Mesencephalon - Neuroanatomy Lab Spring 2025

midbrain

mesencephalon =

-tectum

-tegmentum

-crus cerebri

What are the 3 distinct regions of the mesencephalon?

Aqueduct of Sylvius

What is the fluid filled reservoir in the center of the mesencephalon?

3rd ventricle to the 4th ventricle

What does the Aqueduct of Sylvius connect?

tectum

What makes up the dorsal aspect of the mesencephalon?

tectum

What is the roof of the aqueduct of sylvius?

tegmentum

What is the floor of the aqueduct of sylvius?

crus cerebri

white matter (descending motor fibers) of the mesencephalon

no they have not -- from the same right of motor cortex/internal capsule

Have the descending fibers that run through the crus cerebri decussated?

cerebral peduncles

What are the "cables" that run in the mesencephalon?

interpeduncular fossa/cistern

What is the space that separates the cerebral peduncles?

interpeduncular fossa/cistern

The oculomotor nerve exits the mesencephalon near what structures?

-Reduced saccadic eye movements

-Superior colliculi will take over (saccades can occur just less accurate)

What happens with damage to BA 8?

periaqueductal grey matter

grey matter that surrounds the aqueduct of sylvius

resting tremors -- Parkinsons disease

if you damage the substantia nigra what presentation will you see?

they are ventral

Are the crus cerebri ventral or dorsal to the substantia nigra of the mesencephalon?

decussate

The cerebral peduncles _______ before they reach the red nucleus

SR, IR, IO, LPS, MR

CN III innervates what muscles of the eye?

sphincter and CB

parasympathetic Edinger Westphal nucleus goes to what structures of the eye?

superior colliculi

The oculomotor complex of the mesencephalon is at the level of what?

oculomotor fascicles

Before leaving the mesencephalon (entering interpeduncular fossa), what is the oculomotor nerve called?

anteriolateral and then anteriomedial

(arch out and then move medially)

In what direction do the oculomotor fascicles run?

red nucleus

The oculomotor fascicles move through what structure in the mesencephalon?

medial longitudinal fasiculus

MLF =

coordination of eye movements

What is the MLF important for?

true

True or False:

The nucleus of the cranial nerves are in a perfect column down the brainstem?

decrease

As you move down the mesencephalon, the spacing between the red nuclei will (decrease/increase)

location in the mesencephalon

Spacing between the red nuclei in a cross section helps determine what?

superior colliculus

Oculomotor complex is at the level of the _______

pupillary fibers important for conceptual light reflex of the pupil

What runs through the posterior commissure?

losing any response to light but the patient can still accommodate at nearby objects, parasympathetic fibers lost = pupil dilated

What is dorsal midbrain system?

interior colliculus

What is the ducusation point for the superior cerebellar peduncle (brachium conjunctiva) and where there is no discrimination between the 2 red nuclei in the mesencephalon?

Trochlear nerve

What cranial nerve nucleus is present in the mesencephalon at the level of the inferior colliculi?

below

In the Mesencephalon at the level of the inferior colliculus, you will have the trochlear nerve nuclei. The trochlear nerves decussation point is (above/below) the nucleus for the trochlear nerve

trochlear nerve

What is the only nerve to exit on the dorsal side of the brainstem?

left

The right trochlear nucleus creates the fibers for the _____ trochlear nerve?

right -- nerve = after it leaves the brainstem, the nerve has already decussated at this point

Right trochlear nerve goes to the (right/left) eye

away from the side of the lesion

Does a patient with a trochlear nerve palsy tilt toward or away from the side of the lesion?

-nucleus of the inferior colliculus :)

-auditory nucleus

What is the nucleus of the inferior colliculus called and what is it used for?

4th nerve (trochlear) -- back of the brainstem to the eye

The ____ nerve has the longest intracranial route?

trochlear nerve

What is the only cranial nerve to exit the back (dorsal) brainstem?

torticollis, double vision

What would be a presentation of a trochlear nerve palsy?