Ascending and Descending Pathways (Teach Sheet) Flashcards
Nucleus proprius
Origin of spinal thalamic tract
Nucleus dorsalis of Clark
Origin of dorsal spinocerebellar tract
Dorsal Column Pathway
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)
Spinal thalamic pathway
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
Dorsal spinocerebellar tract
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)
Ventral spinocerebellar tract
starts in intermediate gray of spinal cord, samples interneuronal activity, crosses in the cord, crosses in the superior cerebellar peduncle, enters cerebellum
Corticospinal tract
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
Rubrospinal tract
red nucleus, crosses midline and travels with CST to synapse on anterior horn cells in cervical cord controlling flexion in large muscle groups
What does ALS kill?
anterior horn cells and CST
What is positive Rhomberg?
Syphilis (need eyes to stand with feet together)
Nucleus proprius
Spinal thalamic tract
Area 312
STT and DCP (not SCT because it ends up in cerebellum)
Area 4
CST (corticospinal tract)
Crossed in cord
STT, VSCT, and ACST
Medial lemniscus
dorsal column pathway
Nucleus dorsalis
dorsal spinocerebllar tract
VPM
(Spinal trigeminal)
Clark’s nucleus
dorsal spinocerebellar tract
Pyramid
corticospinal tract
Crossed in medulla
CST, DCP
Medial and lateral motor nuclei
CST
IML
sympathetics
ICP
SCT, CCT, DSCT (VSCT uses SCP)
Summarize DCP.
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
Summarize STT.
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.
Describe CST.
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
Describe muscle spindles.
have intrafusal fibers, innervated by gamma fibers from the cord and respond to muscle stretch. GTO’s respond to isometric tension increase
Describe Pacinian corpuscles.
have capsules, are rapidly adapting, and respond to vibration
Cerebellar deficits result in…
ipsilateral deficits (think CCT and DSCT)
DSCT shoots up…
inferior cerebellar peduncle
VSCT crosses in the…
cord, shoots up SCP and crosses again - so its double crossed
