Control of Eye Movements (pt 1)

EOM medial walls are oriented on the _____ _____

sagittal plane

EOM lateral walls are ____ from sagittal plane

45 degrees

in primary gaze, axis of orbit is ___degrees laterally from axis of globe

23

each EOM plane contains what muscle pair?

agonist and antagonist

EOMS with horizontal plane parallel to orbital floor

MR and LR

EOMS involved in midsagittal plane

SO and IO

EOMS perpendicular to SO and IO plane

SR and IR

the three EOM muscle planes are nearly parallel to ______ _____

vestibular canals

recti muscle origin is...

common tendinous ring

to isolate SR and IR...

abduction 23 degrees

inferior oblique originates on _____ side of orbital floor

medial

inferior oblique passes over ____ and under _____ and attaches to ____ aspect of posterior portion of glbe

IR LR lateral

primary function of IO

extorsion of eye

secondary function of IO

elevation

the superior oblique originates lateral to _____ ______ _____

common tendinous ring

the SO travels through _______ at anterior/edial pole of orbit, attaches _______, and passes _____ SR

trochlea superiorly under

when eye is ADDUCTED, SO _____ eye

depresses

when eye is ABDUCTED, SO ______ the eye

intorts

to isolate SO and IO, isolate vertical movement at ____ degrees _________

51 adducted

to isolate cyclotorsion of SO and IO, isolate ______degrees ______

39 abduction

two components of CN III

somatic efferent and visceral efferent

somatic efferent division of CN III innervates ______EOMS and ______

4/6 levator

visceral efferent division of CN III is involved in _______ innervation of ____ and _____ ______

parasympathetic pupil ciliary body

oculomotor nuclear complex lies in _________ of ________

tegmentum midbrain

_____ leave oculomotor nuclear complex and enter orbit

LMNs

superior rami of oculomotor nuclear complex innervates what 2 structures?

SR and levator

inferior rami of oculomotor nuclear complex innervates what 4 things?

IR, IO, MR and parasympathetic fibers

the trochlear nerve is the _____ and _______ cranial nerve = most susceptible to trauma

longest thinnest

somatic efferent division of CN IV innervates what?

SO

CN IV nucleus is located in _______ at level of ______ ______

midbrain inferior colliculus

CN IV axons course _______ from nucleus, decussate, and exit _____ aspect of midbrain

posterior dorsal

CN IV axons course ______ to reach orbit through ____.

pass between posterior cerebral and anterior _____ arteries near ______

runs parallel with CN ____

travels through cavernous sinus lateral to _____

anteriorly SOF cerebellar brainstem III ICA

2 components of abducens nerve

somatic efferent and interneurons

somatic efferent division of CN VI innervates what muscle?

LR

interneurons of CN VI are responsible for what?

relay center for coordination of horizontal eye movements (MLF)

CN VI nucleus is located in _____ at level of ____ _____

pons facial colliculus

axons of CN VI emerge on _____ surface of pons, course through ______, over petrous ridge of temporal bone, through cavernous sinus, and enters orbit through _____ aspect of _____

anterior cranium medial SOF

CN III motor nuclei innervate what muscles of IPSILATERAL eye?

MR, IO, IR

CN III motor nuclei innervate what muscles of the CONTRALATERAL eye

SR

CN IV motor nuclei innervate what muscles of the CONTRALATERAL eye?

SO

CN VI innervates what muscles of the IPSILATERAL eye?

LR

CN VI innervates what muscles of the CONTRALATERAL eye?

MR (via interneurons)

the MLF interconnects CNs ____, ____ and ____ to each other and with the vestibular nuclei of CN ______

III IV VI VIII

the MLF is responsible for

_______ movements of two eyes together

adjustments of eye position in response to _____ __ ______

synergistic movements of head

descending MLF:

vestubulospinal tract (lateral and medial)

ascending MLF:

coordination of eye movements

the MLF mediates eye movements in response to ______ ______(VOR)

vestibular stimuli

MLF projections from vestibular nuclei innervate ________ CN ____ nucleus

contralateral VI

MFL is a heavily _____ tract

myelinated

_____ - coordinated movement of both eyes to target in environment

gaze

gaze directs projection of target onto the _____

fovea

gaze is coordinated by higher centers in the ______ and ______, projecting to motor nuclei of CN ___ ___and ___

cortex brainstem III IV VI

horizontal gaze center:

paramedian pontine reticular formation (PPRF)

vertical gaze center:

midbrain reticular formation and pretectal area

many different types of horizontal gaze are associated with different types of wiring patterns, but all end up in ______ _____ _____

final common pathway

the final common pathway of horizontal gaze is the:

ipsilateral PPRF

vertical gaze is mediated by:

_____ ______ _______ of MLF

interstitial nucleus of _____

______ area

rostral interstitial nucleus cajal pretectal

anterior portion of vertical gaze centers mediate _____, and posterior portions mediate ______

downgaze upgaze

frontal eye fields and visual association areas project to vertical gaze centers via the ______ ______

superior colliculus

_____ _____ _______ and ______ ______ areas project to vertical gaze centers via the superior colliculus

frontal eye fields visual association

from vertical gaze centers, signals travel _____ to needed CN nuclei (CN III for SR, IR, and IO) (CN IV for SO)

bilaterally

________ - rapid eye movements that redirect out gaze to an object of interest and result in projection of said object onto fovea

saccades

visual system is ______ during saccadic movement

suppressed

saccades are the result of _____ and ______ input to _____

cortical subcortical PPRF

(saccades) cortical areas involved in input to PPRF:

parietal lobe (visual association area) and frontal lobe (frontal eye fields)

(saccades) from cortical areas, fibers project to _______ _______ ______ ----> ______ PPRF (initiates ipsilateral gaze)

ipsilateral superior colliculus contralateral

_______ saccades - visually guided (prosaccades), occur in response to external visual cues

reflexive

_______ saccades (antisaccades) - independent of visual stimulus, more cognitively complex

volitional

two types of volitional saccades

memory saccades and predictive saccades

the ______ ______ is the main input for reflexive saccades

superior colliculus

the layers of the superior colliculus (reflexive saccades):

superficial layer --> ______ ____

______ layers --> motor neurons projecting to PPRF

middle layer --> synaptic contact between _____ and _____ layers

visual input deep superficial deep

the connections in the superior colliculus creates correlation between the _____ _____ and _____ ____ for eye movement

visual map motor map

saccadic neurons shape innervation controlling what 4 factors of a saccadic movment?

onset, velocity, amplitude and duration

saccades are movements up to ____ degrees/sec

1000

three classes of saccadic neurons

pause, burst, tonic

_____ neurons constantly inhibit burst cells, engage saccade by releasing _______ on burst cells

pause inhibition

____ cells produce a brief pulse of innervation, controls _____ of saccade, overcomes viscosity of _____ and _____

burst velocity eye orbit

_____ neurons controls final position of eye, overcomes _______ ______ of EOMs and orbit

tonic elastic forces

firing rate of tonic cells is derived from _____ _____ (burst cells)

pulse innervation

sites of integration of pulse:

medial vestibular nucleus of CN VIII and prepositus are responsible for ______ _______

horizontal pulses

sites of integration of pulse:

interstitial nucleus of cajal is responsible for ______ _____

vertical pulses

sites of integration of pulse:

________ __ _____ integrates velocity signals with position signals to control eye movements

flocculus of cerebellum

saccadic latency - combination of ____ and ____ results in smooth movement

pulse step

normal saccade has a gain of ____

0.92

_________ saccade - overshooting

hypermetric

_____ saccade - undershooting

hypometric

typical saccadic latency is ____-____msec (can be shorter if movement is ________)

180 200 predictable

a corrective saccade can occur after ____msec, if small error a glissade will occur instead

190