Exam #2: Corticonuclear Projections Flashcards
Which cranial nerves contain motor projections?
V, VII, IX, X, XI, XII
What cranial nerves are involved in the movement of the eyes?
III, IV, VI
What are corticonuclear projections?
Axons that arise from neurons in the sensory & motor cortex that synapse with cranial nerve motor nuclei
Specifically, which areas of the brain give rise to axons that form the corticonuclear tract?
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
What is the general function of the corticonuclear tract?
Production of voluntary movement in the face & head
What are the parts of the internal capsule?
Anterior limb
Genu
Posterior limb
Where does the corticonuclear tract course through the internal capsule?
1) Corona Radiata
2) Internal Capsule
- Genu & then shifts to the anterior aspect of the PL next to the corticospinal tract
What structures do the lenticulostriate arteries supply?
- Internal capsule
- Basal Ganglia
What will an occlusion of the lenticulostriate arteries result in?
Extensive motor & sensory deficits of contralateral side of the body
Outline the path of the corticonuclear tract.
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
Where do the corticonuclear tracts synapse with the Trigeminal nerve? What do the axons of the trigeminal nerve motor nucleus innervate?
- Caudal pons
- Form the roots of the motor branch of the trigeminal nerve that innervates muscles of mastication
Where is the facial nuclues located? What are the two parts of the facial nucleus?
- Caudal pons
- Two parts are:
1) Upper
2) Lower
What does the upper nucleus of the facial nucleus receive?
Bilateral projections i.e. projections from BOTH sides
What type of projections does the lower facial nucleus recieve?
ONLY contralateral projections
Where do the axons of the upper facial nucleus project?
Upper facial muscles
Where do the axons of the lower facial nucleus project?
Lower facial muscles
Where does the facial nerve exit the brain?
Stylomastoid foramen
What are the neurons of the facial nucleus considered, upper or lower?
Lower Motor Neurons
What happens when there is a lesion to the ipsilateral upper motor neuron to the upper facial nucleus?
Minimal changes, mostly asymptomatic
*****There are projections from IPSILATERAL & CONTRALATERAL UMNs; CONTRALATERAL COMPENSATES
What happens when there is a lesion to the contralateral upper motor neuron to the upper facial nucleus?
Minimal changes, mostly asymptomatic
*****There are projections from IPSILATERAL & CONTRALATERAL UMNs; IPSILATERAL COMPENSATES
What happens when there is a lesion to the contralateral upper motor neuron to the lower facial nucleus?
Weakness of the lower facial muscles on the CONTRALATERAL side
What happens when there is a lesion to BOTH of the contralateral upper motor neurons?
Weakness of the lower facial muscles
*This is the basis for differentiating between a stroke & Bell’s Palsy
What differentiates a CVA from Bell’s Palsy?
Ability to raise bilateral eyebrows
*****If the patient CANNOT raise both eyebrows–>Bell’s Palsy
What arteries supply the facial nucleus?
1) AICA
2) Basilar artery
Describe the corticonuclear projections to the nucleus ambiguus.
Bilateral, but predominantly CONTRALATERAL
Which way will to uvula deviate when there is a UMN lesion?
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
What nucleus do the corticonuclear projections to the spinal cord innervate?
Accessory nucleus
Corticonuclear projections to the hypoglossal nucleus.
UMN corticonuclear fibers innervate the CONTRALATERAL hypoglossal nucleus
Which direction will the protruded tongue deviate when there is a UMN lesion? Why?
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
Where are the eye fields located?
Frontal & Parietal Lobes
Outline the path of the projections from the Frontal Eye Fields to CN III, IV, VI.
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
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?
Conjugate eye movement
