Dorsal Column Pathway

Question 1

What information does the DCP relay?

Answer 1

1. Two-point discrimination (stereogenesis)
2. Vibration sense (w/ a tuning fork)
3. Proprioception: conscious perception of muscle spindle and golgi tendon organs.

Question 2

What receptors does the DCP mainly use?

Answer 2

Meissner’s corpuscle, Pacinian corpuscle, Merkel’s disk, joint receptors, and ruffini endings.

Question 3

Describe the course of the DCP

Answer 3

1. Nerve travels from receptor through DRG, posterior funiculus up to nucleus cuneatus in lower medulla where it synapses.
2. Second order axon goes from nucleus cuneatus, crosses midline (as internal arcuate fibers), reconvenes as medial lemniscus fiber bundle, and synapses on neurons in the VPL of thalamus.
3. Third order axons go from thalamus to area 312 leading to perception.

Question 4

Distinguish between fasciculus/nucleus cuneatus and gracilis.

Answer 4

Cuneatus=arm stuff (doesn’t exist below T6). Gracilis=leg stuff (more medial than cuneatus).

Question 5

What is a positive romberg’s sign?

Answer 5

Patient requires vision to stand with feet together. Represents damage to DCP. If patient unsteady with eyes open then cerebellum may be damaged.

Question 6

What does syphylis do to this pathway?

Answer 6

Destroys dorsal column and DRGs.

Question 7

Where does the DCP cross the midline?

Answer 7

In the caudal medulla