10 Questions
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:
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:
Cortex = Primary motor cortex Internal capsule = Posterior limb Midbrain = Cerebral peduncles Medulla = Pyramids
Match the following statements about myelination with the correct information:
Are fibers in corticospinal tract myelinated at birth? = NO, they are not myelinated when born Development of myelination in corticospinal tract over time takes approximately 1.5-2 years. = Different kinds of reflexes in babies and adults
Where do upper motor neurons (UMN) influence the activity of lower motor neurons (LMN)?
Pyramids in the medulla
Which tract originates from the red nucleus in the rostral part of the midbrain?
Rubrospinal tract
What happens when rubrospinal tract functions without corticospinal involvement?
Spastic paralysis
Which part of the brainstem gives origin to the vestibulospinal tract?
Caudal pons
Which structure makes up 3% of the cells in the primary motor cortex?
Betz cells
At what level do most fibers of the corticospinal tract decussate?
Medulla
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
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.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
