM) sleep
REM sleep appears to promote brain
development.
• Total sleep time = 16 to 17 hours / 24 hour period
with frequent awakenings for feeding and
nurturing
91. • As people age, total time asleep declines, and
number of awakenings increases.
• The most dramatic decline is the loss of time
spent in stages 3 and 4
• by age 90 stages 3 and 4 have disappeared
Our Sleep Patterns Change
across the Life Span
92. Age-Related Changes
Non-REM
◦ Less slow wave sleep (stage 3 and 4), may be
entirely absent, easier to awaken
REM
◦ Shorter REM latency
◦ Decreased REM percentage and duration
Architecture
◦ Increased overall sleep latency
◦ More awakenings/arousals = less sleep
efficiency
◦ Less sleep in 24 hour period
◦ Reduced sleep latency during day – harder to
stay awake
Espiritu JR. Clin Geriatr Med 2008;24:1-14.
93. Age-Related Changes
• Sleep during the night changes with increasing age:
– Less deep sleep and more lighter sleep
– More difficulty maintaining sleep due to
arousals and awakenings
– Sleep is less efficient and more fragmented
• The internal biological clock shifts to earlier
bed and wake times
• Older persons experience a higher prevalence of
medical conditions and take meds that interrupt
sleep and are associated with sleep
problems/disorders
• Older persons experience a higher prevalence
of sleep disorders
94. Sleep changes and aging
• Aging is associated with malfunction or decrease
in sensitivity of the SCN to environmental cues to
adjust circadian rhythm to a natural 24-hour
day/night cycle
• More fragmented sleep
• Increased in stage 1 and 2 sleep with more
fragmented REM sleep indicating more dreaming
• Slow wave sleep is reduced
98. Vertebrate Species Differ in Their
Patterns of Sleep
• For laboratory rats, one sleep cycle lasts an
average of 10–11 minutes
• for humans, one cycle lasts 90–110 minutes.
• Across species, cycle duration is inversely
related to metabolic rate; that is, small animals,
which tend to have high metabolic rates , have
short sleep cycles, and large species have long
sleep cycles.
