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Title: Physiology of Sleep
Description: Summarized note for Physiology of Sleep. I combined the theories form a few books.
Description: Summarized note for Physiology of Sleep. I combined the theories form a few books.
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SLEEP PHYSIOLOGY!
!
Sleep is defines as unconsciousness from which the person can be aroused by sensory or other
stimuli
...
!
!
There are 2 types of sleep:!
1
...
Rapid eye movement sleep (REM): The eyes undergo rapid movement despite the fact that the
!
person is still asleep
...
!
REM sleep occurs in episodes that occupy the 25% of sleep time in young adults, each episode
normally recurs about every 90 minutes
...
!
!
SLOW-WAVE SLEEP (NON REM)!
This sleep is exceeding restful and associated with decreases in
both peripheral vascular tone and many other vegetative functions of
the body
...
g
...
!
It is also called “dreamless sleep” although sometimes even
nightmares do occur during slow-wave sleep
...
!
!
Stages:!
• Stage 1: Transition stage between wakefulness and sleep that normally lasts 1-7 minutes
...
People awakened during this stage
often say they have not been sleeping
...
A theta rhythm (4-7 Hz) can be seen at this early
stage of slow-wave sleep
...
A person is a little more difficult to awaken
...
!
EEG: Appearance of sinusoidal waves called sleep spindles (12-14 Hz) and occasional high
voltage biphasic waves called K complexes
...
Body temperature and blood pressure decrease, and
it is difficult to wake the person
...
EEG: High amplitude delta rhythm (0
...
!
• Stage 4: The deepest level of sleep
...
Sleepwalking occurs usually during this stage
...
!
When the person is extremely sleepy, REM sleep is short and may be even absent
...
!
!
REM has several important characteristics:!
1
...
!
2
...
!
3
...
!
4
...
!
5
...
!
6
...
EEG shows a pattern go brain waves similar to those that occur during wakefulness
...
!
!
!
Neuronal Centers, Neurohumoral Substances and Mechanism That Can Cause Sleep!
Stimulation of several specific areas of the brain can produce sleep with characteristics near those
of natural sleep
...
!Raphe nuclei in the lower half of the pons and in the medulla!
N
! erve fibres from these nuclei spread locally in the brain stem reticular formation and also into
the thalamus, hypothalamus, most areas of the limbic system, even the neocortex of the
cerebrum
...
When a drug blocks
the formation of serotonin is administered to an animal, the animal cannot sleep for days
...
!
2
...
Stimulation of several regions in the diencephalon, including the rostral part of the hypothalamus
!
(mainly in the suprachiasmal area), and in the diffuse nuclei of the thalamus
...
Reticular formation in the central portion of the medulla and midbrain!
!
It contains the cell bodies and fibbers of many of the serotonergic, noradrenergic, and !
!
cholinergic systems
...
Muramyl peptide: A low molecular weight substance that accumulates in the CSF and urine in
animals kept awake for several days
...
!
2
...
Adenosine
binds to specific receipts called A1 receipts and inhibits certain cholinergic neurone of the RAS
that participate in arousal
...
!
Possible cause of REM Sleep:!
Large acetylcholine-secreting neurons in the upper brain stem reticular formation through their
extensive efferent fibres activate many portions of the brain
...
!
!
!
Importance of Sleep!
1
...
Facilitation of learning or memory!
3
...
Conservation of metabolic energy!
5
...
Orexin is produced in hypothalamic neurone and
appear to be important in switching between sleep and
wakefulness
...
!
Pineal arises from the roof of the third ventricle in the diencephalon and is encapsulated by the
meninges
...
Both are G protein
coupled receptors, with MT1 receptors inhibiting
adenylyl cyclase and resulting in sleepiness
...
!
Melatonin synthesis and secretion are increased during
the dark period of the day and maintained at a low level
during daylight!
!
Brain Waves!
Electrical recordings from the surface of the brain or even from the outer surface of the head
demonstrate that there is continuous electrical activity in the brain
...
!
The undulations in the recorded electrical potentials, shown in, are called brain waves, and the
entire record is called an EEG (electroencephalogram)
...
It occur most intensely in the occipital region
...
stimulation in the nonspecific layer of reticular nuclei that surround the
thalamus or in “diffuse” nuclei deep inside the thalamus often sets up
electrical waves
Occurs at frequencies greater than 14 cycles per second and as high
as 80 cycles per second
...
Occurs at frequencies between 4 and 7 cycles per second
...
It also occurs
in many brain disorders, often in degenerative brain states
...
5 cycles
per second, and they often have voltage 2-4x greater than most other
types of brain waves
...
Transection of the fiber tracts from the thalamus to the cerebral cortex,
which blocks thalamic activation of the cortex and thereby eliminates
the alpha waves, nevertheless does not block delta waves in the
cortex
...
Normally they become entrained, that is, synchronized to the day—night light cycle
in the environment
...
!
! The entrainment process in dependent on the
! suprachiasmatic nuclei (SCN) located !
! bilaterally above the optic chiasm
...
Efferents from the
! SCN initiate neural and hum oral signals that
! entrain the circadian rhythms including the !
! sleep-wake cycle and the secretion of the !
! pineal hormone melatonin
Title: Physiology of Sleep
Description: Summarized note for Physiology of Sleep. I combined the theories form a few books.
Description: Summarized note for Physiology of Sleep. I combined the theories form a few books.