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Dr.Roshith Chekkadan
Dr.Rohith Chekkadan
Pain is standard, evolutionary drawn
pathologic process, which appears during the
effect of damaging(nociceptive or algogenes)
factors on organism or during weakening of
antinociceptive system and is characterized
by perception, activation of vegetative,
emotional, behavioral, motor, antinociceptive
reactions, directed to the protection of an
organism from damage and to the elimination
of pain.
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Nociceptive
Neuropathic
Somatic
Visceral
Psychosomatic
Referred
Phantom (illusory)
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the neospinothalamic tract,
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the paleospinothalamic tract and
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the archispinothalamic tract.
The first-order nociceptive neurons (in the DRG)
make synaptic connections in Rexed layer I neurons
(marginal zone). Axons from layer I neurons
decussate in the anterior white commissure and
ascend in the contralateral anterolateral quadrant.
Most of the pain fibers terminate in the
ventroposterolateral
(VPL)
nucleus
and
ventroposteroinferior
(VPI)
nucleus
of
the
thalamus.The VPL is thought to mainly be concerned
with discriminatory functions. The VPL sends axons
to the primary somatosensory cortex (SCI).
Nociceptors—DRG—spinalcord(layer1)—crossed—LST—
VPL $ VPI—SCI
The majority of the first-order nociceptive neurons
make
synaptic
connections
in
substantia
gelatinosa(rexed layer II). Axons of second order
neurons cross and ascend in the spinal cord primarily
in the anterior region, called the anterior spinal
thalamic tract (AST). These fibers contain several
tracts. Each of them makes a synaptic connection in
different locations: 1) in the mesencephalic reticular
formation (MFR) and in the periaqueductal gray (PAG),
and they are also called spinalreticular tract; 2) in the
tectum, and these fibers are known as the
spinaltectal or spinalmedullary tract; 3) in the PF-CM
complex (IL) and they are known as the
spinalthalamic tract). The above three fiber tracts are
known also as the paleospinalthalamic tract.
The archispinothalamic tract is a multisynaptic
diffuse tract or pathway. The first-order
nociceptive neurons make synaptic connections
in Rexed layer II (substantiagelatinosa) and
ascend to laminae IV to VII. From lamina IV to VII,
fibers ascend and descend in the spinal cord via
the
multisynapticpropriospinal
pathway
surrounding
the
grey
matter.Further
multisynaptic diffuse pathways ascend to the
intralaminar (IL) areas of the thalamus (PF-CM
complex) and also send collaterals to the
hypothalamus These fibers mediate visceral,
emotional and autonomic reactions to pain.
Pain control system in brain
This system blocks the pain impulses before
entering the brain. This system is present in
grey matter surroundung aqueduct of sylvius
and in raphe magnus nucleus in pons.
The posterior grey horn is the site of pain
control system of spinalcord. The posterior
gray horn is the gateway for the pain
impulses to reach the brain via spinalthalamic
tract.
During pain sensation, considerable changes
occours in blood, a major one is leukocytosis.
An elevation in the leucocytotic count can be
observed.
Reduction of nonspecific resistance after 30
minutes of acute visceral pain and restoration
of protective-adaptive reactions in 3 hours
occours.
Thank you