Sleep has two types - rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. REM sleep is associated with dreaming and eye movements while NREM sleep has four stages with different brain wave patterns. Sleep is regulated by circadian rhythms and homeostasis. The brainstem contains sleep centers like the raphe nucleus and locus ceruleus that induce REM and NREM sleep respectively. Common sleep disorders include insomnia, sleep apnea, nightmares, night terrors and somnambulism. Movement disorders during sleep include restless legs syndrome and leg cramps.

1. PHYSIOLOGY OF SLEEP
By
Dr.M.Selvin Innocent Dhas,MD(s)
Maria Siddha Medical College

2. SLEEP
 Sleep is the natural periodic state of rest
for mind and body with closed eyes
characterized by partial or complete loss
of consciousness.
 Loss of consciousness leads
To decreased response to external
stimuli
Decreased body movements.
 Depth of sleep is not constant throughout
the sleeping period.
 It varies in different stages of sleep.

3. SLEEP REQUIREMENT
Sleep requirement is not constant.
However, average sleep requirement per
day at different age groups is:
1. Newborn infants : 18 to 20 hours
2. Growing children : 12 to 14 hours
3. Adults : 7 to 9 hours
4. Old persons : 5 to 7 hours.

4. PHYSIOLOGICAL CHANGES
DURING SLEEP
 1. PLASMA VOLUME
 2. CARDIOVASCULAR SYSTEM
 3. RESPIRATORY SYSTEM
 4. GASTROINTESTINAL TRACT
 5. EXCRETORY SYSTEM
 6. SWEAT SECRETION
 7. LACRIMAL SECRETION
 8. MUSCLE TONE
 9. REFLEXES
 10. BRAIN

5. 1. PLASMA VOLUME
 Plasma volume decreases by about 10% during
sleep.

6. 2. CARDIOVASCULAR SYSTEM
„
Heart Rate
During sleep, the heart rate reduces.
It varies between 45 and 60 beats per minute.
Blood Pressure
Systolic pressure falls to about 90 to 110 mm Hg.
Lowest level is reached about 4th hour of sleep
and remains at this level till a short time before
waking
up. Then, the pressure commences to rise.
If sleep is disturbed by exciting dreams, the
pressure is elevated above 130 mm Hg.

7. „3. RESPIRATORY SYSTEM
Rate and force of respiration are decreased.
Respiration becomes irregular and Cheyne-
Stokes type of periodic breathing may
develop.

8.  Cheyne–Stokes respiration is an abnormal
pattern of breathing characterized by
progressively deeper, and sometimes faster,
 Breathing followed by a gradual decrease that
results in a temporary stop in breathing called
an apnea.

9. GASTROINTESTINAL TRACT
 Salivary secretion decreases during sleep.
 Gastric secretion is not altered or may be increased
slightly.
 Contraction of empty stomach is more vigorous.

10. 5. EXCRETORY SYSTEM
Formation of urine decreases
Specific gravity of urine increases.
Decreased kidney function is associated
with less sleep, not that less sleep causes
the decline in kidney function.
reduced sleep and diminished kidney
function might be the result of medical
conditions that affect kidney function,
such as diabetes and high blood pressure

11. 6. SWEAT SECRETION
Sweat secretion increases during sleep
7. LACRIMAL SECRETION
Lacrimal secretion decreases during sleep.

12. 8. MUSCLE TONE
 Tone in all the muscles of body except ocular
muscles decreases very much during sleep.
 It is called sleep paralysis.

13. 9. REFLEXES
 Certain reflexes particularly knee jerk, are
abolished.
 Threshold for most of the reflexes increases.
 Pupils are constricted. Light reflex is retained.
Eyeballs move up and down.
 Babinski sign becomes positive during deep sleep.

14. 10. BRAIN
 Brain is not inactive during sleep.
 There is a characteristic cycle of brain wave activity
during sleep with irregular intervals of dreams.
 Electrical activity in the brain varies with stages of
sleep.

15. SUMMARY

16. TYPES OF SLEEP

17. TYPES OF SLEEP
Sleep is of two types:
1. Rapid eye movement sleep or REM sleep
(Deep Sleep)
2. Non-rapid eye movement sleep,
(NREM sleep or non-REM sleep)

18. 1. RAPID EYE MOVEMENT SLEEP –
REM SLEEP (DEEP SLEEP)
 Rapid eye movement sleep is the type of sleep
associated with rapid conjugate movements of the
eyeballs, which occurs frequently.
 Though the eyeballs move, the sleep is deep.
So, it is also called paradoxical sleep. It occupies
about 20% to 30% of sleeping period.
accompanied with low muscle tone throughout
the body, and the propensity of the sleeper to
dream vividly.
 REM sleep is "paradoxical" because of its
similarities to wakefulness.

19. EYE MOVEMENTS
Most of the eye movements in “rapid eye
movement” sleep are in fact less rapid than those
normally exhibited by waking humans.
 They are also shorter in duration and more likely
to loop back to their starting point.

20. DREAMING
Rapid eye movement sleep (REM) has since its
discovery been closely associated with
dreaming.
 Waking up sleepers during a REM phase is a
common experimental method for obtaining
dream reports
Sleepers awakened from REM tend to give
narrative descriptions of the dreams they
were experiencing.
 80% of dreams occur during REM.

21. 2. NON-RAPID EYE MOVEMENT SLEEP –
NREM OR NON-REM SLEEP
Non-rapid eye movement (NREM) sleep is the type
of sleep without the movements of eyeballs.
 It is also called slow-wave sleep.
 Dreams do not occur in this type of Sleep
It occupies about 70% to 80% of total sleeping
period.
 Non-REM sleep is followed by REM sleep.

22.  Non-rapid eye movement sleep (NREM), also known
as quiescent sleep.
 Unlike REM sleep, there is usually little or no eye
movement during these stages.
 Dreaming is rare during NREM sleep,
 Muscles are not paralyzed as in REM sleep.
 People who do not go through the sleeping stages
properly get stuck in NREM sleep, and because
muscles are not paralyzed a person may be able to
sleepwalk.
 The mental activity that takes place during NREM
sleep is believed to be thought-like, whereas REM
sleep includes hallucinatory and bizarre content.

23. EEG PATTERN
RAPID EYE MOVEMENT SLEEP
 During REM sleep, electroencephalogram (EEG) shows
irregular waves with high frequency and low amplitude.
 These waves are desynchronized waves

24. NON-RAPID EYE MOVEMENT SLEEP
The NREM sleep is divided into four stages, based
on the EEG pattern
. During the stage of wakefulness, i.e.while lying
down with closed eyes and relaxed mind, the
alpha waves of EEG appear.
When the person proceeds to drowsy state, the
alpha waves diminish.
EEG PATTERN

25. Stage I: Stage of Drowsiness
 Alpha waves are diminished and abolished.
 EEG shows only low voltage fluctuations
and infrequent delta waves.
Stage II: Stage of Light Sleep
Stage II is characterized by spindle bursts
at a frequency of 14 per second,
superimposed by low voltage delta waves.

26. Stage III: Stage of Medium Sleep
 During this stage, the spindle bursts disappear.
 Frequency of delta waves decreases to 1 or 2 per
second
 Amplitude increases to about 100 μV.
State IV: Stage of Deep Sleep
 Delta waves become more prominent with low
frequency and high amplitude.

29. MECHANISM OF SLEEP
 Sleep occurs due to the activity of some sleep-
inducing centers in brain.
 Stimulation of these centers induces sleep.
 Damage of sleep centers results in sleeplessness
or persistent wakefulness called insomnia.

30. SLEEP MECHANISMS
Two internal biological mechanisms–
 Circadian rhythm
 Homeostasis –work together to regulate when
you are awake and sleep.

31. Circadian rhythms
 Direct a wide variety of functions from daily
fluctuations in wakefulness to body temperature,
metabolism, and the release of hormones.
 They control your timing of sleep and cause you to be
sleepy at night and your tendency to wake in the morning
without an alarm.
 Your body’s biological clock, which is based on a
roughly 24-hour day, controls most circadian
rhythms. Circadian rhythms synchronize with
environmental cues (light, temperature) about the actual
time of day, but they continue even in the absence of
cues.

32. Sleep-wake homeostasis
 keeps track of your need for sleep.
 The homeostatic sleep drive reminds the body
to sleep after a certain time and regulates sleep
intensity.
 This sleep drive gets stronger every hour you
are awake and causes you to sleep longer and
more deeply after a period of sleep deprivation.

33. SLEEP CENTERS
 Complex pathways between the reticular formation of
brainstem, diencephalon and cerebral cortex are
involved in the onset and maintenance of sleep.
 However, two centers which induce sleep are located in
brainstem:
1. Raphe nucleus
2. Locus ceruleus of pons.(REM Sleep)
 Recently, many more areas that induce sleep are
identified in the brain of animals. Inhibition of ascending
reticular activating system also results in sleep.

34. 1. ROLE OF RAPHE NUCLEUS
 Raphe nucleus is situated in lower pons and medulla.
 Activation of this nucleus results in non-REM sleep.
 It is due to release of serotonin by the nerve fibers
arising from this nucleus. Serotonin induces non-REM
sleep.

35. 2. ROLE OF LOCUS CERULEUS OF PONS
 Activation of this center produces REM sleep.
 Noradrenaline released by the nerve fibers
arising from locus ceruleus induces REM sleep.

36. INHIBITION OF ASCENDING RETICULAR ACTIVATING
SYSTEM
 Ascending reticular activating system (ARAS) is responsible
for wakefulness because of its afferent and efferent
connections with cerebral cortex.
 Inhibition of ARAS induces sleep.
 Lesion of ARAS leads to permanent somnolence, i.e.
coma.

37. APPLIED PHYSIOLOGY –
SLEEP DISORDERS
 „1. INSOMNIA
 2. HYPERSOMNIA
 3. NARCOLEPSY AND CATAPLEXY
 4. SLEEP APNEA SYNDROME
 5. NIGHTMARE
 6. NIGHT TERROR
 7. SOMNAMBULISM
 8. NOCTURNAL ENURESIS
 9. MOVEMENT DISORDERS DURING SLEEP

38. 1. INSOMNIA
 Insomnia is the inability to sleep or abnormal wakefulness.
 It is the most common sleep disorder.
 It occurs due to systemic illness or mental conditions such
as psychiatric problems, alcoholic addiction and drug
addiction.

39. 2. HYPERSOMNIA
Hypersomnia is the excess sleep or excess need to
sleep. It occurs because of lesion in the floor of
the third ventricle, brain tumors, encephalitis,
chronic bronchitis and disease of muscles.
 Hypersomnia also occurs in endocrine disorders
such as myxedema and diabetes insipidus.
„

40. MYXEDEMA
 Myxedema is a term used synonymously with severe
hypothyroidsm.
 The term is also used to describe a dermatological
change that can occur in hypothyroidism and some forms
of hyperthyrodism
 In this later sense, myxedema refers to deposition
of mucopolysacharides in the dermis, which results
in swelling of the affected area.

41. 3. NARCOLEPSY AND CATAPLEXY
 Narcolepsy is the sudden attack of uncontrollable sleep.
 Cataplexy is sudden outburst of emotion.
 Both the diseases are due to hypothalamic disorders.
 Narcolepsy is a long-term (chronic) problem that affects
your sleep.
 You feel excessively tired during the daytime but have
disturbed night-time sleep. You can also have sleep attacks
where you fall asleep during the day without any warning.
 Many people with narcolepsy also have cataplexy.
 This is a condition in which you have sudden loss of
control over some of your muscles.
 There is no cure for narcolepsy.

42. 4. SLEEP APNEA SYNDROME
 Sleep apnea is the temporary stoppage of breathing
repeatedly during sleep.
 Sleep apnea syndrome is the disorder that involves
fluctuations in the rate and force of respiration during
REM sleep with short apneic episode.
 Sleep apnea syndrome occurs in obesity, myxedema,
enlargement of tonsil and lesion in brainstem.
 Common features of this syndrome are loud snoring
restless movements, nocturnal insomnia, daytime
sleepiness, morning headache and fatigue.
 In severe conditions, hypertension, right heart failure and
stroke occur.

43. 5. NIGHTMARE
Nightmare is a condition during sleep that is
characterized by a sense of extreme uneasiness
or discomfort
 After a period of extreme anxiety, the subject
wakes with a troubled state of mind.
 It occurs mostly during REM sleep.
 Nightmare occurs due to improper food intake,
digestive disorders or nervous disorders.
It also occurs during drug withdrawal or alcohol
withdrawal.

44.  A nightmare, also called a bad dream is an unpleasant dream that can
cause a strong emotional response from the mind, typically fear but
also despair, anxiety and great sadness. However, psychological
nomenclature differentiates between nightmares and bad dreams,
specifically, people remain asleep during bad dreams whereas
nightmares awaken individuals.
 Those with nightmares experience abnormal sleep architecture and
that the results of having a nightmare during the night were very
similar to those of people who have insomnia. This is thought to be
caused by frequent nocturnal awakenings and fear of falling asleep

45. 6. NIGHT TERROR
 Night terror is a disorder similar to nightmare.
 It is common in children.
 It is also called pavor nocturnus or sleep terror.
 The child awakes screaming in a state of the attack in
the morning.
 Nightmare occurs shortly after falling asleep and during
non-REM sleep.
 There is no psychological disturbance.

47. 7. SOMNAMBULISM
Somnambulism is getting up from bed and walking in
the state of sleep.
It is also called walking during sleep or sleep
walking (somnus = sleep; ambulare = to walk).
The episode lasts for few minutes to half
an hour.
 It occurs during non-REM sleep.
 In children, it is associated with bedwetting or night
terror without any psychological disturbance.
 However, in adults it is associated with
psychoneurosis.

48. PSYCHONEUROSIS.
Neuroses are characterized by anxiety,
depression, or other feelings of unhappiness or
distress that are out of proportion to the
circumstances of a person's life.

49. 8. NOCTURNAL ENURESIS
 Nocturnal enuresis is the involuntary voiding of urine at
bed. It is also called or bedwetting. It is common in
children.
 Nocturnal enuresis is involuntary urination that
happens at night while sleeping, after the age when a
person should be able to control his or her bladder.
(Involuntary urination that happens during the day is
known as diurnal enuresis.)
 .Bed-wetting can occur up to age 5 as part of normal
childhood development.
 In adults, it can be caused by alcohol intoxication.

50. 9. MOVEMENT DISORDERS DURING SLEEP
Movement disorders occur immediately after
falling asleep.
 Sleep start or hypnic jerk is the common
movement disorder during sleep.
 It is characterized by sudden jerks of arms
or legs.
 Sleep start is a physiological form of clonus.
Other movement disorders are teeth grinding
(bruxism), banging the head and restless
moment of arms or legs.

51. SLEEP MOVEMENT DISORDERS
 Restless Legs Syndrome This sleep disorder causes a
burning or itching inside your legs when you lie down,
making it difficult to get comfortable enough to fall
asleep. The symptoms may go away when you get up.
 Limb Movements This sleep movement disorder
involves a series of uncontrollable repetitive muscle
movements that severely disrupt your sleep during the
night. These movements occur most often in the lower
legs.
 Leg Cramps Sleep related leg cramps are sudden and
intense feelings of pain in the leg or foot. The pain is
caused when a muscle contracts and tightens. These
may happen while you are awake or after you are asleep.

52.  Sleep Rhythmic MovementSleep rhythmic movement
disorder involves repeated body movements that occur
while drowsy or asleep. This happens most often in
children and can result in body rocking, head banging or
head rolling.
 BruxismThis sleep movement disorder involves the
grinding or clenching of teeth during sleep. It is common
for the jaw to contract while you sleep. When these
contractions are too strong, they produce the sound of
tooth grinding.