Chapter 6

Question 1

psychophysics

Answer 1

the measurable relationship b/n the physical qualities of a sensory stimulus and the perception of that stimulus

• establishing a map from stimulus to percept

Question 2

what is the difference b/n a sensation and a percept

Answer 2

sensation: the detection of information about our environmental context
perception: the interpretation of information about our environmental context

Question 3

difference threshold or just noticeable difference (JND)

Answer 3

the minimum amount that a stimulus must change for the subject to detect a difference, regardless of whether the stimulus was light, sound, pressure, or heat

Question 4

Weber’s law

Answer 4

The empirical principle that the JND is a constant proportion of the initial stimulus

ex. for a subject to detect a JND in the loudness of low-intensity sounds, one sound must be about 10% louder than the other sound

Question 5

sensory receptor organs

Answer 5

organs specialized to detect a certain stimulus

Question 6

receptor cells

Answer 6

within the organ convert the stimulus into an electrical signal

Question 7

sensory receptors

Answer 7

• the neurons that detect incoming information from the environment and body areas
• all types have a receptor potential that needs to be altered in order to send a sensory signal to the brain

Question 8

what is the range in which we can hear in?

Answer 8

We can hear from 20 hertz to about 17 kHz

Know that each sensory system has a restricted range of stimuli to which it can respond.

For example: the frequency range for hearing, which varies with species
- it is beyond our threshold

Question 9

photoreceptors

Answer 9

specialized neurons that are sensitive to light

Question 10

Light

Answer 10

is the type of physical energy that photoreceptors in the eye respond to effectively

light is the adequate stimulus for photoreceptors

Question 11

range in which humans can detect

Answer 11

Humans can detect wavelengths ranging from 400 to 750 nm, with purple and blue represented by the shorter waves, green by medium-length waves, and red by the longer waves

Question 12

electromagnetic spectrum

Answer 12

all possible wavelengths of electromagnetic radiation (of which light is only a narrow band)

Question 13

three dimensions of the light stimulus that influence color qualities perceived by humans

Answer 13

• hue
• brightness
• saturation

Question 14

phosphodiesterase

Answer 14

an enzyme that reduced cGMP concentrations that maintain the open channels

• leads to the closure of sodium channels and hyperpolarization of the receptor

–> results in the activation to the ganglion cells that carry information to the brain

Question 15

The human eye

Answer 15

containing photoreceptors , is held in the optic socket by the extracellular muscles and optic nerve.

Light enters through the eye through the pupil, which accommodates darkness by dilating to let more light in and accommodates brightness by constricting to minimize the amount of incoming light

the iris controls the size of the pupil

the pupil and the iris are covered by a transparent surface known as the cornea

along with the lens that is located behind the pupil, the cornea focuses the image so that it is projected to the specialized photoreceptors contained in the retina at the back of the eye.

Question 16

vitreuous humor

Answer 16

a jellylike substance that consists mostly of water with specific amounts of salt, sugar, and proteins in the internal cavity of the eye

• more viscous than the watery aqueous humor

Question 17

aqueous humor

Answer 17

occupies the space b/n the cornea and lens

Question 18

visual transduction

Answer 18

light triggers a series of chemical events that transform the light stimulus into neural messages that are ultimately interpreted as visual stimuli

• when a photon of light is absorbed by the photopigment rhodopsin in the rods, a change occurs in the shape of the photopigment component retinal
• this activates the transformation of one form of a G-protein known as transducin to another from that activates a cGMP phosphodiesterase

Question 19

lateralization of visual neural pathways

Answer 19

as visual information travels from the eye to the visual cortex, portions of the visual neural pathways cross over at the optic chiasm and are directed to the opposite hemisphere

Question 20

optic chiasm

Answer 20

a midline structure where portions of the optic nerves of each eye cross over so that signals from the right and left visual field proceed to the contralateral hemisphere

Question 21

optic tract

Answer 21

The pathway of visual information after exiting the optic chiasm that proceeds to the lateral geniculate nucleus of the thalamus

Question 22

lateral geniculate nucleus (LGN)

Answer 22

The portion of the thalamus that receives visual information from the optic tract and transmits to the primary visual cortex via fibers called optic radiations

Question 23

primary visual cortex (V1) or striate cortex

Answer 23

the large area of the cortex that receives visual input from the richly detailed fovea region of the retina

Question 24

on-center cells

Answer 24

retinal cells stimulated when a light is focused on the center of the cell

Question 25

off-center cells

Answer 25

retinal cells inhibited when a light is focused on the enter of the ell

Question 26

concentric receptive field

Answer 26

characteristic of cells in the retina and lateral geniculate nucleus that respond to detailed visual information only in very specific areas of their representative visual fields