The Visual System Flashcards

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1
Q

What is the retina?

A

The retina is actually one of the last places where the light shines –the light passes through other parts of the eye first. The conversion of light into electrochemical signals happens here.

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2
Q

What is the cornea?

A

The cornea is the front, transparent layer of the eye. This part is usually shaved down during LASIK SURGERY.

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3
Q

What occurs in the cornea?

A

Refraction (bending/focusing)

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4
Q

What is the iris?

A

The colored part of the eye

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5
Q

What is the pupil?

A

The little hole where the light enters the eye. It can dilate and let in the right amount of light.

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6
Q

What happens in bright lights vs. low and dim lights?

A

Bright lights : the iris becomes the size of the pupil

Dim lights : the iris relaxes and pupil expands

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7
Q

What happens after the light enters the eye?

A

The light passes through the crystalline lens, a structure with many layers behind the cornea. This works to further refract the light to focus the image on the retina.

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8
Q

What is the lens?

A

The lens is dynamic and flexible because it changes shape to focus on different parts of the visual field. There are special muscles that help it be flexible.

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9
Q

What does aging do to the lens?

A

The lens flexibility reduces with age. This causes a form of farsightedness.

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10
Q

How does farsightedness occur?

A

This is caused because the lens isn’t flexible or the eyeball is shaped so that the distance between the cornea and the retina is too short. The image falls behind the retina.

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11
Q

How does myopia (nearsightedness) occur?

A

This is because the eyeball is shaped so that the distance between the cornea and the retina is too long. The image falls in front of the retina.

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12
Q

What can fix myopia and/or farsightedness?

A

Glasses, corrective lenses, or LASIK surgery which can change the curve of the cornea to bend the light so the image falls exactly on the retina.

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13
Q

What is the retina?

A

This is a many layered sheet of neurons that converts light in the back of the eye.

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14
Q

Describe the process for the light to get to the back of the retina.

A

The light must first go through this sticky, thick liquid and around the first layers of the retina to get to the photoreceptors.

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15
Q

What are photoreceptors?

A

They recieve and convert light.

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16
Q

What is the one reason that the retina’s layers are seemingly “inside out”?

A

The pigmented epithelium needs to be just outside these cells to help support their function.

17
Q

What are the pigmented epithelium cells?

A

They absorb excess light so it doesn’t scatter and blur the image. They get rid of old light absorbing segments of the photoreceptors.

18
Q

What is just outside the pigmented epithelium layer?

A

The choroid, which brings oxygen and nutrients to the photoreceptor cells.

19
Q

What is in the very center of the retina?

A

The fovea - this is where the vision the sharpest and the best.

20
Q

What are the two general types of photoreceptors.

A

Rods and cones.

21
Q

What do both rods and cones have in common?

A

Rods and cones both have disks of membranes where a pigment absorbs light and communicates with the molecular machinery needed to convert the light.

They both convert light in a similar way. They use different pigments.

22
Q

What is different about rods?

A

Rods have more disks which therefore are more sensitive to low light settings.

23
Q

What is different about cones?

A

Cones are clustered in the center of the retina, in the fovea. The cornea has a good response to bright light which makes them good for a bright light setting and full color vision.

24
Q

What’s another word for pigments?

A

Opsins, which each absorb a different wavelength or color of light.

25
Q

What opsin do rods have?

A

Rods have an opsin called rhodopsin. There are usually three types of cones which each absorb a different wavelength.

26
Q

What do primates use?

A

Primates use a trichromatic (three-cone) which allows them to see in hundreds of thousands of colors.