sensory - vision Flashcards
(17 cards)
sight
perception of objects in environment by means of the light they emit or reflect
accessory structures (4)
eyebrows eyelids conjunctiva lacrimal apparatus entrinsic eye muscles
anatomy of eye (3)
tunics
optical apparatus
neural apparatus
tunics
3 layers form wall
- fibrosa sclera = white of eye
- cornea = transparent region - vasculosa = choroid, ciliary body, iris
- interna = retina
optical apparatus
transparent elements to admit light
- cornea, aqueous humour, lens, vitreous body
aqueous humour
optical apparatus
produced by ciliary body
flows pupil -> anterior chamber
reabsorbed by canal of Schlemm
if reabsorption < secretion = glaucoma
how image formed
pupil admits light
- diameter controlled by iris
light bent/refracted - by curvature of cornea towards centre of retina
- refractive index = measure of light
the near response
- adjustment to close range vision
near response
3 processes to focus image on retina
- convergence of eyes
- constriction of pupil
- accommodation of lens
near point of vision
the closest an object can still be in focus
increased with age
hyperopia
far-sighted
correct with convex lens
image behind retina
myopia
short sighted
correct with concave lens
image within vitreous
sensory transduction in retina
light energy -> action potentials
retina: cellular layout
(5 layers)
pigment cell layer photoreceptor layer bipolar layer ganglion layer nerve fibre layer
visual pigments
rods = rhodopsin cones = photopsin
photochemical reaction
cyclical process, same in cones + rods
cis retinal -> trans retinal -> dissociates from opsin -> cis retinal
colour vision
based on 3 types of cones: blue, green, red
perception of colour based on mixture of nerve signals
focusing by lens
by changing the curvature of the lens
incoming rays bent by corneathlens
image inverted
