Ascending and Descending Pathways (Teach Sheet)

Question 1

Nucleus proprius

Answer 1

Origin of spinal thalamic tract

Question 2

Nucleus dorsalis of Clark

Answer 2

Origin of dorsal spinocerebellar tract

Question 3

Dorsal Column Pathway

Answer 3

Meissner’s
Pacinian
muscle spindles up fasciculus gracilus or cuneatus

synapse in nucleus gracilis or cuneatus

2nd order fibers cross midline (internal arcuate fiber) to synapse in the VPL, 3rd order fibers to post-central gyrus (312)

Question 4

Spinal thalamic pathway

Answer 4

free nerve endings - synapse in nucleus propius, 2nd order fibers cross midline to form the tract proper in the “anterolateral funiculus,” then synpase in VPL. 3rd order fiber rise to 312

Question 5

Dorsal spinocerebellar tract

Answer 5

joint receptors, GTO’s or muscle spindles send unconscious proprioceptive info to Clark’s Nucleus, 2nd order fibers form the DSCT which travels in the outer portion of the lateral funiculus, up the inferior cerebellar peduncle, into the cerebellum (without crossing)

Question 6

Ventral spinocerebellar tract

Answer 6

starts in intermediate gray of spinal cord, samples interneuronal activity, crosses in the cord, crosses in the superior cerebellar peduncle, enters cerebellum

Question 7

Corticospinal tract

Answer 7

starts in area 4 of the pre-central gyrus, travels through posterior part of internal capsule, down through middle of cerebral peduncle, travels in medullary pyramids which decussate, course in the lateral funiculus, synapses on anterior horn cells and you move

Question 8

Rubrospinal tract

Answer 8

red nucleus, crosses midline and travels with CST to synapse on anterior horn cells in cervical cord controlling flexion in large muscle groups

Question 9

What does ALS kill?

Answer 9

anterior horn cells and CST

Question 10

What is positive Rhomberg?

Answer 10

Syphilis (need eyes to stand with feet together)

Question 11

Nucleus proprius

Answer 11

Spinal thalamic tract

Question 12

Area 312

Answer 12

STT and DCP (not SCT because it ends up in cerebellum)

Question 13

Area 4

Answer 13

CST (corticospinal tract)

Question 14

Crossed in cord

Answer 14

STT, VSCT, and ACST

Question 15

Medial lemniscus

Answer 15

dorsal column pathway

Question 16

Nucleus dorsalis

Answer 16

dorsal spinocerebllar tract

Question 17

VPM

Answer 17

(Spinal trigeminal)

Question 18

Clark’s nucleus

Answer 18

dorsal spinocerebellar tract

Question 19

Pyramid

Answer 19

corticospinal tract

Question 20

Crossed in medulla

Answer 20

CST, DCP

Question 21

Medial and lateral motor nuclei

Answer 21

CST

Question 22

IML

Answer 22

sympathetics

Question 23

ICP

Answer 23

SCT, CCT, DSCT (VSCT uses SCP)

Question 24

Summarize DCP.

Answer 24

relays proprioception, 2 point discrimination, and vibration to 312.

Second order neurons cross in the medulla - so lesions in the spinal cord produce ipsilateral effects

lesion in 312 or brainstem above sensory decussation produce contralateral defects

Question 25

Summarize STT.

Answer 25

relays pain to brain (312). crosses in spinal cord so lesion in cord produce contralateral effects. Unilateral lesions above the cord would also produce contralateral deficits.

Question 26

Describe CST.

Answer 26

starts in area 4. crosses in medullary pyramids and synapses on anterior horn cells, resulting in fine movements. lesions in cord produce ipsilateral deficits. lesions or strokes above the pyramids produce contralateral effects

Question 27

Describe muscle spindles.

Answer 27

have intrafusal fibers, innervated by gamma fibers from the cord and respond to muscle stretch. GTO’s respond to isometric tension increase

Question 28

Describe Pacinian corpuscles.

Answer 28

have capsules, are rapidly adapting, and respond to vibration

Question 29

Cerebellar deficits result in…

Answer 29

ipsilateral deficits (think CCT and DSCT)

Question 30

DSCT shoots up…

Answer 30

inferior cerebellar peduncle

Question 31

VSCT crosses in the…

Answer 31

cord, shoots up SCP and crosses again - so its double crossed