Ch 13 Pt 2

Question 1

PS pathway : ciliary muscles of lens

Answer 1

Adjusts thickness of the lens in response to changing viewing distances
• The lens focuses the image on
the retina

Visual cortex signals pretectal nuclei that image is out of focus Parasympathetics to the ciliary muscle are activated to adjust the shape of the lens (to keep the image in focus)

Question 2

sympathetic pathway: pupillary dilation

Answer 2

Visual cortex sends signal to autonomic nuclei in the hypothalamus —>
Descending neurons travel in lateral brainstem and cervical cord to the T1-T2 level —>
Synapse occurs on preganglionic sympathetic neurons in the intermediolateral cell column (T1-T2 level) —>
Preganglionic sympathetic neurons enter the sympathetic trunk (chain) —>
Ascend to synapse on superior cervical ganglion —>
Postganglionic sympathetic neurons ascend beside the ICA to the orbit to then synapse on pupillary dilator muscle

Question 3

Other sympathetic fx

Answer 3

Superior tarsal muscle
• Elevates upper eyelid during increased sympathetic outflow

Orbitalis muscle
• Prevents eye from sinking back in
the orbit

Cutaneous arteries and sweat glands of face and neck

Question 4

Pupillary abnormality causes

Answer 4

Peripheral or central lesions, sympathetic or

parasympathetic lesions, or disorders of the iris muscle or visual pathways

Question 5

Anisocoria

Answer 5

Pupillary asymmetry

Question 6

CN III lesion : pupillary

Answer 6

Complete lesion, pupil is very large

Ptosis (drooping of upper eyelid) and eyemovement abnormalities associated w/ CN III Fox

Question 7

Why is aniscoria more obvious in a room w/ light than a dark room?

Answer 7

In a room w/ light, it should be constricting, but will stay open due to loss of PS for pupillary constriction

Question 8

Horner’s syndrome

Answer 8

Lesion affecting sympathetic pathway to face and eye

Ipsilateral:
Ptosis (mild)
• Miosis -Decreased pupillary size

Anhidrosis - Decreased
sweating
of face and neck

Question 9

Honors syndrome can be caused by

Answer 9

Lesion anywhere that affects the sympathetic pathway to face and eye

Question 10

Common causes of ptosis

Answer 10

Horner’s syndrome (mild)

CN III palsy (weakness of levator palpebrae superior)

Also could be due to myasthenia
gravis (MG), an orbital mass, or
excess skin folds

Question 11

widened palpebral fissure

Answer 11

Can be mistaken for ptosis

Sagging of lower face due to
UMN lesion can slightly widen the palpebral fissure and pull the eyelid down slightly as well
• Examine entire eyelid using
iris as a reference point 
• Examine the facial muscles
below the eye (UMN lesion)

Question 12

Supranuclear pathways

Answer 12

pathways in the CNS for eye movement control via activation of CN III, IV, and VI nuclei

Question 13

Three known circuits in supranuclear -

Answer 13

Control CN III, IV, and VI to produce

• Horizontal eye movements
• Vertical eye movements
• Vergence eye movements

Question 14

Supranuclear pathways also generate eye movements for other purposes

Answer 14

• Saccades
• Smooth Pursuit
• Vergence
• Reflex Eye Movements
- (Optokinetic) Nystagmus  
-Vestibulo-Ocular Reflex (VOR)

Question 15

Actions of CN III, IV, and VI nuclei are coordinationed through

Answer 15

Medial longitudinal fasciculus

Question 16

CN VI nucleus acts as

Answer 16

Horizontal gaze center

Controls horizontal movement of both
eyes via the MLF
• To move eyes to the Left:
• Neurons from L CN VI nucleus
project to L lateral rectus 
• Other neurons from L CN VI
nucleus project to R CN III
nucleus (via MLF) to R medial
rectus

Question 17

Paramedics pontine reticular formation

Answer 17

Also serves as a horizontal gaze center via input to CN VI nuclei

Question 18

Vertical eye movements

Answer 18

• Superior and inferior recti

* Superior and inferior obliques

Question 19

Brainstem centers for controlling vertical eye movements

Answer 19

upper midbrain reticular formation and pretectal area
• Anterior portion - Mediates downgaze
• Posterior portion -Mediates upgaze

Question 20

Convergence eye movements

Answer 20

Medial recti

Question 21

Divergence eye movements

Answer 21

Lateral recti

Question 22

Vergence movements

Answer 22

• exact control centers in brainstem have not been defined

- likely controlled by neurons in midbrain reticular formation

Question 23

Cortical control of eye movements influence by

Answer 23

Visual inputs arriving at the PVC and visual association cortex

Question 24

Multiple pathways descend form cortex to control eye movement circuits

Answer 24

These travel directly to the brainstem centers for horizontal, vertical, or
vergence eye movements, or through the the midbrain superior collicul

Question 25

Frontal eye fields

Answer 25

Best-known cortical area that controls eye movements (for contralateral eye movements)

Question 26

Saccades

Answer 26

• rapid eye movements to switch gaze from one object to another
• reach velocities of 700 deg/sec

Question 27

Smooth pursuit

Answer 27

Allows for stable viewing of moving objects

-reaches velocities of 100 deg/sec

Question 28

Vergence

Answer 28

Movement of eyes toward or away from midline as targets move toward and away from the viewer
-reach velocities of 20 deg/sec

Question 29

Nystagmus

Answer 29

Slow eye movement in one direction interrupted repeatedly by fast movements in opposite direction

Normal occurs during attempts to view a visual scene moving in front of the eyes

Question 30

Nystagmus is abnormal when

Answer 30

It occurs at rest w/out changing visual or vestibular inputs

Question 31

Vestibulospinal-ocular reflex

Answer 31

Stabilizes the eyes on a visual image during head movements

• inputs from vestibular nuclei travel in the MLF to control the extraocular eye muscle nuclei
• cerebellum and proprioception of cervical SC also influence VOR