Auditory & Visual Practical Flashcards Preview

Symposium > Auditory & Visual Practical > Flashcards

Flashcards in Auditory & Visual Practical Deck (21):

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?

-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
-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