Mesencephalon

Why can you get cerebral aquaduct and 3rd ventricle in the same section?

because cross section at midbrain is diagonal

What is the dorsal aspect of the. midbrain?

tectum

What is the ventral aspect of the midbrain?

most ventral: crus cerebri

general ventral: cerebral peduncles

What is the roof of the midbrain?

tectum

What is the floor of the midbrain?

crus cerebri

What is in the center of the midbrain?

tegmentum

What type of fibers does the tegmentum of the midbrain have?

ascending sensory

What are the cerebral peduncles?

bundles of fibers from the crus cerebri + part of the tegmentum of the midbrain

What kind of fibers does the crus cerebri have?

descending motor fibers from internal capsule

What is the interpeduncular fossa/cistern of the midbrain?

accumulation of CSF between the cerebral peduncles

What does the tectum of the midbrain contain?

4 colliculi (2 superior + 2 inferior)

What are the 4 colliculi of the midbrain called?

corpa quadragemina

What does the superior colliculus do?

does saccades

What is the superior colliculus called in lower animals?

optic tectum

What does the inferior colliculus do?

auditory

If you do a midsagittal section of the midbrain, what will you not see?

colliculi

What is the periaquaductal grey? What part of the midbrain is it in?

grey matter surrounding cerebral aquaduct

part of both tectum + tegmentum

What is the cerebral aquaduct also called?

Aquaduct of sylvius

Where is the red nucleus located?

midbrain, rostral to superior colliculus

What won't you see in a cross section of the midbrain at level of inferior colliculus?

red nucleus

interpeduncular fossa

Where does the red nucleus receive info from?

fibers from the cerebellum

What is the substantia nigra?

part of the basal ganglia,

stripe of grey matter in midbrain with lots of melanin

What would damage to the substantia nigra cause?

resting tremor (damage to basal ganglia)

When can you see CN III complex in a cross section?

cross section of midbrain @ level of superior colliculus

What would damage to the crus cerebri cause?

spastic paralysis

Where is the CN III complex located?

in tegmentum section of periaquaductal grey matter @ level of superior colliculus

Where does CN III leave the midbrain?

@ interpeduncular fossa

Right red nucleus receives fibers from where?

left cerebellum

The fibers running from the cerebellum to red nucleus are called?

superior cerebellar peduncles

What would damage to the red nucleus cause?

cerebellar ataxia [intention tremor] (to contralateral cerebellum)

What runs between the two superior cerebellar peduncles?

superior medullary vellum

Where is CN IV nucleus located?

tegmentum portion periaquaductal grey at level of inferior colliculus

Where do CN IV fascicles run?

leave nucleus + run around periaquaductal grey + come off back of brain stem

What is the only cranial nerve to exit at the back of the brainstem?

CN IV

Where does CN VI exits the brainstem relative to its nucleus?

caudal (inferior)

Where does CN IV decussate?

in the brainstem @ apex of superior medullary vellum

Damage to right CN IV nucleus would cause what?

left superior oblique palsy

damage to right CN IV nerve would cause what?

right superior oblique palsy

CN IV exits the brainstem close to what structure? Why is this important?

tentorium cerebelli

with injury causing brain to side back, tentorium cerebelli can really damage CN IV causing bilateral 4th nerve palsy

What is the #1 and #2 cause of 4th nerve palsy?

1. trauma

2. diabetes

If you take a section of the mesencephalon at the level of the third ventricle, what can you see? What can't you see?

corpus callosum

fornix

pulvinar

Red nucleus

CN III nerve fiber

interpeduncular fossa

CANNOT see:

tectum or any colliculi

cerebral aqueduct

If you take a section of the mesencephalon at the level of the posterior commissure, what can you see? What can't you see?

3rd ventricle in 2 areas

pulvinar

MGN + LGN

posterior commissure

red nucleus

pons

Cannot see:

tectum/colliculi

cerebral aquaduct

If the cross section of the midbrain does not have tectum in it, what will you NEVER see?

never see cerebral aquaduct

If you see CN III nucleus in cross section, where are you at?

midbrain @ level of superior colliculus

What can you see above the superior colliculus in cross section?

pineal gland

What non-midbrain structures can you see in a cross-section of the midbrain?

pulvinar

LGN

MGN

When can you see the superior cerebellar peduncles decussate?

in cross section of midbrain at level of inferior colliculus

If you take a cross section moving down midbrain starting at inferior colliculus, what does the cerebral peduncles do?

move lateral, inferior, dorsal

If you take a cross section moving down midbrain above inferior colliculus, what does the cerebral peduncles do?

move medial, inferior, dorsal

Why can't you see the interpeduncular fossa @ level of inferior colliculus?

base of pons takes up that space

What is lateral to the CN IV nucleus?

medial longitudinal fasiculus

What does the MLF do?

connects CN III, IV, VI, VIII + proprioceptors of neck to coordinate eye movement with neck movement + vestibular system

What does damage to the MLF cause?

transient diplopia: double vision with eye movement

What is transient diplopia associated with MLF damage due to?

phase lag