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Physiology for Pharmacy > Visual System > Flashcards

Visual System Flashcards

1
Q

what structures make up the optical part of the eye?

A

iris, cornea, lens, colliery muscles and zonular fibers

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2
Q

what is the function of the optical portion of the eye?

A

regulation of amount of light entering the eye, refraction

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3
Q

what structures make up the neural part of the eye?

A

retina an doptic nerve

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4
Q

what is the function of the neural part of the eye?

A

phototransduction and signal transduction

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5
Q

what are the intraocular structures of the eye?

A

choroid, sclera, aqueous and vitreous humorist, cilliary body, canal of schlemm

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6
Q

function of choroid

A

contains blood vessels

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7
Q

function of sclera

A

protective connective tissue

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8
Q

function of aqueous and vitreous humour

A

fill anterior and posterior eye cavities

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9
Q

function of the optic nerve

A

bundle of axons that transmit information to visual cortex and subcortical areas

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10
Q

the choroid provides nutrition to the __

A

retina

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11
Q

structure of the iris

A

fibrovascular structure with embedded circular and radial muscles and central pupil

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12
Q

what causes pupil to constrict?

A

contraction of circular muscles

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13
Q

what causes pupil to dilate?

A

contraction of radial muscles

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14
Q

iris muscles are under the control of a __

A

reflex arc

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15
Q

myopia is also known as

A

shortsightedness

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16
Q

what causes myopia?

A

long egg eyes that are too long to allow lens to focus distant objects on the retina

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17
Q

hyperopia is also known as __

A

farsightedness

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18
Q

what causes hyperopia?

A

eye to short to focus near objects on the retina

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19
Q

what is presbyopia?

A

loss of lens elasticity with age, becomes less spherical

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20
Q

what is an astigmatism?

A

irregular curve of cornea/lens, causing light to be detracted unevenly and resulting in a blur

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21
Q

what is cataract?

A

opaque lens caused by the accumulation of pigments, causing less light to be absorbed

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22
Q

refraction is carried out by __ and __ . What % does each contribute?

A

cornea 75% and lens 25%

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23
Q

what is accommodation?

A

adjustment of lens convexity by colliery muscles, allowing images both near and far to be focused on the retina

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24
Q

what is the cornea?

A

transparent structure at anterior of eye

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25
Q

lens can change its power by ___ muscles attached to ___fibers

A

colliery; zonular

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26
Q

what lens type is used to correct myopia

A

concave

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27
Q

what type of lens is used to correct hyperopia

A

convex

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28
Q

a convex lens adds __ power

A

refractive

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29
Q

when the colliery muscles are relaxed, the zonular fibers are __ and the lens is __, leading to what change in refractive power?

A

tightened, less convex, less refraction

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30
Q

when the colliery muscles are contracted, the zonular fibers are __ and the lens is ___, leading to what change bin refractive power?

A

loosened, more spherical, increased refraction

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31
Q

the fovea contains only

A

cones

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32
Q

the fovea lacks a __ cell layer

A

bipolar ganglion

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33
Q

why does the fovea lack a bipolar ganglia layer?

A

allows for more direct light without it

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34
Q

the fovea is the site of greatest visiual __

A

acuity

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35
Q

t/f there is convergence in the fovea

A

false

36
Q

the peripheral retina contains mostly __

A

rods

37
Q

the density of cones decreases with increasing distance from the __

A

fovea

38
Q

in the peripheral retina there is convergences between ___ and __ as well as __ an __

A

rods and bipolar cells; bipolar cells and ganglion cells

39
Q

what is theistic disc?

A

area where retinal ganglion axons bundle to form the optic nerve

40
Q

there are not __ in the blindspot (optic disc)

A

photoreceptors

41
Q

cones allow for __ vision

A

colour

42
Q

rods allow for ___ vision

A

low-light

43
Q

___ are the site of phototransduction

A

photoreceptors

44
Q

what are the 3 types of higher-order sensory neurons involved in vision?

A
  1. bipolar cells
  2. ganglion cells
  3. inhibitory interneurons
45
Q

bipolar cells are excited or inhibited by __ , ___, ___ and ___

A

rods, cones, action potential, nT release

46
Q

ganglion cells are activated (result in ap) when __

A

excitatory signal from bipolar cells

47
Q

what are the only neurons to enter the retina?

A

ganglion cells

48
Q

ganglion cells die in __ and __

A

glaucoma and macular degeneration

49
Q

what are the 2 types of inhibitory interneurons and where they are located

A
  1. horizontal cells (between photoreceptors)

2. amacrine cells (between bipolar and ganglion cells)

50
Q

lateral inhibition increases__ an __

A

contrast and acuity

51
Q

light enters the retina by the __ cells

A

ganglia

52
Q

___ are the only cells to create action potential and carry information from the retina out through the optic nerve to the cortex

A

ganglia

53
Q

t/f cones are not as sensitive as rods and require more light to function

A

ture

54
Q

what is the purpose of the pigment epithelium at the back of the retina?

A

to absorb stray light

55
Q

what is phototransduction?

A

turning light into the release of NT (neuronal response )

56
Q

what is the NT in the eye?

A

glutamate

57
Q

how does light provoke a neuronal response?

A
  1. photoreceptors transduction it to glutamate
  2. bipolar cells detect glutamate resulting in graded potentials
  3. graded potentials cause release of glutamate to ganglion cells
  4. ganglion cells detect glutamate and if depolarization is large enough, an cation potential will happen
58
Q

photoreceptors have membrane stacks called __ in the outer segment

A

disks

59
Q

disks contain __

A

photopigment

60
Q

what is photopigment?

A

proteins with covalently bound light-absorbing retinal cofactor

61
Q

what photopigment is found in rods?

A

rhodopsin

62
Q

what photopigments are found in cones?

A

opsins (red, green, blue)

63
Q

rhodopsin absorbs light from what range?

A

blue to orange

64
Q

light leads to the isomerization of __ and the activation of __

A

retinal; opsins

65
Q

what is the isomerization of retinal?

A

conformational change from cis to trans

66
Q

light-activated trans-retinal dissociates from ___ and is converted to __ before re-binding to __

A

opsin; cis-retinal; opsin

67
Q

describe the process of phototransduction in the dark

A

cGMP is constantly made by guanylyl, cGMP gated ion channels open, persistent depolarization and constant NT release

68
Q

describe the process of phototransduction in light

A

conformational change of retinal, activation of transducer G protein, degradation of cGMP, close ion channels, hyperpolarization, decreased NT release

69
Q

the retina has 2 kinds of bipolar cells ___ and __

A

ON and OFF

70
Q

ON bipolar cells have __ receptors

A

inhibitory metabotropic glutamate

71
Q

light leads to ___ of ON bipolar cells and a ___ in NT and action potential

A

depolarization; increase

72
Q

ON bipolar cells synapse onto __ ganglion cells

A

ON

73
Q

darkness leads to ___ of ON bipolar cells and a ___ in NT and action potential

A

hyper polarization; decrease

74
Q

ON bipolar cells synapse onto

A

ON ganglion cells

75
Q

OFF bipolar cells have __ receptors

A

excitatory inotropic glutamate receptors

76
Q

light leads to __of OFF bipolar receptors

A

hyper polarization

77
Q

OFF bipolar cells synapse onto __

A

OFF ganglion cells

78
Q

due to lateral inhibition, light in the receptive field periphery leads to ___ of ON bipolar cells and ___ of OFF cells

A

inhibition; activation

79
Q

lateral inhibition is caused by the influence of neighbouring ___ cells

A

horizontal

80
Q

activity of bipolar cells is not only affected by the photoreceptors that synapse directly to them, but also by __

A

surrounding horizontal cells

81
Q

retinal ganglion cell axons form the ___ that travels to the neurons in the __ and ___

A

optic nerve and tract; thalamus; visual cortex

82
Q

what us decussation?

A

axons from ganglion cells in nasal half of retinas cross the optic chasm so that the right visual field is presented to the left visual cortex

83
Q

t/f the temporal half of ganglion neurons do not decussate

A

true

84
Q

retinal ganglion travel to the midbrain to control changes in ___ in response to illumination and to control movements of ___, __ and__

A

pupil size, illumination; eye, head, neck

85
Q

nasal halves of the retina receive info from the __ side

A

epsilateral

86
Q

temporal halves of the retina revive info from the __ side

A

contralateral

Physiology for Pharmacy (39 decks)

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