Vision I, II, and III

Question 1

The aqueous humor is in the ____________, while the vitreous humor is in the _____________.

Answer 1

eye compartment anterior to the lens; eye compartment posterior to the lens

Question 2

What two parts of the eye focus light?

Answer 2

The cornea (2/3) and lens (1/3); this allocation is what allows ophthalmologists to perform laser correction.

Question 3

The zonule fibers connect what to what?

Answer 3

The zonule fibers connect the lens to the ciliary muscle

Question 4

Lenses focus what colors of light better?

Answer 4

Red and green

Question 5

There are five types of cells in the reina. Briefly describe each.

Answer 5

1) . Photoreceptors (rods and cones)
2) . Bipolar cells (on/off)
3) . Horizontal
4) . Amicrine
5) . Ganglion (output neurons that leave the eyeball)

• The first four types do not fire action potentials.

Question 6

The vertical flow of information through the retina proceeds through what cells?

Answer 6

Photoreceptor -> bipolar cells -> gaglion

Question 7

The horizontal flow of information through the retina is mediated by _____________.

Answer 7

horizontal cells and amicrine cells; they communicate what neighboring cells are doing

Question 8

How many rods and cones are in each eye?

Answer 8

Rods: 100,000,000
Cones: 8,000,000

Question 9

The fovea is predominantly ___________.

Answer 9

cones cells

Question 10

In the center of the retina, photoreceptors are in a _______ ratio with ganglion cells; in the periphery, however, the ratio is ___________.

Answer 10

1 photoreceptor : 1 ganglion cell

1 photoreceptor : many ganglion cells

Question 11

Rhodopsin = ___________ + _____________.

Answer 11

opsin (a 7 transmembrane G protein); retinal (light sensitive molecule)

Question 12

On-ganglions have both a positive center and an __________ periphery. Off-ganglions have the opposite.

Answer 12

inhibitory (the area around it can actually inhibit the ganglion if stimulated)

Question 13

______________ are another form of stimulation for the inhibitory cells of the ganglion.

Answer 13

Rebound signals (action potentials that occur when the inhibitory area ceases to be stimulated)

Question 14

Uniform stimulation (that is, both center and periphery) is not a good stimulator of on-off ganglion receptor fields. Why?

Answer 14

Because those areas detect contrast

Question 15

Horizontal cells use the inhibitory transmitter _________. How does this affect their target cells?

Answer 15

GABA; it further hyperpolarizes the photoreceptors

Question 16

Describe the anatomy of the lateral geniculate nucleus.

Answer 16

It is a horseshoe-shaped, six-layered complex. The layers are numbered from bottom to top (with 1 on the bottom).

Question 17

Which layers of the LGN are from the contralateral eye?

Answer 17

1, 4, and 6

Question 18

Cells in layers _______ are large.

Answer 18

1, 2 (these are the magnocellular layers)

Question 19

Layers 3 - 6 are referred to as the ___________.

Answer 19

parvocelular layers

Question 20

The magnocellular layers sense ________.

Answer 20

motion and depth

Question 21

The parvocellular layers sense __________.

Answer 21

color, form, and fine detail

Question 22

The primary visual cortex (V1) is Brodmann’s area _____.

Answer 22

17

Question 23

Topographically, the upper visual field is __________ to the calcarine fissurer. The retinal center is most _________.

Answer 23

inferior; posterior

Question 24

Input to the cortex from the lateral geniculate nucleus arrives at what cortical layer?

Answer 24

IV

Question 25

Binocular vision occurs at the level of the ________.

Answer 25

cortex; there is no mixing or synthesizing information at the lateral geniculate nuclei

Question 26

The right hemisphere process information from which sides of the retinas?

Answer 26

Right, because the right sides of the retinas capture light coming from the left visual field, and the right hemisphere process left-visual-field information

Question 27

Describe Hubel and Wiesel’s findings on binocular cells in the cortex.

Answer 27

They assigned cells a value of 1 - 7; neurons that only responded to signals from the left eye were given a score of 1, while neurons that only responded to signals from the right eye were given a score of 7. Cells that required bilateral stimulation received a score of 4. Hubel and Wiesel found that roughly 80% of the cells in the cortex are binocular.

Question 28

True or false: monocular deprivation leads to blindness in children.

Answer 28

True! As does binocular deprivation

Question 29

Hubel and Wiesel demonstrated that ___________ is necessary for binocular cells in the cortex to develop.

Answer 29

simultaneous bilateral stimulation

Question 30

When, in the age of the individual, does the deprivation effect cease to happen?

Answer 30

About 2-3 years; it’s much less in cats – only 16 weeks. Researchers think that the sensitive period is longer in humans because our heads take longer to achieve their adult sizes. As the head grow, the distance between the eyes increases, thus changing the angle between the eyes and a given focal distance.

Question 31

What wavelength can the photoreceptors of the eye detect?

Answer 31

400 nm - 700 nm

Question 32

True or false: the posterior chamber of the anterior eye contains the vitreous humor.

Answer 32

False! There are two compartments of the anterior eye, both of which contain aqueous humor.

Question 33

Only the ___________ neurons (in the retina) make action potentials.

Answer 33

ganglion (all others – the photoreceptors, bipolar cells, horizontal cells, and amacrine cells – engage only in passive electrical diffusion)

Question 34

What evidence demonstrates that the retina processes light?

Answer 34

There are 100x as many photoreceptors as ganglionic axons.

Question 35

What determines the type of receptor field (e.g., on-center, linear, etc.)?

Answer 35

The type of bipolar cell! Some are excited by the glutamate secreted by photoreceptors, while some are inhibited by glutamate.

Question 36

Hyperpolarization results in less or more neurotransmitter being released?

Answer 36

Less

Question 37

What neurotransmitter do photoreceptors secrete?

Answer 37

Glutamate

Question 38

Horizontal cells behave as though they have __________ receptors.

Answer 38

excitatory glutamate (meaning they excite other cells when they touch glutamate from photoreceptors)

Question 39

The lateral geniculate nucleus is within what structure?

Answer 39

The thalamus

Question 40

Axons from the ____________ side of each eye cross at the chiasm.

Answer 40

medial

Question 41

Cells in the _________cellular system contain information about movement, spatial layout, and crude outline.

Answer 41

magno

Question 42

All cells in a central column are sensitive to ___________.

Answer 42

the same orientation of light

Question 43

Simple cells have orientation fields that are ______________.

Answer 43

simple lines

Question 44

Complex cells account for ________________.

Answer 44

position

Question 45

There are two pathways of visual information from the V1 area of the cortex: _______________.

Answer 45

dorsal (from V1 to the parietal cortex, being spatial information) and ventral (from V1 to the temporal cortex, being object information)

Question 46

The middle temporal cortex is also called _______ and is sensitive to __________. Where pathway leads here?

Answer 46

V5; motion direction; dorsal

Question 47

In accommodating for near objects, the lens gets __________.

Answer 47

fatter

Question 48

What is transducin?

Answer 48

The G protein that activates PDE

Question 49

The on-center / off-center distinction occurs at the level of the ____________.

Answer 49

ganglion cells (because they receive input on the different fields)

Question 50

What does the “rebound” show?

Answer 50

That light is the inhibitory part