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NS 11: Motor Pathways (ii) (Motor Cranial Ns (all have bilateral…
NS 11: Motor Pathways (ii)
Motor Cranial Ns
I (also parasymp)
4
V3 (also sensory)
VI
VII (also sensory + parasymp)
IX (also sensory + parasymp)
X (also sensory + parasymp)
XI
XII
all have bilateral innervation
2 UMNs from each side
EXCEPT 7 + 12
UMN 7 lesion: paralysis below eyes, sparing above
LMN 7 lesion: paralysis above + below eyes (ipsilat)
Extrapyrimidal tracts
Rubrospinal
red nucleus in midbrain receives inputs from cortex + cerebellum
protects to interneurons in cord
controls flexor tone in limbs
Tectospinal
from sup colliculi to cervical cord
reflexes in response to visual stimuli
Vestibulospinal
from vestibular nuclei (in medulla + pons) to ant. horn cells
controls extensor muscle tone (antigravity- maintain posture)
stops working when too far underground
Tectum
in midbrain, post to aqueduct of Sylvius
divides into sup (visual) + inf (auditory) colliculi
Tegmentum
involved in homeostatic + reflex pathways
in all 3 parts of brainstem
ant to aqueduct of sylvius
Pyrimidal lesions
UMN
e.g. stroke
if in cerebral hemisphere - contralat
if in cord - ipsilat
initial weakness/paralysis, then hypertonicity
spasticity (increased resistance in response to stretch)
hyperreflexia (clonus)
Babinski's sign: when sole of foot stroked, bog toe points up + others stretch out (instead of facing down + curling like normal)
not present in babies (neurologically undeveloped)
LMN
e.g. polio
ipsilat
weakness, paralysis or paresis (mild paralysis), muscle wasting, fasciculations, hypotonicity (decreased resistance), hyporeflexia