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67 Cards in this Set

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  • Back
sclera
a tough conn. tissue
makes up the "white" of the eye
cornea
front of eye
a transparent structure that allow light to enter the eye.
choroid
middle layer of the eye
a highly pigmented layer of tissue beneath the sclera.

absorbs light that reaches the back of the eye so that it is not reflected, which cause distortion of the visual image.
ciliary body
contain ciliary muscles attached to the lens by strands of conn. tissue called zonular fibers.
zonular fibers
attached to the lens by strands of conn. tissue called ________ ______.
lens
focuses the light on the retina where the visual info is transduced.
ciliary muscles
change the shape of the lens to focus light waves.
pupil
a hole in the center of the iris that allows light to enter the post. part of the eye
it is NOT a structure
iris
regulates the diameter of the pupil, thereby regulating the amount of light that reaches the back of the eye.
middle layer
The ________ _______ of the eye consists of the choroid, ciliary body, and iris.
retina
The innermost layer of the eye is the ______.
retina
consists of neural tissue
contains photoreceptors
functions as phototransduction
Photoreceptors
cells that detect light waves
two types, rods and cones
Phototransduction
the conversion of light energy to electrical energy.
fovea
where light from the center of the visual field strikes.
The area of the retina w/ the greatest visual actuity
Optic disk
the portion of the retina where the optic nerve and blood vessels supplying the eye pass through the retina.
blind spot
there are no photoreceptors in the optic disk
a reion where light striking the retina cannot be transduced into neural impulses and cannot be perceived.
ant. cavity
aqueous humor
In front of the lens and ciliary body is the called the ________ _______ containing a clear, watery fluid called __________ ______, which supplies nutrients to the cornea and lens.
vitreous chamber
vitreous humor
Behind the lens and ciliary body is the __________ ________ containing a firmer, jellylike material called _________ ______, which maintains the spherical structure of the eye.
electromagnetic waves
Light is a form of energy. Light exists as ________________ ______.
reflection
a phenomenon in which light waves strike and bounce off a surface.

important in vision because much of the light we perceive has reflected off the objects we are observing.
refraction
the bending of light waves as they pass through transparent materials of different densities.

its path from objects to the photoreceptors in the retina, light must pass through several different materials, including air, cornea, the lens, and the vitreous and aqueous humor.
focal point
the convex lens causes the light waves to converge at a single point called the ______ ______.
focal length
The distance from the long axis of the convex lens to the focal point is called the _______ _______.
Concave
surfaces cause a divergance of light waves
Convex
surfaces cause convergence of light waves to a focal point.
visual field
what we are looking at
must converge at a single point on the retina.
rounder
When viewing close objects, the lens becomes ________, increasing its refractive power to focus the image on the retina.
parallel
When viewing something far away, the light waves enter the eye almost ________ to each other, so little refractive power of a rounder lens is needed to focus the light on the retina.
Accomodation
reflex adjustments of the eye to view near objects

including rounding of the lens, constriction of the pupil, and post. movement of the lens.
accommadation
under control of the parasympathetic nervous system, which triggers contraction of the ciliary muscle for near vision.
myopia
nearsightedness

a person can see near objects clearly, but not distant objects because the lens or cornea is too strong for the length of the eyeball and therefor bends light rays too much.

close-up objects can be focused w/out accommadation, but light from distant objects is focused in from of the retina, resulting in a blurred image.
hyperopia
farsightedness

the lens or cornea is too weak for the length of the eyeball.

distant objects can be focused only w/ accommadation, which means that the lens cannot increase accommadation enough to adjust for near vision.

Light from close-up objects comes to focus behind the retina, resulting in a blurred image.
emmetropia
normal vision
a person can see both distant and close up objects clearly becuase the eye can focus light from far sources without accommadation, and from near sources w/ accomadation.
astigmatism
irregularities on the surface of the cornea or lens cause erratic bending of light waves.
presbyopia
a hardening of the lens that occurs w/ aging; as the lens hardens, its loss of elasticity decreases its ability to become spherical, making accommadation for near vision more difficult.
cataract
an age-related discoloration of the lens that decreases its transparency.
glaucoma
increase in the volume of aqueous humor raises pressure in the ant. carity of the eyeball, which can distort the shape of the cornea and shift the position of the lens.
myopia
_________ can be corrected by using a concave lens to produce divergence of light waves before they enter the eye.
hyperopia
_________ can be corrected by using a convex lens to produce convergence of light waves that supplements the convergence produced in the eye.
circular muscle
(constrictor muscle)
form concentric rings around the pupil
when they contract, the diameter of the pupil decreases.
pupillary contriction
The contraction of the circular muscles cause __________ __________.
radial muscles
dialator muscle
are arranged like spokes in a wheel
When they contract, the diameter of the pupil increases
leads to pupillary dialation.
parasympathetic neurons
___________ _______ innervate the circular muscles, which leads to pupillary constriction.
sympathetic neurons
____________ ________ innervate the radial muscles, which leads to pupillary dialation.
Rods
provide the ability to see in black and white during relatively low light conditions, such as the light provided by the moon at night.
Cones
provide us with color vision, but they are active only relatively bright light, such as the sunlight during the day.
retina
1. an inner layer containing neurons called ganglion cells
2. a middle layer containing neurons called bipolar cells
3. an outer layer containing rods and cones.

amacrine cells & horizontal cells(communication btwn cells in the retina)
Macula lutea
a depression in the center of the retina that surrounds the fovea.
fovea
The ______ contains cones only; the ratio of rods to cones increases w/ distance from the ______, until at the periphery of the retina only rods are present.
phototransduction
the conversion of light energy into elecrical signals, is carried out by the rods and cones.
outer and inner segments
The two types of photoreceptors is the same; each consists of 2 major portions referred to as _______ and ________ _________.
outer segment
contains invaginations w/membranous disks that contain the molecules that absorb light waves, giving the photoreceptors the ability to respond to light.
inner segment
contains the cell nucleus and various organelles and ends at the receptor's synaptic terminal, which is anaglogus to an ordinary neuron's axon terminal and is where a chemical messenger is stored in synaptic vesicles.
photopigment
absorption of light is the first step in phototransduction, and the molecule in the photoreceptors that absorbs light
retinal
opsin
Each photopigment molecule contains a light-absorbing portion called _______ and a protein called an _______.
retinal
opsin
The _______ portion is the same in all photopigments, but the kind of ______ present determines which light wavelengths are absorbed by a given photopigment by altering the electromagnetic energies to which the retinal is sensitive.
high
Is the degree of convergence w/ bipolar cells in rods high or low?
low
Is the degree of convergence w/ bipolar cells in cones high or low?
at the periphery of retina
Where is the site of greatest concentration in the rods?
in the fovea
Where is the site of greatest concentration in the cones?
low
What is the visual actuity for rods?
high
What is the visual actuity for cones?
high
Do rods have a high sensitivity or a low sensitivity to light?
low
Do cones have a high sensitivity or a low sensitivity to light?
rods
rhodopsin
When exposed to bright light, the ____ become "bleached"; that is, most of the ___________ has absorbed light, and the opsin in in its active form. No more light can be absorbed until the ___________ has been returned to original (bleached) state.
unbleached
____________ rods are extremely sensitive to light.