Chapter 7 (part 2) Sensory Physiology

Question 1

The eyes are composed of:

Answer 1

An optical component, which focuses the visual image on the receptor cells.
A neural component, which transforms the visual image into a pattern of graded and action potentials.

Question 2

The Optics of Vision: Refraction

Relaxed ciliary muscles, tension on zonular fibers, flattened lens.
Light rays from distant objects are nearly parallel.

Answer 2

In focus

Question 3

The Optics of Vision: Refraction

Relaxed ciliary muscles.
Light rays from near objects diverge.

Answer 3

Out of focus:

Question 4

The Optics of Vision: Refraction

Near object with accommodation

Firing of parasympathetic nerves, contracted ciliary muscles, slackened zonular fibers, rounded lens.

Answer 4

In focus

Question 5

eyeball too long

Answer 5

nearsighted

Question 6

eyeball too short

Answer 6

farsighted

Question 7

nearsighted glasses

Answer 7

concave

Question 8

farsighted glasses

Answer 8

convex

Question 9

Neural Pathways of Vision

Light signals are converted into action potentials by the interaction of _________, ______, and ____________

Answer 9

photoreceptors, bipolar cells and ganglion cells.

Question 10

Neural Pathways of Vision

Photoreceptor and bipolar cells only undergo graded responses due to lack of

Answer 10

voltage-gated channels.

Question 11

Neural Pathways of Vision

________ are the first cells in the pathway where action potentials can be initiated.

Answer 11

Ganglion cells

Question 12

Photoreceptors interact with bipolar and ganglion cells in two distinct ways

Answer 12

“ON-pathways” and “OFF-pathways”

Question 13

Light striking the photoreceptors of either pathway _________ the photoreceptors, resulting in a __________ in glutamate release onto bipolar cells.

Answer 13

hyperpolarizes, decrease

Question 14

in both “ON-pathways” and “OFF-pathways”, photoreceptors are depolarized in the ___________of light, causing the neurotransmitter __________ to be released onto bipolar cells

Answer 14

absence, glutamate

Question 14

which neural pathway is this

Bipolar cells spontaneously depolarize in the absence of input,

Answer 14

(ON-pathway)

Question 15

which neural pathway is this

bipolar cells hyperpolarize in the absence of input

Answer 15

(OFF-pathway)

Question 16

which neural pathway is this

Glutamate receptors bipolar cells are inhibitory

Answer 16

(ON-pathway)

Question 17

which neural pathway is this

glutamate receptors bipolar cells are excitatory.

Answer 17

(OFF-pathway)

Question 18

ON-pathway steps

Answer 18

Photoreceptor is depolarized in the absence of light rays

LIGHT RAYS ⇄

Light hyperpolarizes photoreceptor cell

Decreased glutamate release onto bipolar cell

Bipolar cell depolarizes and releases more excitatory neurotransmitter

Ganglion cell depolarizes and generates more action potentials

Question 19

OFF-pathway steps

Answer 19

Photoreceptor is depolarized in the absence of light rays

LIGHT RAYS ⇄

Light hyperpolarizes photoreceptor cell

Decreased glutamate release onto bipolar cell

Bipolar cell hyperpolarizes and releases less excitatory neurotransmitter

Ganglion cell hyperpolarizes and generates fewer action potentials

Question 20

Co-existence of ON and OFF pathways in the retina greatly improves image resolution by

Answer 20

increasing the brain’s ability to perceive contrast.

Question 21

related to the wavelengths of light that the pigments in the objects of our visual world reflect, absorb, or transmit.

Answer 21

Color Vision

Question 22

an object appears red because it absorbs ___________, while it reflects the __________

Answer 22

shorter wavelengths
longer wavelengths

Question 23

Light perceived as ___________ is a mixture of all wavelengths

Answer 23

white

Question 24

________ is the absence of all light.

Answer 24

black

Question 25

three kinds of cones with the wavelengths they respond to

Answer 25

"L" cones respond optimally at long wavelengths "M" cones respond at medium wavelengths "S" cones best stimulated at short wavelengths

Question 26

most common form of color blindness, is present predominantly in men, affect 1 out of 12 either lack the red or the green cone pigments entirely or have them in an abnormal form

Answer 26

red-green color blindness

Question 26

results from a recessive mutation in genes encoding the cone pigments

Answer 26

Color Blindness

Question 27

macula lutea becomes impaired in __________ producing a defect characterized by loss of vision in the center of the visual field.

Answer 27

Macular Degeneration

Question 28

* The ___________ region of the retina provide the highest visual acuity.

Answer 28

macula lutea

Question 28

Incidence of age-related macular degeneration ______________ (approx. 30% of individuals over the age of 75)

Answer 28

(AMD)increases with age

Question 29

- small, jerking movements that rapidly bring the eye from one fixation point to another to allow a search of the visual field - move the visual image over the receptors, thereby preventing adaptation - occur during certain periods of sleep when dreaming occurs, though not thought to be involved in "watching" the visual imagery of dreams

Answer 29

Eye Movement

Question 30

Involved in tracking visual objects as they move and during compensation for movements of the head

Answer 30

Slow eye movements

Question 31

in Slow eye movements, Control centers obtain information about head movement from the vestibular system; require

Answer 31

continuous feedback of visual information about the moving object