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MCAT Behavioral Sciences > Sight (Vision) > Flashcards

Sight (Vision) Flashcards

(48 cards)

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1
Q

Conjunctiva

A

thin layer of cells that lines the inside of your eyelids from the eye

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2
Q

Cornea

A

transparent thick sheet of fibrous tissue, anterior 1/6th; first part of the eye that light hits and starts to bend light

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3
Q

Anterior chamber

A

space filled with aqueous humor, which provides pressure to maintain shape of eyeball
- allows nutrient and minerals to supply cells of cornea/iris

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4
Q

Pupil

A

the opening in the middle of the iris; the size of the pupil can get bigger/smaller based on the iris relaxing/contracting respectively
- pupil modulates the amount of light able to enter the eyeball

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5
Q

Iris

A

gives the eye color, the muscle that constricts or relaxes to change the size of the pupil

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6
Q

Lens

A

bends the light so it goes to back of eyeball
- focuses light specifically on the fovea of the retina
- adjust how much it bends the light by changing its shape, using suspensory ligaments

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7
Q

Suspensory Ligaments

A

attached to a ciliary muscle
- together form ciliary body, what secretes the aqueous humor

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8
Q

Posterior Chamber

A

area behind the iris to the back of lens, also filled with aqueous humor

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9
Q

Vitreous Chamber

A

filled with vitreous humor, a jelly-like substance to provide pressure to eyeball and give nutrients to inside of eyeball

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10
Q

Retina

A

inside back area filled with photoreceptors, where the ray of light is converted from a physical waveform to an electrochemical impulse that the brain can interpret

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11
Q

Macula

A

special part of retina rich in cones, but also rods

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12
Q

Fovea

A

special part of macula. completely covered in cones, no rods
- rest of retina is covered in primarily rods

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13
Q

Cones

A

detect color and discern high level of detail from what is being observed
- cone-shaped

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14
Q

Rods

A

detect light
- rod-shaped

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15
Q

Choroid

A

pigmented black in humans, a network of blood vessels that helps nourish the retina
- black so all light is absorbed
- some animals have a different-colored choroid which gives them better night vision

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16
Q

Sclera

A

usually absorbs by the time the light gets to this
- whites of the eye, thick fibrous tissue that covers posterior 5/6th of the eyeball
- attachment point for muscles
- extra layer of protection an

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17
Q

Transmission

A

electrical activation of one neuron by another neuron

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18
Q

Perception

A

conscious sensory experience of neural processing

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19
Q

Processing

A

neural transformation of multiple neural signals into a perception

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20
Q

Transduction

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A

occurs whenever energy is transformed from one form to another

in eyes, light energy is transformed to electrical energy by rods and cones

21
Q

Sensation

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A

requires a physical stimulus to be converted into a neural impulse

in eyes, light is being converted to a neural impulse by a photoreceptor

22
Q

What is light?

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A

light is an electromagnetic wave

23
Q

Electromagnetic Spectrum

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A

includes everything from gamma rays (short wavelength) to AM/FM waves (long wavelength)

visible light is in the middle of the EM spectrum

24
Q

Visible light

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A

violent (400nm) to red (700nm)

highest to lowest wavelength ROYGBV

25
Trichromatic Theory of color
Types of Cones: Red, Green, Blue red, green, and blue combine to make all the colors we see cones are 60% red, 30% green, 10% blue
26
Purpose of Rods
night vision
27
Phototransduction Cascade (PTC)
process of making the brain recognize there is light entering the eyeball (turn light into neural impulse) When light enters the pupil and goes to retina... - normally rod is turned on, but when light hits it is turned off - When rod is off, it turns on a bipolar cell, which turns on a retinal ganglion cell (attached to optic nerve and enter the brain) light -> rod (turned off) -> bipolar cell (turns on) -> retinal ganglion cell (turns on) -> optic nerve -> brain
28
Mechanism for PTC
1. inside rods there are optic disks stacked on top of one another 2. proteins inside disks: rhodopsin (which contains 11-cis retinal) 3. when light hits the rod, retinal isomerizes to 11-trans retinal -> cascade begins 4. transducin (attached to rhodopsin, made of 3 different parts alpha, beta, gamma) that breaks off from rhodopsin and alpha subunit binds another disk protein phosphodiesterase (PDE) 5. PDE takes cGMP and converts it to regular GMP 6. Na+ channels on rods allow Na+ to come in with cGMP bound. As cGMP concentration decreases, Na+ channel closes and cell turns "off" 7. Next, off rod -> turns on active bipolar cells 8. activates on center in retinal ganglion cell 9. send signal to optic nerve to brain
29
When dark -> Mechanism for PTC
1. rod is turned on 2. off center of bipolar cells is active 3. activates off center of retinal ganglion cells 4. sends signal to optic nerve to brain
30
Bipolar Cells
found in the retina, send visual signals from the rods and cones to ganglion cells
31
Ganglion Cells
found in the retina, takes electrical impulse from the bipolar cells and the impulse travels down its axons axons of ganglion cells makes up the optic nerve
32
Optic Nerve
visual signals, after having been picked up by rods and cones and transferred to bipolar cells to ganglion cells, finally leave the eye through the optic nerve leave through the retina at the back of your eye ("blind spot")
33
Opponent Process Theory of Color Vision
states that the cones we have perceive 4 colors: red, green, blue, and yellow Colors oppose each other, between opponents only one color can dominate at a time red vs. green blue vs. yellow black vs. white
34
Phototopic vision
occurs at levels of high light levels
35
Mesopic vision
occurs at dawn or dusk and involves both rods and cones
36
Scotopic vision
occurs at levels of very low light
37
Photoreceptors
Specialized nerve that can take light and convert it to a neural impulse
38
Optic Disks
inside rods large membrane bound structures that contain proteins that fire action potentials (APs) to the brain
39
Rhodopsin
inside rods, triggers PTC
40
Photopsin
inside cones
41
Difference between rods and cones
- more rods than cones (more important to see light than detail initially) - rods are 1000x more sensitive to light - cones are concentrated in the fovea (no axons in the way of light to get higher resolution) - rods are found mostly in the periphery (light has to go through bundle of axons so some energy is lost, less light gets to rods) - cones detect colors primarily - rods have slow recovery time (need to be reactivated) - cones have fast recovery time (adapt to change quickly)
42
Blind Spot
where optic nerve connects to retina (no cones or rods
43
Visual Field Processing
all right visual field goes to left side of brain and all left visual field goes to the right side of the brain - light from left field hits NASAL side of left eye and TEMPORAL side of right eye (vice verse for light from right field)
44
Optic Chiasm
where optic nerves from each eye converge and then dig deeper into the brain - all light from nasal sides of both sides cross each other - all light from temporal sides DO NOT CROSS CHIASM
45
Feature Detection
when looking at an object, you need to break it down into its component features to make sense of what you are looking at need to consider color, form, motion
46
Parvocellular pathway
good at spatial resolution and color (form = boundaries and shape, high levels of detail) - poor temporal resolution (TIME = motion) - cones responsible
47
Magnocellular pathway
has high temporal resolution (motion) - poor spatial resolution - rods responsible
48
Parallel Processing
detect/focus all information (color, form, motion) at the same time

MCAT Behavioral Sciences (3 decks)

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