the eye Flashcards
receptors definition
specialized cells that detect stimuli and convert them into nerve impulses
photoreceptors
receptors which detect light stimuli
position of the eye
two eyes positioned in bony eye sockets at the front of the skull
eye structure
- spherical ish and has six eye muscles which help w movement
- front of eye is covered by conjunctiva
- tear gland is above the eye
conjunctiva
thin mucous membrane which triggers a blink reflex when foreign objects enter the eye
things that protect the eye
eyelids, eyelashes
tear gland
secreted antiseptic tears that protect the conjunctiva from bacteria and dehydration
three layers of the eye
outer fibrous
middle vascular
inner light-sensitive retina
outer fibrous consists of
sclera
cornea
cornea
transparent part of the sclera, allows light rays through to the inner layers of the eye and refracts them
sclera
a strong white connective tissue that forms the outer layer of the eyeball
- protects internal parts, serves for muscle attachment
middle vasc layer consists of
choroid
ciliary body
iris
also: pupil; lens; susp ligaments
choroid
a thin, dark vascular layer
pigment absorbs excess light rays to prevent blurred images
ciliary body
a thickening of the front of the choroid, consisting of ciliary muscles and is attached to the lens by suspensory ligaments
ciliary body functions
contract and relax to change lens curvature during accomodation
iris
- round structure in the middle of the eye
- at the front of the lens and contains pigments to give it color
pupil
opening in the middle of the iris through which light rays enter the eye
iris function
regulates the amount of light that enters the eye by controlling pupil size
lens
rubbery elastic structure that changes shape
lens function
changes shape to refract light rays and form an image on the retina
inner-light sensitive retina consists of
pigment layer
nervous tissue layer
yellow spot
optic nerve
pigment layer
outer layer that is in contact w choroid
pigment absorbs light rays, prevents internal reflection
nervous tissue layer
consists of rods and cones which detect light stimuli (photoreceptors)
rods
are stimulated in low light and give rise to b&w vision
cones
stimulated in high light intensity and give rise to intense color vision
yellow spot function
where the clearest most accurate image is formed
function of optic nerve
conducts nerve impulses to the brain where they are interpreted to give sensation of sight
divisions of the lens
anterior cavity
posterior cavity filled w vitreous humor (behind)
anterior cavity
in front, aqueous humor
anterior chamber - betw cornea and iris
posterior - betw iris and lens
vitreous humor functions
- maintains eyeball shape
- refracts light rays
- hold retina in position
what is the pupillary mechanism
reflex action which responds to the stimulus of the amount of light that enters the eye
pupillary mechanism process
BRIGHT LIGHT radial musc relax (RR) circular musc contract (CC) pupil constricts less light vice versa for low light
accommodation
the process during which the eye adapts for the observation of nearby objects (6m) by changing the lens shape
accommodation for distant objects
circular musc relax (CR) ciliary body further away from lens sus lig are taut (slacken) lens less convex less light refracted sharp focused image on retina
binocular vision
each eye forms its own image of the object, brain combines the two images to form a 3D image
what binocular vision does
provides a wider field of vision and depth perception
stereoscopic vision
the ability to see in 3D
myopia
- short sightedness
- elongated eyeball, cornea curve
fixing myopia
- concave lenses to diverge rays before they enter the eye
- laser surgery
hypermetropia
shorter eyeball, flat cornea
correcting hypermetropia
convex lenses, converges light rays to focus on the retina
laser surgery
astigmatism
causes light rays to focus on more than one focal point
- causes a blurry image
- glasses, contacts, lasers
cataracts
the clouding of the eyes lens, prevents light from reaching the retina, blurred vision
- initially glasses, or laser surgery
