BRAINSTEM: MIDBRAIN

Long axis if midbrain inclines __ as it ascends through _

anteriorly

opening in tentorium cerebelli

Midbrain is traversed by a narrow channel called

cerebral aqueduct

Longest intercranial nerve

trochlear

Pos surface of medulla has

4 colliculi (corpora quadrigemina)

Corpora quadrigemina

2 superior colliculi

2 inferior colliculi

What separates the sup and inf colliculi

vertical and transverse groove

Purpose of the 2 superior colliculi

visual reflexes

Purpose of the 2 inferior colliculi

auditory centers

Small diameter n that winds around lat aspect of the midbrain to enter __

lateral wall of cavernous sinus

What emerges in the midline below the inferior colliculi

trochlear nerve

On the lateral aspect of the midbrain the __ and _ ascend in an anterolateral direction

superior and inferior brachia

Where does the superior brachium pass and where does it go

Superior colliculus

LGB & optic tract

What does the inferior brachium connect

inferior colliculus to MGB

Deep depression in the midline of ant aspect of midbrain

Interpeduncular fossa

Interpeduncular fossa is bounded by __ on either side

crus cerebri

Many BV perforate the floor of the __ and is called

Interpeduncular fossa

Pos perforated substance

This nerve emerges from a groove on the medial side of the crus cerebri and passes forward in the lateral wall of the cavernous sinus

Oculomotor nerve

Lateral halves of the midbrain are called

cerebral peduncles

Divisions of the cerebral peduncles & by what

anterior part: crus cerebri

posterior part: tegmentum and tectum

substantia nigra

Substantia nigra produces

dopamine

Part of the midbrain posterior to the cerebral aquedut

tectum

Narrow cavity of the midbrain

cerebral aqueduct

T or F: tegmentum is not continuous across the median plane

tegmentum

The interpeduncular fossa separates the crus cerebri at what plane

transverse plane

T or F: The inferior coliculus has small nucleus of gray matter

False

Largge

What fibers do the inf colliculus receive

terminal fibers of lateral lemniscus

Terminal fibers of lat lemniscus → inf colliculus → continues through __ to _

inferior brachium to MGB

Lies posterior to MLF

Trochlear n

Trochlear nerve in relation to central gray matter

go lat and pos around central gray matter

Where does the trochlear nerve leave the midbrain

below inferior colliculi

Decussation of trochlear nerve

superior medullary velum

Pathway of trochlear nerve

Pos to MLF → Lat and Pos around central gray matter → Leaves midbrain below inferior colliculi → decussates completely @ sup medullary velum

Mesencephalic nuclei of trigeminal nerve in relation to cerebral aqueduct

lateral

Where is the decussation of superior cerebellar peduncle

central part of tegmentum and to cerebral aqueduct

Reticular formation is __ to decussation

lateral

Where is the reticular formation larger: Pons or midbrain

Pons

Which is more posterior: med lemniscus or substantia nigra

med lemniscus

What is lateral to the medial lemniscus

spinal and trigeminal lemnisci

What is posterior to the trigeminal lemniscus

lateral lemniscus

Large motor nucleus bw tegmentum and crus cerebri

substantia nigra

neurons of substantia nigra

medium multipolar neurons

Purpose of substantia nigra

muscle tone

Contains important descending tracts

crus cerebri

What separates the crus cerebri and tegmentum

substantia nigra

Fibers of the crus cerebri

Corticospinal and corticonuclear fibers

• middle 2/3 of crus

frontopontine fibers

• medial part of crus

temporopontine fibers

• lateral crus

Afferent fibers in superior colliculi from

tectospinal and tectobulbar tracts

Responsible for mvmt of eyes head neck in response to visual stimuli

tectospinal and tectobulbar tracts

Afferent pathway for light reflex

ends in pretectal nucleus → edinger westphal nucleus (oculomotor n) → oculumotor n

What lemnisci does not extend superiorly to the level of the superior colliculus

lateral lemnisci

Where is red nucleus located

bw cerebral aqueduct & substantia nigra

Red nucleus is red d/t

vascularity and iron pigment

Afferent fibers go to red nucleus through __ and through

1. cerebral cortex - corticospinal fibers

2. cerebellum - sup peduncle

3. Lentiform, subthalamic, hypothalamic nuclei, substantia nigra, spc

Efferent fiber leave red nucleus through

1. Spc through rubrospinal (deccusates as it descends)

2. Reticular formation trough rubroreticular tract

3. Thalamus

4. Substantia nigra

Reticular formation in relation to red nucleus

In tegmentum lateral and pos to red nucleus

Crus cerebri contains what tracts

corticospinal, corticonuclear, corticopontine fibers