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Neuroscience Exam #2 > Corticospinal Tract > Flashcards

Corticospinal Tract Flashcards

1
Q

Volitional movements for the body are carried out by what tract?

A

corticospinal tract

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2
Q

Volitional movements for the cranial nerve motor nuclei that innervate muscles of the face are carried out by what tract?

A

corticobulbar tract

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3
Q

Where do the corticospinal and corticobulbar tracts arise from?

A

cerebral cortex

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4
Q

The corticospinal and corticobulbar tracts descend through what to end where?

A

descend through the internal capsule to end in the brainstem motor nuclei or in the ventral horn of the spinal cord

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5
Q

Where do most of the descending fibers of these two pathways cross to the contralateral side?

A

lower medulla at the pyramidal decussation

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6
Q

Where do the remainder of the descending fibers of these two pathways go/do once leaving the cortex?

A

descend ipsilaterally to individual segments and then cross

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7
Q

What side of the brain controls volitional movements on the left side of the body?

A

right side of the brain

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8
Q

What is the voluntary motor pathway for the body?

A

corticospinal tract

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9
Q

Where are the primary cells of origin of the corticospinal tract located?

A

precentral gyrus (primary motor cortex; area 4)

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10
Q

In addition to area 4, where else can the primary cells of the corticospinal tract be located?

A
  • area 6 (premotor region; lateral premotor and supplementary motor)
  • area 8 (frontal eye fields)
  • areas 3, 1, 2 (primary somatosensory cortex)
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11
Q

The fibers that make up the corticospinal tract exit the gray matter of the cortex and travel through what?

A

medullary white matter (the fiber bundles underlying the cortex)

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12
Q

What are the 5 fiber bundles of the medullary white matter?

A
  • corona radiata
  • posterior limb of the internal capsule
  • cerebral peduncles
  • corticospinal fibers in the ventral pons
  • pyramids
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13
Q

85% of the descending fibers of the corticospinal tract cross where and then continue their descent as what?

A

cross at the pyramidal decussation and continue their descent as the lateral corticospinal tract

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14
Q

Where is the lateral corticospinal tract located?

A

lateral funiculus

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15
Q

The remaining fibers that do not cross at the pyramids descend as what and then cross where to innervate what?

A

descend as the anterior corticospinal tract then cross at the segmental level of the spinal cord where they innervate the lower motor neuronal pool

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16
Q

Where is the anterior corticospinal tract located?

A

anterior funiculus

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17
Q

97% of termination of the corticospinal fibers is primarily on what?

A

interneurons

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18
Q

55% of corticospinal fibers terminate in what region of the spinal cord?

A

cervical region

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19
Q

20% of corticospinal fibers terminate in what region of the spinal cord?

A

thoracic region

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20
Q

25% of corticospinal fibers terminate in what region of the spinal cord?

A

lumbar region

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21
Q

What excite or inhibit the lower motor neurons to influence the activity of a given motor unit?

A

interneurons

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22
Q

What neurons are in the ventral horn that make up the ventral root?

A

lower motor neurons

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23
Q

What type of lower motor neurons are responsible for activation of extrafusal muscle fibers (volitional movements)?

A

alpha motor neurons

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24
Q

What type of LMN are the final common pathway to the muscle or effector organ?

A

alpha motor neurons

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25
Q

What type of LMN innervate the intrafusal muscle fibers of the muscle spindle?

A

gamma motor neurons

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26
Q

What pathway runs parallel to the corticospinal tract?

A

corticoreticulospinal pathway

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27
Q

The cells giving rise to the fibers of the corticoreticulospinal pathway are located where?

A

supplementary motor and lateral premotor areas

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28
Q

The descending fibers of the cortioreticulospinal pathway synapse bilaterally at what 2 locations?

A

pons and medulla

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29
Q

After synapsing bilaterally, reticulospinal fibers then descend into the spinal cord where they synapse with what?

A

lower motor neuron pool (primarily interneurons) in the ventral horn of the spinal cord

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30
Q

What 2 motor areas of the brain provide information to the primary motor cortex for voluntary movement?

A

premotor and secondary motor areas

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31
Q

The information from the primary motor cortex then descends for fine motor control distally on the extremities. This precise individual movement is termed?

A

fractionated movement

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32
Q

The premotor areas of the brain also activate what?

A

reticular formation and the reticulospinal fibers

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33
Q

The information from the reticular formation and reticulospinal fibers is transferred where to initiate what?

A

transferred to the spinal cord for initiation of complementary activation of axial and proximal limb musculature (it sets the platform for movement in anticipation of the fractionated movement)

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34
Q

Pontine (medial) reticulospinal pathway is primarily contralateral, ipsilateral, or bilateral?

A

ipsilateral

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35
Q

Pontine (medial) reticulospinal pathway facilitates what?

A

axial and limb musculature, especially the extensors

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36
Q

Pontine (medial) reticulospinal pathway works with what other UMN pathway?

A

medial vestibulospinal tract

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37
Q

Medullary (lateral) reticulospinal pathway is contralateral, ipsilateral, or bilateral?

A

bilateral (greater ipsilateral)

38
Q

Medullary (lateral) reticulospinal pathway facilitates what?

A

flexor musculature

39
Q

Medullary (lateral) reticulospinal pathway inhibits what?

A

axial and limb extensor musculature

40
Q

Lateral vestibulospinal pathway is contralateral, ipsilateral, or bilateral?

A

ipsilateral

41
Q

Lateral vestibulospinal pathway facilitates/excites what?

A

extensors of lower extremity musculature

42
Q

Lateral vestibulospinal pathway inhibits what?

A

flexor musculature

43
Q

Medial vestibulospinal pathway projects contralateral, ipsilateral, or bilateral?

A

bilateral

44
Q

Medial vestibulospinal pathway descends to only what two regions of the spinal cord?

A

cervical and upper thoracic levels

45
Q

Medial vestibulospinal pathway facilitates what?

A

control of neck and upper thoracic musculature

46
Q

Tectospinal pathway descends only to what level of the spinal cord?

A

cervical levels

47
Q

Tectospinal pathway coordinates movement of what?

A

neck movement toward a stimulus

48
Q

Rubrospinal pathway is contralateral, ipsilateral, or bilateral?

A

contralateral

49
Q

What pathway is described as descending the entire length of the spinal cord?

A

Rubrospinal pathway

50
Q

Rubrospinal pathway is involved in what movements?

A

flexor activation of the upper extremity, primarily distal musculature and plays a role in fractionated movements

51
Q

What pathway has diminished in importance for bipedal locomotion?

A

Rubrospinal pathway

52
Q

Rubrospinal pathway functions only at what level of the spinal cord?

A

cervical level

53
Q

Which activation pathways (medial or lateral) are involved in more postural movements and activities?

A

medial activation pathways

54
Q

Medial activation pathways are named for what two things?

A
  • their position in the cord

- their function

55
Q

Which activation system (medial or lateral) is more involved with the distal limb musculature, i.e., fractionated movement?

A

lateral activation system

56
Q

The medial activation system is located where?

A

in the anterior funiculus

57
Q

The medial activation system consists of what 5 pathways?

A
  • anterior corticospinal
  • medial reticulospinal
  • medial vestibulospinal
  • lateral vestibulospinal
  • tectospinal
58
Q

The lateral activation system is located where?

A

in the lateral funiculus

59
Q

The lateral activation system consists of what 3 pathways?

A
  • lateral corticospinal
  • rubrospinal
  • lateral reticulospinal
60
Q

The primary somatosensory cortex sends axons caudally through what pathway?

A

lateral cotricospinal pathway

61
Q

Termination location of the axons traveling from the primary somatosensory cortex through the lateral corticospinal pathway?

A

dorsal horn of the spinal cord

62
Q

Function of the axons traveling from the primary somatosensory cortex through the lateral corticospinal pathway?

A

function as a feedback mechanism that integrates cortical understanding of sensation with incoming sensory information

63
Q

What 2 pathways are also involved in the modification of afferent sensory information at the dorsal horn level?

A
  • Raphespinal

- Cerulospinal

64
Q

The raphespinal and cerulospinal pathways originate what 2 reticular formation nuclei?

A
  • raphe nuclei

- Locus Ceruleus

65
Q

What 2 pathways activate a number of reticular system components that play a role in the modulation of incoming pain stimuli?

A
  • spinomesencephalic

- spinoreticular

66
Q

The entire motor component of cranial nerves (both sides) receives bilateral input from what pathway?

A

corticobulbar pathway

67
Q

What are the two exceptions to the motor component of CN’s receiving BILATERAL info from the corticobulbar pathway?

A
  • The UMN for the two CN’s below ONLY provide CONTRALATERAL innervation:
    - Facial Motor Nucleus (muscles of facial expression)
    - Hypoglossal Nucleus (muscles controlling tongue movements)
68
Q

Tongue atrophy and tongue deviation is ipsilateral or contralateral to the loss?

A

ipsilateral

69
Q

Tongue atrophy and tongue deviation is an LMN or UMN deficit?

A

LMN deficit

70
Q

Intrinsic muscles receive bilateral input from LMN or UMN?

A

UMN

71
Q

Extrinsic muscles receive contralateral or ipsilateral input from LMN or UMN?

A

contralateral input from LMN

72
Q

UMN has a contralateral or ipsilateral deficit? Why?

A

contralateral deviation with UMN because there is NO way to excite LMN of that side

73
Q

What two areas are lower motor neurons located?

A
  • ventral horn of the spinal cord

- cranial nerve motor nucleus

74
Q

The axons of lower motor neurons leave the spinal cord or brainstem to innervate what?

A

motor units of skeletal muscle

75
Q

Any deficit to LMN is ipsilateral or contralateral to the muscle?

A

ipsilateral

76
Q

Four symptoms resulting from a lesion to a lower motor neuron (damage to axon or cell body)?

A
  • flaccid paralysis (atonia or hypotonia)
  • areflexia or hyporeflexia
  • atrophy of muscle (muscle wasting)
  • fasciculations and fibrillations
77
Q

Cell bodies of UMN are located where?

A

suprasegmental levels of the CNS

78
Q

Where do the axons of UMN terminate?

A

the ventral horn or cranial nerve motor nucleus

79
Q

UMN synapse on what?

A

interneurons or alpha/gamma motor neurons

80
Q

Any deficit to UMN is contralateral or ipsilateral damage to the muscle?

A

contralateral

81
Q

UMN activate what?

A

LMN

82
Q

Six symptoms resulting from a lesion to an UMN (damage to descending fiber tracts classified as UMN)?

A
  • Initial flaccid paralysis followed by:
  • -> abnormal cutaneous reflexes (babinski)
  • -> abnormal reflexes (clonus; clasp knife)
  • -> spasticity - velocity dependent hypertonia
  • -> abnormal timing of muscle activation (slower onset, prolonged contraction)
  • -> paresis or plegia (weakness)
83
Q

What is defined as total loss of motor function?

A

paralysis

84
Q

What is defined as a loss of activation of voluntary motor activity sometimes incorrectly referred to as paralysis?

A

plegia

85
Q

What is defined as weakness?

A

paresis

86
Q

What syndrome is a result of the lesion being a hemisection of the spinal cord?

A

Brown-Sequard Syndrome

87
Q

What pathology is the result of a lesion caused by cavitation of the central canal, the remnant of the lumen of the neural tube?

A

Syringomyelia

88
Q

Effects of the lesion resulting syringomyelia?

A
  • lesion encroaches upon the anterior white commissure
  • further ventral and lateral enlargement of the cavity will then encroach upon the ventral horn, effecting LMNs of axial then appendicular musculature
89
Q

What is the disease that attacks LMNs in the ventral horn of the spinal cord and cranial nerve nuclei?

A

poliomyelitis

90
Q

What pathology is a chronic and progressive disease of unknown origin that destroys LMNs in the ventral horn and brainstem nuclei in addition to destroying white matter pathways?

A

Amyotrophic Lateral Sclerosis (ALS)

91
Q

What pathology is a multifocal disease an, thought to be an autoimmune attack on myelin, and is known as a disease of UMNs?

A

Multiple sclerosis

92
Q

What 3 locations does multiple sclerosis develop?

A
  • spinal cord
  • brainstem
  • optic nerve

Neuroscience Exam #2 (8 decks)

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