Download Posterior column- medial lemniscal pathway

1383
Medical Science University of Isfahan,
Department of Anatomy
1
‫من لم یعلم التشریح والنجوم فهو عنّین فی معرفت هللا‬
• One who do not have the knowledge of
Anatomy and Astronomy, will not be able to
know God
‫کسی که علم‬
‫تشریح و نجوم را‬
‫نداند از شناخت‬
‫خدا ناتوان ا ست‬
1383
Medical Science University of Isfahan,
Department of Anatomy
2
Figure 12.2b
SPINAL CORD
2nd Lecture
Cross Section of Spinal Cord
Ascending & Descending
pathways
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Medical Science University of Isfahan,
Department of Anatomy
3
Figure 12.2b
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Somatotopic organization:
A useful generalization for
remembering the somatotopic
representations:
• The arms are medial to the legs
with 2 exceptions:
The primary sensorimotor
cortices
Posterior columns of S.C.
1383
Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
9
The neural pathways :
• Sensory chain
– 1st order neuron
– 2nd order neuron
– 3rd order neuron
• Motor neurons
– Upper motor N
– Lower Motor N
1383
Medical Science University of Isfahan,
Department of Anatomy
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Somatosensory Pathways
• Two main pathways for somatic
sensation:
– Posterior column- medial lemniscal
pathway- conveys conscious
proprioception, vibration sensation &
fine discriminative touch
– Anterolateral pathways- includes the
spinothalamic tract convey pain,
temperature sense, and crude touch
1383
Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Spinothalamic Tract & Other
Anterolateral Pathways
• Smaller-diameter & unmyelinated axons
carrying info about pain & temp also enter
spinal cord via dorsal root entry zone
• Make first synapses immediately in the
grey matter, esp laminae I, V
• Some axon collaterals ascend or descend
for a few segments in Lissauer’s before
entering central grey
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Medical Science University of Isfahan,
Department of Anatomy
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Spinothalamic Tract & Other
Anterolateral Pathways con…
• Axons from the 2nd order neurons in
central grey cross over in the spinal cord
anterior (ventral) commissure to ascend
in the anterolateral white matter (takes 2
or 3 segments for crossing fibers to
reach other side); synapses in thalamus;
• 3rd order neurons as the thalamic
somatosensory radiations synapse in
primary somatosensory Cx
1383
Medical Science University of Isfahan,
Department of Anatomy
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Posterior Column - Medial
Lemniscal Pathway
• Large diameter myelinated axons carrying
info about proprioception, VS, fine touch
enter spinal cord via median portion of
dorsal root entry zone
• Many of these axons then enter the
ipsilateral posterior columns to ascend all
the way to the posterior column nuclei in
medulla (nucleus cuneatus, gracilis)
• In addition, some axon collaterals enter the
spinal cord grey matter to synapse onto
interneurons and motor neurons--esp
laminae III,IV Medical Science University of Isfahan,
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Department of Anatomy
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Posterior Column - Medial Lemniscal
Pathway con…
• Gracile fasciculus—info from LEs, lower
trunk
• Cuneate fasciculus—info from above T6,
UEs, neck
• 1st order neurons synapse on 2nd order
neurons in the nucleus cuneatus, gracilis;
axons of 2nd order neurons decussate
(internal arcuate fibers) & become the medial
lemniscus; 2nd order synapse on 3rd order in
VPL nucleus of thalamus; 3rd order project
through poster limb of internal capsule in the
thalamic somatosensory radiations to reach
the primary somatosensory Cortex
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Anterolateral Sensory
Pathways...
• Spinothalamic (pain, temp discrimination)—
arise esp from laminae I, V; main thalamic relay
is the VPL; also intralaminar, medial thalamic
• Spinoreticular (emotional, arousal aspects of
pain); arises diffusely from intermediate zone &
laminae VI-VIII; terminates on reticular form’n
which projects to the intralaminar thalamic
nucleus (centromedian) diffuse cortical
projections
• Spinomesencephalic (pain modulation) arises
esp from laminae I, V; projects to midbrain
PAG, superior colliculi
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Can you ID these structures?
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Medical Science University of Isfahan,
Department of Anatomy
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Cross-Sectional Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Motor Pathways
• LATERAL MOTOR SYSTEMS
– Travel in the lateral columns of the spinal cord &
synapse on the more lateral groups of ventral
horn motor neurons & interneurons
– Consist of: 1) lateral corticospinal tract
2)rubrospinal tract
– Control the movement of extremities
– Cross to descend in contralateral spinal cord
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Medical Science University of Isfahan,
Department of Anatomy
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Motor Pathways
• MEDIAL MOTOR SYSTEMS
– Travel in the anteromedial columns to
synapse on medial ventral horn motor
neurons & interneurons
– Consist of:
• 1) anterior corticospinal tract
• 2) vestibulospinal tracts
• 3) reticulospinal tracts
• 4) tectospinal tract
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Medical Science University of Isfahan,
Department of Anatomy
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Functions of medial motor
system
– Control the proximal axial & girdle muscles
involved in postural tone, balance, orienting
mov’ts of the head & neck and automatic
gait-related mov’ts
– Descend ipsilaterally or bilaterally
– terminate on interneurons that project to
both sides of spinal cord, controlling mov’ts
that involve multiple bilateral spinal
segments so unilateral lesion has little effect
1383
Medical Science University of Isfahan,
Department of Anatomy
25
Somatotopic Organization of
Motor System Projections to
AHCs
• Lateral motor
systems project to
lateral AHCs
• Medial motor
systems project to
medial AHCs
• AHCs = ant. horn
columns
1383
Medical Science University of Isfahan,
Department of Anatomy
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Anterior Corticospinal Tract
• SITE OF ORIGIN: Primary motor
Cortex and supplementary motor
area
• LEVELS OF TERMINATION: cervical
and upper thoracic cord
• FUNCTION: Control of bilateral axial
and girdle muscles
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Medical Science University of Isfahan,
Department of Anatomy
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Lateral Corticospinal Tract
• SITE OF ORIGIN: Primary motor Cortrex,
other frontal & parietal areas
• SITE OF DECUSSATION: Pyramidal
decussation at the cervicomedullary
junction
• LEVELS OF TERMINATION: Entire cord
(esp cervical, lumbosacral enlargements)
• FUNCTION: movement of contralateral
limbs
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
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Medical Science University of Isfahan,
Department of Anatomy
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Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Syringomyelia
• Bilateral limb anesthesia
• The first site of lesion is
anterior white commissure
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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What is your diagnosis?
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Medical Science University of Isfahan,
Department of Anatomy
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Brown Square Syndrome
• 1 - Ipsilateral upper motor neuron
paralysis beneath the lesion
• 2 - Ipsilateral fine touch anesthesia
beneath the lesion
• 3 - Contralateral pain &
temperature anesthesia beneath
the lesion
• 4 - Ipsilateral lower motor neuron
paralysis at the level of lesion
1383
Medical Science University of Isfahan,
Department of Anatomy
45
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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THE END
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Medical Science University of Isfahan,
Department of Anatomy
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The neural pathways :
• Sensory chain
– 1st order neuron
– 2nd order neuron
– 3rd order neuron
• Motor neurons
– Upper motor N
– Lower Motor N
1383
Medical Science University of Isfahan,
Department of Anatomy
54
1383
Medical Science University of Isfahan,
Department of Anatomy
55
1383
Medical Science University of Isfahan,
Department of Anatomy
56
1383
Medical Science University of Isfahan,
Department of Anatomy
57
Somatotopic Organization of
Motor System Projections to
AHCs
• Lateral motor
systems project to
lateral AHCs
• Medial motor
systems project to
medial AHCs
• AHCs = ant. horn
columns
1383
Medical Science University of Isfahan,
Department of Anatomy
58
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Medical Science University of Isfahan,
Department of Anatomy
59
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
64
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Medical Science University of Isfahan,
Department of Anatomy
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Medical Science University of Isfahan,
Department of Anatomy
66
Syringomyelia
• Bilateral limb anesthesia
• The first site of lesion is
anterior white commissure
1383
Medical Science University of Isfahan,
Department of Anatomy
67
1383
Medical Science University of Isfahan,
Department of Anatomy
68
What is your diagnosis?
1383
Medical Science University of Isfahan,
Department of Anatomy
69
Brown Square Syndrome
• 1 - Ipsilateral upper motor neuron
paralysis beneath the lesion
• 2 - Ipsilateral fine touch anesthesia
beneath the lesion
• 3 - Contralateral pain &
temperature anesthesia beneath
the lesion
• 4 - Ipsilateral lower motor neuron
paralysis at the level of lesion
1383
Medical Science University of Isfahan,
Department of Anatomy
70
1383
Medical Science University of Isfahan,
Department of Anatomy
71