Auditory & Visual Practical Flashcards
How is visual acuity measured?
Similar triangles
What does the similar triangles theory tell us?
Represents the minimum distance on the retina necessary to allow discrimination between 2 points
What refraction errors are there? Describe them and how they are corrected
- Myopia= short sighted, concave lens
- Emmetropia=normal, eye relaxed
- Hyperopia= long sighted, convex lens
What is visual acuity?
Clarity of vision
What does visual acuity depend on?
- the sharpness of the retinal focus within the eye
- the health and functioning of the retina
- the sensitivity of the interpretative faculty of the brain
What is relative visual acuity?
Visual acuity of an uncorrected eye
Describe regular astigmatism
- Refraction of meridian is different
- Curvature along each meridian is even
Describe irregular astigmatism
-Curvature along each meridian is different
What will be observed for short/long sighted people in the duo chrome test? Why?
- Coloured Snellen’s test
- Green light refracted more than red light
- Short=Red letters seem more clear
- Long= Green letters seem more clear
Where is the blind spot?
Optic disc= blood vessels enter & leave & optic axons leave the eye
What is the function of the semicircular canals?
- Give info about movements of the head occurring in the plane of each canal
- Anterior vertical, horizontal, posterior canals
What is the sensory end organ? Where is it?
- Cupula
- In the ampulla of the canal
How does cupola movement stimulate nerves?
- Movements of endolymph displace cupula in certain direction
- Stimulates nerve endings
What components of the inner ear send impulses via the superior branch of the vestibular nerve?
- Anterior vertical ampulla
- Horizontal ampulla
- Utricle
- Anterior superior part of saccula macula
What components of the inner ear send impulses via the inferior branch of the vestibular nerve?
- Posterior vertical ampulla
- Main portion of saccula macula
What does the vestibule-ocular reflex connect?
- Shortest reflex connection
- Semicircular canals and ocular muscles
What are the 3 neurons in the vestibule-ocular reflex?
- Primary vestibular-connects sensory cells in crista ampullaris with neurons in vestibular nuclei
- Secondary vestibular- send axons to oculomotor nuclei via ascending branch of medial longitudinal fasciculus
- Motor neurons- innervating various extra ocular muscles
Where do the majoirty of the fibres from the SCC synapse?
-Medial & superior vestibular nuclei
What 3 things need to be available for accurate sound localisation?
- Interaural phase timing differences (low frequencies)
- Interaural intensity/amplitude differences (high frequencies)
- Head related transfer function (how the external ear modifies sound)
What are the 2 types of deafness?
- Sensorineural= injury or degeneration of the nerve elements on the cochlea/auditory nerve
- Conductive= disease of the middle ear interfering with transmission of sound to the cochlea
What is conductive & sensorineural deafness in regards to tuning folk testing?
- C= subject deaf to air conduction but no deafness to bone conduction
- S=Deaf to both air & bone conduction
