Flashcards in Auditory & Visual Practical Deck (21):
How is visual acuity measured?
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
-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