A05 Assessment of Vision and Hearing

Question 1

Where does the visual system start and end?

Answer 1

• It starts at the rods and cones of the retina.

- It ends at the gyri on either side of the calcarine sulcus of the occipital lobe.

Question 2

What is meant when the visual pathway is said to be retinotopically arranged?

Answer 2

The regions of the retina are represented in discrete regions throughout the tract.

Question 3

List the layers of the eye from superficial to deep.

Answer 3

1 - Sclera.

2 - Uveal tract.

3 - Retina.

Question 4

Describe the structure of the sclera.

Answer 4

• It is a continuation of the dura mater surrounding the optic nerve.
• At its most anterior pole it is transparent, forming the cornea.

Question 5

Describe the structure of the uveal tract.

Answer 5

• It is mostly choroid, which is the vascular layer of the eye.
• Anteriorly, it becomes the ciliary body (which contains the muscles which moves the lens), and the stroma of the iris.

Question 6

Describe the structure of the retina.

Answer 6

• It is an outgrowth of the CNS.
• The outermost part of the retina which is in contact with the choroid is the retinal pigment epithelium.
• The innermost layer of the retina is the neural retina.

Question 7

What is the lens?

Answer 7

The transparent, biconvex elastic disc behind the uveal tract that separates the anterior 1/5 of the eye from the posterior 4/5.

Question 8

What maintains the position and shape of the eye?

Answer 8

Intraocular pressure that is generated by production of aqueous and vitreous humour.

Question 9

What is a cataract?

Answer 9

Opacity of the lens.

Question 10

Where are aqueous and vitreous humour stored?

Answer 10

• Aqueous humour is contained within the anterior and posterior chambers.
• Vitreous humour is contained within the postremal / vitreous chamber.

Question 11

Where are the anterior and posterior chambers?

Answer 11

• The anterior chamber is between the cornea and the uveal tract.
• The posterior chamber is between the uveal tract and the lens.

Question 12

Which layer of the eye accounts for most refraction of light?

Why is this?

Answer 12

• The cornea.

- Because the refractive index of the aqueous humour, vitreous humour and lens are all very similar.

Question 13

What is the function of the lens?

Answer 13

It adjusts the focus of the eye for near and far objects by action of the ciliary muscles.

Question 14

What is the advantage of the refraction that arises from the cornea?

Answer 14

It enables peripheral vision.

Question 15

Define accommodation.

Answer 15

Changing the focus from viewing one object to another.

Question 16

What is the effect of contraction of the ciliary muscles?

Answer 16

They cause the anterior surface of the lens to bulge, causing the eye to accommodate to near subjects.

Question 17

What is the pupil?

Answer 17

The densely pigmented aperture in the middle of the iris.

Question 18

List the main components of the ear.

List the main contents of each component.

Answer 18

1 - Outer ear, consisting of:

• Auricle (visible part of the ear).
• External auditory canal.

2 - Tympanic membrane (eardrum).

3 - Middle ear (tympanic cavity), consisting of:

• Auditory ossicle bones.
• Eustachian tube.

4 - Inner ear, consisting of:

• Cochlea.
• Vestibule.
• Semicircular canals.

Question 19

What is the eustachian tube?

What is its function?

Answer 19

• The canal that connects the middle ear to the nasopharynx.

- It controls the pressure within the middle ear, making it equal with the pressure outside the body.

Question 20

What is the barrier between the external and middle ear?

Answer 20

The tympanic membrane.

Question 21

Through which passage does sound travel before vibrating the tympanic membrane?

Answer 21

The external acoustic meatus.

Question 22

Which group of bones vibrate as a result of vibration of the tympanic membrane?

Which bones are included in this group of bones?

Answer 22

• The auditory ossicles.

- The malleus, incus and stapes.

Question 23

Which structure vibrates as a result of vibration of the auditory ossicles?

Answer 23

A membrane which vibrates the perilymph.

Question 24

What is perilymph?

Where is it located?

Answer 24

• Extracellular fluid.

- It is found within the scala tympani and scala vestibuli of the cochlea.

Question 25

What results from the action of the waves in the perilymph?

Answer 25

The spiral organ of Corti transmits action potentials via the cochlear part of CNVIII.

Question 26

List the components of CNVIII.

Answer 26

1 - The vestibular nerve.

2 - The cochlear nerve.

Question 27

What is the function of the vestibular nerve?

Answer 27

To transmit information regarding the position of the head in space.

Question 28

What is the function of the cochlear nerve?

Answer 28

To transmit auditory information from the cochlea.

Question 29

What is the optic disk?

What is the significance of the optic disk?

Answer 29

• The point of exit for ganglion cell axons leaving the eye.

- It is the cause of the blind spot, since no photoreceptors, interneurones or ganglion cells are present here.

Question 30

Define myopia.

Answer 30

Near-sightedness.

Question 31

Define hyperopia.

Answer 31

Long-sightedness.

Question 32

List the muscles that control the size of the pupils.

Answer 32

1 - DIlator pupillae.

2 - Sphincter pupillae.

Question 33

What is the direct pupillary light reflex?

Answer 33

Constriction of the pupil when it is directly illuminated.

Question 34

What is the consensual pupillary light reflex?

Answer 34

Constriction of the pupil when the other eye is illuminated.

Question 35

Define hemianopia.

Answer 35

Blindness in half of the visual field of either or both eyes.

Question 36

Define homonymous.

Answer 36

Affecting the same part of the field of each eye.

Question 37

Define heteronymous.

Answer 37

Affecting different parts of the field of each eye.

Question 38

List 2 arteries that supply the ear.

Which component(s) of the ear does each artery supply?

Answer 38

1 - External carotid artery (middle and outer ear).

2 - Labyrinthine artery (inner ear).

Question 39

What is the function of the inferior colliculus?

Answer 39

• It is the principal midbrain nucleus of the auditory pathway and receives input from several peripheral brainstem nuclei in the auditory pathway, as well as inputs from the auditory cortex.
• It is a point of integration and enables spatial localisation.