Exam #2: Corticonuclear Projections Flashcards

1
Q

Which cranial nerves contain motor projections?

A

V, VII, IX, X, XI, XII

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2
Q

What cranial nerves are involved in the movement of the eyes?

A

III, IV, VI

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3
Q

What are corticonuclear projections?

A

Axons that arise from neurons in the sensory & motor cortex that synapse with cranial nerve motor nuclei

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4
Q

Specifically, which areas of the brain give rise to axons that form the corticonuclear tract?

A

Precortical motor areas=

  • SMA= Brodmann’s area 6
  • PMC= Brodmann’s area 6

Primary Motor Cortex= Brodmann 4

Primary Somatosensory Cortex= Brodmann 3, 1, 2

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5
Q

What is the general function of the corticonuclear tract?

A

Production of voluntary movement in the face & head

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6
Q

What are the parts of the internal capsule?

A

Anterior limb
Genu
Posterior limb

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7
Q

Where does the corticonuclear tract course through the internal capsule?

A

1) Corona Radiata
2) Internal Capsule
- Genu & then shifts to the anterior aspect of the PL next to the corticospinal tract

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8
Q

What structures do the lenticulostriate arteries supply?

A
  • Internal capsule

- Basal Ganglia

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9
Q

What will an occlusion of the lenticulostriate arteries result in?

A

Extensive motor & sensory deficits of contralateral side of the body

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10
Q

Outline the path of the corticonuclear tract.

A

1) Layer V of the Cortex
2) Corona Radiata
3) Genu–> Posterior limb of the Internal Capsule
4) Termination at cranial nerve motor nuclei in the:
- Pons (V & VII)
- Medulla (Nucleus ambiguous= IX, X, XI)
- Cervical spinal cord

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11
Q

Where do the corticonuclear tracts synapse with the Trigeminal nerve? What do the axons of the trigeminal nerve motor nucleus innervate?

A
  • Caudal pons

- Form the roots of the motor branch of the trigeminal nerve that innervates muscles of mastication

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12
Q

Where is the facial nuclues located? What are the two parts of the facial nucleus?

A
  • Caudal pons
  • Two parts are:
    1) Upper
    2) Lower
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13
Q

What does the upper nucleus of the facial nucleus receive?

A

Bilateral projections i.e. projections from BOTH sides

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14
Q

What type of projections does the lower facial nucleus recieve?

A

ONLY contralateral projections

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15
Q

Where do the axons of the upper facial nucleus project?

A

Upper facial muscles

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16
Q

Where do the axons of the lower facial nucleus project?

A

Lower facial muscles

17
Q

Where does the facial nerve exit the brain?

A

Stylomastoid foramen

18
Q

What are the neurons of the facial nucleus considered, upper or lower?

A

Lower Motor Neurons

19
Q

What happens when there is a lesion to the ipsilateral upper motor neuron to the upper facial nucleus?

A

Minimal changes, mostly asymptomatic

*****There are projections from IPSILATERAL & CONTRALATERAL UMNs; CONTRALATERAL COMPENSATES

20
Q

What happens when there is a lesion to the contralateral upper motor neuron to the upper facial nucleus?

A

Minimal changes, mostly asymptomatic

*****There are projections from IPSILATERAL & CONTRALATERAL UMNs; IPSILATERAL COMPENSATES

21
Q

What happens when there is a lesion to the contralateral upper motor neuron to the lower facial nucleus?

A

Weakness of the lower facial muscles on the CONTRALATERAL side

22
Q

What happens when there is a lesion to BOTH of the contralateral upper motor neurons?

A

Weakness of the lower facial muscles

*This is the basis for differentiating between a stroke & Bell’s Palsy

23
Q

What differentiates a CVA from Bell’s Palsy?

A

Ability to raise bilateral eyebrows

*****If the patient CANNOT raise both eyebrows–>Bell’s Palsy

24
Q

What arteries supply the facial nucleus?

A

1) AICA

2) Basilar artery

25
Q

Describe the corticonuclear projections to the nucleus ambiguus.

A

Bilateral, but predominantly CONTRALATERAL

26
Q

Which way will to uvula deviate when there is a UMN lesion?

A

To the side of the lesion i.e.

**Lesion to RIGHT corticonuclear fibers innervating the nucleus ambiguous will result in a uvula that deviates TO THE RIGHT

27
Q

What nucleus do the corticonuclear projections to the spinal cord innervate?

A

Accessory nucleus

28
Q

Corticonuclear projections to the hypoglossal nucleus.

A

UMN corticonuclear fibers innervate the CONTRALATERAL hypoglossal nucleus

29
Q

Which direction will the protruded tongue deviate when there is a UMN lesion? Why?

A

Opposite the side of the lesion

  • Genoglossus muscle only receives contralateral projections
  • B/c of muscle fiber orientation, the normal muscle will push the tongue in the direction of the weak side
30
Q

Where are the eye fields located?

A

Frontal & Parietal Lobes

31
Q

Outline the path of the projections from the Frontal Eye Fields to CN III, IV, VI.

A

NOT corticonuclar*****

Instead there are bilateral projections to the reticular formation in the midbrain & pons. These reticular formation fibers then project to the motor nuclei of:

  • CN III Oculomotor
  • CN IV Trochlear
  • CN VI Abducent
32
Q

What is the function of the motor nuclei projects from the frontal eye fields to the motor nuclei of the oculomotor, trochlear, and abducent nerves?

A

Conjugate eye movement