Midbrain Flashcards
Which cranial nerve arises from midbrain dorsally? Ventromedially?
Dorsally - IV
Ventromedially - III
Two characteristic levels of midbrain
Inferior and superior colliculus
Two major modulating nuclei of midbrain
Substantia nigra
Red nucleus
Inferior Colliculus
Important for _____ pathways.
Inputs from ______ that originate from ___ and ____
Outputs to _____
Auditory
Inputs from: Lateral lemniscus - from superior olivary nucleus of pons and cochlear nuclei of medulla
Outputs to: medial geniculate nucleus of thalamus
What area surrounding cerebal aqueduct is rich in enkephalins for modulation of autonomics and pain?
Which colliculi is it present in?
Periaqueductal Grey
Both inferior and superior colliculi
In inf colliculus:
Controls superior oblique muscle of eye; axons exit dorsally just inferior to inf. colliculus
Nucleus of CN IV
In inf colliculus:
Feeds from vestibular nuclei to nucleus of IV; located immediately ventral to IV
MLF - medial longitudinal fasciculus
In inf colliculus:
Contains reticular formation - serotonin fibers which regulate wakefulness
Central tegmental area
In inf colliculus:
Where does decussation of superior cerebellar peduncle travel?
To red nucleus and ventrolateral nucleus of thalamus
In inf/sup colliculus:
Medial 1/5 of crus cerebri?
Frontopontine fibers
In inf/sup colliculus:
Middle 3/5 of crus cerebri?
Corticobulbar (medially) and corticospinal (laterally) fibers
In inf/sup colliculus:
Lateral 1/5 of crus cerebri from what lobes
Parietal, occipital, and temporal lobes to pontine nuclei
In inf/sup colliculus:
Medial part of substantia nigra that has dopamine fibers to basal ganglia?
Pars compacta- important in Parkinson’s
In inf/sup colliculus:
Lateral part of substantia nigra that has GABA fibers to thalamus
Pars reticulata
If you see this nucleus, you know you are at the level of superior colliculus.
Red nucleus
Superior Colliculus
Important for ____ pathways.
Inputs from ____.
Outputs to ____ via ____ for coordination of visual tracking.
Visual pathways
Inputs: retina
Outputs: to cervical muscles via tectospinal tract
In sup colliculus:
- Contains both somatic GSE and autonomic GVE fibers; axons exit ventromedially, anterior to pons
Nucleus of CN III
In sup colliculus:
- Feeds from vestibular nuclei to nucleus of III, located immediately ventral to III
MLF - medial longitudinal fasiculus
In sup colliculus:
Important source of dopaminergic fibers to forebrain, adjacent to pars compacta
Ventral tegmental area
In sup colliculus:
Receives fibers from superior cerebellar peduncle and projects to flexor muscles and inf. olivary nucleus
Red nucleus
What two structures do you see at extreme rostral end of midbrain?
Pretectal area:
- Edinger Westphal nucleus (presynaptic parasymp fibers of III to ciliary ganglion)
- Posterior commissure for coordinated mvt of both eyes
What syndrome?
Ipsilateral oculomotor paralysis w/ contralateral upper motor neuron lesion. Results from vascular insufficiency in medial aspect of midbrain at sup. colliculus.
Weber’s syndrome
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.
Benedikt’s syndrome
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
Gaze palsy - Parinaud’s syndrome
