Occulomotor, trochlear, abducens

Question 1

how to remember which extraocular muscles are not innervated by CN III and what they are innervated by

Answer 1

LR6SO4
Lateral rectus 6
Sup Oblique is 4

Question 2

Rectus muscles of eye

Answer 2

do as name implies (sup –> up)

Question 3

Oblique eye mucles

Answer 3

move eye opposite of eye implies (sup oblique moves eye down) - this is because the tendon wraps around

Question 4

levator palpebrae

Answer 4

holds eye open

Question 5

holds eye open

Answer 5

levator palpebrae

Question 6

location of the occulomotor n.

Answer 6

extends 5mm rostrocaudally near the midline in the mesencephalon at the level of the sup. colliculus

Question 7

Cells in the oculomotor complex

Answer 7

multiple columns of cells, each containing neurons that send somatic efferents to specific extraocular muscles

Question 8

Axons of oculomotor cortex go where

Answer 8

they go ventrally to exit medial to the cerebral peduncles

Question 9

dorsomedial and sup part of oculomotor complex

Answer 9

Edinger westphal nucleus which carries visceral (parasympathetic preganglionic) efferents to ciliary ganglion

Question 10

CN III runs from _______ space to ______

Answer 10

subarachnoid space to the cavernous sinus; passes between sup cerebellar and post cerebral arteries on its way and by uncus of the temporal lobe

Question 11

CN III runs _____ to CN IV, VI, and V1 in the sinus

Answer 11

superior to

Question 12

CN III divides into superior division and inf where

Answer 12

at the sup orbital fissure

Question 13

Split of CN III that supplies preganglionic outflow to ciliary ganglion

Answer 13

inferior division

Question 14

Inf. divison of CN III supplies

Answer 14

inf and med rectus, inf oblique, and preganglionic outflow to ciliary ganglion

Question 15

Sup division of CN III supplies

Answer 15

Sup rectus and levator palpebrae

Question 16

Damage to CN III

Answer 16

eyelid drooping and dilated eye b/c parasympathetics run with it so no constricting

Question 17

The oculomotor complex lives where in the brain, leaves where

Answer 17

midbrain, leaves out the sup. orbital fissure into the orbit and divides into branches that go to the 5 muscles

Question 18

N. that also lives in midbrain

Answer 18

CN III and Trochlear (CNIV)

Question 19

only nerve to exit brain dorsally; then goes out through

Answer 19

trochlear; sup orbital fissure to SO m. –> tilts eye down

Question 20

Small and wispy CN

Answer 20

Trochlear

Question 21

Where CN IV leaves vault; where does it go? what does it do?

Answer 21

goes dorsally, goes into cavernous sinus below CN III, leaves out Sup orbital fissure to SO m. to tilt eye down and in

Question 22

Lesion to trochlear n.

Answer 22

causes eye to turn up and out (extorsion) which causes double vision; person tilts head forward and to opposite side to see

Question 23

double vision is mainly caused by

Answer 23

damage to trochlear n.

Question 24

which n. causes a horizontal gaze

Answer 24

abducens

Question 25

where in the brain is abducens n.

Answer 25

in the pons, seperated from 4th ventricle by facial n.

Question 26

which CN is located in the pons

Answer 26

Abducens, CN VI

Question 27

CN that coordinates horizontal gaze

Answer 27

Abducens

Question 28

Axons of abducens --> ______ --> pierce _____ --> emerge between _____ and _____ --> ascend along the base of ____ --> travel below _____

Answer 28

``` ventrally medial leminiscus pons and medulla pons Gruber's ligament ```

Question 29

In the lateral wall of the cavernous sinus Abducens n. lies between ______ medially and _________ laterally

Answer 29

carotid artery | opthalmic branch of trigeminal laterally (V1)

Question 30

Contents and order (sup to inf) of cavernous sinus

Answer 30

ICA < III, IV, VI, V1 and V2 (NOT V3)

Question 31

aneurism of internal carotid artery would first effect which nerve

Answer 31

abducens, sits closest to the int. carotid a. in the cavernous sinus, CN III, IV, V2, and V3 are all more lateral

Question 32

PPRF

Answer 32

Paramedian Pontine Reticular Formation-aka Horizontal Gaze Center; a collection of nuerons located near the midline of the pons; innervate abducens nuclei on the same side of the brain and oculomotor complex on the opposite side

Question 33

Two types of neurons that PPRF innervate of abducens nucleus

Answer 33

motor neurons that innervate LR on same side (moves lat) Internuclear neurons --> send axons across midline --> ascend in medial longitudinal fasciculis --> terminate i oculomotor complex which innervates medial rectus m. are

Question 34

internuclear neurons of the abducens nucleus send axons where

Answer 34

across the midline --> ascend in medial longitudinal fasciculis (mlf) --> terminate in oculomotor complex which targets medial rectus m.

Question 35

activation of PRRF on the right does what

Answer 35

causes both eyes to gaze to the right

Question 36

How many abducens nuclei does PRRF project to?

Answer 36

Just ONE! but... each abducens nuclei has two neurons that will target lateral and medial rectus

Question 37

controls horizontal gaze

Answer 37

PRRF

Question 38

Controls vertical gaze

Answer 38

riMLF

Question 39

riMLF

Answer 39

rostral interstitial nucleus of medial longitudinal fasciculus (riMILF) in the midbrain, controlled by frontal eye fields in the frontal lobe

Question 40

Location of riMILF

Answer 40

in the midbrain

Question 41

riMLF is controlled by

Answer 41

frontal eye fields in the frontal lobe, that sit infront of the motor cortex; this projects to the oculomotor complex or all the way back to the PRRF

Question 42

Frontal eye fields

Answer 42

in frontal lobe infront of motor cortex, control riMLF and thus vertical gaze; project to oculomotor complex or PRRF

Question 43

lesion in the right abducens (look left and right)

Answer 43

left --> ok b/c LR is ok b/c oculomotor ok | Right --> oh no, 2x vision b/c MR is a goner

Question 44

Lesion in R abducens nucleus

Answer 44

Da faq, nothing happens, cannot look right b/c both MR shot

Question 45

Lesion in R PRRF

Answer 45

gaze left is fine | Gaze right --> cannot, loss of LR on that side and opposite MR

Question 46

Lesion in MLF left

Answer 46

gaze left --> fine Gaze right --> only right eye (contralateral) can b/c other lost MR; the one that can move does not want to (nystagmus) and leads to left intranuclear opthalmoplegia (INO)

Question 47

Nystagmus

Answer 47

when only one eye is able to move, the other shoots back into place

Question 48

Can be the result of having one MLF out

Answer 48

intranuclear opthalmoplegia on the opposite side (INO)

Question 49

lesion in Left MLF and L Abducens nucleus

Answer 49

knocks out left MR and right MR and left LR; good luck cannot look left at all can move right eye laterally but cannot move left eye M so causes nystagmus; this mess is 1 1/2 syndrome; where one horizontal gaze is completely paralyzed and half of the other is

Question 50

Class including CN III, IV, and VI

Answer 50

Strictly motor; general somatic efferents; innervate skeletal m. derived from somites during embrylogical development