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PHYSIOLOGY SEMESTER 2 > lecture 7 and 8- vision > Flashcards

lecture 7 and 8- vision Flashcards

1
Q

define refraction

A

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

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2
Q

define degree of refraction

A

amount of bending of light

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3
Q

what does degree of refraction depend on

A

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

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4
Q

define refractive index

A

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

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5
Q

define refractive power

A

measure of how much a lens bends light waves

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6
Q

define a diopter

A

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

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7
Q

define focal point

A

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

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8
Q

define focal length

A

distance from the center of the lens to the focal point

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9
Q

what does the iris do

A

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

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10
Q

define emmetropia

A

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

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11
Q

define hyperopia

A

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

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12
Q

define myopia

A

nearsightedness due to too long of an eyeball

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13
Q

define visual acuity

A

measure of the resolving power of the eye

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14
Q

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

A

2 micrometers

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15
Q

define glaucoma

A

build up of fluid pressure in the eye

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16
Q

what is a tonometer sued for

A

used to measure the intraocular pressure

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17
Q

what is the normal intraoccular pressure

A

15 mm Hg

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18
Q

what is the photosensitive pigment in rods

A

rhodopsin

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19
Q

describe the outer segment of rods/cones

A

site of light sensitive photochemicals

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20
Q

describe the inner segment of rods/cones

A

contains organelles, especially mitochondria

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21
Q

describe the synaptic body of rods/cones

A

connects with horizontal and bipolar cells

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22
Q

what does excitation of rods cause

A

increased negativity of the intrarod membrane potential (hyper polarization)

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23
Q

what does decomposition of rhodopsin do

A

decreases rod membrane conductance for sodium ions in the outer segment

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24
Q

what colors are cones sensitive to

A

blue, green and red

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25
Q

list the layers of the retina in order

A

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

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26
Q

define the plexiform layer

A

layer of synaptic connections

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27
Q

where do photoreceptors transmit signals to

A

outer plexiform layer

28
Q

what do photoreceptors synapse with

A

bipolar cells and horizontal cells

29
Q

what type of signals do horizontal cells do

A

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

30
Q

where do bipolar cells transmit signals from

A

rods, cones and horizontal cells

31
Q

where do bipolar cells transmit signals to

A

inner plexiform layer

32
Q

what do bipolar cells synapse with

A

amacrine and ganglion cells

33
Q

describe the signals of amacrine cells

A

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

34
Q

where do ganglion cells transmit signals from

A

retina to brain

35
Q

what type of cell axons make up optic nerves

A

ganglion cell axons

36
Q

what do interplexiform cells transmit signals from

A

from inner plexiform layer to outer plexiform layer (retrograde)

37
Q

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

A

cones, bipolar cells and ganglion cells

38
Q

what type of neurons are in the pure rod vision

A

rods, bipolar cells, amacrine cells and ganglion cells

39
Q

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

A

glutamate

40
Q

what type of neurotransmitters are used by amacrine cells

A

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

41
Q

what is the main role of amacrine cells

A

interneurons that help analyze visual signals before they leave the retina

42
Q

where is visual acuity strongest

A

central retina (central fovea)

43
Q

what is the peripheral retina most sensitive to

A

weak light

44
Q

how fast do W ganglion cells transmit signals

A

8 m/sec

45
Q

describe the fields of W ganglion cells

A

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

46
Q

where do W ganglion cells get most of their excitement

A

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

47
Q

how fast do X ganglion cells transmit signals

A

14 m/sec

48
Q

describe the fields of X ganglion cells

A

they have small fields (signals represent discrete retinal locations)

49
Q

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

A

X ganglion cells

50
Q

how fast do Y ganglion cells transmit signals

A

50m/sec or faster

51
Q

where does the dorsal lateral geniculate nucleus receive input from

A

optic nerve

52
Q

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

A

optic radiation (geniculoalcarine tract)

53
Q

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

A

2, 3 and 5

54
Q

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

A

1, 4, and 6

55
Q

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

A

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

56
Q

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

A

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

57
Q

define transmission gating and what controls it

A

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

58
Q

what is the source of gating control

A

corticofugal fibers from primary visual cortex and reticular areas of mesencephalon

59
Q

where is the primary visual cortex located

A

occipital lobes

60
Q

where do geniculocarine fibers mainly terminate

A

in layer 4

61
Q

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

A

layer IVc-alpha

62
Q

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

A

layer IVc-beta and IVa

63
Q

where are color blobs located

A

among the columns of the secondary visual areas

64
Q

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

A

from adjacent visual columns and are activated specifically by color signals

65
Q

what do meridional fibers do

A

control and release tension in the lens

66
Q

what do circular fibers do

A

decrease tension in lens

67
Q

what cranial nerve controls both sets of ciliary muscles

A

CN III

PHYSIOLOGY SEMESTER 2 (20 decks)

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