eye ! Flashcards
frontal view !
cornea conjunctiva pupil iris eyelid eyelash tear gland
cornea !
refract light rays into the eye
conjunctiva !
secretes mucus -> keep front of eyeball moist
pupil !
allow light to enter eye
iris !
controls amt of light entering eye + contains pigment -> gives eye its colour
eyelid !
protects cornea from mechanical damage
eyelash !
shields the eye from dust particles
tear gland !
secretes tears
- wash away dust particles
- keep the cornea moist for atmospheric oxygen to dissolve -> diffuse into cornea
- lubricate conjunctiva -> reduces friction when eyelids move
vertical view !
sclera choroid retina forea blind spot optic nerve lens suspensory ligament aqurous chamber viterous chamber
sclera !
protects eyeball from mechanical damage
choroid !
contains blood vessels that carry oxygen & nutrients to eyeball + remove metabolic waste products
retina !
light-sensitive layer on which images are formed
contains photoreceptors
- rods : enable us to see in black&white in dim light
cones : enable us to see colours in bright light
forea !
images are formed here
- contains cones, no rods -> enables a person to have detailed colour vision in bright light
blind spot !
does not contain photoreceptors -> not sensitive to light
optic nerve !
transmit nerve impulses to brain when photoreceptors in retina are stimulated
lens !
transparent, circular & biconcave structure
elastic : able to change its shape & thickness to refract light onto retina
aqueous & vitreous chamber !
filled with aqueous/viterous humour : transparent, watery fluid
- keeps front of eyeball firm
- helps refract light into pupil
image formation on retina !
light rays : refracted through cornea & aqueous humour onto lens
- further refracted when passed through lens
image on retina : stimulates photoreceptors depending on intensity of light -> nerve impulses transmitted through optic nerve -> brain
- vertically inverted (upside down)
- laterally inverted (mirror image)
- diminished (smaller than object)
brain : corrective function
- makes image upright
pupil reflex process !
change in light intensity detected by retina (receptor) -> sends nerve impulses to optic nerve (sensory neurone) -> synapse -> brain (relay neurone) -> synapse -> motor neurone -> iris’ circular & radial muscles (effector) -> response (constrict/dilate)
bright light !
circular muscles of iris : contract
radial muscles of iris : relax
pupil : becomes smaller, constricts
- reduces amount of light entering eye to prevent mechanical damage to retina
dim light !
circular muscles of iris : relax
radial muscles of iris : contract
pupil : enlarges, dilates
- increases amt of light entering eye -> see better in the dark
distant object !
ciliary muscles : relax -> pulling on suspensory ligaments
suspensory ligaments : taunt -> pulling on the edge of lens
lens : becomes thinner, less convex -> increases focal length
light rays : sharply focused on retina -> stimulating photoreceptors
nerve impulses : produced & transmit to brain by optic nerve
brain : interprets impulses -> person sees distant object
near object !
cililary muscles : contract -> relaxing pull on suspensory ligaments
suspensory ligaments : slacken -> relaxing pull on lens
lens : becomes thicker, more convex -> decreasing focal length
light rays : sharply focused on retina -> stimulates photoreceptors
nerve impulses : produced -> transmitted by optic nerve to brain
brain : Interprets impulses -> person sees nearby object
far vision !
light rays : parallel
- smaller angle of refraction
near vision !
light rays : divergent
- greater angle of refraction
