Descending motor pathways Flashcards
how many motor neurones?
2
upper motor neuron definition
from cortex to cranial nerve nucleus in brain stem or to ventral grey horn of spinal cord
lower motor neuron definition
from ventral grey horn or ventral roots
what happens if lower motor neuron is damaged?
muscle wasting muscle weakness hypotonia absent tendon reflexes fasciculation/fibrillation
corticospinal nerve routes
cortex to spine - spinal nerves
corticobulbar nerve routes
cortex to brainstem - cranial nerves
upper motor neurons path to the brain stem
cerebral cortex -> precentral gyrus -> internal capsule -> brainstem/spinal cord
interruptions of the motor neuron path leads to…
parkinson’s
corticospinal does what type of movement
finer motor movements
descending fibres for the body pass through
the posterior limb
descending fibres for the face pass through
the genu
posterior part of the posterior limb innervates what
the leg
path of motor through brain stem
cerebral peduncles through the pons and then through the pyramids
where does decussation for motor occur
the medulla
left hand pre central gyrus controls
right hand side of body
85% run
contralaterally
15% run via
ipsilateral lateral corticospinal tract
path of the 15%
cross and decussate at appropriate spinal cord level via ventral white commisure
where do these upper motor neurons synapse?
ventral grey horn
corticobulbar pathway features
influences lower motor neurons in cranial nerve motor nuclei
fibres originate laterally within pre central gyrus
invervation of lower motors neurons is largely bilateral with one exception
cranial nerves with motor fibres
oculomotor (III)
trochlear (IV)
abducens (VI)
cranial nerve nuclei are served
bilaterally
all are served bilaterally except
facial and hypoglossal
hypoglossal is served via
the contralateral hemisphere
above lateral sulcus what is mapped
the upper face
below lateral sulcus what is mapped
lower face
upper face lower motor neurons run ipsilateral or contralateral from the facial nerve nucleus?
ipsilateral
damage at lower motor neuron at parotid gland
ipsilateral side damaged
upper face is served
bilaterally
lower face fibres are serving
contralateral side
right corticobulbar damage (UMN) would cause what damage
lower left face
left facial nerve damage would cause
right side of face damage
