Motor Systems S2M1

  1. Pyramidal cells are the origin of what pathways
  2. Granule cells receive information mainly from what structures
    Thalamus and other regions of the cortex
  3. How do the sizes of the granule cells and pyramidal cells compare in the cortex
    • In motor regions, pyramidal cell layers are much greater in size then the granule cell layers.
    • Opposite is true in the sensory regions
  4. What are the Cerebral layers from top to bottom
    • Molecular Layer
    • External Granule Layer
    • External Pyramidal Layer
    • Internal Granule Layer
    • Ganglionic Layer (Internal pyramidal)
    • Multiform Layer
  5. What is unique about the last layer of the cortex
    The Multiform layer is the layer of polymorphic cells
  6. What are the lateral descending motor spinal tracts
    • Corticospinal tract
    • Rubrospinal tract
  7. What are the ventromedial descending motor tracts
    • Tectospinal
    • Vestibulospinal
    • Pontine (medial) reticulospinal
    • Medullary (lateral) reticulospinal
  8. What is the alternate name for the corticospinal tract and what fibers does it carry
    • Pyramidal tract
    • Carries voluntary movement
  9. How many descending tracts are there from the brain and brainstem respectively
    • Brain - 2
    • Brainstem - 6
  10. What are the two motor pathways that descend from the cerebral cortex
    • Corticospinal
    • Corticobulbar
  11. What other tract is functionally similar to the corticospinal tract
    Rubrospinal tract
  12. When can a lesion of the Coritcol spinal tract recover
    • If the rubrospinal tract is intact
    • Subsequent rubrospinal lesion would reverse the recovery
  13. What is the trajectory of the Anterior Corticospinal tract
    • Motor cortex
    • Cervical/Thoracic spinal cord
    • Bilateral for axial musculature (posture)
    • Does not Cross pyramid of decussation
  14. What is the pathway for the Lateral Corticospinal tract
    • Primary motor cortex
    • Internal capsule
    • Cerebral peduncle
    • Pons
    • Pyramid of decussation (cross)
    • Spinal cord
  15. 90% of the corticospinal tract crosses when
    • In the pyramid of decussation (Lateral corticospinal tract)
    • The other 10% are Anterior corticospinl tract (ACT) and Anterolateral corticospinal tract (ALCT) don't cross
  16. What is the origin of the Corticospinal (Pyramidal) tract
    • Primary motor cortex area 4 (30%)
    • Primary somatosensory cortex areas 1, 2, 3 (40%)
    • Supplemental motor & premotor cortex (30%)
  17. In the corticocortical connections, what lobe does the posterior parietal cortex feed
    Premotor and supplementary motor cortices
  18. In the corticocortical connections what area does the supplemental and premotor cortices feed
    Primary motor cortex
  19. In the corticocortical connections what area of the brain does the primary somatosensory cortex feed into
    Primary motor cortex
  20. What are the effects of a lesion to the primary motor cortex, and what is often the cause
    • Initial paralysis and weakness
    • Often due to a stroke invloving the middle cerebral artery or anterior cerebral artery
  21. What are the effects of a lesion to the supplementary motor cortex
    • Reduced ability to coordinate actions on the two sides of the body
    • Often akinesia - difficulty initiating movement
  22. What are the effects of of a lesion to the premotor cortex
    Apraxia - difficulty performing complex motor tasks such as tying shoelaces despite intact motor and sensory tracts
  23. Symptoms of lower motor neuron (LMN) lesions occur where
    Only at the level of the lesion on the ipsilateral side
  24. What would be the effects of a lesion at the internal capsule of the corticospinal tract
    • Contralateral hemiparesis, may also have other physical signs due to the involvement of corticobulbar fibers
    • Lacunar strokes can cause this
  25. What would a lesion just rostral to the Decussation of pyramids effect in a corticospinal tract
    Contralateral hemiplegias with ipsilateral paralysis of the tongue, facial muscles, or lateral rectus muscle as well of most eye movements
  26. What effects would a lesion to the decussation of pyramids have to the corticospinal tract innervations
    Bilateral paresis of the upper limb if on the rostral end and lower limbs if on the caudal end
  27. What tract makes contact either directly or indirectly with all of the cranial nerves nuclei
    Corticobulbar (Corticonuclear) fibers
  28. The corticonuclear (bulbar) innervate all of the cranial nerves motor nuclei bilaterally except which
    • VII ventral cell group (Contralateral) Lower face
    • XII (Contralateral) Tongue
    • XI (Ipsilateral) Trapezius and Sternocleidomastoid
  29. A lesion to the internal capsule would have what clinical features in the corticobulbar fibers
    • Contralateral paralysis of lower face muscles, tongue muscle
    • Ipsilateral deviation of the uvula, ipsilateral paralysis of trapezius and sternocleidomastoid
  30. Supranuclear palsy
    Unilateral lesion of the facial region of the primary motor cortex on the UMN, loss of contralateral lower face muscles
  31. Lesion to the hypoglossal nerve (XII) UMN has what effect on the tongue
    Deviation away from the lesioned side
  32. A lesion to the UMN input to CN XI presents how
    • Inability to rotate head to the contralateral side
    • Inability to elevate shoulder on the ipsilateral side
  33. What does a lesion to one hemisphere of the UMN of the trigeminal nerve cause
    No deficit due to the bilateral innervation and compensation takes place
  34. A lesion to the UMN of the Vagus nerve would have what effect on the uvula
    Deviation towards the lesioned side
  35. What are the functions of the Medial and Lateral reticulospinal tracts
    • Medial - Excitatory to extensor motor neurons and axial musculature
    • Lateral - Inhibitory to extensor motor neurons and neurons innervating muscles of neck and back
  36. What is an example of the Tectospinal tract in action
    An immediate turn of the head to a bright flash of light
  37. What is the origin and decussation of the Tectospinal Tract
    • Origin - Superior Colliculus
    • Decussates - Dorsal tegmental decussation
  38. What is the origin of the medial reticulospinal tract and where does it decussate
    • Origin - Pons
    • Doesn't decussate
  39. What is the origination of the lateral reticulospinal tract and where does it decussate
    • Origin - Medulla
    • Decussation - Medulla
  40. What fibers contribute to tonic extension of the arms and legs seen in decerebrate rigidity
    Medial Reticulospinal and Lateral Vestibulospinal fibers
  41. What is the function of the rubrospinal tract
    • Innervate flexor muscles
    • They are functionally parallel to the corticospinal tracts
  42. What is the origin and decussation site of the rubrospinal tract
    • Origin - Red nucleus
    • Decussation - Midbrain
  43. What is the functional difference beteween lateral and medial vestibulospinal tracts
    • Lateral is used for extensor muscles that maintain posture
    • Medial cause rotation and lifting of the head and shoulder blade as well as changes in posture and balance
  44. What is origin and decussation of the lateral vestibulospinal tract
    • Origin - Lateral vestibular nucleus of medulla
    • No decussation
  45. What is the origin and decussation of the medial vestibulospinal tract
    • Origin - medial, lateral, and inferior vestibular nucleus
    • Decussation - Medulla
  46. Decerebrate Rigidity
    • Damage to brain and midbrain where both medial reticularspinal and lateral vestibulospinal are intact
    • All limbs are extended
    • Jaw is clenched
    • Neck is retracted
    • Damage is done below red nucleus
  47. Decorticate rigidity
    • Damage to brain above the midbrain with the rubrospinal intact
    • Arms flexed and adducted
    • Legs and often trunk are extended
    • Damage above red nucleus
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Motor Systems S2M1