Visual System

Question 1

Which cranial nerves are involved in the visual system?

Answer 1

• CN II, optic
• CN III, oculomotor
• CN IV, trochlear
• CN VI, abducens

Question 2

Which cranial nerves are responsible for somatic motor movement in the visual system?

Answer 2

• CN III, oculomotor
• CN IV, trochlear
• CN VI, abducens

Question 3

Which cranial nerve is responsible for special sensory in the visual system?

Answer 3

CN II, optic

Question 4

Which cranial nerve is responsible for parasympathetic responses in the visual system?

Answer 4

CN III, oculomotor

Question 5

How many extraocular muscles are there?

Answer 5

6

Question 6

What are the extraocular muscles?

Answer 6

4 straight muscles: inferior, superior, medial, lateral rectus muscles
2 oblique muscles: superior, inferior oblique muscles

Question 7

Which cranial nerve innervates majority of the extraocular muscles? Which muscles are theres?

Answer 7

• CN III, oculomotor
• superior, inferior, medial rectus mm + inferior oblique mm

Question 8

Which extraocular muscles are not innervated by CN III? Which cranial nerves are they innervated by instead?

Answer 8

• lateral rectus muscle; CN VI, abducens
• superior oblique muscle; CN IV, trochlear

(hint: LR6SO4)

Question 9

Which muscle opens and moves the eyes? Which cranial nerve is it innervated by?

Answer 9

levator palpebrae superioris, CN III (oculomotor)

Question 10

Through which bone structure does the oculomotor nerve (CN III) leave the cranial cavity?

Answer 10

superior orbital fissure

Question 11

Through which bone structure does CN IV, trochlear nerve leave the cranial cavity?

Answer 11

superior orbital fissure

Question 12

Through which bone structure does CN VI, abducens nerve, leave the cranial cavity?

Answer 12

superior orbital fissure

Question 13

Which extraocular muscles would you have to contract to move your gaze to the left?

Answer 13

right medial rectus and left lateral rectus

Question 14

Which extraocular muscle would you have to contract to cause intorsion of the eye?

Answer 14

superior oblique mm

Question 15

Which extraocular muscle would you have to contract to cause extorsion of the eye?

Answer 15

inferior oblique mm

Question 16

What is the effect of a lesion to the abducens nerve to the right eye? Which way would the eye deviate towards?

Answer 16

paralysis of lateral rectum muscle on right eye –> eye will deviate to the left

Question 17

What is the function of the cornea?

Answer 17

focus light

Question 18

What is the function of the aqueous humour?

Answer 18

maintain pressure inside the eye

Question 19

What is the function of the iris?

Answer 19

dilation/constriction –> control light input

Question 20

What is the function of the ciliary muscles?

Answer 20

change the lens shape to focus light

Question 21

Where are neural tissues found in the eye?

Answer 21

retina

Question 22

What is the macula in the eye?

Answer 22

high concentration of photoreceptors; fovea at the center

Question 23

What is the function of the choroid in the eye?

Answer 23

• supplies oxygen and nutrients to outer retina
• connective tissue between sclera and outer retina

Question 24

What the is the schlera?

Answer 24

whites of the eyes

Question 25

Where is the blind spot on the eyeball?

Answer 25

optic nerve

Question 26

Are there more rods or cones in the eye?

Answer 26

rods

Question 27

Through which bone cavity does the optic nerve (CN II) exit from the cranial cavity?

Answer 27

optic canal

Question 28

Describe the visual pathway

Answer 28

lateral geniculate nucleus --> primary visual cortex --> visual association cortex

Question 29

Which axons in the visual pathway cross the optic chiasm?

Answer 29

nasal RGC axons

Question 30

Which axons in the visual pathway stay ipsilateral?

Answer 30

temporal axons

Question 31

TRUE or FALSE: each optic nerve contains only visual information from the opposite visual field.

Answer 31

FALSE --> each optic TRACT contains only visual info from the opposite visual field

Question 32

What happens if there is lesion in your right optic nerve?

Answer 32

BLINDNESS IN RIGHT EYE b/c no visual info from the right eye is getting to the primary visual cortices

Question 33

What happens if there is lesion at the optic chiasm?

Answer 33

TUNNEL VISION b/c only receive info from temporal retina

Question 34

What happens if there is lesion in the left optic tract?

Answer 34

ONLY SEE LEFT VISUAL FIELD

Question 35

What is the meyer's loop? In which lobe is it located?

Answer 35

- fibers that carry info from contralateral upper quadrant visual field - temporal lobe

Question 36

Which visual field (left/right) projects on the left LGN? right LGN?

Answer 36

- left visual field on right LGN - right visual field on left LGN

Question 37

What is anopsia? What kind of lesion causes it?

Answer 37

blindness in one eye; lesion to ipsilateral optic nerve

Question 38

What is bitemporal hemianopsia? What kind of lesion causes it?

Answer 38

blindness in temporal visual field (both eyes); lesion to optic chiasm

Question 39

What is left homonymous hemianopsia? What kind of lesion causes it?

Answer 39

left visual field impaired in both eyes; lesion to right optic tract

Question 40

What is the dorsal pathway of the visual system responsible for?

Answer 40

spatial relationships of objects

Question 41

What is the ventral pathway of the visual system responsible for?

Answer 41

object recognition

Question 42

How does damage to the temporal cortex affect the visual system? What is this condition known as?

Answer 42

poor object recognition; visual agnosia

Question 43

What are the parasympathetic responses of CN III?

Answer 43

- pupillary light reflex - near (accomodation) reflex

Question 44

Describe the parasympathetic innervation pathway of CN III, oculomotor.

Answer 44

CN III --> ciliary ganglion --> short ciliary nerves --> sphincter pupillae muscle OR ciliary muscle

Question 45

What occurs during the pupillary light reflex?

Answer 45

when light is shined into one eye, both pupils constrict

Question 46

Describe the pupillary light reflex pathway, starting from when light is shined in the right eye.

Answer 46

1. light shined in right eye 2. AP from right eye reach both RIGHT and LEFT PRETECTAL NUCLEI 3. pretectal nuclei stimulate BOTH SIDES of the EDDINGER-WESTPHAL nucleus 4. both sides of eddinger-westphal nuclei generate AP through RIGHT AND LEFT CN III's 5. BOTH PUPILS constrict

Question 47

direct pupil dilation is __________ to light.

Answer 47

ipsilateral

Question 48

consensual pupil dilation is ___________ to light.

Answer 48

contralateral

Question 49

WHere does the optic tract synapse in the pupillary light reflex pathway?

Answer 49

pretectal area

Question 50

Where does the oculomotor nerve (CN III) synapse in the pupillary light refelx pathway?

Answer 50

ciliary ganglion

Question 51

TRUE or FALSE: the cortex is involed in the pupillary light reflex.

Answer 51

FALSE

Question 52

TRUE or FALSE: the cortex is involved in the near (accommodation) reflex

Answer 52

TRUE

Question 53

What does the near (accommodation) reflex do?

Answer 53

- constrict ciliary muscle (accommodation) - pupillary constriction - convergence of the 2 eyes

Question 54

Which extraocular muscles are responsible for the convergence of the two eyes?

Answer 54

medial rectus

Question 55

Describe the near reflex pathway, starting from when visual info reaches the optic tract.

Answer 55

1. optic tract (CN II) 2. primary visual cortex 3. visual association cortex 4. oculomotor nucleus --> oculomotor nerve --> contract medial rectus muscle (converge 2 eyes) 5. EW nucleus --> ciliary ganglion --> contract ciliary muscle and pupillary sphincter (accommodate lens and constrict pupil)