Tracts

Question 1

Lateral Corticospinal Tract

Answer 1

a. Modality: conscious motor activity for complex, fractionated movements
b. Cell bodies:
i. 1/3 from primary motor cx
ii. 2/3 from frontal lobes and somatosensory cx (premotor and sup. Motor areas and frontal eye fields)
c. Destination: ventral horn LMNs that control distal limb movements, esp hands, fractionated, rapid, dexterous movements and facial movements
d. Decussation: Yes, at pyramidal decussation

Question 2

Corticobulbar tract

Answer 2

a. Modality: conscious motor activity
b. Cell bodies: motor cx and frontal eye fields
c. Destination: CN motor nuclei (LMN’s) and UMN’s (vestibular nuclei, reticular nuclei, red nuclei)-allow for voluntary control of postural mm.
d. Decussation: yes, fibers are bilateral

Question 3

Rubrospinal tract

Answer 3

a. Modality: motor input to flexors of arm/forearm
b. Cell bodies: Red nuclei (in midbrain)
c. Destination: Ventral horn LMNs that control arm and forearm flexion
d. Decussation: yes, midbrain

Question 4

Lateral vestibulospinal tract

Answer 4

a. Modality: Motor input to axial and antigravity mm of the trunk and LE
b. Cell bodies: (lateral) vestibular nuclei
c. Destination: Ipsilateral ventral horn LMNs that control postural mm.
d. Decussation: No

Question 5

Medial vestibulospinal tract

Answer 5

aka descending MLF

a. Modality: motor input to neck/head postural mm.
b. Cell bodies: (medial) vestibular nuclei
c. Destination: Ipsilateral and contralateral ventral LMNs that control neck/head postural mm.
d. Decussation: yes

Question 6

medial longitudinal fasciculus

Answer 6

aka ascending MLF

a. Modality: Motor input to CN nuclei III, IV, VI (VOR)
b. Cell bodies: medial/inf vestibular nucleus
c. Destination: CN III (ipsilateral), IV, VI (contralateral) nuclei
d. Decussation: yes

Question 7

lateral reticulospinal tract

Answer 7

a. Modality: back-up voluntary motor input
b. Cell bodies: Reticular formation
c. Destination: ipsilateral and contralateral ventral horn LMNs
d. Decussation yes (b/l projections)

Question 8

medial reticulospinal tract

Answer 8

a. Modality: Back-up voluntary motor input
b. Cell bodies: reticular formation
c. Destination: ipsilateral ventral horn LMNs
d. Decussation: No

Question 9

tectospinal tract

Answer 9

a. Modality: Motor input
b. Cell bodies: superior colliculus
c. Destination: neck mm. to control the visual grasp reflex
d. Decussation: Yes