Midterm 1: Chapter 3

Question 1

What is vision based on?

Answer 1

Visible light; a band of energy within the electromagnetic spectrum.

Question 2

The distance between the peaks of the electromagnetic waves.

Answer 2

Wavelength

Question 3

The energy within the electromagnetic spectrum that humans can perceive has wavelengths ranging from about 400-700 nm.

Answer 3

Visible light

Question 4

Light reflected from objects in the environment enters the eye through the _________.

Answer 4

Pupil

Question 5

The clear, dome-shaped outer layer of the eye that covers the iris and pupil, and lets light in/ focuses the light reflected.

Answer 5

Cornea

Question 6

From sharp images of the objects/focuses light onto the retina

Answer 6

Lens

Question 7

The network of neurons that covers the back of the eye and that contains the receptors from vision.

Answer 7

Retina

Question 8

Receptors for vision; function by converting light into electrical signals; has cones, and rods.

Answer 8

Photoreceptors

Question 9

Reacts to light and triggers electrical signals; in the outer segments

Answer 9

Visual Pigments

Question 10

The part of the receptor that contains light-sensitive chemicals is called visual pigments.

Answer 10

Outer Segment

Question 11

Contains a million optic nerve fibers that conduct signals toward the brain.

Answer 11

Optic Nerve

Question 12

When we look directly at an object, the object’s image falls on the __________, contains only cones

Answer 12

Fovea

Question 13

Includes all of the retina outside of the fovea, contains both rods and cones.

Answer 13

Peripheral Retina

Question 14

Destroys the cone-rich fovea and a small area that surrounds it. This creates a blind region in central vision.

Answer 14

Macular Degeneration

Question 15

Degeneration of the retina that is passed from one generation to the next. First attacks the peripheral rod receptors and results in poor vision in the peripheral visual field.

Answer 15

Retinitis Pigmentosa

Question 16

Area in the retina where there are no photoreceptors.

Answer 16

Blind Spot

Question 17

What don’t we see our blind spot?

Answer 17

A mechanism in the brain fills in the place where the image disappears.

Question 18

What two parts of the eye focuses light reflected from an object into the eye onto the retina?

Answer 18

Cornea and lens

Question 19

Can change its shape to adjust the eye’s focus for objects located at different distances

Answer 19

Lens

Question 20

What is important about lens being able to adjust?

Answer 20

It controls a process called accommodation; comes to the rescue to help prevent blurring.

Question 21

The change in the lens’ shape that occurs when the ciliary muscles at the front of the eye tighten and increase the curvature of the lens so that it gets thicker.

Answer 21

Accommodation

Question 22

Age-related loss of ability to accommodate

Answer 22

Presbyopia

Question 23

An inability to see distant objects clearly; occurs when the optical system brings parallel rays of light into focus at a point in front of the retina, so the image that reaches the retina is blurred.

Answer 23

Myopia/Nearsightedness

Question 24

The cornea and/or the lens bends the light too much

Answer 24

Refractive Myopia

Question 25

Eyeball is too long

Answer 25

Axial Myopia

Question 26

Can see distant objects clearly but have trouble seeing nearby objects because the focus point for parallel rays of light is located behind the retina.

Answer 26

Hypertonia/Farsightedness

Question 27

The transformation of one form of energy into another form of energy.

Answer 27

Transduction

Question 28

What are the two parts of visual pigments?

Answer 28

a long protein called opsin and a much smaller light-sensitive component called retinal.

Question 29

How is the first step of transduction initiated?

Answer 29

When the incoming light hits the retina.

Question 30

What happens during the first step of transduction?

Answer 30

The visual pigment molecule absorbs the light. This causes the retinal within that molecule to change its shape from bent to straight.

Question 31

Creates a chemical chain reaction that activates thousands of charged molecules to create electrical signals in receptors.

Answer 31

Isomerization

Question 32

The process of increasing sensitivity in the dark and is measured by determining a dark adaption curve.

Answer 32

Dark Adaption

Question 33

a dark adaptometer is used to measure the brightness of light needed to achieve a threshold response after bleaching the retina with an intense light

Answer 33

Dark Adaption Curve

Question 34

the least intensity of light visible to the eye

Answer 34

Threshold

Question 35

1/threshold=

Answer 35

Sensitivity

Question 36

High threshold corresponds to _______ ___________.

Answer 36

low sensitivity

Question 37

What does the dark adaption curve show?

Answer 37

As adaption proceeds, the participant becomes more sensitive to light.

Question 38

On a dark adaption curve, since higher sensitivity is at the bottom of the graph, what does the downward movement of the curve mean?

Answer 38

The participant's sensitivity is increasing.

Question 39

At how many minutes does the participant sensitivity increase? (dark adaption curve)

Answer 39

The first 3-4 minutes and at about 7-10 minutes.

Question 40

How do we measure cone adaption?

Answer 40

Have the participant look directly at the test light so its image falls on the all-fovea, and by making the test light small enough so that its entire image falls within the fovea.

Question 41

How do we measure rod adaption?

Answer 41

We use people who have a rare genetic defect called rod monochromats. These individuals have no cones.

Question 42

When do rods reach their final dark-adapted level?

Answer 42

25 minutes.

Question 43

What happens as soon as the light is extinguished?

Answer 43

the sensitivity of both the cones and the rods begins increasing

Question 44

When do cones reach their maximum sensitivity?

Answer 44

3-5 minutes

Question 45

How long does it take for rods' sensitivity to catch up to cones?

Answer 45

7 minutes

Question 46

The place where the rods begin to determine the dark-adaption curve instead of the cones

Answer 46

rod-cone break

Question 47

How long does it take rods to reach their maximum sensitivity?

Answer 47

20-30 minutes

Question 48

The change in shape and separation from the opsin causes the molecule to become lighter in color

Answer 48

Visual pigment bleaching.

Question 49

Cone pigment takes ________ minutes to regenerate completely.

Answer 49

6

Question 50

Rod pigment takes more than _________ minutes to regenerate completely.

Answer 50

30

Question 51

What does our sensitivity depend on?

Answer 51

the concentration of the visual pigment

Question 52

What does the speed at which our sensitivity increases in the dark depends on what?

Answer 52

the regeneration of the visual pigment

Question 53

The eye's sensitivity to light as a function of the light's wavelength.

Answer 53

Spectral sensitivity

Question 54

the relationship between wavelength and sensitivity

Answer 54

Spectral Sensitivity Curve

Question 55

How to determine one's spectral sensitivity?

Answer 55

We determine the person's threshold for seeing monochromatic lights across the spectrum using one of the psychophysical methods for measuring threshold.

Question 56

Threshold is higher at _________ and __________ wavelengths.

Answer 56

short, long

Question 57

Threshold is lower at _________ wavelengths.

Answer 57

middle

Question 58

________ are more sensitive to short-wavelength light.

Answer 58

rods

Question 59

________ are most sensitive to light of 500 nm.

Answer 59

rods

Question 60

________ are most sensitive to light of 560 nm.

Answer 60

cones

Question 61

A plot of the amount of light absorbed versus the wavelength of the light

Answer 61

Absorption spectrum

Question 62

Short-wavelength pigment absorbs light best at about _______ nm.

Answer 62

419

Question 63

Medium-wavelength pigment absorbs light best at about _______ nm.

Answer 63

531

Question 64

long-wavelength pigment absorbs light best at about _______ nm.

Answer 64

558