Topic 2- The Eye and the Retina

Question 1

What does the ability to see an object depend on?

Answer 1

The ability to see an object depends on visible light being reflected from that object into the eye

Question 2

The light within the electromagnetic spectrum that we can see

What is this?

Answer 2

Visible spectrum

Question 3

Shorter wavelengths we tend to see as BLANK, longer wavelengths are perceived as BLANK

Answer 3

blues, reds

Question 4

The eyes contain BLANK BLANK for vision and BLANK light into perceptual information

Answer 4

sensory receptors, transform

Question 5

What is the pupil of the eye?

Answer 5

Opening of the eye through which light from the environment enters

Question 6

What is the sclera of the eye?

2 points

Answer 6

-The “whites” of the eyes
- Tough membrane; provides a protective coating

Question 7

What is the cornea?

2 points

Answer 7

-Clear, transparent, outermost surface of the sclera that allows light to pass
- Begins the process of focusing light on to the back of the eye

Question 8

What is the lens

2 points

Answer 8

• Adjustable focusing element of the eye
• Flexible; muscles change the shape of the lens to focus objects at different distances

Question 8

What is the iris? Where is it located? What is a pupillary reflex?

5 points

Answer 8

• “Eye colour”
• Located just behind the cornea
• Controls the size and diameter of the pupil
• Controls the amount of light reaching the back
  –> Pupillary reflex: Iris relaxes in bright light and contracts in dim light

Question 9

What is the retina?

Answer 9

Light-sensitive surface at the back of the eye that contains the sensory receptors for vision - the photoreceptors

Question 10

What are the two photoreceptors?

3 points each

Answer 10

Rods: cylinder shaped, vision at dim light levels, night vision

Cones: Cone-shaped, vision at bright light, colour vision, & fine detail

Question 11

Outer segments contain….

Answer 11

light sensitive visual pigment molecules

Question 12

What are optic nerves?

Answer 12

Bundles of millions of nerve fibers that carry signals from the retina into the brain

Question 13

What is the peripheral retina? What does it contain?

3 points

Answer 13

• Retinal area “away from the center”
• Contains both photoreceptors types
• Many more rods though

Question 13

What is the fovea?

3 points

Answer 13

• Region at the center of the retina that only contains cones
• Specialized for high visual acuity
• Vision is “sharpest” in the center of the visual field than in the periphery

Question 14

Area at the back of the eye where axons forming the optic nerve leave the eye, and blood vessels enter/leave

What is this?

Answer 14

Blind spot

Question 15

What two part system helps light focus on the retina and what percent is it divided into?

Answer 15

80% of the work is done by the cornea

20% of the work is done by the lens

Question 16

How do lens accomplish changing its shape, increase curvature what muscle help do this?

Answer 16

Through ciliary muscles

Question 17

What is the process of visual accommodation

2 points

Answer 17

• The ciliary muscles increase the curvature of the lens, this changes the lens shape
• This increase in curvature pulls the focus point forward, so things no longer look blurry

Question 18

What are refractive errors?

Answer 18

Issues with the cornea or lens ability to focus incoming light onto the retina

Question 19

• Often occurs in normal aging
• The ability to BLANK decreases; lens hardens and is less flexible
• In addition, the BLANK muscles weaken

What is this?

Answer 19

-accommodate
-ciliary

Presbyopia

Question 20

Inability to see distant objects clearly

What is this?

Answer 20

Myopia

Question 21

Since focusing on an image on the retina is the initial step in process of vision, where does vision actually occur?

Answer 21

In the brain

Question 22

What is transduction? Where does it occur?

Answer 22

transformation of environmental energy into electrical energy

• Occurs in the photoreceptors

Question 23

What are the two parts of photopigments that are contained in the outer segments? When combined, what can the resulting molecule do? 3 points

Answer 23

Opsin- a long protein Retinal- a smaller -light sensitive component - When combined, the resulting molecule can absorb visible light

Question 24

BLANK and BLANK control how the visual system adjusts to the dark and to dim level of light

Answer 24

Rods and cones

Question 25

In dark adaptation, what increases over time and what is it associated with?

Answer 25

Sensitivity to light increases over time, which is associated with regeneration of the rod and cone visual pigments

Question 26

Explain the dark adaptation curve in terms of what happens for rods and cones separately? What is a rod-cone break? 5 points

Answer 26

- The cones are much more sensitive to light at the beginning of dark adaptation - Controls most of our vision during the first 5 mins and reaches max sensitivity rapidly - The rods are much less sensitive to light at the beginning - Controls most of vision later on - Takes about 25-30 mins to reach max sensitivity rod-cone break: The point at which vision in the dark shifts from cone vision to rod vision

Question 27

Our BLANK to light at any point depends on the concentration of the BLANK visual BLANK that is present

Answer 27

sensitivity, unbleached, pigment

Question 28

What is the rate of pigment regeneration in cones and rods during dark adaptation? 2 points

Answer 28

Cones pigments regenerate extremely fast in approx 5-6 min Rods pigments regenerate much slower approx 25 mins

Question 29

Why do object in dimmed light/dark lighting appear to be more blueish/green? A tendency for sensitivity of the eye to shift towards the blue-green end of the colour spectrum at low levels of illumination/dimmed lighting.

Answer 29

Purkinje shift --> which is basically when rods are more sensitive to shorter wavelengths than cones

Question 30

What happens as the signals travel through the retina? Signals from the photoreceptors travel to BLANK cells and then to BLANK cells

Answer 30

bipolar, ganglion

Question 31

How many rods vs cones are in the retina? (1 point) What is the ratio of signals sent to ganglion? (2 points) Do rods or cones converge more? (1 point) What are the two differences in perception? (2 points)

Answer 31

- There are 120 million rods vs 6 million cones in the retina - Means 120 million rods send their signal to a single ganglion cell (120:1) vs 6 million cones to a single ganglion cell (6:1) - Rods converge far more than cones do -Rods result in more sensitivity to light (better vision in low light) as it takes less light to generate a response from a rod than from a cone - Cones result in better visual acuity (seeing fine details)

Question 32

Signals from BLANK travel through the retina and eventually reach the BLANK cells

Answer 32

photoreceptors, ganglion

Question 33

They are the final layer of cells in the retina before the optic nerve

Answer 33

Ganglion cells