Sensations And Perception Chapter Two

Front 1

Absorb

Back 1

To take up light, noise, or energy and not transmit it at all.

Front 2

Accomodation

Back 2

The process by which the eye changes its focus (in which the lens gets fatter as gaze is directed toward nearer objects).

Front 3

Amacrine Cells

Back 3

Retinal cells found in the inner synaptic layer that make synaptic contacts with bipolar cells, ganglion cells, and one another.

Front 4

Aqueous Humor

Back 4

The watery fluid in the anterior chamber of the eye.

Front 5

Astigmatism

Back 5

A visual defect caused by the unequal curving of one or more of the refractive surfaces of the eye, usually the cornea.

Front 6

Bipolar Cells

Back 6

Retinal cells that synapse with either rods or cones (not both) and with horizontal cells, and then pass the signals on to ganglion cells.

Front 7

Cataract

Back 7

Opacity of the crystalline lens.

Front 8

Chromophore

Back 8

The light-catching part of the visual pigments of the retina.

Front 9

Cones

Back 9

Photoreceptors specialized for daylight vision, fine visual acuity, and color.

Front 10

Contrast

Back 10

The difference in luminance between an object and the background, or between lighter and darker parts of the same object.

Front 11

Cornea

Back 11

The transparent “window” into the eyeball.

Front 12

Crystalline Lens

Back 12

The lens inside the eye that enables changing focus.

Front 13

Diffuse Bipolar Cells

Back 13

Bipolar retinal cells whose processes are spread out to receive input from multiple cones.

Front 14

Duplex

Back 14

In reference to the retina, consisting of two parts: the rods and cones, which operate under different conditions.

Front 15

Eccentricity

Back 15

The distance between the retinal image and the fovea.

Front 16

Emmetropia

Back 16

The condition in which there is no refractive error, because the refractive power of the eye is perfectly matched to the length of the eyeball.

Front 17

Filter

Back 17

An acoustic, electrical, electronic, or optical device, instrument, computer program, or neuron that allows the passage of some frequencies or digital elements and blocks the passage of others.

Front 18

Fundus

Back 18

The back layer of the retina—what the eye doctor sees through an ophthalmoscope.

Front 19

Ganglion Cells

Back 19

Retinal cells that receive visual information from photoreceptors via two intermediate neuron types (bipolar cells and amacrine cells) and transmit that information to the brain and midbrain.

Front 20

Graded Potential

Back 20

An electrical potential that can vary continuously in amplitude.

Front 21

Horizontal Cells

Back 21

Specialized retinal cells that contact both photoreceptor and bipolar cells.

Front 22

Hyperopia

Back 22

A common condition in which light entering the eye is focused behind the retina.

Front 23

Hyperpolarization

Back 23

An increase in membrane potential such that the inner membrane surface becomes more negative than the outer membrane surface.

Front 24

Image

Back 24

A picture or likeness.

Front 25

Inner Segment

Back 25

The part of a photoreceptor that lies between the outer segment and the cell nucleus.

Front 26

Iris

Back 26

The colored part of the eye, consisting of a muscular diaphragm surrounding the pupil and regulating the light entering the eye by expanding and contracting the pupil.

Front 27

Myopia

Back 27

A common condition in which light entering the eye is focused in front of the retina and distant objects cannot be seen sharply.

Front 28

OFF Bipolar Cells

Back 28

Bipolar cells that respond to a decrease in light captured by the cones.

Front 29

OFF-Center Cells

Back 29

A cell that depolarizes in response to a decrease in light intensity in its receptive field center.

Front 30

On Bipolar Cells

Back 30

Bipolar cells that respond to an increase in light captured by the cones.

Front 31

On-Center Cells

Back 31

A cell that depolarizes in response to an increase in light intensity in its receptive field center.

Front 32

Outer Segment

Back 32

The part of a photoreceptor that contains photopigment molecules.

Front 33

P Ganglion Cell

Back 33

Small ganglion cells that receive excitatory input from single midget bipolar cells in the central retina and feed the parvocellular layer of the lateral geniculate nucleus.

Front 34

Photoactivation

Back 34

Activation by light.

Front 35

Photon

Back 35

A quantum of visible light or other form of electromagnetic radiation demonstrating both particle and wave properties.

Front 36

Photoreceptors

Back 36

Light-sensitive receptors in the retina.

Front 37

Presbyopia

Back 37

Literally “old sight.” The loss of near vision because of insufficient accommodation.

Front 38

Pupil

Back 38

The dark circular opening at the center of the iris in the eye, where light enters the eye.

Front 39

Receptive Field

Back 39

The region on the retina in which visual stimuli influence a neuron’s firing rate.

Front 40

Reflect

Back 40

To redirect something that strikes a surface—especially light, sound, or heat—usually back toward its point of origin.

Front 41

Refract

Back 41

1. To alter the course of a wave of energy that passes into something from another medium, as water does to light entering it from the air. 2. To measure the degree of refraction in a lens or eye.

Front 42

Retina

Back 42

A light-sensitive membrane in the back of the eye that contains rods and cones, and that receives images from the lens and sends them to the brain through the optic nerve.

Front 43

Retinitis Pigmentosa (RP)

Back 43

A progressive degeneration of the retina that affects night vision and peripheral vision. RP commonly runs in families and can be caused by defects in a number of different genes that have recently been identified.

Front 44

Rhodopsin

Back 44

The visual pigment found in rods

Front 45

Rods

Back 45

Photoreceptors specialized for night vision.

Front 46

Scatter

Back 46

To disperse light in an irregular fashion.

Front 47

Sensitivity

Back 47

1. The ability to perceive via the sense organs. 2. Extreme responsiveness to radiation, especially to light of a specific wavelength. 3. The ability to respond to transmitted signals.

Front 48

Synaptic terminal

Back 48

The location where axons terminate at the synapse for transmission of information by release of a chemical transmitter.

Front 49

Transduced

Back 49

Referring to the conversion from one form of energy (e.g., light) to another (e.g., electricity).

Front 50

Transmit

Back 50

To convey something (e.g., light) from one place or thing to another.

Front 51

Lateral Inhibition

Back 51

Antagonistic neural interaction between adjacent regions of the retina.

Front 52

M Ganglion Cells

Back 52

Ganglion cells resembling little umbrellas that receive excitatory input from diffuse bipolar cells and feed the magnocellular layer of the lateral geniculate nucleus.

Front 53

Midget Bipolar Cells

Back 53

Small cone bipolar cells in the central retina that receive input from a single cone.

Front 54

Visual Acuity

Back 54

A measure of the finest detail that can be resolved by the eyes.

Front 55

Vitreous Humor

Back 55

The transparent fluid that fills the vitreous chamber in the posterior part of the eye.

Front 56

Wave

Back 56

An oscillation that travels through a medium by transferring energy from one particle or point to another without causing any permanent displacement of the medium.