Sensation And Perception Ch.2

Front 1

Absorption spectrum

Back 1

A plot of the amount of light absorbed by a visual pigment versus the wavelength of light.

Front 2

Accommodation (focus)

Back 2

In vision, bringing objects located at different distances into focus by changing the shape of the lens.

Front 3

Action potential

Back 3

Rapid increase in positive charge in a nerve fiber that travels down the fiber. Also called the nerve impulse.

Front 4

Axon

Back 4

The part of the neuron that conducts nerve impulses over distances. Also called the nerve fiber.

Front 5

Blind spot

Back 5

The small area where the optic nerve leaves the back of the eye; there are no visual receptors in this area so small images falling directly on the blind spot cannot be seen.

Front 6

Cell body

Back 6

The part of a neuron that contains the neuron’s metabolic machinery and that receives stimulation from other neurons.

Front 7

Cones

Back 7

-vision in high illumination
-color vision and detail vision

Front 8

Cornea

Back 8

-MAJOR FOCUSING ELEMENT

-The transparent focusing element of the eye that is the first structure through which light passes as it enters the eye.

Front 9

Dark adaptation

Back 9

-sensitivity to light increases

-This increase in sensitivity is associated with regeneration of the rod and cone visual pigments.

Front 10

Dark adaptation curve

Back 10

The function that traces the time course of the increase in visual sensitivity that occurs during dark adaptation.

Front 11

Dark-adapted sensitivity

Back 11

The sensitivity of the eye after it has completely adapted to the dark.

Front 12

Dendrites

Back 12

Nerve processes on the cell body that receive stimulation from other neurons.

Front 13

Depolarization

Back 13

When the inside of a neuron becomes more positive, as occurs during the initial phases of the action potential. Depolarization is often associated with the action of excitatory neurotransmitters.

Front 14

Detached retina

Back 14

A condition in which the retina is detached from the back of the eye.

Front 15

Doctrine of specific nerve energies

Back 15

-Mueller

-perceptions depend on “nerve energies” reaching the brain and that the specific quality we experience depends on which nerves are stimulated.

ex: activating the optic nerve results in seeing, and activating the auditory nerve results in hearing

Front 16

Electromagnetic spectrum

Back 16

Continuum of electromagnetic energy that extends from very-short-wavelength gamma rays to long-wavelength radio waves.

Visible light is a narrow band within this spectrum.

Front 17

Enzyme cascade

Back 17

Sequence of reactions triggered by an activated visual pigment molecule that results in transduction.

Front 18

Excitatory response

Back 18

The response of a nerve fiber in which the firing rate increases.

Front 19

Excitatory transmitters

Back 19

Neurotransmitters that cause the inside of a neuron to become more positively charged.

Excitatory neurotransmitters increase the probability that an action potential will be generated and are also associated with increases in the rate of nerve firing.

Front 20

Eye

Back 20

The eyeball and its contents, which include focusing elements, the retina, and supporting structures.

Front 21

Focusing power

Back 21

The degree to which a structure such as the lens or the cornea bends light. The greater the focusing power, the more the light passing through the structure is bent.

Front 22

Fovea

Back 22

-only cone receptors

The fovea is located on the line of sight, so that when a person looks at an object, the center of its image falls on the fovea.

Front 23

Hyperpolarization

Back 23

-More Negative

When the inside of a neuron becomes more negative. Hyperpolarization is often associated with the action of inhibitory neurotransmitters.

Front 24

Inhibition

Back 24

A condition that decreases the likelihood that nerve impulses will be generated.

Front 25

Inhibitory response

Back 25

The response of a nerve fiber in which the firing rate decreases due to inhibition from another neuron.

Front 26

Inhibitory transmitters

Back 26

Neurotransmitters that cause the inside of a neuron to become negatively charged. Inhibitory transmitters decrease the possibility that an action potential will be generated and are also associated with decreases in the rate of nerve firing.

Front 27

Ions

Back 27

Charged molecules found floating in the liquid that surrounds nerve fibers.

Front 28

Isomerization

Back 28

Change in shape of the retinal part of the visual pigment molecule that occurs when the molecule absorbs a quantum of light. Isomerization triggers the enzyme cascade that results in transduction from light energy to electrical energy in the retinal receptors.

Front 29

Lens

Back 29

The transparent focusing element of the eye through which light passes after passing through the cornea and the aqueous humor. The lens’s change in shape to focus at different distances is called accommodation.

Front 30

Light-adapted sensitivity

Back 30

The sensitivity of the eye when in the light-adapted state. Usually taken as the starting point for the dark adaptation curve because it is the sensitivity of the eye just before the lights are turned off.

Front 31

Macular degeneration

Back 31

A clinical condition that causes degeneration of the macula, an area of the retina that includes the fovea and a small surrounding area.

Front 32

Microelectrode

Back 32

A thin piece of wire that is small enough to record electrical signals from a single neuron.

Front 33

Modular organization

Back 33

The organization of specific functions into specific brain structures.

Front 34

Monochromatic light

Back 34

Light that contains only a single wavelength.

Front 35

Near point

Back 35

The distance at which the lens can no longer accommodate enough to bring close objects into focus. Objects nearer than the near point can be brought into focus only by corrective lenses.

Front 36

Nerve

Back 36

A group of nerve fibers traveling together.

Front 37

Nerve fiber

Back 37

In most sensory neurons, the long part of the neuron that transmits electrical impulses from one point to another. Also called the axon.

Front 38

Nerve impulse

Back 38

The rapid increase in positive charge that travels down the nerve fiber.

-AKA action potential

Front 39

Neuron

Back 39

A cell in the nervous system that generates and transmits electrical impulses.

Front 40

Neurotransmitter

Back 40

A chemical stored in synaptic vesicles that is released in response to a nerve impulse and has an excitatory or inhibitory effect on another neuron.

Front 41

Occipital lobe

Back 41

A lobe at the back of the cortex that is the site of the cortical receiving area for vision.

Front 42

Opsin

Back 42

The protein part of the visual pigment molecule, to which the light-sensitive retinal molecule is attached.

Front 43

Optic nerve

Back 43

Bundle of nerve fibers that carry impulses from the retina to the lateral geniculate nucleus and other structures. Each optic nerve contains about 1 million ganglion cell fibers.

Front 44

Outer segments

Back 44

Part of the rod and cone visual receptors that contain the light-sensitive visual pigment molecules.

Front 45

Parietal lobe

Back 45

A lobe at the top of the cortex that is the site of the cortical receiving area for touch and is the termination point of the dorsal (where or how) stream for visual processing.

Front 46

Peripheral retina

Back 46

All of the retina except the fovea and a small area surrounding the fovea.

Front 47

Permeability

Back 47

A property of a membrane that refers to the ability of molecules to pass through it. If the permeability to a molecule is high, the molecule can easily pass through the membrane

Front 48

Pigment bleaching

Back 48

The process that begins when a visual pigment molecule absorbs light. The molecule changes shape, and the color of the rod visual pigment changes from red to transparent. Visual transduction occurs at some point, early in this process.

Front 49

Pineal gland

Back 49

Gland at the base of the brain that René Descartes identified as being the seat of the soul.

Front 50

Presbyopia ("old eye")

Back 50

The inability of the eye to accommodate due to the hardening of the lens and a weakening of the ciliary muscles. It occurs as people get older.

Front 51

Primary receiving areas

Back 51

Areas of the cerebral cortex that first receive most of the signals initiated by a sense’s receptors. For example, the occipital cortex is the site of the primary receiving area for vision and the temporal lobe is the site of the primary receiving area for hearing.

Front 52

Propagated response

Back 52

A response, such as a nerve impulse, that travels all the way down the nerve fiber without decreasing in amplitude.

Front 53

Purkinje shift

Back 53

The shift from cone spectral sensitivity to rod spectral sensitivity that takes place during dark adaptation. See also Spectral sensitivity.

Front 54

Receptor

Back 54

A sensory receptor is a neuron sensitive to environmental energy that changes this energy into electrical signals in the nervous system.

Front 55

Receptor site

Back 55

Small area on the postsynaptic neuron that is sensitive to specific neurotransmitters.

Front 56

Refractory period

Back 56

The time period of about 1/1,000th of a second that a nerve fiber needs to recover from conducting a nerve impulse. No new nerve impulses can be generated in the fiber until the refractory period is over.

Front 57

Resting potential

Back 57

The difference in charge between the inside and the outside of the nerve fiber when the fiber is not conducting electrical signals. Most nerve fibers have resting potentials of about –70 mV, which means the inside of the fiber is negative relative to the outside.

Front 58

Retina

Back 58

A complex network of cells that covers the inside back of the eye. These cells include the receptors, which generate an electrical signal in response to light, as well as the horizontal, bipolar, amacrine, and ganglion cells.

Front 59

Retinal

Back 59

The light-sensitive part of the visual pigment molecule. Retinal is attached to the protein molecule, opsin, to form the visual pigment.

Front 60

Retinitis pigmentosa

Back 60

A retinal disease that causes a gradual loss of vision.

Front 61

Rod

Back 61

Rod-shaped receptor in the retina primarily responsible for vision at low levels of illumination. The rod system is extremely sensitive in the dark but cannot resolve fine details.

Front 62

Rod monochromat

Back 62

A person who has a retina in which the only functioning receptors are rods.

Front 63

Rod-cone break

Back 63

The point on the dark adaptation curve at which vision shifts from cone vision to rod vision.

Front 64

Spectral sensitivity

Back 64

The sensitivity of visual receptors to different parts of the visible spectrum. See also Spectral sensitivity curve.

Front 65

Spectral sensitivity curve

Back 65

The function relating a subject’s sensitivity to light to the wavelength of the light. The spectral sensitivity curves for rod and cone vision indicates that the rods and cones are maximally sensitive at 500nm and 560nm, respectively. See also Purkinje shift.

Front 66

Spontaneous activity

Back 66

Nerve firing that occurs in the absence of environmental stimulation.

Front 67

Staining

Back 67

A technique in which neurons take up a dye that make their structure visible.

Front 68

Synapse

Back 68

A small space between the end of one neuron (the presynaptic neuron) and the cell body of another neuron (the postsynaptic neuron). See also Synaptic vesicles.

Front 69

Temporal lobe

Back 69

A lobe on the side of the cortex that is the site of the cortical receiving area for hearing and the termination point for the ventral, or what stream for visual processing. There are a number of areas in the temporal lobe, such as the fusiform face area and the extrastriate body area, that serve functions related to perceiving and recognizing objects.

Front 70

Ventricles

Back 70

Cavities located at the center of the brain which were identified by Galen as the source of “spirits” that determined human health, thoughts, and emotions.

Front 71

Visible light

Back 71

The band of electromagnetic energy that activates visual system and which we can, therefore, perceive.

For humans, visible light has wavelengths between 400 and 700 nanometers.

Front 72

Visual pigment

Back 72

A light-sensitive molecule contained in the rod and cone outer segments. The reaction of this molecule to light results in the generation of an electrical response in the receptors.

Front 73

Visual pigment molecules

Back 73

Light-sensitive molecules in the outer segments of the rod and cone visual receptors that are responsible for the transformation of light energy into electrical energy. The molecule consists of a large protein component called opsin and a small light-sensitive component called retinal.

Front 74

Visual pigment regeneration

Back 74

Occurs after the visual pigment’s two components—opsin and retinal—have become separated due to the action of light. Regeneration, which occurs in the dark, involves a rejoining of these two components to reform the visual pigment molecule. This process depends on enzymes located in the pigment epithelium.

Front 75

Visual transduction

Back 75

Transformation of light energy into electrical energy that occurs in the rod and cone receptors in the retina.

Front 76

Wavelength

Back 76

For light energy, the distance between one peak of a light wave and the next peak.