1. Motor pathways
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2. General organization of motor systems
Cerebral cortex contains numerous circuits for motor control
Cerebellum and basal ganglia also participate in important feedback loops in which they project back to cerebral cortex via thalamus
Sensory inputs also plays an essential role in motor circuits and feedback loops
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3. The circuits within the cerebral cortex involve the primary cortex and the association cortices regions like Premotor cortex, supplementary motor area and parietal association cortex which are crucial to the planning and formulation of motor activities
Lesion of the association cortices regions can lead to apraxia which is loss of ability to execute or carry out learned purposeful movements, despite having the desire and the physical ability to perform the movements
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4. Cortical areas involved in motor function
Primary motor area (Broadmann’s area 4) is the major area involved
execution of movements
determining force and direction of movements
adapting movements to changes in sensory feedback
Lesion of this area leads to motor deficit
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5. Premotor & Supplementary motor areas are also involved in higher-order motor planning and project to primary motor cortex
Planning of complex movements
Mental rehearsal of movements
Learning movement sequence
Lesions in these areas do not produce severe movement deficit but rather deficit in motor planning
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6. Cortical areas involved in motor function
Posterior parietal cortex (sensory association area)
Provides information to premotor cortex about environment
Posterior parietal cortex
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7. Cortical areas involved in motor function
Prefrontal association cortex
Planning of behavior
Major input to premotor areas
Prefrontal association
cortex
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8. The motor homunculus
Functional mapping and lesion studies have demonstrated that primary motor area is somatotopically organized
Thus adjacent regions of the cortex correspond to adjacent areas on the body surface
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9. Descending tracts
Descending motor pathways arise from the cerebral cortex and brainstem
Divided into 2 based on their location in the spinal cord
Lateral motor systems travel in lateral column of spinal cord and synapse in the more lateral groups of ventral horn neurons
Control movements of the extremities
Medial motor systems travel in anteromedial spinal cord columns to synapse on medial ventral horn motor neurons
Control the proximal axial and girdle muscles involved in postural tone, balance, orienting movements of the head and neck
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12. 4/27/2017
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13. to body to face Rubrospinal tract (to face) (to mouth) Lufukuja G.
Modified from Purves et al., 2004
to body
to face
Rubrospinal tract
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14. At cervicomedullary junction (level of foramen magnum), 75-85% of pyramidal tract fibres cross over in the pyramidal decussation to enter lateral white column of spinal cord forming the lateral corticospinal tract
The remaining (approx 15%) of corticospinal fibres continue into the spinal cord ipsilaterally, without crossing, and enter anterior white matter column to form anterior corticospinal tract that occupy anterior white column at cervical and upper thoracic levels to supply deep muscles of the neck
(to face)
(to mouth)
Modified from Purves et al., 2004
to body
to face
Rubrospinal tract
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15. During its descent through the brainstem, the corticospinal tract gives off fibres that activate motor cranial nerves nuclei (Corticobulbar/ Corticonuclear), notably those serving the muscles of the face, jaw and tongue
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20. Unilateral face, arm, leg paralysis (Hemiplegia) Without sensory loss
(Hemiplegia) With sensory loss
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21. Paraplegia
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23. Lower motor neurons Lower motor neuron Upper motor neuron
Motor neurons in the anterior gray horns of spinal cord & their axons that innervate skeletal muscles
Upper motor neuron
Carry motor output from cerebral cortex and brainstem to lower motor neuron in spinal cord & brainstem which in turn, project to muscles in the periphery
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24. Consequences of injury to the motor systemX
Lower motor neuron lesion e.g. nerve transection or motor neuron disease
Paralysis/weaknes
Decreased stretch reflexes including:
decreased muscle tone (flaccidity/hypotonea)
decreased resistance to stretch
Muscle fasciculations and atrophy
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27. Consequences of injury to the motor system
Upper motor neuron injury e.g. stroke or brain trauma, spinal cord injury
Paralysis/weakness for fine movements
Increased stretch reflexes including:
Increased muscle tone (hypertonia)
Increased resistance to stretch (spasticity)
Clonus (rhythmic contraction of flexor muscles in response to passive dorsiflexion)
Positive Babinski sign (extensor plantar response  withdrawa  fanning of toes) X
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28. Babinski sign
From Blumenfeld, 2002
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29. Paraplegia
Paraplegia is an impairment in motor or sensory function of the lower extremities.
The area of the spinal canal that is affected in paraplegia is either the thoracic, lumbar, or sacral regions. If all four limbs are affected by paralysis, tetraplegia or quadriplegia is the correct term. If only one limb is affected, the correct term is monoplegia.
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30. Unilateral face, arm, leg paralysis (Hemiplegia) Without sensory loss
(Hemiplegia) With sensory loss
Lufukuja G.

31. Test yourself
A 53-year-old widower was admitted to HKMU hospital complaining of a burning pain over his right shoulder region and the upper part of his right arm. The pain had started 3 weeks previously and, since that time, had progressively worsened. The pain was accentuated when the patient moved his neck or coughed. Two years previously, he had been treated for osteoarthritis of his vertebral column. The patient stated that he had been a football player at college, and since that time, he continued to take an active part in the game until he was 42 years old. Physical examination revealed weakness, wasting, and fasciculation of the right deltoid and biceps brachii muscles. The right biceps tendon reflex was absent. Radiologic examination revealed extensive spur formation on the bodies of the fourth, fifth, and sixth cervical vertebrae. The patient demonstrated hyperesthesia and partial analgesia in the skin over the lower part of the right deltoid and down the lateral side of the arm. Using your knowledge of neuroanatomy, make the diagnosis. How is the pain produced? Why is the pain made worse by coughing?
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