eye Flashcards
iris
Circular sheet of muscles
Has pigment to give iotseye color
Controls amount of light entering the eye (circular muscles and radial muscles)
conjunctiva
Thin transparent mucous membrane covering sclera
Mucous membrane that keeps the front of eyeball moist
sclera
Tough, white, outer covering of eyeball
Continuous with cornea
Protects the eye from mechanical damage
pupil
allows light to enter the eye
eyelashes
Shields eyes from dust particles
tear gland
Secretes tears
Washes the duct particles away
Keeps the cornea moist for atm oxygen to dissolve into. The dissolved oxygen diffuses into cornea
Lubricate conjunctiva, reducing friction when eyelids move
eyelids
Protect cornea from mechanical damage
Squinting prevents excessive kight from entering the eye and damaging light sensitive tissues (retina) inside
Blinking spreads tears over the cornea and conjunctiva and wipes off the dust particles off cornea
suspensory ligaments
Connective tissues that attaches edge of lens to ciliary body
cornea
dome shaped transparent layer
Continuous with sclera
Refrcats and bends light rays into eye
aqueous chamber
Filled with aqueous humour
Keeps eyeball firm
Refracts light into pupil
lens
Transparent, circular, biconcave
Elastic
Changes shape/thickness to focus light into retina
choroid
Pigented black to prevent interna reflectin of light
Contains blood vessels that bring oxygen and nutrients to eyeball and remove metabolic waste products
vitreous chamber
Filled with vitreous humour
Keeps eyeball firm
Helps refract light rays into retina
fovea
Directly behind lens
Contains greatest numbe of cones but has no rods (fc)
Allows for coloured detailed vision in bright light
blind spot
Region where optic nerve leaves the eye
No rod and cones
No photoreceptors
Not sensitive to light
No image perceived by brain
optic nerve
transmits nerve impulses to brain when phptoreceptrs in retina are stimulated
retina
Light sensitive layer where images are formed
Contains photorecpetors
Contains rods and cones
Photorecpetors are connected to nerve endings from optic nerve
bright light
Circular muscles contract
Radial muscles relax
Pupil constricts
Reduces amount of light enerting the eye
dim light
Circular muscles relax
Radial muscles contract
Pupil dilates
Increases amount of light entering the eye
relfex arc in dim light
Lowering of light intensity
Photorecpetors in retina are stimulated
Nerve impulses are generated and sent through sensory neurone in opticenerve to brain
In brain, nerve impulses are transmitted through a synapse to relay neurone then through another synapse to the motor neurone
The motor neurone trnamsits nerve impulses from brain to muscle in iris
Circular muscles of iris relaxes and radial muscles pf iris contracts
Pupil dilates, allowing more light to enter th light
focusing on distant object
Ciliary muscles relax, pulling on suspnesory ligaments
Suspensory ligament become taut, pulling on the edges of lens
Lens become thinner and less convex
Increase focal length of lens
Light rays from the distant object are sharply focused onto the retina
Photorecpetors in retina are stimulated
Nerve impulses are transmitted by the optic nerve to brain
Brain interprets the impulses and person sees the object
focusing on near object
Ciliary muscles contract, relaxing their pull on suspensory ligaments
Suspensory ligaments slacken, relaing their pull on the lens
Lons become thicker and more convex
Decreases in focal length
Lights rays from object is sharply focused onto the retina
Photorecpetos in retina is stimulated
Nerve impulsesare generated and transmitted by optic nerve to the brain
Brain interprets the image and person sees the object
nuclear cataract on eye
disrupt ability of lens to refrcat light rays onto retina, difficulty for vision under dim light
lens cant adjust to focus on obj at diff dist
cloudy vision
