SC Tracts

Question 1

Dorsal Columns

Answer 1

ASCENDING

• Pressure, vibration, light touch, position sense
• Do not synapse on DRG –> enter SC –> ascend ipsilaterally in posterior cord –> synapse 1st in nucleus gracilus or cuneatus
• Decussate in medulla –> ascend contralaterally to medial lemniscus –> VPL thalamus

Question 2

Spinothalamic

Answer 2

ASCENDING

Lateral - pain & temp

Medial - crude touch & pressure

-Do not synapse in DRG –> enter SC –> synapse in ipsilateral gray matter then decussate in anterior white commisure –> ascend contralaterally –> VPL thalamus

Question 3

Corticospinal

Answer 3

DESCENDING

• Voluntary movement of contralateral limbs
• Lateral and anterior branches (lateral is majority)
• UMN cell body in primary motor cortex –> descend ipsilaterally thru internal capsule –> decussate at caudal medulla (pyramids) –> descend contralaterally and synapse in anterior horn (LMN)
• LMN then leaves SC –> NMJ

Question 4

Fasiculus Gracilis v Fasiculus Cuneatus

Answer 4

Gracilis = lower body

Cuneatus = upper body

Question 5

Dorsal Column Organization

Answer 5

“As you are”

-arms on outside then legs inside (arms/cervical lateral and legs/sacral medial)

Question 6

Corticospinal and Spinothalamic Organization

Answer 6

All Ls

Both have a lateral branch

L = legs are lateral