CNS Unit 10 Eye movements and Brainstem pt. 3 Flashcards
What muscles does the Oculomotor Nerve Innervate?
CN 3
- Levator Palpebae
- Superior Rectus
- Inferior Rectus
- Middle Rectus
- Inferior Oblique
The oculomotor nerve has a parasympathetic function. What is the name of the Accessory Parasympathetic Nucleus?
What is this for?
Edinger-Westphal Nucleus
This is for Pupil Constriction
What is the difference between Direct Response and Consensual (Indirect) Response in terms of pupil constriction?
If light is shined on the Right eye and the Right eye constricts, this is called Direct Response. On the opposite eye its called the Consensual (Indirect) Response.
What is the Accommodation-Convergence Reflex in the eye?
This is when there is a change in shape of the lens and constriction of pupil, while the eyes move in to focus on the near object
Example: Holding a pen in front of your face and looking at the wall then switching to looking at the pen.
What would happen if CN 3 were damaged?
- The eye would deviate laterally
- The pt would have Diplopia (Blurred Vision)
- The pt would have Ptosis (Drooping eyelid)
- The pupil will not constrict (But this wont affect the contralateral side)
Both the Pupilary and Accommodation-convervence reflex will be affected on the ipsilateral side
What is the function of the Trochlear Nerve?
CN 4
Motor to Superior Oblique
Where is the nucleus for the Trochlear Nerve found?
Found in the Periaqueductal Gray at the level of Inferior Colliculus
How does the Trochlear Nerve leave to get to the Superior Oblique muscle?
Leaves posterior and wraps around to the ventral side of cerebral peduncle into cavernous sinus area then into Superior Orbital Fissue then to the Superior Oblique muscle
What would happen if the Trochlear Nerve were damaged?
- There would be difficulty moving the eye down and laterally
- There may be a vertical/medial strabisums or vertical diplopia
What is the Function of the Abducens Nerve?
CN 6
Motor to Lateral Rectus
Where is the nucleus for Abducens Nerve found?
The nuclei is found in the pons below the floor of the 4th ventricle near the Facial Colliculus
How does the Abducens exit to get to the Lateral Rectus?
Exits at Pontomedullary Junction and travels through cavernous sinus area and then through the Superior Orbital Fissue to the Lateral Rectus
What would happen if the Abducens Nerve were to be damaged?
- There would be difficulty turning the eye outward (laterally)
- Leads to medial strabismus or diplopia
What test is very good at testing the different CN of they eye along with the muscles?
The “H” Test
When the Eye is Abducted, what does the Superior Rectus act as?
The Superior Rectus acts as a Pure Elevator when the eye is abducted
When the eye is Abducted, what does the Inferior Rectus act as?
The Inferior Rectus acts as a Pure Depressor when the eye is abducted
When the eye is Adducted, what does the Superior Oblique act as?
The Superior Oblique acts as a Pure Depressor when the eye is adducted
When the eye is Adducted, what does the Inferior Oblique act as?
The Inferior Oblique acts as a Pure Elevator when the eye is adducted
What are the Main Components of the Brainstem?
- Cranial Nerves
- Long Tracts (Motor and Sensory Pathways)
- Reticular Formation (The core of the brainstem)
- Cerebellum
On the Ventral side, what CN is associated with the Midbrain?
Oculomotor Nerve
On the Dorsal side, what CN is associated with the Midbrain?
Trochlear Nerve
What are the 3 main areas of the Midbrain?
Tectum, Tegmentum, and Basis
- The Tectum is the “roof”, its a cut of either the superior or inferior colliculi
- The Tegmentum makes the bulk of the midbrain, here you find the red nucleus
- The Basis is the most ventral portion, this is where we have a large collectionof fibers for the corticobulbar and corticospinal tracts
(Corticobulbar pathways carrying info from the cortex to brainstem;
Corticospinal is info carried from cortex to spinal cord-motor info)
What are the Myelin-Stained sections of the Midbrain at the level of the Superior Colliculi?
- Edinger-Westphal Nucleus (CN 3)
- Oculomotor Nucleus
- Mesencephalic Trigeminal Nucleus (CN 5)
- Red Nucleus
What are the Myelin-Stained sections of the Midbrain at the level of the Inferior Colliculi?
- Trochlear Nucleus
- Fascicles of Trochlear nerve
- Superior Cerebellar Peduncle and Decussation
In the Midbrain what is the function of th Periaqueductal Gray?
Pain Modulation
Associated with the Spinothalamic Tract
On the Ventral side, what CN is associated with the Pons?
- Trigeminal (V)
- Abducens (VI)
- Facial (VII)
- Vestibulocochlear (VIII)