Motor tracts Flashcards
a lesion in what location is implicated by spasticity?
upper motor neuron lesion
a lesion in what location is implicated by rigidity
basal ganglia
a lesion to what structure may cause hyper reflexia
upper motor neuron
what is babinski sign and what causes it
inverted plantar reflex
upper motor neuron lesion
what pathways are lost in an upper motor neuron lesion
corticospinal tract
indirect brainstem motor control (via collaterals of the CST)
a lesion to what structure is associated with flaccid paralysis, muscle wasting, hyporeflexia and fasciculations
lower motor neuron lesion
which part of the corticospinal tract innervates the axial/postural muscles?
medial corticospinal tract
which part of the corticospinal tract innervates the muscles of the extremities
lateral corticospinal tract
are cranial nerves upper or lower motor neurons
LOWER MOTOR NEURONS
what are the UMNs going to cranial nerves called?
cortioconuclear/corticobulbar tract
where do the fibers innervating skeletal muscle of the extremities decussate
at the pyramids of the medulla
lateral corticospinal tract
where do the fibers innervating axial skeletal muscle decussate
at the ventral grey horn of the spinal level that they exit
medial corticospinal tract
what is the target of gamma motor neurons
intrafusal fibers
what is the target of alpha motor neurons
extrafusal fibers
what is the function of the indirect motor pathways
modulate movement
what are the major structures through which fibers of the direct pathway of the CST pass?
posterior limb of internal capsule =>
cerebral peduncles of the midbrain
anterior pons =>
pyramids
which portion of the motor cortex controls voluntary movement of the face
lateral 1/3
how do the paths of the lateral and medial CSTs differ
lateral - decussates in the inferior medullary pyramids
medial - continues ipsilaterally until it reaches spinal level
what is the target of the corticobulbar tract
muscles innervated by cranial nerves
EXCEPT PERIORBITAL MS
does the corticobulbar tract innervate ipsilateral or contralateral muscles
contralateral
** CN XI is an exception and innervates on the ipsilateral side
how does the path of the corticobulbar tract differ from that of the lateral corticospinal tract
UMN cell body is more lateral within the primary motor cortex=>
descends through GENU of internal capsule
how are lower motor neurons of the CST organized functionally within the spinal cord
neurons innervating extensors lie VENTRAL
neurons innervating flexors lie DORSAL
what are the two lateral UMN indirect tracts
rubrospinal
lateral reticulospinal
what are the four medial UMN indirect tracts
tectospinal
medial reticulospinal
medial AND LATERAL vestibulospinal
what is the function of the lateral vestibulospinal tract
extension against gravity
where is the lateral vestibular nucleus and to where do its axons extend
dorsal pons
extends to all spinal levels
where is the medial vestibular nucleus and to where do its axons extend
dorsal pons
to cervical and thoracic spinal levels
what is the function of the medial vestibular spinal tract
muscle tone/posture of the neck and shoulders
coordination of head movements
what indirect pathway originates at the red nucleus
rubrospinal
where is the red nucleus
anteromedial midbrain
what is the function of the rubrospinal tract
UE flexion
where do the medial and lateral reticulospinal tracts originate
M: reticular formation of the PONS
L: reticular formation of the MEDULLA
what is the target of the medial reticulospinal tract
ipsilateral LMNs of the postural ms. and limb extensors
what is the function of the of the lateral reticulospinal tract
inhibition of extensor LMNs
facilitation of flexor LMNs
what tract is responsible for your head turning towards what you are looking at or loud noises
tectospinal
where is the origin of the tectospinal tract
superior colliculus
what pathways are lost in UMN syndrome
direct pathway of CST and indirect pathways supplied by it’s collateral branches
what tract is implicated in loss of sensation of the face
trigeminal
what tract is implicated in facial paralysis
corticobulbar
will a lesion of a LMN illicit sxs on the same or opposite side (of the lesion)
same side
will a lesion of an UMN above the medulla illicit sxs on the same or opposite side (of the lesion)
to what tracts does this apply?
opposite side
CST AND PCMLS
will a lesion of an UMN below the medulla illicit sxs on the same or opposite side (of the lesion)
same side
what is decorticate posture
hands in fists, elbows flexed, forearms pronated, LE internally rotated
what causes decorticate posture
lesion above the red nucleus
what is decerebrate posture
UE pronated, UE and LE extended
what causes decerebrate posture
lesion between red nucleus and above the vestibulospinal/reticulospinal nuclei
in a complete transection of the spinal cord, where would anesthesia begin and why
1-3 levels below the lesion b/c of overlapping dermatomes
where would upper- and lower- motor neuron signs be present in a complete transection of the SC
UMN signs below the lesion
LMN signs at the level of the lesion
what sensation would be lost from the CONTRALATERAL side in the case of a hemisection of the spinal cord
pain and temperature
2-3 dermatomes below lesion
In a SC hemisection, why is there an area at the level of the lesion where all sensation and voluntary movement would be lost? Is this section ipsilateral or contralateral to the lesion?
because the DRG was severed
ipsilateral to the lesion
what lesion is associated with Brown-Sequard’s syndrome
spinal cord hemisection
what tract/sense is usually first affected by syringomyelia
ALS/pain and temperature
occlusion of what artery causes anterior cord syndrome
anterior spinal a
in anterior cord syndrome, are LMN sxs contralateral or ipsilateral
ipsilateral
what are two causes of central cord syndrome
syringomyelia
cervical hyperextension
does central cord syndrome ever effect the PCMLS
NO
what three structures are lesioned in medial medullary syndrome
pyramids
medial lemniscus
CN XII nucleus
occlusion of what artery causes medial medullary syndrome
anterior spinal artery
what sxs are associated w/ medial medullary syndrome
contralateral UMN sxs
contralateral loss of proprioception, vibration, discriminative touch
tongue deviation towards lesion
central seven palsy is caused by a lesion to what tract
corticobulbar tract
what is the hallmark of central seven palsy
lower face drooping with intact muscles of the upper face (pt can wrinkle forehead)
where is the lesion in central 7 palsy
contralateral lower pons
why does innervation to the upper face remain intact when there is a lesion to the corticobulbar tract
the muscles of the upper face have bilateral innervation
what is the dx for a lesion to the cerebral peduncle
weber syndrome
what nervous structures are effected in weber syndrome
CST
corticobulbar
CN III, X, XI, XII
what pattern of sensory impairment is associated with polyneuropathy
stocking/glove distribution
what neurons are destroyed in amyotropic lateral sclerosis (ALS)
somatic motor neurons
What artery supplies the posterior limb of the internal capsule
Lenticulostriate arteries and anterior choroidal a
What is the blood supply to the nucleus ambiguous
PICA
