Midbrain I (CN 3-lvl of sup colliculus)

Question 1

where does the superior colliculus receive input from?

auditory input?

Answer 1

• input: retina, cerebral cortex, brainstem nuclei, and spinal cord
• auditory input: from inf colliculus to mediate audiovisual reflexes

Question 2

what is the sup colliculus involved in

Answer 2

reflexive eye movements w/ head and neck

Question 3

where does the red nucleus receive input from? where does it receive output from?

Answer 3

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)

Question 4

what will a lesion in the red nucleus cause

Answer 4

tremor and ataxia (lack of motor coordination) in the contralateral body

Question 5

what are the 2 layers of substantia nigra

Answer 5

pars compacta (dorsal) 
pars reticularis (ventral)

Question 6

what kind of neurons does the par reticulata contain?

what does the pars compacta contain?

Answer 6

• neurons that project to the SC and thalamus

- compacta: darkly pigmented region that contains large dopaminergic neurons, which project to the basal ganglia

Question 7

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?

Answer 7

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

Question 8

what is the subnucleus for the levators

why is it weird

Answer 8

central caudal nucleus (CCN) and is unpaired

Question 9

why is the subnucleus that sends out fibers to the superior recti unique

Answer 9

the fibers cross

Question 10

is the Edinger westphal parasympathetic or sympathetic

Answer 10

para to ciliary ganglion for constriction and acc

Question 11

what is a rubral tremor

Answer 11

an unusual tremor present at rest or w/ intention and it’s usually from a midbrain stroke

Question 12

what does the substatia nigra pars compacta (SNc) contain

Answer 12

large pigmented melanin cells; projects to the striatum (basal ganglia)

Question 13

where does the ventral tegmental area project to

Answer 13

the prefrontal cortex

Question 14

what is the medial geniculate body a part of

Answer 14

the thalamus NOT MIDBRAIN

Question 15

the 3rd nerves leave their nuclear complex to eventually innervate the striated skeletal muscle of the…

Answer 15

SR, IR, MR, IO and levator

Question 16

where does CN 3 start at

Answer 16

oculomotor nuclear complex in the tegmentum of the midbrain at the level of the sup colliculus

Question 17

how is innervation to the superior recti done

Answer 17

its crossed. WEIRD.

Question 18

what happens when there is a lesion to the right Cn 3 at the right middle crus cerebri? (weber’s syndrome)

Answer 18

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

Question 19

CN 3 exits the brainstem to enter the subarachnoid space but they specifically enter into the….

Answer 19

interpeduncular cistern (fossa)

Question 20

when CN3 is compressed by an expanding aneurysm or by a herniating uncus why do pupil problems occur first

Answer 20

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

Question 21

why are the pupillary fibers particularly prone to compression

Answer 21

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

Question 22

CN 3 divides into a superior and inf division just before entering the orbit through the _______

Answer 22

superior orbital fissue (w/in the tendinus annulus)

-it is near the optic nerve here

Question 23

what division of CN 3 do pupillary fibers travel w/

Answer 23

inf division of 3

Question 24

what will a CN3 lesion at the brainstem do

Answer 24

contralateral neurologica deficits: ataxia (loss of full control of body movements), hemiparesis, tremor, UMN CN7 palsy

Question 25

what will a CN 3 lesion at the subarachnoid space do

Answer 25

pain, dilated pupil, subhyaloid hem, incomplete or sup divisoin 3 palsy

Question 26

wat will a CN 3 lesion at the cavernous sinus do

Answer 26

4, V1, V2, horner’s, proptosis, contralateral CN 3 palsy

Question 27

what sill a CN 3 lesion at the orbit do

Answer 27

proptosis, optic neuropathy (CN 2)