Ch 50 B

Question 1

Who has the most simple light-detecting organs? What is it?

Answer 1

Planarians
Pair of ocelli called eyespots

Question 2

What is negative phototaxis?

Answer 2

when animals move away from light

Question 3

What are compound eyes composed of? What are its benefits?

Answer 3

Ommatidia
Effective at detecting movement
Have excellent color vision

Question 4

What changes the diameter of the pupil?

Answer 4

iris

Question 5

What controls how much light enters?

Answer 5

Pupil

Question 6

How many lens do vertebrates have?

Answer 6

single lens

Question 7

What is the choroid?
What is its function?

Answer 7

Thin, pigmented layer
Provides nutrients and blood

Question 8

Where is the choroid located?

Answer 8

outside the retina

Question 9

What is the Retina?

Answer 9

a layer of photoreceptors cells and glial cells within the eye

Question 10

What is the lens?

Answer 10

a transparent disk of protein

Question 11

What is in front of the lens and is clear and watery

Answer 11

aqueous humor

Question 12

What is behind the lens and is jellylike?

Answer 12

Vitreous humor

Question 13

When light enters and strikes the retina it reaches?

Answer 13

Rods and cones
(Photoreceptors)

Question 14

Where does the neurons of the retina then relay visual information to?

Answer 14

Optic nerve and brain

Question 15

What lacks photoreceptors and doesn’t detect light

Answer 15

Optic disk

Question 16

Human two main types of photoreceptor cells

Answer 16

Rods: sensitive light but no color
Cones: provide color vision

Question 17

light absorbing pigment bound to a membrane protein opsin

Answer 17

Retinal

Question 18

Rhodopsin

Answer 18

visual pigment
contains retinal and opsin

Question 19

What does absorption of light cause?

Answer 19

shape change in retinal

Question 20

What does the transduction of visual information to the nervous system begin with?

Answer 20

conversion of cis-retinal to trans-retinal (from light)

Question 21

What is the process of converting trans-retinal to cis-retinal called?

Answer 21

bleaching

Question 22

What activates rhodospin?

Answer 22

Trans-retinal

Question 23

What does rhodopsin activate?

Answer 23

G protein (transducin) which activates phosphodiesterase which leads to hydrolysis of cyclic GMP

Question 24

What is the function of Cyclic GMP in the eye?

Answer 24

In the dark binds sodium ion channels and keeps them open

Question 25

What happens with cyclic GMP breaks down? (3)

Answer 25

1) Na channels close 2) Causes hyper polarizes the cell 3) Signal Transduction pathway usually shuts off again as enzymes convert retinal back to the cis form

Question 26

Processing of visual information begins

Answer 26

Retina

Question 27

Rods and cones continually release the neurotransmitter? into what?

Answer 27

Glutamate into synapses with neurons called bipolar cells

Question 28

What happens when light strikes the rods and cones? (very general)

Answer 28

They hyperpolarize shutting off their release of glutamate

Question 29

What does the decrease in glutamate cause?

Answer 29

Change membrane potential of bipolar cells

Question 30

What is lateral inhibition

Answer 30

When a rod or cone stimulates a horizontal cell and the horizontal cell then inhibits more distant photoreceptors and bipolar cells

Question 31

What does lateral inhibition help?

Answer 31

Helps enhances contrast

Question 32

What is a receptive field?

Answer 32

the cones and rods defined by a single ganglion

Question 33

What causes sharper images?

Answer 33

A smaller receptive field

Question 34

Where do the optic nerves meet at?

Answer 34

At the optic chiasm near the center of the base of the cerebral cortex

Question 35

Where do sensations of visual fields from each side of the brain go to?

Answer 35

The opposite side of the brain

Question 36

What do mammals that are nocturnal have high proportion of

Answer 36

They have high proportions of rods and don't see vivd colors during the day

Question 37

What are the three types of cones

Answer 37

Red Green Blue

Question 38

What are RGB pigments are called

Answer 38

photopsins

Question 39

How are photopsins formed?

Answer 39

formed when retinal binds to three distinct opsin proteins

Question 40

Where do abnormal color vision results from?

Answer 40

Mutations in the genes for one or more photospin proteins

Question 41

what is focusing?

Answer 41

changing shape of the lens

Question 42

What is the fovea?

Answer 42

Center of the visual field and contains no rods but a high density of cones

Question 43

What are the 2 types of accommodation?

Answer 43

1) near vision 2) distance vision

Question 44

explain near vision accommodation (3)

Answer 44

1) ciliary muscles contract 2) suspensory ligaments relax 3) lens becomes rounder

Question 45

explain distance vision accommodation (3)

Answer 45

1) ciliary muscle relax 2) suspensory ligaments 3) lens becomes flatter