Midbrain

Question 1

Which cranial nerve arises from midbrain dorsally? Ventromedially?

Answer 1

Dorsally - IV

Ventromedially - III

Question 2

Two characteristic levels of midbrain

Answer 2

Inferior and superior colliculus

Question 3

Two major modulating nuclei of midbrain

Answer 3

Substantia nigra

Red nucleus

Question 4

Inferior Colliculus

Important for _____ pathways.

Inputs from ______ that originate from ___ and ____

Outputs to _____

Answer 4

Auditory

Inputs from: Lateral lemniscus - from superior olivary nucleus of pons and cochlear nuclei of medulla

Outputs to: medial geniculate nucleus of thalamus

Question 5

What area surrounding cerebal aqueduct is rich in enkephalins for modulation of autonomics and pain?

Which colliculi is it present in?

Answer 5

Periaqueductal Grey

Both inferior and superior colliculi

Question 6

In inf colliculus:

Controls superior oblique muscle of eye; axons exit dorsally just inferior to inf. colliculus

Answer 6

Nucleus of CN IV

Question 7

In inf colliculus:

Feeds from vestibular nuclei to nucleus of IV; located immediately ventral to IV

Answer 7

MLF - medial longitudinal fasciculus

Question 8

In inf colliculus:

Contains reticular formation - serotonin fibers which regulate wakefulness

Answer 8

Central tegmental area

Question 9

In inf colliculus:

Where does decussation of superior cerebellar peduncle travel?

Answer 9

To red nucleus and ventrolateral nucleus of thalamus

Question 10

In inf/sup colliculus:

Medial 1/5 of crus cerebri?

Answer 10

Frontopontine fibers

Question 11

In inf/sup colliculus:

Middle 3/5 of crus cerebri?

Answer 11

Corticobulbar (medially) and corticospinal (laterally) fibers

Question 12

In inf/sup colliculus:

Lateral 1/5 of crus cerebri from what lobes

Answer 12

Parietal, occipital, and temporal lobes to pontine nuclei

Question 13

In inf/sup colliculus:

Medial part of substantia nigra that has dopamine fibers to basal ganglia?

Answer 13

Pars compacta- important in Parkinson’s

Question 14

In inf/sup colliculus:

Lateral part of substantia nigra that has GABA fibers to thalamus

Answer 14

Pars reticulata

Question 15

If you see this nucleus, you know you are at the level of superior colliculus.

Answer 15

Red nucleus

Question 16

Superior Colliculus

Important for ____ pathways.

Inputs from ____.
Outputs to ____ via ____ for coordination of visual tracking.

Answer 16

Visual pathways

Inputs: retina
Outputs: to cervical muscles via tectospinal tract

Question 17

In sup colliculus:

• Contains both somatic GSE and autonomic GVE fibers; axons exit ventromedially, anterior to pons

Answer 17

Nucleus of CN III

Question 18

In sup colliculus:

• Feeds from vestibular nuclei to nucleus of III, located immediately ventral to III

Answer 18

MLF - medial longitudinal fasiculus

Question 19

In sup colliculus:

Important source of dopaminergic fibers to forebrain, adjacent to pars compacta

Answer 19

Ventral tegmental area

Question 20

In sup colliculus:

Receives fibers from superior cerebellar peduncle and projects to flexor muscles and inf. olivary nucleus

Answer 20

Red nucleus

Question 21

What two structures do you see at extreme rostral end of midbrain?

Answer 21

Pretectal area:

• Edinger Westphal nucleus (presynaptic parasymp fibers of III to ciliary ganglion)
• Posterior commissure for coordinated mvt of both eyes

Question 22

What syndrome?

Ipsilateral oculomotor paralysis w/ contralateral upper motor neuron lesion. Results from vascular insufficiency in medial aspect of midbrain at sup. colliculus.

Answer 22

Weber’s syndrome

Question 23

What syndrome?

Ispilateral III paralysis w/ contralateral tremor and possible contralateral somatosensory loss. Results from vascular lesion to III and red nucleus and superior cerebellar peduncle and medial lemniscus (dorsal columns), as well as possible spinothalamic tract.

Answer 23

Benedikt’s syndrome

Question 24

What syndrome?

Pineal tumor affects pretectal area and posterior commissure. Results in upward gaze paralysis - vertical gaze - large pupil and abnormal elevation of upper eyelid, paralysis of accomodation

Answer 24

Gaze palsy - Parinaud’s syndrome