VISION Flashcards
1
Q
how are mecahno receptors activated
A
mechanical deformation in nerve endings
2
Q
how are thermo receptors activated
A
temp
3
Q
how are chemo receptors activated
A
chemicals in enviro
4
Q
what energy is required to activate photo receptors
A
photon energy
5
Q
what do osmo receptors regulate
A
osmolarity of body fluids
6
Q
what are AP s of nociceptors interpreted as
A
pain
7
Q
what receptors are involved in hearing
A
meachno receptors
8
Q
what mechanical deformation occurs in mechano receptors for hearing
A
bending of hair
9
Q
what receptors are involved in vision
A
photo receptors
10
Q
what is sensory perception
A
converting en from outside of body into form that body can interpret
11
Q
what form of en can body interpret
A
AP s
12
Q
what is adequate stimulus
A
particular type of energy that sensory ending responds to
13
Q
what must all energy be converted to
A
- electrochemical energy (AP s)
- change in mem potential
14
Q
what is primary transduction process
A
conversion of one form of energy / event to electrochemical energy
15
Q
what is primary transduction process for vision
A
photons of light converted to AP
16
Q
what is primary transduction process for hearing
A
- sound waves in air get converted to sound waves in fluid
- sound waves in fluid cause bending of hair
- bending of hair opens channels
- opening of channels changes mem potential
17
Q
what is generator potential
A
stimulus that causes depolarization or hyper polarization in sensory nerve
graded
18
Q
when is generator potential hyper polarizing
A
if K + leaves cell
19
Q
what is generator potential proportional to
A
strength of stimulus
20
Q
what determines how many stimuli can be discriminated
A
- range
2. stimuli
21
Q
VISION what does range of visual system depend on
A
the wavelengths visible to humans
22
Q
VISION what is sclera
A
white fibrous part of eye
23
Q
VISION what is cornea
A
clear continuation of sclera
24
Q
VISION what is conjunctiva
A
thin protecting mem covering cornea
25
VISION what is most powerful part of light focusing system
cornea
26
VISION where does light get partially focused
cornea
27
VISION what is anterior chamber
small chamber behind cornea
28
VISION what is anterior chamber filled with
aqueous humor
29
VISION what secretes aqueous humor
ciliary body
30
VISION what drains aqueous humor
canal of schlemm
31
VISION where is canal of schlemm
where cornea and sclera join
32
VISION what is posterior chamber
chamber behind anterior chamber
33
VISION what is posterior chamber filled with
aqueous humor
34
VISION where is crystalline lens located
behind anterior chamber
35
VISION what are characteristics of lens
1. convex
| 2. elastic
36
VISION what does fluid filled anterior chamber allow cornea and lens to do
act as single optical unit
37
VISION what is cornea analogous to
coarse adjustment
38
VISION what is lens analogous to
fine adjustment
39
VISION where is vitreous chamber located
behind lens
40
VISION what is vitreous chamber filled with
vitreous humor
41
VISION what is the function of vitreous humor
maintain shape of eye
42
VISION what does fibrous tissue and fluid in eye allow
deformation without breaking
43
VISION where is retina located
back of eye
44
VISION what kind of layers of cells does retina contain
1. receptor cells
| 2. processing cells
45
VISION where is choroid layer located
behind retina
46
VISION what is choroid layer composed of
layer of pigment cells
47
VISION what do pigment cells contain
melanin
48
VISION what does melanin absorb
light not absorbed by receptor cells to prevent light scatter
49
VISION what would light scatter result in
blurred image
50
VISION what is accommodation
process by which curvature of lens increased
51
VISION when does accommodation occur
during near vision
52
VISION what holds lens in place behind iris
suspensory ligaments
53
VISION what are suspensory ligaments attached to
ciliary muscles
54
VISION what are ciliary muscles
sphincter like muscles
55
VISION what happens when ciliary muscle relaxes
1. tension on suspensory ligaments increases
2. lens flattens
- distance vision (unaccomodated)
56
VISION what happens when ciliary muscle contracts
1. tension on suspensory ligaments decreases
2. lens roundens
- near vision (accomodated)
57
VISION what is refraction
deflection of light from straight path when passing from one medium to another
58
VISION what is focal distance
distance from refractive surface to point where parallel light rays converge
59
VISION what is refractive surface
cornea
60
VISION what is refractive power
reciprocal of focal distance
61
VISION what is unit for refractive power
diopter
62
VISION what is refractive power of cornea
42 dioptewrs
63
VISION what does refractive power of cornea mean
parallel light striking surface of cornea will be focused 2.4 cm behind it
64
VISION what is 2.4 cm behind cornea
retina
65
REFRACTIVE ERRORS what is myopia
nearsightedness
66
REFRACTIVE ERRORS what causes myopia
eyeball too long
67
REFRACTIVE ERRORS what is hyperopia
farsightedness
68
REFRACTIVE ERRORS what is cause of hyperopia
eyeball too short
69
REFRACTIVE ERRORS in myopia where is image focused
in front of retina
70
REFRACTIVE ERRORS in hyperopia where is image focused
behind retina
71
REFRACTIVE ERRORS how is myopia corrected
- concave / neg lens
| - moves focal point back
72
REFRACTIVE ERRORS how is hyperopia corrected
- convex / pos lens
| - moves focal point forward
73
REFRACTIVE ERRORS what is presbyopia
lens stiffening
74
REFRACTIVE ERRORS what causes presbyopia
age
75
REFRACTIVE ERRORS what does presbyopia result in
decreased ability to focus for close up vision
76
REFRACTIVE ERRORS why is there decreased ability to focus
- lens loses flexibility
| - lens loses ability to accomodate
77
REFRACTIVE ERRORS what is astigmatism
when cornea or lens is more curved in one plane than another
78
REFRACTIVE ERRORS what are cornea and lens both involved in
focusing light to retina
79
REFRACTIVE ERRORS what is result of astigmatism
eye unable to focus light rays to single point causing vision to be out of focus
80
REFRACTIVE ERRORS what is correction for astigmatism
cylindrical lens
81
REFRACTIVE ERRORS how is cylindrical lens diff from spherical lens
focus light into a line instead of a point
82
REFRACTIVE ERRORS what does uneven curvature result in
1. difference in refraction
| 2. point of light seen as line or oval
83
REFRACTIVE ERRORS what is emmetropia
normal vision
84
what is fovea
area of greatest visual acuity
85
what is fovea lacking
blood vessels
86
RETINA why does retina appear to be built upside down
- first layer of cells light strikes is ganglion cells
| - second layer light strikes is receptor cells
87
RETINA what are ganglion cells a part of
final common pathway
88
RETINA how are axons of ganglion cells diff from other cells in retina
able to conduct AP
89
RETINA what happens despite retinal being transparent
- some light absorbed
| - some light reflected away
90
RETINA what is pathway of light once it reaches retina
1. ganglion cells (processing)
2. bipolar cells (processing)
3. receptor cells
- rods
- cones
4. choroid layer
91
RETINA what does outer segment of photoreceptors contain
discs
92
RETINA what do discs contain
visual pigment rhodopsin
93
RETINA what happens to discs
1. shed
2. phagocytized by retinal pigment epithelium
3. replaced (from bottom to top)
94
RETINA what are 2 types of receptor cells
1. rods
| 2. cones
95
RETINA which of receptor cells is more numerous
rods
96
RETINA what is vision w rods
shades of grey
97
RETINA what is sensitivity of rods
- high ==> require lower light
| - night vision
98
RETINA what kind of acuity pathways do rods have
low acuity (not a lot of sharp detail)
99
RETINA what happens to pathways that serve rods
- converge
| - multiple rods feeding into fewer bipolar cells
100
RETINA what is vision w cones
colour
101
RETINA what is sensitivity of cones
- low ==> require brighter light
| - day vision
102
RETINA what kind of acuity pathways (cones)
high acuity (a lot of sharp detail)
103
RETINA what happens to pathways that serve cones
- little convergence
104
RETINA what does little convergence result in
no loss of acuity
105
RETINA where are cones concentrated
in fovea
106
DARK in the dark what do receptor cells have a high conc of
cyclic GMP
107
DARK what does high conc of cGMP allow
- Na channels open
- Na flow into cell
- mem depol
108
DARK what does mem depol result in
1. Ca channels open
2. Cell increases release of inhibitory glutamate
3. inhibitory glutamate inhibits bipolar cells
109
DARK what does inhibition of bipolar cells result in
- no AP conducted to ganglion cells
- no AP conducted to optic nerve
- no AP conducted to lateral geniculate nucleus of thalamus
110
STEPS IN PHOTO RECEPTION what are steps in photo reception
1. light strikes 11-cis retinal
2. 11-cis retinal converted to all trans retinal
3. conformational changes in opsin leads to production of metarhodopsin 2
4. metarhodopsin 2 activates transducin G protein
5. transducin activates phosphodiesterase
6. phosphodiesterase catalyzes conversion of c GMP to 5'-GMP
(cGMP levels decrease)
7. Na channels close
8. hyper polarization decreases release of inhibitory glutamate
111
what are 2 types of glutamate receptors on bipolar cells
1. ionotropic (depolarization)
| 2. metabotropic (hyper polarizing)
112
what does decreased release of glutamate result in for ionotropic receptors
- no depol
- hyper polarization
- inhibit bipolar cells
113
what does decreased release of glutamate result in metabotropic receptors
- no hyper polarization
- depolarization
- excite bipolar cells
114
LIGHT in light what do receptor cells have low concentration of
cyclic GMP
115
LIGHT what does low concentration fo cGMP allow
- Na channels close
- no Na flow into cell
- mem hyper polarization
116
LIGHT what does hyper polarization result in
1. Ca channels close
2. decrease release of inhibitory glutamate
3. bipolar cells not inhibited
117
LIGHT what does lack of inhibition of bipolar cells result in
- AP in ganglion cell
- AP in optic nerve
- AP in lateral geniculate nucleus of thalamus
118
what surrounds receptor cells
retinal pigment of epithelium
119
what is the function of RPE
1. absorb light that does not get absorbed by photoreceptors
2. transport nutrients and ions to photoreceptors
3. required for regeneration of 11-cis retinal
4. required for shedding of photoreceptor disks
120
how is trans retinal converted back to 11 cis retinal
1. trans retinal reduced to trans retinol
2. trans retinol exits rod and goes to RPE
3. trans retinol converted to 11 cis retinol
4. 11 cis retinol converted to 11 cis retinal
5. 11 cis retinal returns to rod
6. 11 cis retinal combines w opsin to form rhodopsin pigment
121
RECEPTIVE FIELD what is receptive field
area on retina which when stimulated enhances / inhibits activity of bipolar or ganglion cells
122
RECEPTIVE FIELD how are receptor fields set up
1. RF s have areas that excite ganglion cell when stimulated
2. RF s have areas that inhibit ganglion cell when stimulated
123
what is pathway of axons from ganglion closest to nose
1. ganglion cell to optic nerve
2. optic nerve to optic chiasm
3. cross over to opposite side
124
what is pathway of axons from ganglion closest to temporal lobe
1. ganglion cell to optic nerve
2. optic nerve to optic chiasm
3. do not cross over to opposite side
125
where does info about L visual field go
R side of brain
126
where does info about R visual field go
L side of brain
