TIMS VISION

Question 1

what is the predominant sensory input regarding the external environment?

Answer 1

vision

Question 2

what does vision require?

Answer 2

transduction of photon energy into a frequency of action potentials in the retina of the eye

Question 3

where are the action potentials conducted?

Answer 3

primary visual cortex of the brain

Question 4

optic nerve becomes what after it crosses the optic chiasm?

Answer 4

optic tract

Question 5

left and right visual field in relation to the LGN of the right hemisphere

Answer 5

left visual field projects medially and the right visual field projects laterally

Question 6

the retina contains what kind of cells?

Answer 6

photosensitive cells of the eye

Question 7

what structure of the eye bends incident light? what about the fine tuning and focus?

Answer 7

cornea and lens with the cornea doing most of the bending

lens

Question 8

T/F, light passing through the midline is bent by the cornea or lens?

Answer 8

F, it tis not

Question 9

what helps us accommodate for near or far objects?

Answer 9

circular and meridional fibers attached to suspensory ligaments

Question 10

this type of focus is accomplished by relaxing the fibers, which tightens the ligaments and elongating the lens and results in less bending of light

Answer 10

distant focus

Question 11

affect of suspensory ligaments relaxed?

Answer 11

no pulling and lens are more spherical, more bending of light

Question 12

affect of suspensory ligaments contracted?

Answer 12

pulling and so lens ends up in a more elongated or contracted state, less bending of light

Question 13

normal vision?

Answer 13

emmetropia

Question 14

near sighted? lens to treat?

Answer 14

myopia

concave lens

Question 15

far sighted? lens to treat?

Answer 15

hypermetropia

convex lens

Question 16

this disorder of the lens results from a bulge developing one axis along the lens and is corrected by placing a lens with a concavity along the same axis in front of the eye?

Answer 16

astigmatism

Question 17

what cells are involved in the encoding of incoming light?

why are the axons of the ganglion cells significant?

Answer 17

rods and cones for transduction

horizontal, bipolar and amacrine cells for processing

ganglion cells for transmission of the action potentials to the brain

*they become the optic nerves

Question 18

these cells are used for white and black vision?

Answer 18

rod cells

Question 19

these cells are used for color vision?

Answer 19

cone cells

Question 20

where are the cones concentrated?

Answer 20

behind the pupil in an area called the macula

Question 21

this is the region of greatest visual acuity and is predominantly comprised of cone cell transducers?

Answer 21

fovea, located in the center of the macula

Question 22

this is what we have in our vision which results from the location where the ganglion cell axons congregate and lead the eye to form the optic nerve?

Answer 22

blind spot

Question 23

T/F, rods and cones are located in the optic disk and so light striking the area can be transduced?

Answer 23

F, the cannot and so light cannot be transduced

Question 24

what is the purpose of the pigment epithelium?

Answer 24

the pigment absorbs photons which manages to pass by the ads and cones without being absorbed

storage for vitamin A

Question 25

this is needed for rhodopsin synthesis by rod cells?

Answer 25

retinol

Question 26

this type of vitamin deficiency will result in rods not being as effective leading to night blindness

Answer 26

vitamin A

Question 27

what is the chemical responsible for light transduction?

Answer 27

rhodopsin

Question 28

what are the three photopsins the cones are sensitive too? shortest waveleght to longest?

Answer 28

blue, green, red

blue
green
red

Question 29

what colors are the most common forms of color blindness?

Answer 29

red
green
red-green

Question 30

briefly describe the mechanism of light transduction?

Answer 30

photon strikes rhodopsin, retinal is converted from cis to trans producing metarhodopsin II and so the trans-retinal dissociates and detaches from scotopsin by the rhodopsin kinase

the trans retinal is converted back to cis retinal by retinal isomerase and also have the formation of the rhodopsin

*constant illumination causes a decrease in rhodopsin

Question 31

what happens when the metarhodopsin is activated?

Answer 31

transducin is activated with activates phosphodiestreae molecules which catabolizes cAMP, cGMP to GMP an inactivating mechanism decreasing Na conductance therefore causing the membrane potential to hyper polarize leading to the inactivation of the metarhodopsin by the rhodopsin kinase

Question 32

what is the effect of the hyperpolarization on the rod cells?

Answer 32

increase in frequency of APs in the ganglion cells and so these depolarize affecting the ganglion cells via bipolar cells that result an inhibitory NT, but the ganglions cells are further depolarized

keep in mind that ganglion cells receive information from both cones and rods

Question 33

how are images pieced together?

Answer 33

picture is associated by modality and cannot be reassembled except by the visual association cortex which helps us put it into a picture