Corticospinal Tract

Question 1

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

Answer 1

corticospinal tract

Question 2

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

Answer 2

corticobulbar tract

Question 3

Where do the corticospinal and corticobulbar tracts arise from?

Answer 3

cerebral cortex

Question 4

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

Answer 4

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

Question 5

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

Answer 5

lower medulla at the pyramidal decussation

Question 6

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

Answer 6

descend ipsilaterally to individual segments and then cross

Question 7

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

Answer 7

right side of the brain

Question 8

What is the voluntary motor pathway for the body?

Answer 8

corticospinal tract

Question 9

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

Answer 9

precentral gyrus (primary motor cortex; area 4)

Question 10

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

Answer 10

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

Question 11

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

Answer 11

medullary white matter (the fiber bundles underlying the cortex)

Question 12

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

Answer 12

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

Question 13

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

Answer 13

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

Question 14

Where is the lateral corticospinal tract located?

Answer 14

lateral funiculus

Question 15

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

Answer 15

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

Question 16

Where is the anterior corticospinal tract located?

Answer 16

anterior funiculus

Question 17

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

Answer 17

interneurons

Question 18

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

Answer 18

cervical region

Question 19

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

Answer 19

thoracic region

Question 20

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

Answer 20

lumbar region

Question 21

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

Answer 21

interneurons

Question 22

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

Answer 22

lower motor neurons

Question 23

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

Answer 23

alpha motor neurons

Question 24

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

Answer 24

alpha motor neurons

Question 25

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

Answer 25

gamma motor neurons

Question 26

What pathway runs parallel to the corticospinal tract?

Answer 26

corticoreticulospinal pathway

Question 27

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

Answer 27

supplementary motor and lateral premotor areas

Question 28

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

Answer 28

pons and medulla

Question 29

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

Answer 29

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

Question 30

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

Answer 30

premotor and secondary motor areas

Question 31

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

Answer 31

fractionated movement

Question 32

The premotor areas of the brain also activate what?

Answer 32

reticular formation and the reticulospinal fibers

Question 33

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

Answer 33

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)

Question 34

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

Answer 34

ipsilateral

Question 35

Pontine (medial) reticulospinal pathway facilitates what?

Answer 35

axial and limb musculature, especially the extensors

Question 36

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

Answer 36

medial vestibulospinal tract

Question 37

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

Answer 37

bilateral (greater ipsilateral)

Question 38

Medullary (lateral) reticulospinal pathway facilitates what?

Answer 38

flexor musculature

Question 39

Medullary (lateral) reticulospinal pathway inhibits what?

Answer 39

axial and limb extensor musculature

Question 40

Lateral vestibulospinal pathway is contralateral, ipsilateral, or bilateral?

Answer 40

ipsilateral

Question 41

Lateral vestibulospinal pathway facilitates/excites what?

Answer 41

extensors of lower extremity musculature

Question 42

Lateral vestibulospinal pathway inhibits what?

Answer 42

flexor musculature

Question 43

Medial vestibulospinal pathway projects contralateral, ipsilateral, or bilateral?

Answer 43

bilateral

Question 44

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

Answer 44

cervical and upper thoracic levels

Question 45

Medial vestibulospinal pathway facilitates what?

Answer 45

control of neck and upper thoracic musculature

Question 46

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

Answer 46

cervical levels

Question 47

Tectospinal pathway coordinates movement of what?

Answer 47

neck movement toward a stimulus

Question 48

Rubrospinal pathway is contralateral, ipsilateral, or bilateral?

Answer 48

contralateral

Question 49

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

Answer 49

Rubrospinal pathway

Question 50

Rubrospinal pathway is involved in what movements?

Answer 50

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

Question 51

What pathway has diminished in importance for bipedal locomotion?

Answer 51

Rubrospinal pathway

Question 52

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

Answer 52

cervical level

Question 53

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

Answer 53

medial activation pathways

Question 54

Medial activation pathways are named for what two things?

Answer 54

- their position in the cord | - their function

Question 55

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

Answer 55

lateral activation system

Question 56

The medial activation system is located where?

Answer 56

in the anterior funiculus

Question 57

The medial activation system consists of what 5 pathways?

Answer 57

- anterior corticospinal - medial reticulospinal - medial vestibulospinal - lateral vestibulospinal - tectospinal

Question 58

The lateral activation system is located where?

Answer 58

in the lateral funiculus

Question 59

The lateral activation system consists of what 3 pathways?

Answer 59

- lateral corticospinal - rubrospinal - lateral reticulospinal

Question 60

The primary somatosensory cortex sends axons caudally through what pathway?

Answer 60

lateral cotricospinal pathway

Question 61

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

Answer 61

dorsal horn of the spinal cord

Question 62

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

Answer 62

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

Question 63

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

Answer 63

- Raphespinal | - Cerulospinal

Question 64

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

Answer 64

- raphe nuclei | - Locus Ceruleus

Question 65

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

Answer 65

- spinomesencephalic | - spinoreticular

Question 66

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

Answer 66

corticobulbar pathway

Question 67

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

Answer 67

- 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)

Question 68

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

Answer 68

ipsilateral

Question 69

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

Answer 69

LMN deficit

Question 70

Intrinsic muscles receive bilateral input from LMN or UMN?

Answer 70

UMN

Question 71

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

Answer 71

contralateral input from LMN

Question 72

UMN has a contralateral or ipsilateral deficit? Why?

Answer 72

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

Question 73

What two areas are lower motor neurons located?

Answer 73

- ventral horn of the spinal cord | - cranial nerve motor nucleus

Question 74

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

Answer 74

motor units of skeletal muscle

Question 75

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

Answer 75

ipsilateral

Question 76

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

Answer 76

- flaccid paralysis (atonia or hypotonia) - areflexia or hyporeflexia - atrophy of muscle (muscle wasting) - fasciculations and fibrillations

Question 77

Cell bodies of UMN are located where?

Answer 77

suprasegmental levels of the CNS

Question 78

Where do the axons of UMN terminate?

Answer 78

the ventral horn or cranial nerve motor nucleus

Question 79

UMN synapse on what?

Answer 79

interneurons or alpha/gamma motor neurons

Question 80

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

Answer 80

contralateral

Question 81

UMN activate what?

Answer 81

LMN

Question 82

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

Answer 82

- 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)

Question 83

What is defined as total loss of motor function?

Answer 83

paralysis

Question 84

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

Answer 84

plegia

Question 85

What is defined as weakness?

Answer 85

paresis

Question 86

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

Answer 86

Brown-Sequard Syndrome

Question 87

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

Answer 87

Syringomyelia

Question 88

Effects of the lesion resulting syringomyelia?

Answer 88

- 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

Question 89

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

Answer 89

poliomyelitis

Question 90

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?

Answer 90

Amyotrophic Lateral Sclerosis (ALS)

Question 91

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

Answer 91

Multiple sclerosis

Question 92

What 3 locations does multiple sclerosis develop?

Answer 92

- spinal cord - brainstem - optic nerve