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DPT704: Neuro Hank > Coticospinal and Corticobulbar Pathways > Flashcards

Coticospinal and Corticobulbar Pathways Flashcards

1
Q

What kind of movements are carried out by the corticospinal tract and corticobulbar (corticonuclear) tracts?

A

volitional

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2
Q

Corticospinal tract is responsible for the ___ and Corticobulbar (corticonuclear) tracts for the ___.

A

Corticospinal tract is responsible for the BODY and Corticobulbar (corticonuclear) tracts for the CRANIAL NERVE MOTOR NUCLEI THAT INNERVATE MUSCLES OF THE FACE.

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3
Q

These pathways arise in the ____

A

cerebral cortex

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4
Q

descend through the ____

A

internal capsule

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5
Q

to end in the ____ or ____

A

brainstem motor nuclei or the ventral horn of the spinal cord.

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6
Q

Most fibers descending to the spinal cord cross in the ____ at the _____.

A

lower medulla at the pyramidal decussation.

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7
Q

The remainder of the fibers descend ____ to ____ and then cross.

A

ipsilaterally to individual segments.

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8
Q

This organization describes how volitional movement on the left side of the body is controlled by the ___ side of the brain; and the right side of the body to be controlled by the ___ side of the brain.

A

This organization describes how volitional movement on the left side of the body is controlled by the RIGHT side of the brain; and the right side of the body to be controlled by the LEFT side of the brain. (CONTRALATERAL)

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9
Q

Sensory information from the left side of the body ____ of the brain, and information from the right side of the body ___ of the brain.

A

Sensory information from the left side of the body CROSSED AND ASCENDED TO END IN THE RIGHT SIDE of the brain,

and information from the right side of the body CROSSED AND ASCENDED TO END IN THE LEFT SIDE of the brain.

(CONTRALATERAL)

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10
Q

voluntary motor pathway for the body

A

corticospinal tract

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11
Q

For the corticospinal pathway, primary cells of origin are located in the ____

A

precentral gyrus (primary motor cortex; area 4)

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12
Q

For the corticospinal pathway, there are also neurons found in ___ (3)

A
  1. area 6 (premotor region; lateral premotor and supplementary motor)
  2. area 8 (frontal eye fields)
  3. and also to a lesser extent in the primary somatosensory cortex (areas 3,1,2)
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13
Q

The fibers that make up the corticospinal tract exit the ___ of the ____

A

gray matter of the cortex

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14
Q

and travel through the ____

A

medullary white matter (the fiber bundles underlying the cortex.

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15
Q

What are included in the medullary white matter in sequence? (5)

A
  1. Corona Radiata
  2. Posterior Limb of the Internal Capsule
  3. Cerebral Peduncles
  4. Corticospinal Fibers (in the ventral pons)
  5. Pyramids (medulla)
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16
Q

At the lower end of the medulla, 85% of the fibers cross at the ____

A

Pyramidal decussation

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17
Q

these 85% then continue their descent as the ____ located in the ____.

A

lateral corticospinal tract (located in the lateral funiculus)

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18
Q

The remaining 15% of fibers that do not cross, descend as the ____ located in the ____.

A

anterior corticospinal tract (located in the anterior funiculus)

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19
Q

These latter fibers then cross at the ____ where the innervate the ____

A

segmental level where they innervate the lower motor neuronal pool.

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20
Q

The organization of the fibers as they descend is ____

A

topographically arranged

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21
Q

The termination of corticospinal fibers is primarily on ____.

A

interneurons (97%)

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22
Q

The majority of the corticospinal fibers terminate in the ____

A

cervical region (55%)

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23
Q

and lesser numbers terminate in the ____ and ___.

A

thoracic region (20%) and lumbosacral region (25%) regions

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24
Q

It is the interneurons that then excite or inhibit ___ to influence activity of a given motor unit.

A

lower motor neurons (neurons in the ventral horn that make up the ventral root)

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25
Q

Lower motor neurons that are responsible for activation of extrafusal muscle fibers (volitional movements) are termed

A

alpha motor neurons

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26
Q

alpha motor neurons are the final common pathway to the ___ or ____.

A

muscle or effecter organ

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27
Q

Lower motor neurons that innervate intrafusal muscle fibers of the muscle fiber are termed

A

gamma motor neurons

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28
Q

____ runs parallel to the corticospinal tract.

A

Corticoreticulospinal pathway

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29
Q

The cells giving rise to the corticoreticulospinal pathways are located in the ____ and ___ areas.

A

supplementary motor and lateral premotor areas.

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30
Q

The axons of the corticoreticulospinal pathway descend along with the corticospinal fibers to the level of the ___ and ___.

A

pontine and medullary reticular formation

31
Q

Reticulospinal fibers then descend into the spinal cord where they synapse in the

A

ventral horn on lower motor neuron pool; primarily interneurons.

32
Q

What are the Corticoreticulospinal pathway providing information from and to?

A

premotor and secondary motor areas provide the information to primary motor cortex for voluntary movement.
The information from the primary cortex then descends distally on the extremities, i.e. the fingers.

33
Q

The information from Corticoreticulospinal pathways is used for

A

The information from the primary cortex the descends for fine motor control distally on the extermities, i.e. the fingers.
This precise individual movement is termed fractionated movement.

34
Q

At the same time, what are the Corticoreticulospinal pathway activating besides fractionated movement?

A

At the same time, these premotor areas are activating the reticular formation and subsequently reticulospinal fibers.

35
Q

What does this activation reticular formation and subsequently reticulospinal fibers do?

A

The information is then 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 fractionated movement.

36
Q

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

a. Pontine (medial) reticulospinal pathway
b. Medullary (lateral) reticulospinal pathway
c. Lateral vestibulospinal pathway
d. Medial vestibulospinal pathway
e. Tectospinal pathway
f. Rubrospinal pathway

A

a. Pontine (medial) reticulospinal pathway

37
Q

descends only to cervical levels and coordinates neck movement towards stimulus

a. Pontine (medial) reticulospinal pathway
b. Medullary (lateral) reticulospinal pathway
c. Lateral vestibulospinal pathway
d. Medial vestibulospinal pathway
e. Tectospinal pathway
f. Rubrospinal pathway

A

e. Tectospinal pathway

38
Q

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

a. Pontine (medial) reticulospinal pathway
b. Medullary (lateral) reticulospinal pathway
c. Lateral vestibulospinal pathway
d. Medial vestibulospinal pathway
e. Tectospinal pathway
f. Rubrospinal pathway

A

b. Medullary (lateral) reticulospinal pathway

39
Q

projects bilaterally and descends only to cerbical and upper thoracic levels. Contol of neck and upper thoracic musculature.

a. Pontine (medial) reticulospinal pathway
b. Medullary (lateral) reticulospinal pathway
c. Lateral vestibulospinal pathway
d. Medial vestibulospinal pathway
e. Tectospinal pathway
f. Rubrospinal pathway

A

d. Medial vestibulospinal pathway

40
Q

ipsilateral and excitatory on extensors of lower extremity musculature (inhibits flexor musculature).

a. Pontine (medial) reticulospinal pathway
b. Medullary (lateral) reticulospinal pathway
c. Lateral vestibulospinal pathway
d. Medial vestibulospinal pathway
e. Tectospinal pathway
f. Rubrospinal pathway

A

c. Lateral vestibulospinal pathway

41
Q

contralteral and described as descending the entire length of the cord. However, in bipedal locomotion this tract has diminished in importance and functions mostly at the cervical level. Current thinking is that in humans this pathway is involved in flexor activation of the upper extermity, primary distal musculature and plays a role in fractionated movments.

a. Pontine (medial) reticulospinal pathway
b. Medullary (lateral) reticulospinal pathway
c. Lateral vestibulospinal pathway
d. Medial vestibulospinal pathway
e. Tectospinal pathway
f. Rubrospinal pathway

A

f. Rubrospinal pathway

42
Q

How is the differentiation primarily defined for Medial vs. Lateral Activation Systems?

A

by the location of the axons of the upper motor neurons.

43
Q

Which activation pathways are involved in more postural movements and activities?

A

Medial Activation Pathways (named for both their position in the cord and their function)

44
Q

Which activation system is more involved with distal limb musculature, i.e., fractionated movement?

A

Lateral Activation System

45
Q

Where is the medial activation system located?

A

in the anterior funiculus

46
Q

What pathways does the medial activation system consist of? (4)

A
  1. anterior corticospinal
  2. medial reticulospinal
  3. medial and lateral vestibulospinal
  4. tectospinal
47
Q

Where is the lateral activation system located?

A

in the lateral funiculus

48
Q

What pathways does the lateral activation system consist of? (3)

A
  1. lateral corticospinal
  2. rubrospinal
  3. lateral reticulospinal pathways
49
Q

Other Descending Components: Where does the primary somatosensory cortex send axons?

A

caudally through the lateral corticospinal pathway.

50
Q

Other Descending Components: where do these axons terminate?

A

dorsal horn

51
Q

Other Descending Components: how are they thought to function?

A

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

52
Q

Where do the Raphespinal and Cerulospinal pathways originate?

A

in reticular formation nuclei - Raphae nuclei and Locus Ceruleus

53
Q

What are the Raphespinal and Cerulospinal pathways involved in?

A

modification of afferent sensory information at the dorsal horn level.

54
Q

What do the Spinomesencephalic and spinoreticular pathways activate?

A

a number of reticular system components.

55
Q

What do the descending Spinomesencephalic and spinoreticular pathways play a role in?

A

modulation of incoming pain stimuli

56
Q

The entire motor component of cranial nerves (both sides) receives (IPSILATERAL/BILATERAL) corticobulbar input?

A

Bilateral

57
Q

What does bilateral corticobulbar input mean in respect to strokes damaging the descending control?

A

We have the ability of one corticial side to influence activity of Lower Motor Neurons, kind of a backup system.

58
Q

What are the exceptions of bilateral corticobulbar input? (2)

A

Cortical control of

  • Facial Motor Nuucleus (muscles of facial expression)
  • Hypoglossal Nucleus (muscles controlling tongue movment)
59
Q

Where are Lower Motor Neruons located?

A

either in the Ventral Horn of the spinal cord or in a Cranial Nerve Motor Nucleus

60
Q

The axon of a lower motor neuron cell body leaves the spinal cord or brainstem to

A

innervate motor units of skeletal muscle.

61
Q

Lower Motor Neurons and ___ make up the peripheral nerves dissected in anatomy.

A

sensory axons

62
Q

Lesions of lower motor neurons (damage to axon or cell body) classically are described as resulting in the following symptoms: (4)

A
  1. Flaccid paralysis (atonia or hypotonia)
  2. Areflexia or hyporeflexia
  3. Atrophy of muscle (muscle wasting)
  4. Fasiculations and fibrillations
63
Q

Where are Upper Motor Neurons cell bodies located? Where do their axons end?

A

neurons whose cell bodies are located in the suprasegmental levels of the CNS with axons that end in the ventral horn or cranial nerve motor nucleus.

64
Q

What do UMN synapse on?

A

interneurons or alpha or gamma motor neurons

65
Q

Upper Motor Neuron lesions (damage to descending fiber tracts classified as UMN) clinically are described as resuling in the following symptoms: (5)

A

Initial flaccid paralysis followed by:

  1. Abnormal cutaneous reflexes (Babinski sign)
  2. Abnormal reflexes (clonus, clasp knife)
  3. Spasticitiy - velocity dependent hypertonia
  4. Abnormal timing of muscle activation (slower onset, prolonged contration)
  5. Paresis or plegia (weakness)
66
Q

Define Paralysis?

A

total loss of motor function

67
Q

Define -plegia

A

A loss of activation of voluntary motor activity sometimes incorrectly referred to as paralysis; i.e., hemiplegia is a loss of accurate activation of muscle activity over half of the body.

68
Q

Define -paresis

A

Weakness; small strokes can result in a paresis or weakness, as opposed to the -plegia of a major stroke

69
Q

Define Brown-Sequard Syndome

A

-This lesion is a hemisection of the spinal cord.

(It is not a common occurrence, but is useful in understanding the distribution of symptoms as they relate to the ascending and descending pathways.)

70
Q

Define Syringomyelia

A
  • A lesion caused by cavitation of the central canal, the remnant of the lumen of the neural tube.
  • This lesion encroaches upon the anterior white commissure.
  • Further ventral and lateral enlargement of the cavity will then encroach upon the ventral horn, effecting LMN of axial then appendicular musculature.
71
Q

Define Poliomyelitis

A
  • Disease that attacks LMNs in the ventral horn of the spinal cord or cranial nerve nuclei.
  • This has been almost erradicated with vaccine treatment.
  • Flu-like symptoms followed by weakness (flaccid) of muscles and fasiculations.
  • Post-Polio syndome is now a clinical concern due to overuse of intact motor units.
72
Q

Define Amyotrophic Lateral Sclerosis (ALS; Lou Gehrig’s disease)

A
  • ALS is a chronic and progressive disease of unknown origin.
  • It destroys LMNs in the ventral horn and brainstem nuclei.
  • Slow in onset.
  • This disease also destroys white matter pathways.
73
Q

Define Multiple Sclerosis

A
  • Multifocal disease (can have more than one site of lesion).
  • Thought to be an autoimmune attack on myelin.
  • Disease of upper motor neurons and central myelinated pathways, as well as sensory pathways.

DPT704: Neuro Hank (14 decks)

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