Week 11: Eye and Ear SDL

Question 1

What occupies the anterior chamber of the eye?

Answer 1

clear, watery fluid called aqueous humour

Question 2

What and where is the conjuctiva?

Answer 2

tissue that lines the inside of eyes and covers the sclera (sclera is the white bit of eye)

Question 3

What is the function of the conjuctiva?

Answer 3

• provides protection and lubrication of the eye by the production of mucus and tears
• it prevents microbial entrance into the eye and plays a role in immune surveillance
• provides a covering to the sclera

Question 4

What is the function of the iris?

Answer 4

the iris controls the amount of light that enters the eye by opening and closing the pupil / the iris uses muscles to change the size of the pupil

Question 5

Which nerve supplies the sphincter pupillae muscle?

Answer 5

CN III

Question 6

What effect does contraction of the ciliary muscle have on the lens?

Answer 6

when the ciliary muscle is contracted, the lens becomes more spherical and has more focusing power

Question 7

What is cataracts?

Answer 7

-cataracts is when the lens develops cloudy patches -these usually become bigger overtime, causing blurry, misty vision and eventually blindness

Question 8

What are the 2 functions of the ciliary body?

Answer 8

• controlling the shape of the lens

- production of aqueous humour

Question 9

What is glaucoma?

Answer 9

where the optic nerve becomes damaged, usually due to a build up of aqueous humour in the anterior chamber

Question 10

Give two functions of the choroid layer of the eyeball

Answer 10

• supplies the outer retina with retina

- maintains the temperature and volume of the eye

Question 11

What 2 layers is the retina made up of?

Answer 11

• an outer pigment cell layer - a single layer cuboidal epithelial cells with melanin filled microvilli extending from their inner surface
• a multi layered neural retina

Question 12

What are the major cell types in the retina?

Answer 12

• pigment cell layer
• rod cell
• cone cell
• bipolar cell (=first order neurones of visual pathway)
• ganglion cell (=second order neurones of visual pathway)
• interneurones

Question 13

Give 3 functional differences between rods and cones

Answer 13

• rods are responsible for vision at low light levels, they do not mediate colour vision and have a low spatial acuity
• cones are active at higher light levels, are capable of colour vision and are responsible for high spatial acuity

Question 14

What is papilloedema?

Answer 14

-an optic disc/ nerve swelling that is caused by increased intracranial pressure

Question 15

What is the fovea and how is it specialised for visual acuity?

Answer 15

• centre of macula
• the point on the retina at which the image of the object at the centre of the visual axis falls
• contains only cones for specialised visual acuity

Question 16

Explain the blood supply to the retina

Answer 16

• central retinal artery (CRA)

- the choroidal blood vessels

Question 17

List the structures through which sound waves enter the external ear, until they reach the auditory receptors

Answer 17

1. sound waves arrive at the pinna (auricle)
2. once the sound wave have passed the pinna, they move to the auditory canal before hitting the tympanic membrane
3. sound waves enter the middle ear
4. the vibrations are transmitted via ossicles: malleus, incus and the stapes
5. sound waves then pass through the oval window to enter the cochlear in the inner ear
6. hair cells in the organ of corti (within the cochlea) are stimulated which stimulates the cochlear branch of the vestibulocochlear nerve
7. the cochlear nerve then transmits electrical impulses to the auditory region of the brain in the temporal lobe

Question 18

What is the function of the tympanic membrane (ear drum)?

Answer 18

• separates the outer ear from the middle ear
• when sound waves reach the tympanic membrane, they cause it to vibrate
• these vibrations are transferred to the ossicles

Question 19

What is the function of the ossicles?

Answer 19

to transmit sound waves from the air to the cochler

Question 20

What is the function of the oval window?

Answer 20

receives vibrations from the ossicles which leads to movement of fluid within the cochlear and activation of receptors for hearing

Question 21

What is the function of the auditory tube (eustachian tube)?

Answer 21

• connects the middle ear to the nasopharynx

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

Question 22

What fluid is found in the inner ear?

Answer 22

perilymph –> and within this cavity is an epithelial sac filled with endolymph

Question 23

Which 3 receptors are found in the inner ear?

Answer 23

• maculae
• christae ampullaris
• spiral organ (organ of corti)

Question 24

What is nystagmus?

Answer 24

when a person suffers with involuntary, uncontrollable eye movements

Question 25

What is vertigo?

Answer 25

the sensation that you, or the environment around you, is moving or spinning

Question 26

How does the basilar membrane respond to fluid movement in the inner ear?

Answer 26

• vibrates
• this causes the hairs to be deformed against the overlying tectorial membrane
• this causes depolarisation/hyperpolarisation of the sensory hair cells and generates action potentials in the sensory nerve fibres

Question 27

Which region of the basilar membrane vibrates maximally in response to sounds of:

1. high frequency
2. low frequency

Answer 27

1. high frequency - basal end of the membrane

2. low frequency - apical end of the membrane

Question 28

What is conduction deafness?

Answer 28

deficit related to an obstructed, or altered, transmission of sound to the tympanic membrane or through the ossicle chain of the middle ear

Question 29

What is sensorineural deafness?

Answer 29

hearing loss in which the root cause lies in the inner ear, sensory organ (cochlear and associated structures) or the vestibulocochlear nerve