Descending Motor Tracts Flashcards
What do the medial motor systems control and where do they run?
Axial and proximal limb muscles. Run in ventral and ventrolateral funiculus
What do the lateral motor systems control and where do they run?
Control precise movements of limbs, run in lateral funiculus.
Arises at superior colliculus
Crosses in midbrain (dorsal tegmental decussation)
Terminates in medial intermediate grey.
Controls reflexes to head and arm movement stimuli
Tectospinal Tract
Arises: medial vestibular nucleus
Runs: in MLF
Fn: Reflex adjustment of head position to vestibular stimuli
Medial vestibulospinal tract
Arises: pontine lateral gaze center (PPRF)
Runs: In MLF
Fn: Promotes head movement to follow eye movement.
Pontine reticulospinal tract
Run in cap of ventral horn. regulate muscle tone and produce crude movements. (3)
Ventral corticospinal
Lateral vestibulospinal
Medullary reticulospinal.
Arises: Lateral vestibular nucleus
Runs: Lateral funiculus
fn: excites ipsilateral extensor muscles when head tips to the side.
Lateral vestibulospinal tract.
Useful for gross movements.
Can act as an indirect corticospinl projection pathway
Reticulospinal tracts.
Voluntary control of movement.
Corticospinal tract
Voluntary control of head and face movement.
Corticobulbar tract
What is the path of the corticospinal tract?
- Pyramidal (Betz) cells in precentral gyrus.
- Cerebral peduncles at midbrain.
- Basal pons
- Comprise the pyramids of the medulla.
- Lateral funiculus of the spinal cord.
What do individual cortical motor neurons encode?
A direction of movement
What are the corticofugal fibers?
Collection of corticospinal and corticobulbar tracts leaving the brain and entering the brainstem.
Where is the lesion if a patient has lower facial weakness?
Upper motor neuron.
Where is the lesion if a patient has total facial weakness?
Lower motor neuron.
