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S2 Neuroscience > Corticospinal > Flashcards

Corticospinal Flashcards

1
Q

corticospinal tract function

A

voluntary motor pathway for the body

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2
Q

corticobulbar (corticonuclear) tract function

A

carries out movements for the cranial nerve motor nuclei that innervate the face

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3
Q

corticospinal and corticobulbar tracts

  • arise…
  • descend through…
  • end in…
A 
arise in cerebral cortex
descend through internal capsule
end in
-brainstem motor nuclei or
-ventral horn of spinal cord
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4
Q

where do most of the fibers descending to the spinal cord from the corticospinal and corticobulbar tracts cross
-what about the other fibers

A

in the lower medulla at the pyramidal decussation

descend ipsilaterally to individual segments and then cross

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5
Q

corticospinal tract

-location of primary cells of origin

A 
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)
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6
Q

the fibers that make up the corticospinal tract exit the _____ of the cortex and travel through the _____

A

gray matter

medullary white matter (fiber bundles underlying the cortex)

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7
Q

medullary white matter

  • what is it?
  • specific names, in sequence
A 
fiber bundles underlying the cortex
names
-corona radiata
-posterior limb of the internal capsule
-cerebral peduncles
-corticospinal fibers in the ventral pons
-pyramids
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8
Q

corticospinal tract

-at lower end of medulla, 85% of fibers cross at _____ and continue descent as _____

A

cross at pyramidal decussation

continue as lateral corticospinal tract

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9
Q

lateral corticospinal tract

  • located in
  • function
A

lateral funiculus

innervate extremities

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10
Q

corticospinal tract

  • fibers that do not cross at the pyramidal decussation descend as the _____
  • where do these cross
  • function
A

anterior corticospinal tract
cross at the segmental level
innervate lower motor neuronal pool

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11
Q

anterior corticospinal tract

-located in

A

anterior funiculus

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12
Q

termination location of corticospinal tract fibers

A

interneurons (97%)

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13
Q

where do corticospinal fibers terminate?

A 
cervical region (55%)
thoracic region (20%)
lumbar region (25%)
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14
Q

what excites or inhibits the lower motor neurons to influence the activity of a given motor unit

A

interneurons

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15
Q

lower motor neurons innervate muscles _____ to the cell body location in the spinal cord

A

ipsilateral

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16
Q

corticoreticulospinal pathways

  • runs parallel to…
  • cells giving rise to these fibers are located in the…
A

parallel to corticospinal tract
located in
-supplementary motor area
-lateral premotor area

17
Q

corticoreticulospinal pathway

  • axons descend to the level of the _____
  • what happens at this level
A

descend to level of pontine and medullary reticular formation
synapse bilaterally

18
Q

reticulospinal fibers

  • descend into….
  • what happens there?
A

descend into the spinal cord
synapse in the ventral horn on the lower motor neuron pool
-primarily on interneurons

19
Q

corticoreticulospinal pathway

-purposes

A

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

20
Q

corticoreticulospinal

  • information from primary motor cortex descends for _____
  • this is termed….
A

fine motor control distally on the extremities, i.e. the fingers
this precise individual movement is termed fractionated movement

21
Q

corticoreticulospinal
-purpose of complementary activation of axial and proximal limb musculature by the reticular formation and reticulospinal fibers

A

sets the platform for movement in anticipation of the fractioned movement

22
Q

other descending pathways that are classified as upper motor neurons

A 
pontine (medial) reticulospinal pathway
medullary (lateral) reticulospinal pathway
lateral vestibulospinal pathway
medial vesticulospinal pathway
tectospinal pathway
rubrospinal pathway
23
Q

pontine (medial) reticulospinal pathway

  • ipsi or contra
  • function
  • works with the…
A

primarily ipsilateral
facilitory to axial and limb musculature
-especially the extensors
works with medial vestibulospinal tract

24
Q

medullary (lateral) reticulospinal pathway

  • ipsi or contra
  • function
A

bilateral (greater ipsilateral)
facilitory to flexor musculature
inhibitory to axial and limb extensor musculature

25
Q

lateral vestibulospinal pathway

  • ipsi or contra
  • function
A

ipsilateral

excitatory on extensors of lower extremity musculature (inhibits flexor musculature)

26
Q

medial vestibulospinal pathway

  • ipsi or contra
  • descends to…
  • function
A

projects bilaterally
descends only to cervical and upper thoracic levels
control of neck and upper thoracic musculature

27
Q

tectospinal pathway

  • descends to…
  • function
A

descends only to cervical levels

coordinates neck movement toward a stimulus

28
Q

rubrospinal pathway

  • ipsi or contra
  • descends how far?
  • main functional level
  • -why?
A

contralateral
descends the entire length of cord
functions mostly at cervical level
-in species with bipedal locomotion this tract has diminished in importance and functions mostly at the cervical level

29
Q

rubrospinal pathway

-function

A

involved in flexor activation of the UE
-primarily distal musculature
plays a role in fractionated movements of the wrist and fingers

30
Q

medial vs. lateral activation systems

  • differentaiton defined primarily by…
  • medial are involved in…
  • lateral are involved in…
A

location of the axons of the upper motor neurons
medial
-involved in more postural movements and activities
-named for both their position in the cord and their function
lateral
-involved with distal limb musculature, i.e. fractionated movement

31
Q

medial activation system

  • location
  • consists of what pathways
A 
located in anterior funiculus
consists of
-anterior corticospinal
-medial (pontine) reticulospinal
-medial vestibulospinal
-lateral vestibulospinal
-tectospinal
32
Q

lateral activation system

  • location
  • consists of what pathways
A 
located in lateral funiculus
consists of
-lateral corticospinal
-rubrospinal
-lateral (medullary) reticulospinal
33
Q

other descending components

A 
primary somatosensory cortex
raphespinal
cerulospinal
spinomesencephalic
spinoreticular
34
Q

primary somatosensory cortex

  • sends axons caudally through _____
  • axons terminate _____
  • function
A

sends axons caudally through lateral corticospinal pathway
axons terminate in dorsal horn
though to function as a feedback mechanism that integrates cortical understanding of sensation with incoming sensory information

35
Q

raphespinal and cerulospinal pathways

  • where do they originate
  • function
A

originate in reticular formation nuclei - Raphe nuclei and Locus Ceruleus
involved in modification of afferent sensory information at the dorsal horn level

36
Q

spinomesencephalic and spinoreticular pathways

-function

A

activate a number of reticular system components

these descending components play a role in the modulation of incoming pain stimuli

S2 Neuroscience (25 decks)

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