study guide chpt 3

Question 1

define electromagnetic spectrum

Answer 1

covers a wide range of wavelengths and photon energies

-is energy that is produced by electric charges and radiated as waves

Question 2

UNDERSTAND

Answer 2

the visual spectrum is between 400-700

Question 3

cornea

Answer 3

shapes and focuses the light

accounts for about 80% of focusing

Question 4

iris

Answer 4

responsible for controlling the diameter and size of the pupils and the amount of light reaching the pupil

Question 5

lens

Answer 5

adjusts shape for object distance, accounts for the other 20%.

Question 6

ciliary muscles

Answer 6

permit the lens to change its shape in order to focus on near or distant objects

Question 7

aqueous humor

Answer 7

fluid nourishes the cornea and the lens and gives the eye it’s shape

Question 8

vitreous humor

Answer 8

clear gelatinous substance that fills the eyeball between the retina and the lens

Question 9

retina

Answer 9

a light-sensitive layer at the back of the eye that covers about 65 percent of its interior surface

Question 10

fovea

Answer 10

the absolute center of vision

-center area of the retina; covered in cones, located in the line of sight

Question 11

optic nerve

Answer 11

Either of the second pair of cranial nerves, which carry sensory information relating to vision from the retina of the eye to the brain. Disease or injury of the optic nerve can result in partial or total blindness.

Question 12

UNDERSTAND

Answer 12

cornea is responsible for 80% of focusing power, Lens is 20%

Question 13

eye accomodation

Answer 13

the ability of the eye to change it’s focus from distant to near objects. this process is achieved by the lens changing its place

Question 14

myopia

Answer 14

nearsightedness

light is focused in front of retina and the eyeball is too long

Question 15

hyperopia

Answer 15

farsightedness

light is focused behind the retina and eyeball is short

Question 16

presybopia

Answer 16

progressively diminished ability of the eye to focus. caused by the loss of elasticity of the crystalline lens. starts around middle age 40-45

Question 17

amblyopia

Answer 17

lazy eye- loss or lack of development of central vision in one eye that is unrelated with any health problems and not correctable with lenses.

Question 18

strabismus

Answer 18

cross eye- condition where both eyes do not look at the same place at the same time. usually caused by poor eye muscle control or a high amount of farsightedness

Question 19

blind spot

Answer 19

where the optic nerve leaves the eye; no visual receptors here

Question 20

macular degeneration

Answer 20

common, painless eye condition in which the central portion of the retina deteriorates and does not function adequately

Question 21

what are the eye receptors?

Answer 21

rods and cones

Question 22

where are the visual pigment molecules located?

Answer 22

in their outer segments

Question 23

what are the two main components of the visual pigment molecules?

Answer 23

opsin-protein of the retinal rods adn cones

retinal

Question 24

how does visual transduction occur?

Answer 24

retinal absorbs one photon and changes shape. this is called isomerization. this starts an enzyme cascade

Question 25

enzyme cascade

Answer 25

is what your brain changes what you perceive into an image

Question 26

isomerization

Answer 26

when your retina changes shape

Question 27

dark adaptation curve

Answer 27

rods=turtle;slow but finishes the race meaning they help you see in the dark
cones=rabbit; fast but burns out faster
-visual adaptation that occurs in the dark; during which the sensitivity to light increases

Question 28

stages of dark adaptation curve

Answer 28

Stage 1 takes place for 3 to 4 minutes.
Then sensitivity levels off for 7 to 10 minutes - the rod-cone break.
Stage 2 shows increased sensitivity for another 20 to 30 minutes.
During this time the cones and rods are regenerating. Opsin and retinal are recombining

Question 29

what happens in dark adaptation?

Answer 29

rods and cones are regenerating[this means the opsin and retinal are recombining

Question 30

Purkinje Shift

Answer 30

name for enhanced sensitivity to short wavelengths (blue and greens) during dark adaptation when the shift from cone to rod vision occurs

Question 31

convergence in retina

Answer 31

Rods and cones send signals to the bipolar cells then the ganglion cells and then out the retina through the optic nerve.

Question 32

UNDERSTAND

Answer 32

rods an cones converge to bipolar cells and then into ganglion cells and then to the optic nerve

Question 33

what is lateral inhibition in the retina?

Answer 33

light shown in a receptor leads to rapid rate of firing

-think of inhibitory synpases

Question 34

What is the mechanism behind Hermann Grid?

Answer 34

your eye is trying to see something that is not there (inhibitory)
-inhibitory receptors in the white areas

Question 35

what is the mechanism behind Mach Bands?

Answer 35

another optical illusion

-more in the light areas and less in the dark areas (inhibition)

Question 36

how does simultaneous contrast work?

Answer 36

the change in perception of color that occurs when a colored field is surrounded by a differently colored background

Question 37

what is the explanation for white’s illusion?

Answer 37

an area’s appearance is affected by where we perceive it belongs