Corticospinal tract

Question 1

Origin of primary cells in corticospinal tract

Answer 1

• area 4- primary motor cortex
• area 6- premotor region
• area 8- frontal eye lids
• area 3,1,2- primary somatosensory cortex

Question 2

Sequence of travel through brain and brainstem- Corticospinal tract

Answer 2

• corona radiata
• posterior limb of internal capsule
• cerebral peduncles
• corticopspinal fibers of ventral pons
• pyramids

Question 3

Corticospinal tract fibers terminate on

Answer 3

primarily interneurons

• majority cervical region (55%)
• throacic (20%)
• lumbrosacral (25%)

Question 4

Internerons in corticospinal tract excite/inhibit

Answer 4

lower motor neurons (ventral horn)

Question 5

Alpha motor neurons

Answer 5

activate extrafusal muscle fibers for volitional movements

Question 6

Gamma motor neurons

Answer 6

innervate the intrafusual muscle fibers of the muscle spindle

Question 7

Primary cells of corticoreticulospinal pathway

Answer 7

supplementary motor and lateral premotor areas

Question 8

Pathway of corticoreticulospinal tract

Answer 8

• descend along corticospinal fibers
• synapse bilaterally at pontine and medullary reticular formation
• descend to synapse on ventral horn of LMN pool

Question 9

Corticoreticulospinal tract function

Answer 9

• premotor/secondary motor areas- fractionated movement
• reticulospinal fibers- initiates complementary activation of axial and proximal limb musculature for fractionated movement

Question 10

Fractionated movement

Answer 10

volitional fine motor control of distal extremities

Question 11

Pontine (medial) reticulospinal pathway

Answer 11

UMN; primarily ipsilateral

• facilitory to axial and limb musculature, especially extensors
• works w/ medial vestibulospinal tract

Question 12

Medullary (lateral) reticulospinal pathway

Answer 12

UMN; bilateral (greater ipsilateral)

-facilitory to flexor and inhibitory to axial and limb extensor musculature

Question 13

Lateral vestibulospinal pathway

Answer 13

UMN; ipsilateral

-excitatory on extensors of lower extremity, inhibits flexor

Question 14

Medial vestibulospinal pathway

Answer 14

UMN; projects bilaterally to cervical and upper thoracic levels

Question 15

Tectospinal pathway

Answer 15

UMN; descends only to cervical levels and coordinates neck movement towards a stimulus

Question 16

Rubrospinal pathway

Answer 16

UMN; contralateral and functions mostly at cervical level

-flexor activation of upper extremity, primarily distal musculature, helps w/ fractioned movements

Question 17

Medial activation pathway function

Answer 17

postural movements and actvities

Question 18

Medial activation pathway location and pathways

Answer 18

located in anterior funiculus

includes: anterior corticospinal, medial reticulospinal, medial and lateral vestibulospinal and tectospinal pathways

Question 19

Lateral activation pathway function

Answer 19

distal limb musculature and fractioned movement

Question 20

Lateral activation pathway location and pathways

Answer 20

located in lateral funiculus

includes: lateral corticospinal, rubrospinal and lateral reticulospinal pathways

Question 21

Primary somatosensory cortex pathway

Answer 21

sends axons caudally through lateral corticospinal pathway and terminates in dorsal horn

Question 22

Primary somatosensory cortex function

Answer 22

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

Question 23

Raphespinal and cerulospinal pathway function

Answer 23

modify afferent sensory info at the dorsal horn level

Question 24

Spinomesencephalic and spinoreticular pathways function

Answer 24

activate a number of reticular system components, modulates incoming pain stimuli

Question 25

Corticobulbar tract

Answer 25

all motor components of cranial nerves receives bilateral input more on this??

Question 26

Lower motor neuron

Answer 26

located in the ventral horn or in a cranial nerve motor nucleus, innervates motor units of skeletal muscle (peripheral nerves)

Question 27

Symptoms of LMN lesion

Answer 27

- flaccid paralysis (atonia or hypotonia) - Areflexia or hyporeflexia - muscle atrophy - fasciculations (irritability of nerve) and fibrillations (muscles lose connection to a nerve)

Question 28

Upper motor neuron

Answer 28

cell bodies located at suprasegmental levels of the CNS, ends in ventral horn or cranial nerve motor nucleus, synapse on interneurons or motor neurons

Question 29

Symptoms of UMN lesion

Answer 29

- initial flaccid paralysis - abnormal cutaneous reflexes (Babinski sign) - abnormal reflexes (clonus, clasp knife) - spasticity- velocity dependent hypertonia - abnormal timing of muscle activation - paresis or plegia

Question 30

Paralysis

Answer 30

total loss of motor function

Question 31

Plegia

Answer 31

a loss of activation of voluntary motor activity

Question 32

paresis

Answer 32

weakness (can be caused by small strokes)

Question 33

Brown-sequard syndrome

Answer 33

lesion of hemisection of the spinal cord

Question 34

Syringomyelia

Answer 34

lesion caused by cavication of the central canal that encroaches on the anterior white commissure and ventral horns

Question 35

Syringomyelia effects

Answer 35

effects LMN of axial then appendicular musculature

Question 36

Poliomyelitis

Answer 36

disease that attacks LMN in ventral horn or cranial nerve nuclei

Question 37

Poliomyelitis symptoms

Answer 37

flu like symptoms and weakness (flaccid) of muscles and fasciculations

Question 38

Effect of post polio syndrome

Answer 38

clinical concern due to overuse of intact motor units

Question 39

Amyotrophic lateral sclerosis (ALS)

Answer 39

chronic and progressive disease of unknown origin, slow onset

Question 40

ALS effect

Answer 40

destroys LMN in ventral horn and brainstem nuclei, white matter pathways

Question 41

Multiple sclerosis

Answer 41

multifocal disease, auto immune attack on myelin that develops in spinal cord, brainstem, optic nerve

Question 42

Multiple sclerosis effects

Answer 42

effects UMN, central myelinated pathways, sensory pathways