Module 9 Arpin Review Flashcards
upper motor neurons in the cortex involves waht 2 tracts
-corticospinal tract (CST)
-corticobulbar tract
corticospinal tract (CST) synapses with
neurons in the spinal cord
corticospinal tract (CST) synapses contralateral/ispilateral
-90% of the CST cross over (at the level of the medulla) to control contralateral distal muscles; their axons are located in the lateral white matter of the spinal cord
-this is the lateral CST (“direct pathway” from cortex to spinal cord)
-10% remain ipsilateral – this is the ventral (anterior) CST
what is the direct pathway from cortex to spinal cord
lateral CST (corticospinal tract)
contralateral CST is lateral/ventral
lateral
ipsilateral CST is lateral/ventral
ventral (anterior)
how do corticobulbar axons terminate
bilaterally in the brainstem to coordinate lower motor neurons in the facial motor nucleus
what controls lower facial movements
contralateral motor cortex only
inferior facial muscles are more affected by a lower/upper motor neuron lesion
upper motor neuron lesion
primary motor cortex (M1) neurons are a motor map of contralateral/ipsilateral muscles
contralateral
primary motor cortex (M1) neurons are associated with
a “muscle field”
primary motor cortex (M1) neurons
-motor map of movement/behaviors
-preferred movement direction
-population coding
premotor cortex
-planning of movement
-mirror motor neurons
where are mirror motor neurons
premotor cortex
upper motor neurons in the brainstem are important for
reactive and anticipatory balance control (feedback and feedforward posture control)
upper motor neurons in brainstem give rise to several descending/ascending pathways
descending
4 descending pathways of upper motor neurons
-medial vesitbulospinal tract
-lateral vestibulospinal tract
-medial/lateral vestibulospinal tracts
-reticulospinal pathway
medial vestibulospinal tract
receives vestibular input from the canals and mediates the VCR
lateral vestibulospinal tract
receives vestibular input from the otoliths and mediates the VSR
medial/lateral vestibulospinal tracts
responsible for reactive postural responses
reticulospinal pathway
receives input from upper motor neurons from the cortex
what does the reticulospinal pathway do
indirect pathway from the motor cortex to the spinal cord that helps coordinate anticipatory postural response during voluntary limb movements
lower motor neuron syndrome vs. upper motor neuron syndrome
STRENGTH
LMN: weakness or paralysis
UMN: weakness only
lower motor neuron syndrome vs. upper motor neuron syndrome
MUSCLE BULK
LMN: severe atrophy
UMN: mild or no atrophy
lower motor neuron syndrome vs. upper motor neuron syndrome
REFLEXES
LMN: hypoactive superficial and deep reflexes
UMN: hyperactive deep reflexes after initial spinal shock
special signs and symptoms of lower motor neuron syndrome
-initial signs and symptoms persist
-fasciculations and fibrillations
-geographic distribution of impairment (reflecting distribution of affected spinal segments, cranial nuclei, or spinal/cranial nerves)
-impairments of reflexive and gross and/or fine voluntary movements
special signs and symptoms of upper motor neuron syndrome
-initial period of spinal shock, then spasticity ensues
-babinski’s sign and clonus
-more widespread (nongeographic) distribution of impairment in body regions
-impairment of fine voluntary movements; gross movements relatively unimpaired
