Motor Cortex and Pathways Flashcards
(12 cards)
Where is the motor homunculus located and what does it represent?
In the precentral gyrus; represents body areas controlled by motor cortex
Name the main descending motor pathways and their functions.
Corticospinal (voluntary limb movement), Corticobulbar (face), Reticulospinal (Tone) and Vestibulospinal (Posture *Back & Neck)
Where do motor tracts decussate?
Most corticospinal fibres decussate at the medullary pyramids (medulla oblongata)
Why does demyelination in MS cause weakness?
Loss of myelin slows/block neural transmission → impaired motor control
What part of the brain initiates voluntary movement?
Primary motor cortex.
What is a myotome?
A group of muscles innervated by a single spinal nerve root.
What does the corticobulbar tract control?
Facial and cranial muscles via cranial nerves.
What is the role of the reticulospinal tract?
Regulates posture and muscle tone.
Which descending tract does not decussate?
The anterior corticospinal tract (mostly).
What type of weakness is seen in UMN lesions?
Spastic weakness.
What does a grade 3/5 muscle strength indicate?
Active movement against gravity, but not resistance.
What clinical test evaluates corticospinal tract integrity?
Muscle strength testing and Babinski sign.
