Nociceptive-antinociceptive system. Somatic and sensor analyzer

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Nociceptive-antinociceptive system. Somatic and
sensor analyzer
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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.

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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 limbic-reticular 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.

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Pain and stress reaction

• 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.

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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.

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Ranks of pain

• According to location of pain somatic and
  visceral.
• According 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.

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Reflected pain

• 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.

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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 a-delta 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.

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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.

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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.

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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
  beta-endorphin secretion stimulation in
  hypotalamo-hypophisal 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.

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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

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Cutting off nociceptive conduction bundles

• 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.