NS 4: Motor system Flashcards
2 types of lower motor neurones?
alpha and gamma
define a lower motor neurone
cells of ventral horn of SC or cranial nerve motor nuclei that give rise to axons that supply skeletal muscles
define an upper motor neurone
neurones of cerebral motor cortex and brainstem nuclei that in turn connect with lower motor neurones
upper motor neurone lesion signs?
hypereflexia
spastic paralysis (increased muscle tone)
minimal/no atrophy
no fasciculations
lower motor neurone lesion signs?
flaccid paralysis (atonia)
atrophy
fasciculations
hyporeflexia/areflexia
what is the pyramidal system of upper motor neurones?
those with direct (monosynaptic) contact with lower motorneurones supplying distal muscles of extremities.
3 tracts of pyramidal motor pathways?
lateral corticospinal
anterior/ventral corticospinal
corticoblubar
function of pyramidal motor pathways?
voluntary movement
origin of pyramidal motor pathways?
motor and premotor cortex and precentral gyrus
site of decussation of lateral corticospinal tract?
medulla (pyramidal decussation)
site of decussation of ventral corticospinal tract?
SC
site of decussation of corticobulbar tract?
brainstem
termination of corticospinal tracts?
contralateral SC
termination of corticobulbar tract?
contralateral motor cranial nerve nuclei
extrapyramidal motor pathways?
tectospinal
rubrospinal
reticulospinal
vestibulospinal
function of tectospinal tract and its origin?
turns head toward sights or sounds
origin= tectum(colliculi) of brain
decussation site of tectospinal and rubrospinal tracts?
brainstem
termination site of tectospinal and rubrospinal tracts?
neck and upper thoracic SC
where is the cell body of upper motor neurones located?
cerebral cortex or brain stem
neurones remain in CNS
where is cell body of lower motor neurones located?
ventral horn of SC or cranial nerve motor nuclei
function of rubrospinal tract?
flexor muscle tone