Corticospinal Flashcards
(36 cards)
corticospinal tract function
voluntary motor pathway for the body
corticobulbar (corticonuclear) tract function
carries out movements for the cranial nerve motor nuclei that innervate the face
corticospinal and corticobulbar tracts
- arise…
- descend through…
- end in…
arise in cerebral cortex descend through internal capsule end in -brainstem motor nuclei or -ventral horn of spinal cord
where do most of the fibers descending to the spinal cord from the corticospinal and corticobulbar tracts cross
-what about the other fibers
in the lower medulla at the pyramidal decussation
descend ipsilaterally to individual segments and then cross
corticospinal tract
-location of primary cells of origin
precentral gyrus (primary motor cortex; area 4) area 6 (premotor region; lateral premotor and supplementary motor) area 8 (frontal eye fields) primary somatosensory cortex (areas 3, 1, 2)
the fibers that make up the corticospinal tract exit the _____ of the cortex and travel through the _____
gray matter
medullary white matter (fiber bundles underlying the cortex)
medullary white matter
- what is it?
- specific names, in sequence
fiber bundles underlying the cortex names -corona radiata -posterior limb of the internal capsule -cerebral peduncles -corticospinal fibers in the ventral pons -pyramids
corticospinal tract
-at lower end of medulla, 85% of fibers cross at _____ and continue descent as _____
cross at pyramidal decussation
continue as lateral corticospinal tract
lateral corticospinal tract
- located in
- function
lateral funiculus
innervate extremities
corticospinal tract
- fibers that do not cross at the pyramidal decussation descend as the _____
- where do these cross
- function
anterior corticospinal tract
cross at the segmental level
innervate lower motor neuronal pool
anterior corticospinal tract
-located in
anterior funiculus
termination location of corticospinal tract fibers
interneurons (97%)
where do corticospinal fibers terminate?
cervical region (55%) thoracic region (20%) lumbar region (25%)
what excites or inhibits the lower motor neurons to influence the activity of a given motor unit
interneurons
lower motor neurons innervate muscles _____ to the cell body location in the spinal cord
ipsilateral
corticoreticulospinal pathways
- runs parallel to…
- cells giving rise to these fibers are located in the…
parallel to corticospinal tract
located in
-supplementary motor area
-lateral premotor area
corticoreticulospinal pathway
- axons descend to the level of the _____
- what happens at this level
descend to level of pontine and medullary reticular formation
synapse bilaterally
reticulospinal fibers
- descend into….
- what happens there?
descend into the spinal cord
synapse in the ventral horn on the lower motor neuron pool
-primarily on interneurons
corticoreticulospinal pathway
-purposes
premotor and secondary motor areas provide information to primary motor cortex for voluntary movement
premotor areas activate the reticular formation and subsequently the reticulospinal fibers
-information is transferred to the spinal cord for initiation of complementary activation of axial and proximal limb musculature
corticoreticulospinal
- information from primary motor cortex descends for _____
- this is termed….
fine motor control distally on the extremities, i.e. the fingers
this precise individual movement is termed fractionated movement
corticoreticulospinal
-purpose of complementary activation of axial and proximal limb musculature by the reticular formation and reticulospinal fibers
sets the platform for movement in anticipation of the fractioned movement
other descending pathways that are classified as upper motor neurons
pontine (medial) reticulospinal pathway medullary (lateral) reticulospinal pathway lateral vestibulospinal pathway medial vesticulospinal pathway tectospinal pathway rubrospinal pathway
pontine (medial) reticulospinal pathway
- ipsi or contra
- function
- works with the…
primarily ipsilateral
facilitory to axial and limb musculature
-especially the extensors
works with medial vestibulospinal tract
medullary (lateral) reticulospinal pathway
- ipsi or contra
- function
bilateral (greater ipsilateral)
facilitory to flexor musculature
inhibitory to axial and limb extensor musculature