Midbrain I (CN 3-lvl of sup colliculus) Flashcards
where does the superior colliculus receive input from?
auditory input?
- input: retina, cerebral cortex, brainstem nuclei, and spinal cord
- auditory input: from inf colliculus to mediate audiovisual reflexes
what is the sup colliculus involved in
reflexive eye movements w/ head and neck
where does the red nucleus receive input from? where does it receive output from?
input: motor cortex and from the cerebellum
output: spinal cord, in the contralateral ventral horn gray via the rubrpsinal tract
- also sends descending projections to the inf olivary nucleus via the central tegmental tract (CTT)
what will a lesion in the red nucleus cause
tremor and ataxia (lack of motor coordination) in the contralateral body
what are the 2 layers of substantia nigra
pars compacta (dorsal) pars reticularis (ventral)
what kind of neurons does the par reticulata contain?
what does the pars compacta contain?
- neurons that project to the SC and thalamus
- compacta: darkly pigmented region that contains large dopaminergic neurons, which project to the basal ganglia
what kind of GSE fibers do the oculomotor nuclei send into the tegmentum and through large portions of the red nuclues?
wehre do they then emerge?
both uncrossed and crossed cholinergic GSE fibers ventrally into the tegmentum and through large portions of the red nucleus before emerging from the interpeducular fossa
what is the subnucleus for the levators
why is it weird
central caudal nucleus (CCN) and is unpaired
why is the subnucleus that sends out fibers to the superior recti unique
the fibers cross
is the Edinger westphal parasympathetic or sympathetic
para to ciliary ganglion for constriction and acc
what is a rubral tremor
an unusual tremor present at rest or w/ intention and it’s usually from a midbrain stroke
what does the substatia nigra pars compacta (SNc) contain
large pigmented melanin cells; projects to the striatum (basal ganglia)
where does the ventral tegmental area project to
the prefrontal cortex
what is the medial geniculate body a part of
the thalamus NOT MIDBRAIN
the 3rd nerves leave their nuclear complex to eventually innervate the striated skeletal muscle of the…
SR, IR, MR, IO and levator
where does CN 3 start at
oculomotor nuclear complex in the tegmentum of the midbrain at the level of the sup colliculus
how is innervation to the superior recti done
its crossed. WEIRD.
what happens when there is a lesion to the right Cn 3 at the right middle crus cerebri? (weber’s syndrome)
right CN 3 palsy
- damage to the right corticospinals which would cause a left (contra) spastic hemiparesis
- damage to the right corticobulbar which would cuase a left sided weakness of lower facial muscles (bc right UMN lesion)
basically…CN 3 palsy w/ contra paralysis of the boy and lower face
CN 3 exits the brainstem to enter the subarachnoid space but they specifically enter into the….
interpeduncular cistern (fossa)
when CN3 is compressed by an expanding aneurysm or by a herniating uncus why do pupil problems occur first
the dilated pupil happens first bc the pupillary fibers actually wrap around the EOM fibers
-pupillary fibers are superficial in the nerve, so an expanding aneurysm here would theortetically damage the puillary fibers first before EOm fibers
why are the pupillary fibers particularly prone to compression
w/in the subarachnoid space, the pupillary fibers travel externally and superficially making them particularly prone to compression from aneurysm or uncal herniation, and relatively less prone to damage from vascular insult like diabetes
CN 3 divides into a superior and inf division just before entering the orbit through the _______
superior orbital fissue (w/in the tendinus annulus)
-it is near the optic nerve here
what division of CN 3 do pupillary fibers travel w/
inf division of 3
what will a CN3 lesion at the brainstem do
contralateral neurologica deficits: ataxia (loss of full control of body movements), hemiparesis, tremor, UMN CN7 palsy
what will a CN 3 lesion at the subarachnoid space do
pain, dilated pupil, subhyaloid hem, incomplete or sup divisoin 3 palsy
wat will a CN 3 lesion at the cavernous sinus do
4, V1, V2, horner’s, proptosis, contralateral CN 3 palsy
what sill a CN 3 lesion at the orbit do
proptosis, optic neuropathy (CN 2)
