The motor system

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The motor system
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Components

• Descending motor pathways
• Motor neurons and interneurons
• Basal ganglia
• Cerebellum

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1. Descending motor pathways
Cerebral cortex ? periphery
Brain stem motor pathways automatic
control Cortical motor pathways refined and
adaptative control
2. Motor neurons, interneurons
Ventral horn Intermediate zone
Spinal cord
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Interneurons
Segmental interneurons branches within a single
segment Propriospinal interneurons branches for
multiple sements
Hierarchical motor pathways
Monosynaptic Disynaptic Polysynaptic
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3. Basal ganglia
4. Cerebellum
Motor behaviour Act indirectly via thalamus Do
not contain neurons that project directly to
motor neurons
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Functional classes of descending pathways

• Motor control pathways
• Pathways regulating the functions of the
  autonomic nervous system
• Pathways regulating somatic sensory processing

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Major pathways
From cortex
Lateral corticospinal tract Ventral corticospinal
tract Corticobulbar tract
From brainstem
Rubrospinal tract Reticulospinal
tract Tectospinal tract Vestibulospinal tract
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Limb muscles and voluntary movement control
Lateral corticospinal tract
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Limb muscles and voluntary movement control
Rubrospinal tract
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Axial and girdle muscles, posture
Ventral corticospinal tract Reticulospinal
tract Tectospinal tract Vestibulospinal tract
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Axial and girdlemuscles, posture
Ventral corticospinal tract Reticulospinal
tract Tectospinal tract Vestibulospinal tract
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Cortical regions
Primary motor cortex precentral gyrus Premotor
cortical regions suplementary motor area
premotor cortex cyngulate motor area

• information from association cortices
  (prefrontal, posterior parietal, limbic
  system)
• movement planning and execution