46physio1-151106131300-lva1-app6892 (1).pdf

Sleep
Dr. Humaira kamal
Associate professor

Learning objective
 Define sleep.
 Describe slow wave sleep, REM sleep.
 Describe the neuronal centers, neurohormonal
substances and mechanism that cause sleep.
 Describe the brain waves

Consciousness
 –awareness of the external world &self including
awareness of thoughts, perception and dreams
 Following states of consciousness are listed in
decreasing order of arousal level, based on the
extent of interaction between peripheral stimuli
and the brain:
 maximum alertness
 Wakefulness
 sleep (several different types)
 coma

Definition:
 A natural periodic state of rest for the mind and
body, in which the eyes usually close and
consciousness is completely or partially lost, so
that there is a decrease in bodily movement and
responsiveness to external stimuli
 A state of unconsciousness but still able to
awaken by normal sensory stimuli

 Sleep is an active process
 Brain’s overall activity is not reduced
 During certain stages of sleep, O2 uptake by the
brain is even increased above normal waking
levels
 Types of sleep
 Slow wave sleep
 Rapid-eye-movement sleep

SLEEP
 Types of Sleep
 Slow wave Sleep
 Low level of cerebral cortex activity, vital signs
decline
 REM (rapid eye movement) sleep
 Active dreaming, vital signs change, inhibition
of somatic motor neurons

Slow wave sleep
 Occurs during first hours after sleep
 Exceedingly restful
 Decrease in vascular tone& vegetative functions

Characteristics of Non-REM sleep
 Stage1: stage of drowsiness
 α waves are diminished and abolished
 EEG shows only low voltage and
infrequent delta waves

 Stage2(light sleep)
 Judged by the difficulty of awakening the
sleeper
 12-15HZ
 Sleep spindles are seen
 Stage 3(Medium sleep)
 High amplitude δ waves
 Frequency decreases to 1-2 /sec and
amplitude increases to about 100 υV

 Stage IV:
 δ waves become prominent with low
frequency and high amplitude

REM Sleep
 Paradoxical sleep, Desynchronized sleep
 Characterized by high-frequency& low amplitude EEG
pattern seen in waking hours
 Presence of rapid eye movement
 Dream sleep
 Individual is difficult to arouse
 Muscle tone is depressed-inhibition of excitator
areas of brain stem
 Heart rate & respiratory rate is irregular

Comparison of REM sleep and
NON-REM sleep
Characteristic REM sleep Non-REM sleep
Rapid eye movement Present Absent
Dreams Present Absent
Muscle twitching Present Absent
Heart rate Fluctuating Stable
Blood pressure Fluctuating Stable
Respiration Fluctuating Stable
Body temperature Fluctuating Stable
neurotansmitter Noradrenaline serotonin

Theories of sleep
 Passive theorey
 Sleep is caused by active inhibitory process
 Neuronal Centers, Neurohumoral Substances
 Neuronal centers
 Raphe nuclei in the lower half of the pons & medulla
 Activation results in Non-REM Sleep
 many nerve endings of fibers from these raphe
neurons secrete Serotonin

 Locus Cereleus of Pons
 Activation causes REM sleep
 Noradrenaline is released
 Inhibition of Ascending reticular activating
system
 Responsible for wakefulness because of its
afferent and efferent connections with
cerebral cortex

46physio1-151106131300-lva1-app6892 (1).pdf

 Other transmitters related to sleep
 Muramyl peptide
 Low molecular peptide
 Adenosine
 Back bone of ATP
 Increased levels inactivate the arousal
centers
 Hypocretin also known as orexin
 group of neurons in the hypothalamus that
secrete the excitatory neurotransmitter

Cause of REM sleep
 Large acetylcholine-secreting neuron in the
upper brain stem reticular formation activates
brain
 Importance :to accomplish the long term
structural and chemical adjustments for
learning and memory

Sleep cycle
 The sleep–wake cycle as well as the various
stages of sleep are due to the cyclic interplay of
three different neural systems:
 Arousal system: regulated by a group of
neurons in the hypothalamus and involves the
reticular activating system originating in the brain
stem

 A slow-wave sleep center: in the hypothalamus
that contains sleep-on neurons that induce sleep
 A paradoxical sleep center in the brain stem that
houses REM sleep-on neurons, which become
very active during REM sleep.

 When the sleep centers are not activated, the
mesencephalic and upper pontile reticular
activating nuclei are released from inhibition,
which allows the reticular activating nuclei to
become spontaneously active

 This in turn excites both the cerebral cortex and
the peripheral nervous system, both of which
send numerous positive feedback signals back to
the same reticular activating nuclei to activate
them still further.
 Once wakefulness begins, it has a natural
tendency to sustain itself because of all this
positive feedback activity

 Physiological effects of sleep
 Effects on the nervous system
 Progressive malfunction of thoughts
 Irritable & psychotic behaviour
 Effects on the structure
 The principal value of sleep is to restore natural
balances among the neuronal centers

Sleep disorders
 Narcolepsy
 REM sleep is entered directly
 Intense desire to sleep
 Individual may become paralyzed
 Presence of dream-like state
 Other problem are related with slow wave sleep
 Sleepwalking (somnambulism)
 Bed-wetting (nocturnal enuresis)

Different types of brain waves in the normal
electroencephalogram

 In normal healthy people, most waves in the EEG
can be classified as alpha, beta, theta, and delta
waves

Alpha waves
 Are rhythmical waves
 Occur at frequencies between 8 and 13 cycles/s
 Are found in the EEGs of almost all normal adult
people when they are awake and in a quiet,
resting state of cerebration
 Occur most intensely in the occipital region

Beta waves
 Occur at frequencies greater than 14 cycles /s
 And as high as 80 cycles per second.
 They are recorded mainly from the parietal and
frontal regions during specific activation of these
parts of the brain

Theta waves
 Have frequencies between 4 and 7 cycles /s
 Occur normally in the parietal and temporal
regions in children, but they also occur during
emotional stress in some adults, particularly
during disappointment and frustration.
 Theta waves also occur in many brain disorders,
often in degenerative brain states

Delta waves
 Include all the waves of the EEG with frequencies less than
3.5 cycles /s
 Have voltages two to four times greater than most other
types of brain waves.
 Occur in very deep sleep, in infancy, and in serious organic
brain disease.
 Also in the cortex of animals that have had subcortical
transections separating the cerebral cortex from the

46physio1-151106131300-lva1-app6892 (1).pdf

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