Visual pathways

Question 1

Where does the optic nerve travel to from the eye?

Answer 1

The optic chiasm

Question 2

Where do axons pass into once they move through the optic chiasm?

Answer 2

The optic tract

Question 3

Briefly describe where the optic chiasm is positioned in the brain

Answer 3

Immediately above the pituitary

Question 4

What cells supply the axons that make up the optic nerve?

Answer 4

Retinal ganglion cells

Question 5

Where do majority of retinal ganglion cells project?

Answer 5

Lateral geniculate nuleus (visual thalamic relay)

Question 6

Where do lateral geniculate nucleus cells send axons?

Answer 6

Primary visual cortex (area 17) in the occipital lobe

Question 7

What would happen if the lateral geniculate- occipital pathway is damaged?

Answer 7

The person will be blind

Question 8

What structure is tested when a patient is asked to follow your finger with their eyes?

Answer 8

Superior colliculus

Question 9

Where is the superior colliculus located?

Answer 9

Midbrain

Question 10

What does the superior colliculus connect to, and what is the function of this?

Answer 10

The medial longitudinal fasciculus

Links together and synchronises nuclei

Question 11

What is the optic tectum?

Answer 11

Another name for superior colliculus

Question 12

What nucleus controls pupillary light reflex?

Answer 12

Edinger Westphal nucleus

Question 13

Describe the pathway of axons from cells of LGN to visual cortex

Answer 13

via the optic radiation

project back anteriorly in Meyer’s loop and then run alongside the posterior horn of lateral ventricle to occipital lobe

Question 14

Define left visual field

Answer 14

Everything to the left of your fixation point in both eyes

Question 15

What part of the brain ‘sees’ the left visual field

Answer 15

right visual cortex

Question 16

Why does left visual field project to right visual cortex and vice versa?

Answer 16

Nasal hemiretina from left eye projects to right visual cortex, as does the temporal hemiretina from right eye.

Question 17

Define scotoma

Answer 17

A patch of blindness

Question 18

What is the result of partial optic nerve legion?

Answer 18

Ipsilateral scotoma

Question 19

What is the result of complete optic nerve lesion?

Answer 19

Complete blindness in that eye

Question 20

What is the result of optic chiasm lesion

Answer 20

Bitemporal hemioanopia

Question 21

What is the result of an optic tract lesion

Answer 21

Homonymous hemiapopia

Question 22

What is the result of damage of the Meyer’s loop?

Answer 22

Homonymous upper quadrant anopia

Question 23

What is the result of optic radiation lesion?

Answer 23

Homonymous hemianopia

Question 24

What is the result of visual cortex lesion

Answer 24

Homonymous hemianopia

Question 25

Name the four key visual reflexes

Answer 25

Pupillary eye reflexes Accomodation reflex Vestibulo-ocular reflex Blink reflex

Question 26

How are cranial nerves III, IV and VI linked?

Answer 26

fibre tract called the medial longitudinal fasciculus

Question 27

Which cranial nerves are involved in pupillary light reflex

Answer 27

In on II, out on III

Question 28

Describe the passage of axons in the pupillary light reflex

Answer 28

Axons of CN II go the pretectal nucleus is the superior colliculus. From here, go to Edinger-Westphal nucleus and out on CN III to ciliary ganglion. This sends axons to pupillary constrictor muscle Constrictor of this reduces pupil size

Question 29

What can block the pupillary light reflex?

Answer 29

Atropine

Question 30

What are the 3 components of the accomodation reflex?

Answer 30

Pupillary constriction Thickening of lens Convergence

Question 31

What is the input for pupillary constriction as part of accomodation reflex?

Answer 31

Comes from descending projections from frontal eye fields in premotor cortex

Question 32

What is function of pupillary constriction in accommodation reflex?

Answer 32

Focusing on close objects/ depth of field

Question 33

Can accomodation reflex occur in unconcious person?

Answer 33

No

Question 34

What part of the brain controls the accommodation reflex?

Answer 34

Frontal eye fields (specialised part of premotor area)

Question 35

What is the result of damage to FEFs

Answer 35

Inability to direct gaze from one object to another

Question 36

Describe the shape of the lens at rest

Answer 36

Under tension from ring of suspensory ligaments which flatten it away from relaxed shape

Question 37

Describe the shape of the lens when the ciliary muscle contracts

Answer 37

Reduces diameter of ring of suspensory ligaments, slackens the tension and lens bulges out into relaxed shape

Question 38

How is the lens thickened during accomodation and why?

Answer 38

Tension in suspensory ligaments is reduced and lens thickens to normal shape to focus on obkects

Question 39

Which muscles cause convergence as part of accommodation reflex

Answer 39

Medial rectus muscles

Question 40

What is the vestibulo-ocular reflex?

Answer 40

If you turn your head to the side whilst looking at distant object, eyes rotate in opposite direction of the head to keep direction of gaze constant and object stays in view

Question 41

What is the input and output of the vestibulo-ocular reflex?

Answer 41

In: CN VIII, receiving signals from semicircular canals Out: CN VI and CN III

Question 42

How is the vestibulo-ocular reflex tested clinically?

Answer 42

Holding someones eyes open and gently rotating the head from side to side Eyes should rotate in the head to keep direction constant

Question 43

WHat is nystagmus?

Answer 43

Form of VOR caused by continuing rotation of fluid in the semicircular canals

Question 44

Function of blink reflex

Answer 44

Projects eye from foreign bodies

Question 45

Input and output of blink reflex?

Answer 45

V1 branch of trigeminal nerve | Out- facial nerve input to obicularis oculi muscles