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Phys > vision > Flashcards

vision Flashcards

1
Q

chemoreceptors

A
  • oxygen, pH, various organic molecules such as glucose
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2
Q

mechanoreceptors

A
  • pressure (baroreceptors), cell stretch (osmoreceptors), vibrations,, acceleration, sound
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3
Q

photoreceptors

A
  • photons of light
  • rods and cones
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4
Q

thermoreceptors

A

varying degrees of heat

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5
Q

transduction

A
  • stimulus energy converted into information processed by nervous system
    – Ion channels or second messengers initiate membrane potential change
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6
Q

adequate stimulus

A
  • form of energy to which a receptor is most responsive
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7
Q

threshold

A
  • minimum stimulus
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8
Q

receptor potential (graded potential)

A
  • change in sensory receptor membrane potential
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9
Q

receptive field

A
  • the physical area where a stimuli activates a neuron
    – Primary sensory neuron and secondary sensory neuron
  • Receptive fields frequently overlap
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10
Q

neighboring fields experience what

A

convergence

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11
Q

size determines sensitivity

A

– Two-point discrimination test: gives you a perception of how far something is
- test peripherals too
– Sensitive areas have smaller receptive fields: think color
– Less sensitive areas have larger receptive fields
- large receptive fields = black and white

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12
Q

cones and rods

A
  • cones = pick up color
  • rods = black and white
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13
Q

vision

A

– Light reflected from objects in the environment are translated into a mental image
- based on graded potential

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14
Q

3 steps to vision

A
  1. Light enters the eye, and the lens focuses the light on the retina
  2. Photoreceptors of the retina transduce light energy into an electrical signal
  3. Neural pathways from retina to brain process electrical signals into visual images
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15
Q

anatomy of the eye

A
  • Lens focuses light
    – Suspended by ligaments called zonules
  • Two chambers in the eye
    – Anterior chamber
    ▪ In front of the lens filled with aqueous humor covered by cornea
    – Vitreous chamber
    ▪ Behind the lens, filled with vitreous body (humor)
  • Sclera
    – Outer wall of eye consisting of connective tissue
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16
Q

light is modified

A

– Pupil modulates quantity of light and depth of field
– Focused on retina by changes in the lens

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17
Q

light is directed to the retina

A

– Photoreceptors transduce light energy into electrical signal

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18
Q

neural pathways process electrical signals into visual images

A

– Optic disk (blind spot) is location where neurons join into the optic nerve
– Optic nerves cross over in the optic chiasm
– Neurons synapse in lateral geniculate body in thalamus
– Optic tracts end at the visual cortex in the occipital lobe

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19
Q

what kind of reflex is pupillary reflex?

A
  • consensual reflex
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20
Q

eye and vision

A
  • light enters the pupil
  • dilation = gets more light
  • constrict = less light
21
Q

lateral and medial

A
  • L= same side
  • M= opposite
  • left lateral vision = left side of the brain
  • right medial vision = left side of brain
22
Q

optics describe what?

A
  • light behavior and properties
23
Q

focal point

A
  • point where light rays converge
24
Q

focal length

A
  • distance from the center of lens to the focal point
25
Q

light entering the eye

A
  • refracted or bent at the cornea and lens
    – Lens is modified to have focal point land on retina by ciliary muscles
26
Q

accommodation

A
  • process of the eye adjusting lens shape to keep objects in focus
    – Near point of accommodation is the closest distance at which the lens can focus an object
27
Q

myopia

A
  • focal point falls in front of the retina
28
Q

hyperopia

A
  • focal point falls behind the retina
29
Q

presbyopia

A
  • loss of accommodation
30
Q

astigmatism

A
  • distorted images usually caused by a misshapen cornea
31
Q

phototransduction

A
  • converts light energy into electrical signals
32
Q

what do pigment epithelium absorb?

A
  • light that escape the photoreceptors
33
Q

where do most acute vision occur?

A
  • at the fovea and macula (visual field)
34
Q

photoreceptor cells

A
  • pass sensory information to bipolar cells which pass information to ganglion cells
    – Ganglion cells form the optic nerve which leaves the eye at the optic disk (blind spot)
35
Q

optic disk

A
  • no photoreceptors
  • called blind spot
36
Q

is vision graded potential?

A
  • yes
  • strength –> lots of light coming at it –> lots of stimulus
37
Q

do cones and rods share basic structure?

A
  • yes
  • outer, inner, and basal segments
38
Q

what do rods and cones contain?

A

– Rods contain rhodopsin
– Cones contain three pigments primary excited by red, green, and blue light.
▪ Color-blindness defect in one or more cones

39
Q

rhodopsin

A

– Opsin – protein (GPCR) embedded in rod membrane disks
– Retinal – vitamin A derivative
▪ Light-sensitive pigment, undergoes conformation change
– With light, opsin no longer binds to retinal –> blecahing

40
Q

cyclic-nucleotide gated (CNG) channels

A

– Open when cGMP is present
– Rod is depolarized –> release of glutamate onto bipolar cell

41
Q

transducin – G protein

A

– Light stimulates to start cascade that reduces availability of cGMP
▪ CNG channel closes, rod no longer depolarized –> no glutamate

42
Q

what do photoreceptor cells converge in?

A
  • bipolar neurons
43
Q

what do multiple bipolar neurons converge onto?

A
  • one ganglion cell
44
Q

horizontal cells

A
  • synapse with photoreceptors and bipolar cells
45
Q

amacrine cells

A
  • modulate information between bipolar and ganglion cells
46
Q

ganglion cells have visual receptive fields

A

– Round center
– Doughnut-shaped surround
– Use contrast to interpret visual information
– M cells vs. P cells

47
Q

binocular zone

A

– The central portion of the visual field where the visual field of each eye overlap
– Processed to give 3D vision

48
Q

monocular zone

A

– Visual field of only one eye

49
Q

projected and processed info is highly organized

A

– Topographical organization

Phys (13 decks)

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