general org of motor systems

motor bureaucracy

multi feedback loops w/in cortex (cortex doesn’t work alone)

contralat limbs

lat motor system controls movement of

lat corticospinal, rubrospinal

lateral motor system tracts

lat corticospinal tract

O: 50% of primary motor cortex; other frontal and parietal areas (BA1-7)

entire cord (mainly C and Losacral enlargements)

lat corticospinal tract termination lvls

post limb of internal capsule; basis of midbrain (pedunculus); basis pons; medulla (pyramidal decussation); SC

lat corticospinal tract descends thru ___ → ___ → ___ → ___ → ___

lat corticospinal tract

most clinically important descending motor pathway in NS

voluntary/fine/skilled extremity movements (distal movements) and trunk

lat corticospinal tract controls

lat corticospinal tract

unique contribution is to activate ms independently

1st order neuron (UMN); 2nd order neuron (LMN/alpha m neuron)

2 neuron pathways of lat corticospinal tract

2nd order (LMN/alpha m neuron)

neuron pathway of lat corticospinal tract w/in ant horn that goes directly to m

lat corticospinal; pyramidal decussation; cervicomedullary junction; lat

85-90% of ___ fibers cross over to contralat side at ___ located at ___ to enter ___ portion of SC

lat corticospinal tract; ant corticospinal tract

10-15% of ___ fibers remain ipsilat and forms the ___

contralat weakness

LCST lesion above pyramidal decussation causes

ipsilat weakness

LCST lesion below pyramidal decussation causes

red nucleus (midbrain)

origin of rubrospinal tract

rubrospinal tract

decussates immediately at ventral trigeminal decussation (midbrain)

C cord

rubrospinal tract termination lvls

pons; medulla; lat; ant horn; lat LMN

rubrospinal tract descends thru ___ and ___, then to ___ SC to enter ___ and synapse w/ ___

ant corticospinal, 2 vestibulospinal, 2 reticulospinal, tectospinal

medial motor systems tracts

ant corticospinal tract

O: primary motor cortex and supplementary motor area

C and upper T

ant corticospinal tract termination lvls

medial intermediate zone; bilat medial motor nuclei

ant corticospinal tract ends at ___, divides, and synapses w/ ___

voluntary movements of bilat axial and girdle ms (prox ms, neck, trunk); provides tone, posture, some extension control to head/neck

ant corticospinal tract controls

lat vestibular nucleus (pons)

lat VST origin

entire cord

lat VST termination lvls

lat vestibulospinal tract

provides balance for whole body

medial and inf vestibular nuclei (rostral medulla)

medial VST origin

C and upper T

medial VST termination lvls

medial

VST that divides and descends bilaterally

head/neck positioning (tone)

medial VST func

pontine reticulospinal tract

O: reticular formation in pons

medullary reticulospinal tract

O: reticular formation in medulla

ipsilat; entire; ant horn; medial LMNs

P/MRST descends ___ thru ___ cord to enter ___ to synapse on ___

automatic posture and gait movements

P/MRST func

sup colliculus (tectum of midbrain)

tectospinal tract origin

tectospinal tract

decussates immediately at dorsal tegmental decussation (midbrain)

tectospinal tract

descends contralat, then enters ant horn

C cord

tectospinal tract termination lvl

head/eye movement coordination

tectospinal tract func

corticobulbar fibers

LCST neurons that direct CNs to move face, tongue, jaw, eyelids, eyes; goes from brain (50% from BA4, rest from 6, 3, 1, 2, 5, 7) to brainstem

rubro, tecto, vestibulo, reticulo

6 tracts that all originate in brainstem and descend to ventral horn of SC