Descending pathways

Question 1

pyramidal system

Answer 1

voluntary movement corticofugal pathways
corticospinal and corticonuclear
monosynaptic, bineuronal
fast, uninterrupted/ not modulated
contralateral ending

Question 2

corticospinal tract

Answer 2

from large pyramidal neurons in layer V of M-1 +PMC, SMA, S-1, and PMA
posterior limb of internal capsule
middle of crus cerebri in midbrain
pyramids in medula
85% of fiber decussate at spinomedullary jcn and become lateral CST
15% of fibers don’t decussate and become anterior CST

Question 3

LCST

Answer 3

lateral funiculus of spinal cord
all levels of spinal cord receive it in ventral horn
distal musculature - hands and feet

Question 4

ACST

Answer 4

medial aspect of ventral funiculus
decussate at level that the terminate through anterior white commisure
axial musculature?

Question 5

corticonuclear tract

Answer 5

from pyramidal neurons in layer V of cerebral cortex - M-1+ PMc, SMA, S-1, PMA
synapse with neurons of motor nuclei of the CN - V, VII, IX, X, XI, XII
posterior limb of internal cpsule, middle of crus cerebri in midbrain
pons - basilar synapses - V, VII
medulla synapses - IX, X, XI, XII
bilateral projections except m. of facial expression (VII) and tongue m. (XII)
aka cortico bulbar (through not just medulla)

Question 6

rubrospinal tract

Answer 6

involuntary movement
from red nucleus in midbrain, fibers decussate in midbrain and course in lateral funiculus of spinal cord
input -> corticorubro fibers form ipsilateral motor cortices - arise 4&6
influences flexor musculature to supplement corticospinal system

Question 7

vestibulospinal tracts

Answer 7

two tracts arise from vestibular nuclei in brainstem
descend in ventral funiculus of spinal corn
mediate postural adjustment, head movements

Question 8

reticulospinal tracts

Answer 8

lateral and medial from reticular formation of midbrain

projects to all spinal levels

Question 9

lateral reticulospinal tract

Answer 9

from neurons in medial aspect of medullary RF
axons descend bilaterally in lateral funiculus
powerful excitatory influence from cerebral cortex
inhibit neurons in ventral horn which innervate extensor m.

Question 10

medial reticulospinal tract

Answer 10

neurons in lateral aspect of pontine RF
powerful excitatory influence from ascending systems
ipsilateral in ventral funiculus
excite LMN of extensor m.

Question 11

tectospinal tract

Answer 11

ventral funiculus of cervical spinal cord levels only
originate from neurons in sup. colliculus
decussate in midbrain tegmentum
descent as tectospinal tract through pons and medulla
reflex control and coordination of head, neck, and eye movements in response to visual and auditory stimuli as well as voluntary motor commands

Question 12

extrapyramidal system

Answer 12

involuntary movements and all movements adjustment/synchronization
tectospinal, rubrospinal, vestibulospinal, reticulospinal tracts
pathways are multineuronal/ multisynaptic
impacted by cerebral cortex, basal gangli, several thalamic nuclei, subthalamus and other nuclei of the brainstem