Visual System

Question 1

what structures make up the optical part of the eye?

Answer 1

iris, cornea, lens, colliery muscles and zonular fibers

Question 2

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

Answer 2

regulation of amount of light entering the eye, refraction

Question 3

what structures make up the neural part of the eye?

Answer 3

retina an doptic nerve

Question 4

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

Answer 4

phototransduction and signal transduction

Question 5

what are the intraocular structures of the eye?

Answer 5

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

Question 6

function of choroid

Answer 6

contains blood vessels

Question 7

function of sclera

Answer 7

protective connective tissue

Question 8

function of aqueous and vitreous humour

Answer 8

fill anterior and posterior eye cavities

Question 9

function of the optic nerve

Answer 9

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

Question 10

the choroid provides nutrition to the __

Answer 10

retina

Question 11

structure of the iris

Answer 11

fibrovascular structure with embedded circular and radial muscles and central pupil

Question 12

what causes pupil to constrict?

Answer 12

contraction of circular muscles

Question 13

what causes pupil to dilate?

Answer 13

contraction of radial muscles

Question 14

iris muscles are under the control of a __

Answer 14

reflex arc

Question 15

myopia is also known as

Answer 15

shortsightedness

Question 16

what causes myopia?

Answer 16

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

Question 17

hyperopia is also known as __

Answer 17

farsightedness

Question 18

what causes hyperopia?

Answer 18

eye to short to focus near objects on the retina

Question 19

what is presbyopia?

Answer 19

loss of lens elasticity with age, becomes less spherical

Question 20

what is an astigmatism?

Answer 20

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

Question 21

what is cataract?

Answer 21

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

Question 22

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

Answer 22

cornea 75% and lens 25%

Question 23

what is accommodation?

Answer 23

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

Question 24

what is the cornea?

Answer 24

transparent structure at anterior of eye

Question 25

lens can change its power by ___ muscles attached to ___fibers

Answer 25

colliery; zonular

Question 26

what lens type is used to correct myopia

Answer 26

concave

Question 27

what type of lens is used to correct hyperopia

Answer 27

convex

Question 28

a convex lens adds __ power

Answer 28

refractive

Question 29

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

Answer 29

tightened, less convex, less refraction

Question 30

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

Answer 30

loosened, more spherical, increased refraction

Question 31

the fovea contains only

Answer 31

cones

Question 32

the fovea lacks a __ cell layer

Answer 32

bipolar ganglion

Question 33

why does the fovea lack a bipolar ganglia layer?

Answer 33

allows for more direct light without it

Question 34

the fovea is the site of greatest visiual __

Answer 34

acuity

Question 35

t/f there is convergence in the fovea

Answer 35

false

Question 36

the peripheral retina contains mostly __

Answer 36

rods

Question 37

the density of cones decreases with increasing distance from the __

Answer 37

fovea

Question 38

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

Answer 38

rods and bipolar cells; bipolar cells and ganglion cells

Question 39

what is theistic disc?

Answer 39

area where retinal ganglion axons bundle to form the optic nerve

Question 40

there are not __ in the blindspot (optic disc)

Answer 40

photoreceptors

Question 41

cones allow for __ vision

Answer 41

colour

Question 42

rods allow for ___ vision

Answer 42

low-light

Question 43

___ are the site of phototransduction

Answer 43

photoreceptors

Question 44

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

Answer 44

1. bipolar cells 2. ganglion cells 3. inhibitory interneurons

Question 45

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

Answer 45

rods, cones, action potential, nT release

Question 46

ganglion cells are activated (result in ap) when __

Answer 46

excitatory signal from bipolar cells

Question 47

what are the only neurons to enter the retina?

Answer 47

ganglion cells

Question 48

ganglion cells die in __ and __

Answer 48

glaucoma and macular degeneration

Question 49

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

Answer 49

1. horizontal cells (between photoreceptors) | 2. amacrine cells (between bipolar and ganglion cells)

Question 50

lateral inhibition increases__ an __

Answer 50

contrast and acuity

Question 51

light enters the retina by the __ cells

Answer 51

ganglia

Question 52

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

Answer 52

ganglia

Question 53

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

Answer 53

ture

Question 54

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

Answer 54

to absorb stray light

Question 55

what is phototransduction?

Answer 55

turning light into the release of NT (neuronal response )

Question 56

what is the NT in the eye?

Answer 56

glutamate

Question 57

how does light provoke a neuronal response?

Answer 57

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

Question 58

photoreceptors have membrane stacks called __ in the outer segment

Answer 58

disks

Question 59

disks contain __

Answer 59

photopigment

Question 60

what is photopigment?

Answer 60

proteins with covalently bound light-absorbing retinal cofactor

Question 61

what photopigment is found in rods?

Answer 61

rhodopsin

Question 62

what photopigments are found in cones?

Answer 62

opsins (red, green, blue)

Question 63

rhodopsin absorbs light from what range?

Answer 63

blue to orange

Question 64

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

Answer 64

retinal; opsins

Question 65

what is the isomerization of retinal?

Answer 65

conformational change from cis to trans

Question 66

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

Answer 66

opsin; cis-retinal; opsin

Question 67

describe the process of phototransduction in the dark

Answer 67

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

Question 68

describe the process of phototransduction in light

Answer 68

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

Question 69

the retina has 2 kinds of bipolar cells ___ and __

Answer 69

ON and OFF

Question 70

ON bipolar cells have __ receptors

Answer 70

inhibitory metabotropic glutamate

Question 71

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

Answer 71

depolarization; increase

Question 72

ON bipolar cells synapse onto __ ganglion cells

Answer 72

ON

Question 73

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

Answer 73

hyper polarization; decrease

Question 74

ON bipolar cells synapse onto

Answer 74

ON ganglion cells

Question 75

OFF bipolar cells have __ receptors

Answer 75

excitatory inotropic glutamate receptors

Question 76

light leads to __of OFF bipolar receptors

Answer 76

hyper polarization

Question 77

OFF bipolar cells synapse onto __

Answer 77

OFF ganglion cells

Question 78

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

Answer 78

inhibition; activation

Question 79

lateral inhibition is caused by the influence of neighbouring ___ cells

Answer 79

horizontal

Question 80

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

Answer 80

surrounding horizontal cells

Question 81

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

Answer 81

optic nerve and tract; thalamus; visual cortex

Question 82

what us decussation?

Answer 82

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

Question 83

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

Answer 83

true

Question 84

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

Answer 84

pupil size, illumination; eye, head, neck

Question 85

nasal halves of the retina receive info from the __ side

Answer 85

epsilateral

Question 86

temporal halves of the retina revive info from the __ side

Answer 86

contralateral