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Motor Cortex Center of voluntary motor
movements Located anterior to the
central sulcus Includes;
Primary motor cortex Premotor area Supplementary motor
area
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Motor Cortex Primary motor cortex
Primary source for the motor commands to lower motor neurons.
Somatotopical organization
“Motor homunculus”
Finer muscle control – more motor units – more motor neurons – larger representation areas
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Motor Cortex
Premotor area Topografic organization Complex movement patterns Construction of “motor image”
Supplementary motor area Bilateral complex movement patterns Body posture maintanence
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Motor Cortex
F5
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Mirror neuron system
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Motor Cortex
Cortical columns Motor patterns for synergistic
muscle groups Stimulus amplification for
contraction Dynamic and static neurons
In motor cortex and Red nucleus (n. Ruber) Dynamic neurons: Building up force
at the beginning Static neurons: Maintain the
movement or posture
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Corticospinal tract
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Motor Cortex Betz cells
3% of the pyramidal tract
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Corticospinal tract
Axons of corticospinal tract Primary motor cortex (30%) Premotor&Supp. Motor areas (30%) Somatosensory areas (40%)
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Other motor pathways
Collaterals of Betz cells (lateral inhibition) To Basal ganglia (postural contractions) To Red nucleus (→rubrospinal tract) To Reticular system (→ reticulocerebellar tracts) To Vestibular system (→ vestibulocerebellar tracts) To Pons nuclei (→ pontocerebellar tracts) To Nuc. olivarius inferior (→ olivocerebellar tracts)
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Corticospinal tract
Lateral system Pyramidal tract Rubrospinal tract
Alternative/complementary
Movements of distal extremities
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Corticospinal excitation
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Sensory Feedback
From muscle spindles… From tendon organs… From skin-touch receptors…
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Motor Control from Brainstem
“Defying gravity” Pontine reticular nuclei
(spontaneous exitatory signals to antigravity muscles)
Medullary reticular nuclei (strong cortical input; inhibitory signals via medullary reticulospinal tr.)
Vestibular nuclei (selective signals for balance)
Section below the pontine level Decerebration rigidity
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Lesions of the motor system
Primary motor cortex lesion Paralysis…
Premotor area; Caudate nucleus lesions Loss of voluntary control of fine movements
Widespread “stroke” Overexitability and spasticity
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The End...