7.6

Question 1

The wavelengths of light capable of stimulating the receptors of the eye are between about 400 and 750 nm. These are collectively known as the ___ ___.

Answer 1

visible spectrum

Question 2

The opening in the iris that allows light into the eye is the ___.

Answer 2

pupil

Question 3

When a light ray passes from air into water its direction changes, a phenomenon called ___.

Answer 3

refraction

Question 4

Which of the following cells provide lateral integration between neurons in the retina?

Answer 4

• amacrine cells
• horizontal cells

Question 5

Because of the shapes of their light-sensitive outer segments, the two types of photoreceptors are called ___ and ___.

Answer 5

rods; cones

Question 6

Vision is the perception of ___.

Answer 6

electromagnetic raditation

Question 7

A photoreceptor cell that is extremely sensitive and is responsible for night vision is the ___ cell.

Answer 7

rod

Question 8

When a ray of light enters the cornea perpendicular to the cornea’s surface ___.

Answer 8

it passes straight into the cornea without changing its direction of travel

Question 9

Rod cells of the retina have a unique photopigment called ___.

Answer 9

rhodopsin

Question 10

The correct order of the structures in the figure, beginning with the front of the retina on the far left to the optic nerve fibers on the far right is ___.

Answer 10

choroid, photoreceptor cells, horizontal cells, bipolar cells, amacrine cells, ganglion cells

Question 11

In dim light, rods are ___ cones.

Answer 11

more active than

Question 12

In the neural pathway of vision, the first cells where action potentials can be initiated are the ganglion cells, because these are the only cells in the pathway that ___ ion channels.

Answer 12

posses voltage-gated

Question 13

Put the layers of the retina in the order that light passes through them.

Answer 13

1. ganglion cells
2. bipolar cells
3. photoreceptor cells

Question 14

Visual signals from the left half of the visual field travel to the ___ lateral geniculate nucleus of the thalamus.

Answer 14

right

Question 15

Axons of ganglion cells in both retinas assemble to form the ___ nerves.

Answer 15

optic

Question 16

When light strikes the retina and initiates action potentials that travel to the visual cortex, the first cell type that undergoes an action potential is a(n) ___ cell.

Answer 16

ganglion

Question 17

The back layer of the retina, closest to the choroid, is composed of the ___ (rods and cones), while the front layer consists of the ___ cells, whose axons become the optic nerve.

Answer 17

photoreceptors; bipolar

Question 18

the axons of ___ cells make up the optic nerve.

Answer 18

ganglion

Question 19

The colors we perceive are related to the wavelengths of light that the ___ in the objects of our visual world reflect, absorb, or transmit.

Answer 19

pigment

Question 20

Which statements are true of the condition known as color blindness?

Answer 20

• it occurs mostly in men
• two cone photopigments are coded for by the X chromosome

Question 21

___ are small, jerking movements of the eyeball that rapidly bring it from one fixation point to another.

Answer 21

saccades

Question 22

___ refers to the clouding of the lens caused by lifelong accumulation of precipitated proteins.

Answer 22

cataract

Question 23

Which of the following cells provide lateral integration between neurons in the retina?

Answer 23

• horizontal cells
• amacrine cells

Question 24

Objects that absorb all wavelengths of light are perceived as the color ___, while those that reflect a mixture of all wavelengths of light are perceived as the color ___.

Answer 24

black; white

Question 25

A defect in genes encoding cone photopigments can cause a condition known as ___ ___.

Answer 25

color blindness

Question 26

T/F: Saccades move the visual image over the retina to prevent bleaching and adaptation of the photoreceptors.

Answer 26

T (Saccades do move the visual image over the receptors, thereby preventing adaptation that would result from persistent photobleaching of photoreceptors in a given region of the retina.)

Question 27

An object appears red because it absorbs ___ wavelengths, while simultaneously reflecting the ___ wavelengths.

Answer 27

shorter (blue); longer (red)