visual physiology

Question 1

what is the first site of refraction and is it fixed or variable

Answer 1

cornea

fixed

Question 2

what is the second site of refraction and is it fixed or variable

Answer 2

lens

variable

Question 3

how does a rounder lens affect refraction

Answer 3

more refraction

Question 4

how does curvature of the lens increase

Answer 4

ciliary m. contracts => suspensory ligaments loosen => natural recoil, rounded lens

Question 5

how does curvature of the lens decrease

Answer 5

ciliary m. relaxes => suspensory ligaments tighten, flattening the lens

Question 6

is increased or decreased refraction used for far vision

Answer 6

decreased (lens is flattened)

Question 7

for near vision, is lens curvature increased or decreased

Answer 7

increased (refraction is increased)

Question 8

what are the three steps of the near response

Answer 8

• constriction of ciliary ms
• convergence of eyes to focal point
• pupillary constriction

Question 9

how does pupillary constriction contribute to near vision

Answer 9

less light enters, eliminating diverging light rays and allowing better focus

Question 10

what are the three types of vertially oriented cells in the retina

Answer 10

• receptor cells
• bipolar cells
• ganglion cells

Question 11

are melanopsin ganglion cells horiztonally or vertically oriented

Answer 11

vertically oriented

Question 12

what are the two types of horizontally oriented cells in the retina

Answer 12

• horizontal cells

- amacrine cells

Question 13

do rods or cones facilitate vision in dim light?

Answer 13

rods

Question 14

what aspect of the rod system allows increased sensitivity in dim light

Answer 14

convergence - many rods and bipolar cells converge on one ganglion cell

Question 15

what aspect of the cone system allows maximal acuity

Answer 15

less convergence - one cone and bipolar to each ganglion cell

Question 16

where does cone density peak

Answer 16

the fovea

Question 17

where does rod density peak

Answer 17

20 degrees off center

Question 18

what is the relationship of glumate release by rods and cones to light

Answer 18

inverse relationship - less light, more glutamate released

Question 19

photons stimulate what in the rods and cones

Answer 19

hyperpolarization

Question 20

what occurs if the center of an on-center bipolar cell’s receptive field is activated

Answer 20

depolarization of the bipolar cell

Question 21

what occurs if the periphery of an on-center bipolar cell’s receptive field is activated

Answer 21

hyperpolarization of the bipolar cell secondary

Question 22

what occurs if the periphery of an off-center bipolar cell’s receptive field is activated

Answer 22

depolarization of the bipolar cell

Question 23

what occurs if the center of an off-center bipolar cell’s receptive field is activated

Answer 23

hyperpolarization of the bipolar cell

Question 24

how do amacrine cells assist in low-light vision

Answer 24

inhibit competing visual pathways using GABA/glycine

Question 25

what cells tell where an object ends

Answer 25

off-center cells

Question 26

what are the 5 direct targets of the retina

Answer 26

``` superior colliculus lateral geniculate body (LGN) pretectum accessory optic nuclei (AON) hypothalamus ```

Question 27

what target of the retina controls eye motions to converge on point of interest

Answer 27

LGB

Question 28

what target of the retina controls focus of the eyes based on distance and determines relation position of objects

Answer 28

LGB

Question 29

what target of the retina detects movement relative to an object

Answer 29

LGB

Question 30

what brodmann area is the peristriate cortex

Answer 30

19

Question 31

what brodmann area is the parastriate cortex

Answer 31

18

Question 32

what layer of the primary visual cortex receives input from the LGB

Answer 32

IV

Question 33

what are the main output layers of the primary visual cortex

Answer 33

V and VI

Question 34

what are ocular dominance columns

Answer 34

groups of cells in the primary visual cortex that preferentially respond to one eye over the other

Question 35

what are blobs

Answer 35

regions of neurons in the primary visual cortex that are sensitive to color

Question 36

what is the major function of VI (the primary visual cortex)

Answer 36

identification of edges and contours

Question 37

what is the major function of V2

Answer 37

depth perception

Question 38

what is the major function of V3a

Answer 38

identification of motion

Question 39

what is the major function of V4

Answer 39

processing of color input

Question 40

what is the function of the dorsal pathway

Answer 40

"where" - associating vision with movement

Question 41

through what structures does the dorsal visual pathway pass

Answer 41

primary visual cortex => through V3 => parietal/frontal cortex

Question 42

what is the function of the ventral visual pathway

Answer 42

"what" - naming and recognizing objects

Question 43

through what structures does the ventral visual pathway extend

Answer 43

primary visual cortex => inferior temporal cortex

Question 44

what are the non-image-forming light-responsive cells?

Answer 44

MG (melanopsin ganglion cells)

Question 45

what is the function of melanopsin ganglion cells

Answer 45

regulation of circadian rhythm

Question 46

where do MG cells project their axons

Answer 46

to the suprachiasmatic nucleus within the thalamus