Vision Flashcards
Photoreceptors
respond to light; rods and cones
accessory structures of the eye
eyebrows, eyelids, conjunctiva, lacrimal apparatus, extrinsic eye muscles
orbit of the skull
bony socket in the skull containing eyes
conjunctiva
mucous membrane lining the eyelids and covering the anterior portion of the sclera (not cornea)
conjunctivitis (pink eye)
Inflammation caused by infection of the conjunctiva, characterized by redness and often discharge
tarsal glands (Meibomian glands)
- modified sebaceous glands
- along inner margin of the eyelids
- lipid-rich secretions keep eyelids from sticking together
orbicularis oculi
closes eyelids
evator palpebrae
elevates (opens) eyelid
lacrimal apparatus
the structures that produce, store, and remove tears
The lacrimal glands produce
tears
Lysozyme
an enzyme found in tears that destroys the cell walls of certain bacteria
extrinsic eye muscles
superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, inferior oblique; attached to the sclera; move the eyeball
cranial nerves that innervate extrinsic eye muscles
oculomotor (III), abducens (VI), trochlear (IV)
strabismus
abnormal deviation of the eye
diplopia
double vision
Abduction
Movement away from the midline of the body
Adduction
Movement away from the midline of the body
Elevation
Raising a body part
depression(body movement)
lowering a body part
three tunics of the eyeball
fibrous outer, vascular middle, nervous inner
outer tunic of eye
cornea, sclera;(optic nerve II pierces sclera)
Cornea
The transparent layer forming the front of the eye
Function of cornea
Refracts light
Does the cornea have pain receptors?
Yes
Can the cornea be transplanted?
Yes
Sclera
White of the eye; protects the delicate inner layers of the tissue; extrinsic eye muscles attach here
Optic Nerve (II)
sensory, vision; pierces sclera at posterior of eye
middle tunic of eye
choroid coat, ciliary body, iris
Choroid Coat
nourishes the retina and absorbs scattered light to keep inside the eye dark
Ciliary Body
Structure surrounding the lens that connects the choroid and the iris. It contains ciliary muscles, which control the shape of the lens, and it SECRETES THE AQUEOUS HUMOR
Lens
The transparent structure behind the pupil that changes shape to help focus images on the retina
Accommodation
The process by which the eye’s lens changes shape to focus near objects on the retina
Suspensory Ligaments
A fibrous membrane that holds the lens of the eye in place
Ciliary muscles (eye)
Contract to thicken the lens (closer things), relax to thin the lens (further things)
Iris
A ring of smooth muscle tissue that forms the pigmented portion of the eye around the pupil and controls the size of the pupil opening
Anterior Cavity of the Eye
Between cornea and lens; filled with aqueous humor
Function of aqueous human
Maintains the pressure needed to inflate the eye and provides nutrition for the central cornea and lens
Scleral venous sinus (canal of Schlemm(
The scleral venous sinus (canal of Schlemm) is a circular channel in the eye that collects aqueous humor from the anterior chamber and delivers it into the bloodstream
Pupillary Reflex
The automatic process by which the iris contracts and relaxes to control the size of the pupil, in response to the relative brightness of light entering the eye
Glaucoma
increased intraocular pressure results in damage to the retina and optic nerve with loss of vision; scleral venous sinus does not drain aqueous humor from eye
Cataracts
Clouding of the lens; artificial lens can replace it
Retina
Light sensitive layer of the eye; contains rods and cones
How many rods and cones?
100 million/3 million
Retinal Pigment Epithelium(RPE)
- layers of cells at the back of the eye
- how photoreceptors get nutrients
Macula lutea
yellowish spot on the back of the retina; contains the fovea centralis; area of SHARPEST VISION
Fovea Centralis
pinpoint depression in the center of the macula lutea that is the site of sharpest vision; contains cones
Optic Disc (blind spot)
*site where optic nerve leaves the eye
*lacks photoreceptors
Pathway of light through the eye
Light enters eye -> cornea -> aqueous humor -> lens -> vitreous humor -> neural layer of retina (where photoreceptors are)
Refraction
The bending of a wave as it passes from one medium to another
Parts of eye that refract light
cornea (most), aqueous humor, lens (fine-tunes), vitreous humor
convex lens
A lens that is thicker in the middle than at the edges
concave lens
A lens that is thinner in the center than
A convex lens causes light to
converge
near point of vision
the closest an object can be and still come into focus
presbyopia
farsightedness caused by loss of elasticity of the lens of the eye, occurring typically in middle and old age.
emmetropia
normal refractive condition of the eye
myopia
nearsightedness; due to elongated eyeball or thickened lens; focal point is in front of the retina; corrected with concave lenses
Hyperopia (farsightedness)
farsightedness; due to shorter eyeball or thinner lens; focal point is behind the retina; corrected with convex lenses
astigmatism
defective curvature of the cornea or lens of the eye; vision is blurry
rods or cones? Mores sensitive to light so they can function in dim ligh
rods
Rods or cones? produce color images
cones
Rods or Cones? Concentrated in the fovea centralis of the macula lutea
cones
Rods or Cones? More common in the periphery of the retina
rods
Rods or Cones? Provide less precise image
rods
Rods or Cones? Each one synapses with one nerve fiber
cones
visual pigments
light sensitive chemicals that react to light and trigger electrical signals
rhodopsin
a light-sensitive pigment found in the rod cells that is formed by retinal (derived from vitamin A) and opsin.
kinds of cones
3 types that detect blue, green, and red
stereoscopic vision
combination of two retinal images to give a 3-D perceptual experience and allows depth-perception; requires binocular vision; happens because pupils are 6-7 cm apart
Visual Pathway to the Brain
Light stimulus causes impulses to travel from the: Light > retina > Optic nerves > optic chiasma (medial fibers cross to opposite side) > optic tracts > thalamus > optic radiations > occipital lobe (visual cortex)
age-related macular degeneration
progressive and irreversible destruction of receptors from any of a number of causes
retinal detachment
separation of the retina from the underlying epithelium, disrupting vision and resulting in blindness if not repaired surgically
nystagmus
involuntary, darting movements of the eyes
floaters
particles of cellular debris that float in the vitreous fluid and cast shadows on the retina; see “moving specks”
cataract surgery
Surgical removal of a clouded lens of the eye
