lecture 7 and 8- vision

Question 1

define refraction

Answer 1

bending of light waves at an angulated surface of a transparent material

Question 2

define degree of refraction

Answer 2

amount of bending of light

Question 3

what does degree of refraction depend on

Answer 3

ratio of the 2 refractive indices of the 2 transparent media and the degree of angulation between the interface and the entering wave front of the light waves

Question 4

define refractive index

Answer 4

ratio of the velocity of light in air to the velocity of light traveling in the substance

Question 5

define refractive power

Answer 5

measure of how much a lens bends light waves

Question 6

define a diopter

Answer 6

1 diopter= 1 meter divided by the focal length of a lens

Question 7

define focal point

Answer 7

point through which all parallel rays of light will pass after passing through each part of the lens

Question 8

define focal length

Answer 8

distance from the center of the lens to the focal point

Question 9

what does the iris do

Answer 9

controls the amount of light entering the eye from darkness to light conditions and plays role in depth of focus

Question 10

define emmetropia

Answer 10

normal eye with regard to depth of focus. all distant objects can be seen clearly

Question 11

define hyperopia

Answer 11

farsightedness usually due to an eyeball that is either too short or a lens system that is too weak; all distant objects can be seen clearly

Question 12

define myopia

Answer 12

nearsightedness due to too long of an eyeball

Question 13

define visual acuity

Answer 13

measure of the resolving power of the eye

Question 14

what is the max visual acuity for 2 point sources of light

Answer 14

2 micrometers

Question 15

define glaucoma

Answer 15

build up of fluid pressure in the eye

Question 16

what is a tonometer sued for

Answer 16

used to measure the intraocular pressure

Question 17

what is the normal intraoccular pressure

Answer 17

15 mm Hg

Question 18

what is the photosensitive pigment in rods

Answer 18

rhodopsin

Question 19

describe the outer segment of rods/cones

Answer 19

site of light sensitive photochemicals

Question 20

describe the inner segment of rods/cones

Answer 20

contains organelles, especially mitochondria

Question 21

describe the synaptic body of rods/cones

Answer 21

connects with horizontal and bipolar cells

Question 22

what does excitation of rods cause

Answer 22

increased negativity of the intrarod membrane potential (hyper polarization)

Question 23

what does decomposition of rhodopsin do

Answer 23

decreases rod membrane conductance for sodium ions in the outer segment

Question 24

what colors are cones sensitive to

Answer 24

blue, green and red

Question 25

list the layers of the retina in order

Answer 25

photoreceptors, horizontal cells, bipolar cells, amacrine cells and ganglion cells

Question 26

define the plexiform layer

Answer 26

layer of synaptic connections

Question 27

where do photoreceptors transmit signals to

Answer 27

outer plexiform layer

Question 28

what do photoreceptors synapse with

Answer 28

bipolar cells and horizontal cells

Question 29

what type of signals do horizontal cells do

Answer 29

transmit signals from rods and cones to bipolar cells and transmit signals to outer plexiform layer

Question 30

where do bipolar cells transmit signals from

Answer 30

rods, cones and horizontal cells

Question 31

where do bipolar cells transmit signals to

Answer 31

inner plexiform layer

Question 32

what do bipolar cells synapse with

Answer 32

amacrine and ganglion cells

Question 33

describe the signals of amacrine cells

Answer 33

transmit signals directly from bipolar to ganglion cells; within inner plexiform layer from axons of bipolar cells to dendrites of ganglion cells or to other amacrine cells

Question 34

where do ganglion cells transmit signals from

Answer 34

retina to brain

Question 35

what type of cell axons make up optic nerves

Answer 35

ganglion cell axons

Question 36

what do interplexiform cells transmit signals from

Answer 36

from inner plexiform layer to outer plexiform layer (retrograde)

Question 37

what type of neurons are in the direct pathway of foveal region

Answer 37

cones, bipolar cells and ganglion cells

Question 38

what type of neurons are in the pure rod vision

Answer 38

rods, bipolar cells, amacrine cells and ganglion cells

Question 39

what neurotransmitter is used by rods and cones (bipolar cells)

Answer 39

glutamate

Question 40

what type of neurotransmitters are used by amacrine cells

Answer 40

there are more than 8, but all of them are inhibitory

Question 41

what is the main role of amacrine cells

Answer 41

interneurons that help analyze visual signals before they leave the retina

Question 42

where is visual acuity strongest

Answer 42

central retina (central fovea)

Question 43

what is the peripheral retina most sensitive to

Answer 43

weak light

Question 44

how fast do W ganglion cells transmit signals

Answer 44

8 m/sec

Question 45

describe the fields of W ganglion cells

Answer 45

broad fields in peripheral retina because their dendrites spread widely in the inner plexiform layer

Question 46

where do W ganglion cells get most of their excitement

Answer 46

from rods transmitted by way of small bipolar cells and amacrine cells

Question 47

how fast do X ganglion cells transmit signals

Answer 47

14 m/sec

Question 48

describe the fields of X ganglion cells

Answer 48

they have small fields (signals represent discrete retinal locations)

Question 49

what type of ganglion cells are likely responsible for all color vision

Answer 49

X ganglion cells

Question 50

how fast do Y ganglion cells transmit signals

Answer 50

50m/sec or faster

Question 51

where does the dorsal lateral geniculate nucleus receive input from

Answer 51

optic nerve

Question 52

how does the dorsal lateral geniculate nucleus relay info from optic tract to visual cortex

Answer 52

optic radiation (geniculoalcarine tract)

Question 53

what layers of the lateral geniculate nucleus receive signals from lateral half of ipsilateral retina

Answer 53

2, 3 and 5

Question 54

what layers of the lateral geniculate nucleus receive signals from medial half of opposite retina

Answer 54

1, 4, and 6

Question 55

where do layers 1 and 2 of the dorsal lateral geniculate nucleus receive input from and what type of vision do they transmit and what type of layers are they

Answer 55

from large Y type ganglion cells and transmit only black and white. They are magnocellular layers

Question 56

where do layers 3-6 of the dorsal lateral geniculate nucleus receive input from and what type of vision do they transmit and what type of layers are they

Answer 56

from large X type ganglion cells and transmit color and are parvocellular layers

Question 57

define transmission gating and what controls it

Answer 57

controlled by lateal geniculate nucleus and it is the control of how much signal is allowed to pass to the cortex

Question 58

what is the source of gating control

Answer 58

corticofugal fibers from primary visual cortex and reticular areas of mesencephalon

Question 59

where is the primary visual cortex located

Answer 59

occipital lobes

Question 60

where do geniculocarine fibers mainly terminate

Answer 60

in layer 4

Question 61

where do signals from Y ganglion cels terminate in the primary visual cortex

Answer 61

layer IVc-alpha

Question 62

where do signals from X ganglion cells terminate in the primary visual cortex

Answer 62

layer IVc-beta and IVa

Question 63

where are color blobs located

Answer 63

among the columns of the secondary visual areas

Question 64

where do color blobs receive lateral signals from and how are they activated

Answer 64

from adjacent visual columns and are activated specifically by color signals

Question 65

what do meridional fibers do

Answer 65

control and release tension in the lens

Question 66

what do circular fibers do

Answer 66

decrease tension in lens

Question 67

what cranial nerve controls both sets of ciliary muscles

Answer 67

CN III