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809 - Exam Block 2 > Physiology of Vision - Metz > Flashcards

Physiology of Vision - Metz Flashcards

1
Q

the retina of the eye is responsible for converting the _________ waves of light stimuli into _________

A

electromagnetic ; electrical signals

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2
Q

At a basic level, the photoreceptors of retina (eye) is capable of detecting two different qualities of light, what are they

A

brightness ; light

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3
Q

A large aperture would allow a ____ amount of light to pass through

A

large

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4
Q

a small aperture would allow a _____ amount of light to pass through

A

smaller

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5
Q

The pupil is an aperture that
controls the amount of light transmitted to the interior of the eye –> this process is controlled by the

A

autonomic nervous system

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6
Q

The iris is innervated by both the ______ and ______ divisions of the nervous system

A

sympathetic ; parasympathetic

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7
Q

When a bright light strikes the eye, the ________ nervous system facilitates _______
of the pupil via stimulation of the _______

** This reflex will occur bilaterally in both eyes, even if only one eye has been exposed to the high intensity light **

A

parasympathetic ; constriction ; circular muscles

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8
Q

When the eyes are exposed to a darker environment, the _______ nervous system
stimulates ______ of the radial muscles, leading to pupil ______

A

sympathetic ; constriction ; dilation

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9
Q

The pupillary reflex is important because it regulates the _______ falling upon the retina, and also protects the retina from overexposure to light

A

intensity of light

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10
Q

the aperture also affects the

A

depth of field (sharpness)

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11
Q

A large aperture will result in a larger ________ aka a larger
amount of blur in the background

A

depth of field

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12
Q

For closer vision, ciliary muscle ______ via ______ stimulation

A

contracts ; PS

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13
Q

for closer vision, tension on suspensory fibers is

A

reduced

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14
Q

for closer vision, the lens becomes more

A

spherical

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15
Q

for closer vision, the focal power is ______ for near vision

A

increased

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16
Q

_____ occurs when light passes between two different mediums

A

Refraction

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17
Q

To focus on closer objects, the eye must ______ its focal power through a process called ______

A

increase ; accommodation

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18
Q

High concentration of photoreceptors in the

A

fovea

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19
Q

a relaxed ciliary muscle = a _____ lens

A

flat

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20
Q

a not-relaxed ciliary muscle = lens is

A

round

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21
Q

in myopia/near-sightedness - the axis of the eye is

A

too long

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22
Q

correction for myopia/near-sightedness = ____ lens that ____ the light

A

concave ; diverges

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23
Q

in hyperopia/far-sightedness - the axis of the eye is

A

too short

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24
Q

correction for hyperopia/far-sightednesss = ____ lens that ____ the light

A

convex ; converges

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25
Q

in hyperopia/far-sightedness, the image is focused ____ the retina

A

behind

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26
Q

the lens becomes _____ elastic with age so the ability to accommodate _____

A

less ; decreases

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27
Q

Presbyopia causes difficulty seeing

A

near objections

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28
Q

to correct presbyopia = _____ lens that _____ the light

A

convex ; converges

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29
Q

uneven curvature of cornea and/or lens

A

astigmatism

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30
Q

an astigmatism = the image is _____ on the retina

A

unfocused

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31
Q

to correct an astigmatism = ____ lens that _____ the light

A

cylindrical ; appropriately focuses

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32
Q

the photoreceptors that are
responsible for detecting light are in the _____ regions of the retina

A

deeper

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33
Q

The ganglion cells are the _____ of the retina, and their axon fibers are arranged in the _____

A

output ; optic nerve

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34
Q

Photoreceptors are

A

rods and cones

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35
Q

pigment epithelium absorbs

A

photons

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36
Q

rods and cones send _____ signals

A

electrical

37
Q

The sensory receptors in the retina are called

A

photoreceptors

38
Q

photoreceptors are responsible for converting the
_______ signals from photons into the ______ signals of the
nervous system

A

electromagnetic ; electrical

39
Q

3 types of cones

A

red, green, blue

40
Q

cones see ____ vision ; rods = ______ vision

A

color ; black & white

41
Q

rods work best for ____ vision and cones work best for ____ vision

(hint = what time)

A

night ; day

42
Q

rods are ______ to low-light intensitity

A

sensitive

43
Q

cones are not sensitive to

A

low-intensity light

44
Q

rods are associated with _____ accuity

A

low

45
Q

cones are associated with _____ accuity

A

high

46
Q

rods are not present on the

A

fovea

47
Q

cones are present on the

A

fovea

48
Q

Both rods and cones contain outer segments comprised of

A

photoreceptor disks

49
Q

Both rods and cones have inner segments which contain the

A

nucleus, mitochondria, and other cellular organelles

50
Q

The base of the photoreceptors
contain _______ that communicate with the _______ layer of the eye

A

synaptic bodies ; neural network

51
Q

In these cellular membranes of the disks are embedded molecules of ______

A

photopigments

52
Q

For rods, the photopigment is called ______

A

rhodopsin

53
Q

The detection of light by the photopigment leads to the
conversion of ______ to ______

A

11-cis-retinal ; all-trans-retinal

54
Q

The conversion of 11-cis-retinal to all-trans-retinal leads to a complex signaling cascade that
initiates several downstream effects via a

A

G-protein pathway

55
Q

When rods are in a DARK environment, an enzyme in the cytosol called guanylyl cyclase
continuously converts _____ into _____

A

GTP ; cGMP

56
Q

When rods are in a DARK environment

cGMP leads to activation of ________ in the plasma membrane of the _____ segment

A

non-selective cation
channels ; outer

57
Q

When rods are in a DARK environment

The non-selective cation
channels allow sodium
molecules to diffuse down their electrochemical gradient from the extracellular fluid into the _____ of the ____

A

cytosol ; rod

58
Q

When rods are in a DARK environment

The movement of this Na+ into the cell produces a _____ of the cell

A

depolarization

59
Q

When rods are in a DARK environment

The depolarization of the cell stimulates the release of the neurotransmitter
______ from the _____ of the rod

A

glutamate ; synaptic end bulb

60
Q

When rods are in a LIGHT environment

When a photon of light is detected by a pigment in rods called ________ , the compound _________ is converted to _________

A

rhodopsin ; 11-cis retinal ; all trains retinal

61
Q

When rods are in a LIGHT environment

The conversion of 11-cis retinal to all trains retinal stimulates an associated G-protein called _________ to exchange its
bound _____ for ______

A

transducin ; GDP ; GTP

62
Q

When rods are in a LIGHT environment

Once GDP is exchanged for GTP, the activated _____ subunit of the G-protein then dissociates from the _______

A

alpha ; beta-gamma complex

63
Q

When rods are in a LIGHT environment

The activated alpha subunit of the G-protein then dissociates from the beta-gamma complex leads to the activation of the enzyme ________________, which
catalyzes the breakdown of
_____ into ______

A

cGMP phosphodiesterase ; cGMP ; 5’GMP

64
Q

When rods are in a LIGHT environment

the breakdown of cGMP ; 5’GMP decreases the cytosolic levels of ______ , leading to closure of a _____ channel in the plasma membrane

A

cGMP ; non-selective cation

65
Q

When rods are in a LIGHT environment

The closure of the non-selective cation channel in the plasma membrane causes a drop in sodium _____ which leads to _______ of the plasma
membrane, as the membrane potential become more ______ than at rest

A

influx ; hyperpolarization ; negative

66
Q

In the dark, cGMP levels are _____, and this allows for the non-specific cation channels in the plasma membrane of the outer segment to be ____

A

high ; open

67
Q

in the dark

Sodium will be removed from the cytosol in the inner segment via a ______, leading to the “________”

A

sodium-potassium pump ; “dark current”

68
Q

In the light, as the cGMP levels _____, cellular reactions lead to a _____ of these same non-
specific cation channels

A

decrease ; closure

69
Q

in the light, ____ sodium enters the cell, leading to a ______ of the plasma membrane and a ______ in the release of neurotransmitters from the ______

A

less ; hyperpolarization ; decrease ; synaptic end bulb

70
Q

In the light the decrease in the release of neurotransmitters from the synaptic end bulb would ______ the release of ______ during exposure to light

A

decrease ; glutamate

71
Q

the downstream effects of the neurotransmitter glutamate can be either ______ or ______, depending on the type of receptors activated on the bipolar or horizontal cells

A

excitatory ; inhibitory

72
Q

The bases of the photoreceptors contain synaptic bodies that communicate with the neural
network layer of the eye and is comprised of 3 cell types, what are they?

A

bipolar
horizontal
amacrine

73
Q

Due to the thinness of the retina and the close proximity of these structures, the photoreceptors and interneurons can
communicate effectively using _______

A

graded potentials

74
Q

The ganglion cell layer is responsible for integrating all of the information from the ______ cells and sending ______ via their axons in the ______

A

upstream ; electrical signals ; optic nerve

75
Q

The bases of the photoreceptors contain a synaptic body that releases neurotransmitters onto
the ______

A

bipolar cells

76
Q

Rods are located at the ______ of the retina, and many rods synapse onto a _______ cell

A

periphery ; single bipolar

77
Q

Rods have a high level of ______ with as many as 300 rods ______ onto a _____ cell

A

convergence ; converging ; single ganglion

78
Q

Rods have a high level of convergence = this results a _____ sensitivity of rods, as light striking any of these rods could _____ the bipolar cell

A

higher ; activate

79
Q

Rods have a high level of convergence - this results a higher sensitivity of rods - this arrangement also produces a _____ acuity in rods

A

lower

80
Q

the clearness or sharpness of vision

A

acuity

81
Q

there are relatively _____ cones that converge on a ____ cell

A

few ; ganglion

82
Q

In the fovea, the ratio of cones to ganglion cells is almost _____

A

1:1

83
Q

There are relatively few cones that converge on a ganglion cell. In the fovea, the ratio of cones to ganglion cells is almost 1:1. This allows for ________ of the color image, but ______ light sensitivity

A

greater sharpness/acuity ; lower

84
Q

High sensitivity
Low acuity

A

periphery of the retina

85
Q

periphery of the retina has a ______ of rods and cones

A

mixture

86
Q

periphery of the retina - many rods ______ onto a single ganglion cell

A

synapse

87
Q

low sensitivity
high acuity

A

center of the retina : fovea

88
Q

cones only

A

center of the retina : fovea

89
Q

1:1 ratio of cones to ganglion cells

A

center of the retina : fovea

809 - Exam Block 2 (14 decks)

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