The Visual System Extends from the Eye to the Brain

Question 1

Retina

Answer 1

The receptive surface inside the eye that contains photoreceptors and other neurons.

Question 2

Transduction

Answer 2

The conversion of one form of energy to another, as converting light into neuronal activity.

Question 3

Cornea

Answer 3

The transparent outer layer of the eye, whose curvature is fixed. The cornea bends light rays and is primarily responsible for forming the image on the retina.

Question 4

Figure 7.1

Structures of the Human Eye

Answer 4

Question 5

Refraction

Answer 5

The bending of light rays by a change in the density of a medium, such as the cornea and the lens of the eyes.

Question 6

Lens

Answer 6

A structure in the eye that helps focus an image on the retina.

Question 7

Ciliary Muscle

Answer 7

One of the muscles that control the shape of the lens inside the eye, focusing an image on the retina.

Question 8

Accomodation

Answer 8

The process by which the ciliary muscles adjust the lens to focus a sharp image on the retina.

Question 9

Myopia

Answer 9

Nearsightedness; the inability to focus the retinal image of objects that are far away.

Question 10

Figure 7.2

Focusing Images on the Retina

Answer 10

Question 11

Extraocular Muscle

Answer 11

One of the muscles attached to the eyeball that control its position and movements.

Question 12

Photoreceptor

Answer 12

A neural cell in the retina that responds to light.

Question 13

Rod

Answer 13

A photoreceptor cell in the retina that is most active at low levels of light.

Question 14

Cone

Answer 14

Any of several classes of photoreceptor cells in the retina that are responsible for color vision.

Question 15

Figure 7.3

A.

Anatomy of the Retina

Answer 15

Question 16

Figure 7.3

B.

Anatomy of the Retina

Answer 16

Question 17

Bipolar Cell

Answer 17

An interneuron in the retina that recieves information from rods and cones and passes the information to retinal ganglion cells.

Question 18

Ganglion Cell

Answer 18

Any of a class of cells in the retina whose axons form the optic nerve.

Question 19

Optic Nerve

Answer 19

Cranial nerve II; the collection of ganglion cell axons that extend from the retina to the brain.

Question 20

Horizontal Cell

Answer 20

A specialized retinal cell that contacts both receptor cells and bipolar cells.

Question 21

Amacrine Cell

Answer 21

A specialized retinal cell that contacts both bipolar cells and ganglion cells, and is especially significant in inhibitory interactions within the retina.

Question 22

Scotopic System

Answer 22

A system in the retina that operates at low levels of light and involes rods.

Question 23

Convergence

Answer 23

The phenomenon of neural connections in which many cells send signals to a single cell.

Question 24

Phototopic System

Answer 24

A system in the retina that operates at high levels of light, shows sensitivity to color, and involves the cones.

Question 25

**Table 7.1** Properties of the Photopic and Scotopic Visual Systems

Answer 25

Question 26

**Rhodospin**

Answer 26

The photpigment in rods that responds to light.

Question 27

**Figure 7.4** Hyperpolarization of Photoreceptors

Answer 27

Question 28

**Figure 7.5** The Wide Range of Sensitivity to Light Intensity

Answer 28

Question 29

**Pupil**

Answer 29

The opening, formed by the iris that allows light to enter the eye.

Question 30

**Iris**

Answer 30

The circular structure of the eye that provides an opening to form the pupil.

Question 31

**Figure 7.6** The Iris Controls the Size of the Pupil Opening

Answer 31

Question 32

**Range Refraction**

Answer 32

The means by which sensory systems cover a wide range of intensity values, as each sensory receptor cell specializes in just one part of the overall range of intensities.

Question 33

**Photoreceptor Adaptation**

Answer 33

The tendency of rods and cones to adjust their light sensitivity to match ambient levels of illumination.

Question 34

**Visual Acuity**

Answer 34

Sharpness of vision.

Question 35

**Figure 7.7** **A.** Densities of Retinal Receptors and Visual Acuity

Answer 35

Question 36

**Fovea**

Answer 36

The central portion of the retina, which is packed with the highest density of photoreceptors and is the center of our gaze.

Question 37

**Figure 7.7** **B.** Densities of Retinal Receptors and Visual Acuity

Answer 37

Question 38

**Figure 7.8** An Unobstructed View

Answer 38

Question 39

**Optic Disc**

Answer 39

The region of the retina that is devoid of receptor cells because ganglion cell axons and blood vessels exit the eyeball there.

Question 40

**Blind Spot**

Answer 40

The portion of the visual field from which light falls on the optic disc. Because there are no receptors in this region, light striking the blind spot cannot be seen.

Question 41

**Figure 7.9** Experiencing the Blind Spot

Answer 41

Question 42

**Occiptal Cortex**

Answer 42

Also called visual cortex. The cortex of the occipital lobe of the brain.

Question 43

**Figure 7.10** Visual Pathways in the Human Brain

Answer 43

Question 44

**Optic Chiasm**

Answer 44

The point at which the two optic nerves meet.

Question 45

**Optic Tract**

Answer 45

The axons of retinal ganglion cells after they have passed the optic chiasm; most of these axons terminate in the lateral geniculate nucleus.

Question 46

**Lateral Geniculate Nucleus (LGN)**

Answer 46

The part of the thalamus that recieves information from the optic tract and sends it to visual areas in the occipital cortex.

Question 47

**Optic Radiation**

Answer 47

Axons from the lateral geniculate nucleus that terminate in the primary visual areas of the occipital cortex.

Question 48

**Primary Visual Cortex (V1) or Striate Cortex**

Answer 48

Also called *area 17*. The region of the occipital cortex where most visual information first arrives.

Question 49

**Binocular**

Answer 49

"Two eyed" inputs, used for depth perception.

Question 50

**Extrastriate Cortex**

Answer 50

Visual cortex outside of the primary visual (striate) cortex.

Question 51

**Visual Field**

Answer 51

The whole area that you can see without moving your head or eyes.

Question 52

**Topographic Projection**

Answer 52

A mapping that preserves the point-to-point correspondence between neighboring parts space. For example, the retina extends a topographic projection onto the cortex.

Question 53

**Figure 7.11** Location of the Primary Visual Cortex

Answer 53

Question 54

**Scotoma**

Answer 54

A region of blindness within the visual fields, caused by injury to the visual pathway or brain.

Question 55

**Blindsight**

Answer 55

The paradoxical phenomenon whereby, within a scotoma, a person cannot consciously percieve visual cues but may still be able to make some visual discrimination.