Tract Review Flashcards
Describe the origin of the corticospinal tract
- 50% in M1
- 30% in PMA
- S1
Describe the differences between the lateral and ventral (anterior/medial) corticospinal tract
Lateral: 85% of corticospinal tract, crosses in pyramids, descends in dorsolateral column, largely controls voluntary movement and fine motor control
Medial: 15% of corticospinal tract, DO NOT CROSS, travel in anterior funiculus, terminate BILATERALLY in C/T spine, largely controls neck and trunk
Describe how the corticospinal tract influences LMN
- Direct connections to alpha MN to allow individual movement of DIGITS
- Interneurons (excitatory = multijoint movement; inhibitory = modulates reflexes)
Describe the initial presentation of damage to the corticospinal tract and was movements look like even when the acute stage is over
Initial: contralateral weakness
Weakness recovered BUT
- difficulty performing fractionated movement due to synergy
- difficulty with speed of movement
- difficulty with rate of force development
Describe the function of the corticobulbar tracts
Influences 8 CNs that have motor function
All except CN V, lower VII, XII
[Tracts run from the cortex > corona radiata > internal capsule > CN nuclei in the brainstem]
Pathway: Rubrospinal
- Origin
- Pathway
- Function
- Red nucleus
- Cross immediately in pons
- Gross motor movement, primarily upper limb flexion
Pathway: Vestibulospinal
- Origin
- Pathway
- Function
- Vestibular nuclei
- Projects bilaterally or ipsilaterally
- Medial: controls head/back to stabilize head/posture; Lateral: Extensor LMN to maintain upright/balanced posture
Pathway: Tectospinal
- Origin
- Pathway
- Function
- Superior colliculus
- Terminates in ventral horn
- Reflexive turning of the head
Pathway: Reticulospinal
- Origin
- Pathway
- Function
- Reticular formation
- Travels ipsilaterally or bilaterally
- General alerting, General movements, Postural movements
Describe the difference between the lateral and medial descending spinal tracts?
Lateral: concerned with direct limb movements
Medial: postural control system
Term: involunary stereotypes response to a sensory input from sensory input and motor output, involves interneurons
Reflexes
Describe how the withdrawal reflex and the crossed extension reflex work in unison when you step on a sharp pebble with your right foot
- The withdrawal reflex causes you to pull your right leg up away from the rock (flex hip/knee)
- The crossed extension reflex causes you to extend your left leg in order to stay standing
Describe how you can modify reflexes
The are influenced by descending control
In order to increase the excitability of neurons you distract the pt. from the reflex test you can have them squeeze a pillow between their knees for UE reflex or press hands together/clinch jaw for LE reflex
Describe Central Pattern Generators
A network of interneurons string reflexes together triggering the next to perform rhythmic movements
They can be adapted by higher brain centers and are likely initiated and modified by the motor cortex/descending input
List 3 UMN with axons that descend from cerebral cortex or brain stem and end on LMN
- Corticospinal (Cortex > SC)
- Rubrospinal (Brainstem > SC)
- Corticobulbar (Cortex > CN in Brainstem)
