sleep physiology

1. SLEEP

2. SLEEP
 Approximately one-third of our lives
 Sleep is nature’s way of relaxing our body and recharging
our mind.
 Lack of quality sleep can result in lower quality of life.
 It is very important to detect and manage sleep related
problems at the earliest.

3. Definitions
 Wakefulness: is a state in which the person is aware of
and responds to sensory input from the environment.
 Sleep: is a state of behavioral quiescence accompanied
by an elevated arousal threshold and a species-specific
sleep posture (recumbent sleep posture, closed eyes,
diminished responsiveness to external stimuli and
decrease in or absence of movements)

4. EEG waves
alpha activity
Smooth electrical activity of 8–12 Hz recorded from the brain;
generally associated with a state of relaxation.
beta activity
Irregular electrical activity of 13–30 Hz recorded from the brain;
generally associated with a state of arousal.
theta activity
EEG activity of 3.5–7.5 Hz that occurs intermittently during
early stages of slow-wave sleep and REM sleep.
delta activity
Regular, synchronous electrical activity of less than 4 Hz recorded
from the brain; occurs during the deepest stages of slow-wave sleep.

5. Physiology
Sleep is non-homogenous: 2 distinct states
NREM Sleep
 Constitutes 80% of sleep duration
 Stage 1 (5%) is brief transition from wakefulness to sleep
 Stage 2 (50-55%)- characteristic bursts of 12-16Hz ‘Sleep spindles’
and high amplitude 0.5-1 Hz ‘K-complexes’.
 Stage 3 and stage 4 (Slow Wave Sleep or delta sleep) constitute
20% of sleep duration and has slow 0.5-4Hz high amplitude waves.

6. Sleep is non-homogenous: 2 distinct states
REM Sleep
 Constitutes 20% of sleep duration
 Tonic REM- hypotonia and EEG desynchroniztion
 Phasic REM- bursts of REM and myoclonic twitches of
facial and limb muslces
 Like SWS, REM is considered a restorative sleep stage

7. Sleep waves

8. Sleep waves- frequency

9. Ultradian Rhythm
Cycling between NREM sleep and REM sleep during the night
Typically, 4-6 cycles occur in 90-110 minute intervals
The first REM is usually 70 minutes after sleep onset
REM duration lengthens in subsequent cycles
Longest period of SWS occurs in the first cycle and decreases in
the successive cycles

10. Sleep stages during a single night

11. Biological Clock

12. Biological clock
Circadian Rhythms and Zeitgebers
Zeitgeber (tsite gay ber)
A stimulus (usually the light of dawn) that resets
the biological clock that is responsible for circadian
rhythms.
Suprachiasmatic nucleus (SCN)
A nucleus situated atop the optic chiasm. It
contains a biological clock that is responsible for
organizing many of the body’s circadian rhythms.

13. Circadian Rhythm
Pineal gland
A gland attached to the dorsal tectum; produces
melatonin and plays a role in circadian and
seasonal rhythms.
Melatonin
A hormone secreted during the night by the pineal
body; plays a role in circadian and seasonal rhythms

14. Circadian Rhythm

15. Other Zeitgeber effects
(social interactions, alarm clocks, eating/drinking patterns etc)

16. Sleep-wake Disorders
Classification
1. Primary
a) Dyssomnias
b) Parasomnias
2. Secondary

17. Sleep-wake Disorders
Dyssomnias
1. Insomnia disorder
2. Hypersomnolence Disorder
3. Narcolepsy
4. Breathing related sleep disorders
5. Circadian rhythm related sleep disorders

18. Sleep-wake Disorders
Parasomnias
1. Nightmare Disorder
2. Sleep terror Disorder
3. Sleep walking Disorder
4. Parasomnia NOS (RLS, Sleep Paralysis etc)

19. Sleep-wake Disorders
Secondary
1. Sleep disorders associated with psychiatric disorders
2. Sleep disorders associated with neurological disorders
3. Sleep disorders associated with other medical disorders
4. Substance induced sleep disorders

20. Insomnia
 Difficulty in falling asleep
 Frequently waking up during
the night
 Early morning awakening
 Daytime drowsiness
 Non-refreshing sleep

21. Narcolepsy

22. Narcolepsy
 A sleep disorder characterized by periods of irresistible sleep,
attacks of cataplexy, sleep paralysis, and hypnagogic
hallucinations.
 hereditary autoimmune disorder.
 A peptide known as orexin or hypocretin, produced by neurons
whose cell bodies are located in the hypothalamus; their
destruction causes narcolepsy.
 Treatment- behavioral modification, avoid substances/sedatives,
CNS Stimuants, antidepressants.

23. Maintain regular sleep timings
Avoid coffee/tea, alcohol & smoking
Exercise regularly
Avoid day-time naps
Keep your bedroom comfortable &
free from noise/light
Avoid heavy meals before going to bed
Sleep hygiene

24. Thank You