Podcast
Questions and Answers
Match the following descriptions with the correct feature of descending tracts:
Match the following descriptions with the correct feature of descending tracts:
Contain upper motor neurons (UMN) = Influence the activity of lower motor neurons (LMN) Originate in structures at different levels of the brain = Hierarchical organization Rubrospinal tract = Originates from red nucleus in the rostral part of the midbrain Vestibulospinal tract = Helps with balance
Match the following tracts with their functions:
Match the following tracts with their functions:
Corticospinal tract = Goes to anterior horn of the spinal cord to alpha/lower motor neurons Rubrospinal tract = Spastic paralysis without corticospinal influence Vestibulospinal tract = Works without influence of rubrospinal and corticospinal in cerebral palsy Reticulospinal tract = Multi-synaptic
Match the following structures with their locations along the trajectory of the corticospinal tract:
Match the following structures with their locations along the trajectory of the corticospinal tract:
Cortex = Primary motor cortex Internal capsule = Posterior limb Midbrain = Cerebral peduncles Medulla = Pyramids
Match the following statements about myelination with the correct information:
Match the following statements about myelination with the correct information:
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Where do upper motor neurons (UMN) influence the activity of lower motor neurons (LMN)?
Where do upper motor neurons (UMN) influence the activity of lower motor neurons (LMN)?
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Which tract originates from the red nucleus in the rostral part of the midbrain?
Which tract originates from the red nucleus in the rostral part of the midbrain?
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What happens when rubrospinal tract functions without corticospinal involvement?
What happens when rubrospinal tract functions without corticospinal involvement?
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Which part of the brainstem gives origin to the vestibulospinal tract?
Which part of the brainstem gives origin to the vestibulospinal tract?
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Which structure makes up 3% of the cells in the primary motor cortex?
Which structure makes up 3% of the cells in the primary motor cortex?
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At what level do most fibers of the corticospinal tract decussate?
At what level do most fibers of the corticospinal tract decussate?
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Study Notes
Descending Tracts
- Contain upper motor neurons (UMN) that influence the activity of lower motor neurons (LMN)
- Can have ipsilateral or contralateral, direct or indirect (via interneurons), and excitatory or inhibitory influence on LMN
- Originate from structures at different levels of the brain, showing a hierarchical organization
Corticospinal Tract
- Originates from the cerebral cortex (primary motor cortex)
- Comprises 6 layers, with Betz cells making up 3% of the cells
- Trajectory: Cortex → subcortical white matter → internal capsule (posterior limb) → midbrain (cerebral peduncles) → pons → medulla (pyramids) → most fibers decussate → lateral funiculus (lateral white matter)
- Destination: anterior horn of the spinal cord, where it influences alpha/lower motor neurons that go to extrafusal muscle fibers
- Myelination: yes, with oligodendrocytes; not myelinated at birth, but develops over time (around 1.5-2 years)
Other Descending Tracts
- Rubrospinal tract: originates from the red nucleus in the rostral part of the midbrain; without corticospinal tract, it can cause spastic paralysis
- Vestibulospinal tract: originates from the caudal pons and rostral medulla; helps with balance; in cerebral palsy, it works without influence of rubrospinal and corticospinal tracts
- Reticulospinal tract: a multi-synaptic tract
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Description
Test your knowledge about the descending tracts containing upper motor neurons (UMN) and their influence on lower motor neurons (LMN). Explore the concepts of ipsilateral or contralateral pathways, direct or indirect pathways via interneurons, and the excitatory or inhibitory influence of these tracts.
