Transcript Nociceptive sensation

Nociceptive
sensation.
Anti-nociceptive
system
Physiological importance of pain
► According
to modern notion, pain is subjective
perception of systemic processes, which include
information about tissue damage. Activation of
pain receptors leads to starting different protective
reflexes to avoid tissue damage. However, pain is
unpleasant sense and involve to pain reaction
wide net of regulative and homeostatic systems of
human organism.
► The important specialty in reaction to pain in
human is participation of brain cortex and limbic
system, which leads to severe emotional
experience and autonomic reactions.
Changes in human organism
following pain
► Nociceptive
reactions are accompanied by motion
reactions of entire body towards avoidance the
pain.
► In human organism such motion reactions for the
some part presented by unconditioned reflexes
with short reflector arc formed by neurons of
spinal cord and brain stem. But majority of that
are behavioral and emotional reactions, which
based on conditional reflexes.
► That is why reflector arc includes besides neurons
of spinal cord and brain stem structures of limbicreticular complex and brain cortex.
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Also different changes in
human organism
followed by pain are
observed: increase of
muscle tone, accelerated
heartbeat, increase of
blood pressure,
intensification of
sweating, dilatation of
pupils and elevation of
glucose and cuprum
level in plasma,
activation of hemostasis.
It considered to cause
the majority of both
visceral and biochemical
reactions by excitation
of sympathetic nervous
system, which is
presented by neurons of
hypothalamus,
hypophisis and cells in
medullar substance of
adrenal glands.
Pain and stress reaction
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In fact tissue damage and pain triggers the stress reaction - common
reaction of an organism, which leads to stimulation all the functions,
especially motion and that is why blood circulation due to
cardiovascular system, metabolism, transport of gases due to
activation of breathing. Stimulation of pituitary-adrenal axis increases
secretion of adrenocorticotropic hormone from the anterior pituitary,
and thus there is increased secretion of glucocorticoides from the
adrenal cortex. That is why functions of organism activate to defend
one.
But long lasting stress reaction is rather dangerous for organism.
Adrenalin in high concentration may produce decreasing of blood
supply in visceral organs, which leads to metabolic disorders and
disturbances of its function. Besides that nociceptive nerve endings in
damaged tissues produce a lot of nervous impulses, which spreading
into central nervous system activates wide net of nervous cells. This
considerable excitation leads to disturbances in nervous regulation of
all functions in human organism.
Pain and diagnosing
► Pain
gives useful information about cause of tissue
damage. When determining the origin of pain it is
important to special fiches of pain.
► It is necessary pay attention for location,
character, duration, motion and visceral reactions
and subjective sensations, following the pain.
► It is considered, after diagnosing pain must be
removed.
Ranks of pain
► According
► According
to location of pain: somatic and visceral.
to time of appearance of pain after
tissue damage: early and late pain.
► According to subjective sensation (or character):
acute or burning, dull or spread.
► According to duration: sort or prolonged pain
attacks.
► Subjective sensations in pain may be presented
emotional experience as terror, worry, visual
hallucination, dizziness, which appears before of
followed the pain.
Reflected pain
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Reflected pain is caused by irritation of visceral organs.
Such events as strong constriction of smooth muscles;
disorders of blood supply; tension of vessels, stomach,
intestines result in pain in certain parts of body. It is
determined sensor neurons to connect through
interneurons with autonomic and motor neurons in spinal
cord. In such a way, viscerosomatic autonomic reflexes are
realized.
Due to mentioned intracellular contacts, human capable to
locate nociceptive sensation. These zones of human body
where impulses from certain visceral organs are reflected
called as Zacharjin-Ged zones. For example, in stomach
disorders a human fells pain around navel. Acute pain
caused by blood supply disorders in heart muscle reflected
to the left shoulder, left shoulder blade and left epigastria.
Pain reception
Damage stimuli perception created by the brain from
electrochemical nerve impulses delivered to it from sensory
receptors. These receptors transfuse (or change) different
influences of both internal processes in organism and
surrounding environment into the electric impulses.
► Pain receptors are specific. Pain does not appear in
hyperstimulation of improper receptors. On other hand,
adequate stimuli are not so specific as for other sensations.
That is why pain receptors maybe stimulated by different
kind of irritations.
► Pain receptors may react also to electric, mechanic and
especially chemical energy.
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Afferent nociceptive impulses
are collected into central
nervous system by two kinds
of nervous fibers: quick adelta myelinated nerve fibers
and C-fibers without myelin.
The ascending fibers are
included in spinothalamic
tract, which passes through
the spinal cord and reach
medulla oblongata. Here
there are second order
sensory neurons of
spinomesencephalic tract.
Fibers of spinothalamic tract
synapse with third-order
neurons in the thalamus,
which in turn project to the
postcentral gyrus of the
contralateral cerebral
hemisphere.
Nociceptive structures in central nervous system
► Information
about the pain from head, face
and mouth cavity ascend to central nervous
system by sensory fibers of cranial nerves,
for instance facial, glossopharyngeal, vagus
and trigeminus nerves.
► Central nociceptive neurons lay in nucleus
of thalamus, hypothalamus, midencephalon
central gray substance, reticular formation
and somatosensoric fields of brain cortex.
Anti-nociceptive system
► To
antinociceptive neuro-endocrine system belong
nervous structures, which are concentrated,
obviously, in brain stem.
► High intensity of pain stimuli permits activation of
these structures, which contain neurons capable to
release endogenous opioids.
► To such structure belong, for instance, prefrontal
cortex, hypothalamus, central gray substance,
medial thalamic nuclei and limbic system.
Role of opioid peptides
In brain and digestive tract are located receptors, which
bind to morphine. Investigation endogenous ligands of
these receptors give ability to reveal two similar
pentapeptides, called encephalines, which bind to opioid
receptors: met-encephalin and ley-encepfalin. Such
chemicals are known as opioid peptides.
► Encephalines are containing in nerve endings of digestive
tract and many parts in brain. It function as
neurotransmitters. These peptides are present in
gelatinous substance.
► In injecting into brain stem, opioid peptides manifestate
analgetic effect. Encephalines also may slow down
intestines peristaltic.
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Analgesia with drugs
Drugs may influence in different levels. It is known local
analgesia by inactivation of nociceptors using chloraethil or
by injection of analgesic in tissues adjacent to nervous
fibers. Novocain, analgin and other medicines may prevent
generation and spreading of nervous impulses by
temporarily inactivation of ion gates.
► Some drugs may be injected in the lumbal space. In this
case spreading impulses through ascendant conduction is
obtained. In using common analgesia braking activity of
central neurons leads to both analgesia and
unconsciousness, which cold surgical sleep.
► There are some drugs, capable modulate activity of limbic
system and cause sedative effect.
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Electrostimulation for analgesia
► Electrostimulation
through skin or incorporated
electrodes into sensory tracts and nucleus is
used for analgesia. Acupuncture, electro
puncture and other methods of reflex therapy
are also effective approaches to analgesia.
► It considered causing analgesic effect by betaendorphin secretion stimulation in hypotalamohypophisal system, which may block nociceptive
impulses in the way to higher nervous centers.
► Last time artificial hypothermia or hybernacia,
which is cold analgesia, is used.
Psychological methods reliving pain
► Every
people can use psychological methods
reliving pain by switching attention over
pain for instance. In long duration of
chronicle pain, sensation becomes blunt.
Today psychological therapy of pain is more
spread. For this purpose, biological reverse
connection may be used.
► This method proposed to relive chronicle
pain, migraine attack for instance
Cutting off nociceptive conduction bundles
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To surgical methods of treatment in connection with pain belongs
cutting off corresponding sensory nerve upper the origin place of
pain. It is used peripheral neurotomia, cutting off nociceptive
conduction bundles in spinal cord (lobotomy, comissurotomy or
bulbar tractotomy).
Special place engaged by operations on the brain. The main purpose
of such operations is breaking connections between the brain cortex
and thalamus, because it determined the brain cortex to bi
responsible for subjective pain sensation formation. To such
operations belongs stereotaxic operation on thalamus nuclei
(thalamaectomy), splitting of nervous fibers in the depth of frontal
part of brain, which connect it with thalamus (frontal lobaectimy),
cortex removal in gyrus postcentralis and adjacent parts of parietal
lobe, temporal cortex and lover parts of frontal lobe. It is necessary
to point attention to use last group of analgesic methods in extreme
situations only.
When other methods will not be effective, patient may be operated.
However, field of operations in pain manifestation is considerably
wider and is not limited by operations on nervous system.