Corticospinal And Corticobulbar Pathways

Question 1

Which pathway carries out volitional movement for the face?

Answer 1

Corticobulbar

Question 2

Another name for corticobulbar

Answer 2

Corticonuclear

Question 3

How is volitional movement on the left side of the body controlled by the right side of the brain?

Answer 3

Most of the corticospinal fibers descend and cross at the pyramidal decussation (in the lower medulla). The remaining fibers cross at the spinal segment.

Question 4

Sensory info from the _____ side of the body crossed and ascended to end in the right side of the brain. And vise versa.

Answer 4

Left

Question 5

Voluntary motor pathway for the body

Answer 5

Corticospinal tract

Question 6

Where are the primary cells of origin of the corticospinal and corticobulbar tracts located

Answer 6

Pre central gyrus (primary motor cortex)

Also… Pre motor region, frontal eye fields and a little primary somatosensory cortex

Question 7

What happens in the lower end of the medulla? What % is lateral/anterior CST?

Answer 7

85% cross (lateral CST) - located in the lateral funinculus

15% do not cross (anterior CST) - in the anterior funinculus

Question 8

_____% of CST fibers terminate on inter neurons. What percent terminate at each region of the spine

Answer 8

75
Cervical - 55
Thoracic -20
Lumbosacral -25

Question 9

What excites/inhibits lower motor neurons?

Answer 9

Interneurons. LMN are neurons in the ventral horn that make up the ventral root

Question 10

T/F LMN are alpha or gamma motor neurons

Answer 10

F they are both

Question 11

What do alpha motor neurons do?

Answer 11

Activate extrafusal mm. Fibers (volitional movements)

Question 12

What do gamma motor neurons do?

Answer 12

Innervated intrafusal fibers of mm spindle

Question 13

This pathway runs parallel to CST, originates in the supplementary motor and lateral pre motor areas, descends to pontine and medullary reticular formations, where it synapses bilaterally. Then they descend as reticulospinal fibers into the spinal cord anywhere they synapse in ventral horn on LMN

Answer 13

Corticoreticulospinal pathway

Question 14

What motor area provide information to primary motor cortex for voluntary movement?

Answer 14

Pre motor, secondary motor

Question 15

What is fractionated movement?

Answer 15

Precise individual movement (i.e., fingers)

Fine motor control

Question 16

What is activated simultaneously as fractionated movement?

Answer 16

Pre motor areas activate RF to activate reticulospinal fibers to activate axial and proximal limb mm.
This cause movement in anticipation of fractionated movement

Question 17

Which pathway carries out volitional movements for the body?

Answer 17

Corticospinal

Question 18

What is activated simultaneously as fractionated movement?

Answer 18

RF. (Movement in anticipation of fractionated movement)

Question 19

Upper motor neuron Pontine (medial) reticulospinal pathway

Answer 19

Primarily ipsilateral and facilitory to axial and limb musculature, especially the extensor stand works with the medial vestibulospinal tract

Question 20

UMN Medullary (lateral) reticulospinal pathway

Answer 20

Bilateral (greater ipsilateral) and is facilitory to flexor muscles and inhibitory to axial and limb extensor mm.

Question 21

UMN Lateral vestibulospinal pathway

Answer 21

Ipsilateral and excitatory on extensor so of LE (inhibits flexor mm)

Question 22

UMN Medial vestibulospinal pathway

Answer 22

Bilateral and descends only to cervical and upper thoracic. Control of neck and upper thoracic musculature

Question 23

UMN Tectospinal pathway

Answer 23

Only to cervical and coordinates neck met toward a stimulus

Question 24

UMN Rubiospinal pathway

Answer 24

Contralateral and goes the whole length of spine. However, in bipedal locomotion, this tract is diminished in importance and functions mostly at the cervical level. Flexor activity of the upper extremity (primarily distal musculature and fractionated movement.

Question 25

This system is accountable for more postural movements

Answer 25

Medial activation system

Question 26

System responsible for distal limb musculature i.e. Fractionated movement

Answer 26

Lateral activation system

Question 27

Where is the medial activation system located and what does it consist of?

Answer 27

Anterior funinculus - consists of anterior corticospinal, medial reticulospinal, medial and lateral vestibulospinal, and Tectospinal

Question 28

Where is the lateral activation system located and what does it consist of?

Answer 28

Lateral funinculus - consists of lateral corticospinal, Rubiospinal, and lateral reticulospinal

Question 29

What axons are thought to function as a feedback mechanism that integrates cortical understanding of sensory information

Answer 29

Lateral corticospinal pathway carries axons from primary somatosensory cortex. They terminated in the dorsal horn.

Question 30

These pathways originate in RF nuclei (raphe nuclei, locus ceruleus) and are involved in modification of afferent sensory info at the dorsal horn level.

Answer 30

Raphe spinal pathway and cerulospinal

Question 31

What 2 pathways play a role in the modulation of incoming pain stimuli

Answer 31

Spinomescencephalic

Spinoreticular

Question 32

What is the organization of the corticobulbar system. What are the three exceptions

Answer 32

Entire motor component of cranial nerves receive bilateral corticobulbar input.
Exceptions - facial motor nucleus (facial expression)
Hypoglossal nucleus (tongue movement)
Extraocular eye muscles

Question 33

Where are the LMN of the corticobulbar system located and where do they synapse?

Answer 33

Located either ventral horn of SC or in a cranial nerve motor nucleus. They synapse on motor units of skeletal mm.

Question 34

Lesions of LMN result in what symptoms?

Answer 34

Atonia/hypotonia
Areflexia/hyporeflexia
Atrophy
Fibrillations

Question 35

Where are UMN located? Where do axons synapse?

Answer 35

Supra segmental levels of CNS

They synapse in the ventral horn or cranial nerve motor nucleus on interneurons or motor neurons.

Question 36

Lesions of upper motor neurons result in what symptoms?

Answer 36

Initial flaccid paralysis followed by…
Abnormal cutaneous reflexes
Abnormal deep tendon reflex
Spasticity (velocity dependent hypertonia)
Abnormal timing of muscle activation (slower onset, prolonged contraction)

Question 37

Total loss of motor function

Answer 37

Paralysis

Question 38

Loss of activation of voluntary motor activity

Answer 38

Plegia - i.e., hemiplegia is loss of accurate activation of muscle activity over half of the body.

Question 39

Weakness

Answer 39

Paresis - small strokes can result in a paresis, as opposed to the plegia of a major stroke

Question 40

What occurs with Brown-Sequard Syndrome?

Answer 40

Lesion of a hemisection of the SC
Loss of proprioception on the ipsilateral side of lesion (dc/med lemn)
Loss of pain and temp on contralateral side of lesion (spinothalamic)

Question 41

Syringomyelia

Answer 41

Lesion caused by cavitation of the central canal. This encroaches upon anterior white commisure. Further ventral and lateral enlargement of the cavity will encroach upon the ventral horn, affecting LMN of axial and appendicular musculature (limbs)

Question 42

What disease attacks LMN in ventral horn of SC or cranial nerve nuclei.

Answer 42

Poliomyelitis

Question 43

Why is post-polio syndrome a current clinical concern

Answer 43

Over use of intact motor units.

Question 44

Amyotrophic Lateral Sclerosis

Answer 44

Destroys LMN in the ventral horn and brain stem nuclei (slow onset). It also destroys white matter pathways.