Motor Cortex - bayanbox.irbayanbox.ir/view/8988788415846394404/Motor-Cortex.pdf · Motor cortex...
Transcript of Motor Cortex - bayanbox.irbayanbox.ir/view/8988788415846394404/Motor-Cortex.pdf · Motor cortex...
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Motor Cortex
1. Upper Motor neurons2. Primary Motor area (M1)3. Pre-motor area (PMA)4. Supplementary Motor area (SMA)5. Frontal eye field (area 8)
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Cortical Motor System
Primary motor cortex
Execution of movement• Somatopically organized
• Massive descending projections to spinal
cord
• Damage => pronounced weakness in
affected body parts
• Stimulation => simple mov’t in small
muscle groups
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Two major descending
pathwaysPyramidal vs. extrapyramidal
Striated muscles
Lower motor neurons
(brain stem and spinal cord)
Brain stem
centers
Motor cortex
Pyramidal
system Extrapyramidal
system
• Pathway for
voluntary movement
• Most fibers originate
in motor cortex (BA
4&6)
• Most fibers cross to
contralateral side at
the medula
• Pathways for postural
control/certain reflex
mov’t
• Originates in brainstem
• Fibers do not cross
• Cortex can influence
this system via inputs to
brain stem
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Somatotopy in M1
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Motor Cortex Homunculus
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• Columnar organization:
• Thumb adduction ● Thumb abduction ■
* Mirror Neurons
Sensory Motor Cortex → Betz Neurons
Direct cortico-spinal synapse
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Motor Cortex Symptoms
Upper Motor Neurons Diseases:
• ↑ Pyramid × contra-lateral paralysis
Hypertonocity, Spasticity
• Babinski Sign : Plantar reflex
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• ↓ Pyramid × ipsi-lateral paralysis,
Knee jerk reflex absent, passive
movement, clonus (rythmic contraction
of flexor muscles)
• Corticobulbar lesion► contralateral
lower facial muscles paralysis
• Intensive physiotherapy
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Frontal Eye Field
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Voluntary Eye Movement
• Frontal eye field (caudal area 8)
• Stimulation FEF → eye conjugate deviation to opposite side
• (L) FEF → pontin reticular formation (R) → abducens (R. Lat.Rectus)
• R. abducens → L. oculomotor → (L. Med. Rectus)
Sensory Motor Cortex
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