Vision

Question 1

Refraction

Answer 1

Is the bending of light waves. At an angulated surface of a transparent material

Light does not bend when it strikes a perpendicular surface

Question 2

What does the degree of refraction depend on?

Answer 2

The ratio of the two refractive indices of the two transparent media

The degree of angulation between the interface and the entering wave front of the light waves

Question 3

Refractive index

Answer 3

In the ratio of the velocity of light in air to the velocity of light traveling in the substance

Question 4

Refractive power

Answer 4

In a measure of how much a lens bends light waves, measures in diopters

1 diopter = 1 meter/focal length of lens

Question 5

Focal point

Answer 5

The point through which all parallel rays of light will pass after passing through each part of the lens

Question 6

Focal length

Answer 6

The distance from the center of the lens to the focal point

Question 7

What is the funtion of the iris?

Answer 7

It controls the amount of light entering the eye, according to how much light is available

Question 8

What’s the relationship between the pupillary diameter and the focus of the lens?

Answer 8

Depth of focus of the lens increased as the pupillary diameter decreased

Question 9

Emmetropia

Answer 9

Normal with regard to depth of focus

Parallel light rays from distanct objects are in sharp focus on the retina when the ciliary mescle is completely relased

All distant objects are seen clearly

Question 10

Hyperopia

Answer 10

Farsightedness

Usually due to an eyeball that is too short or weak lense

Distant objects are clear

Question 11

Myopia

Answer 11

Nearsighted ness

When cillary muscle is completely relaxed, light rays from distant objects are focused in front of the retina

Eyeball long

Question 12

What is visual acuity and resolving power? What is the max visual acuity for the human eye for two-point sources?

Answer 12

Visual acuity is the measure of the resolving power of the eye

Average diameter of a cone is 1.5µm
The max for two point source of light is 1.5 to 2µm

Question 13

What are the cellular layer’s of the retina?

Answer 13

Photoreceptors - rods and cones

Horizontal cell

Bipolar cells

Amacrine cells

Ganglion cells

Question 14

Rods and cones use which neurotransmitter?

Answer 14

Glutamate

They synapse with bipolar and horozontal cells

Question 15

Amacrine cells use which type of neurotransmitters?

Answer 15

Inhibitory: GABA, Glycine, dopamine, Acetylcholine, indolamine

Question 16

Horixontal cells

Answer 16

Recieve info from the rods and cones and transfer it to you bipolar cells - outer plexiform layer

the output in always inhibitory - lateral inhibition

Question 17

Bipolar cells

Answer 17

Info from rods, cones and horozontal celss to inner plexiform later and synapse with amacrine and ganglion cells

Question 18

Amacirne cells

Answer 18

Connetor between bipolar and ganglion cells

Interneurons that help analyze visual signals before they leave the retina

Question 19

Ganglion cells

Answer 19

signals from retina to brain and make up optic nerves

Only retina cells that transmit AP

Question 20

Which cells make up the pathway for cones (direct) pathway and the pure rod vision?

Answer 20

Direct pathway: cones, bipolar cells and ganglion cells

Pure rod vision: rods, bipolar cell, amacrine cells and ganglion cells

Rod vision pathway includes amacrine cells

Pathways in the fovea - fine vision

Question 21

What are the functions of amacrine cells?

Answer 21

Part of the direct pathway for rod conductio n

Response to continuouing visual signals but fades quickly

Some respond with or without light

Response to movement across retine

Gen func: analyzing visual signals before they leave the retina

Question 22

Ganglion cells

Answer 22

Make up optic fibers

In the fovea (visual acuity) less cones and rods converge on one ganglion cell

In the peripheral retina which are more sensitive to weak light, many rods converge on one ganglion cell

Three types: W, X and Y

Question 23

W ganglion cells

Answer 23

Small, transmit signals in 8 m/sec

Mostly signals are from rods through bipolar or amacirne cells

Feilds in peripheral retine

40%

Question 24

X ganglion cells

Answer 24

Medium size, signals transmit 14m/sec and the visual feild is small - represent discrete locations in the retina

Ever X ganglion has at least one cone cell. -> color vision?

55%

Question 25

Y ganglion cell

Answer 25

Large, 50m/sec
Rapid changes in visual image
Fast CNS response/perception with lower accuracy

5%

Question 26

How does fluid flow in the eye?

Answer 26

Flows from the anterior chamber into the canal of Schlemm and then into aqueous veins in the sclera

Question 27

how is ion flow in the eye different in the light and the dark?

Answer 27

In the dark membrane is leaky to Na+ and the EN is reduced -> easier firing

In the light rhodopsin is damaged and transducin is released. Transducin causes sodium channels to close by cGMP and the cell is hyperpolarized.

Question 28

What is the dorsal lateral geniculate nucleus? What is it’s purpose?

Answer 28

It relays information from the optic tract to the visual cortex by optic radiation. It serves as a transmission gate in that is controls how much of the signal is allowed to pass to the cortex

• by corticofugal fibers in primary visual cortex
• reticular formation from mesencephalon

Question 29

Layers of the Primary Visual Cortex

Answer 29

Signals from macular area end in the macula
(Fovea)
The cortex extends along the calcarine fissure

Question 30

What are color blobs and where are they?

Answer 30

Column areas intermixed in the columns of the secondary visual area, activated by color signals

Question 31

What is accomadation?

Answer 31

Increasing the refractive power of the the lens. Children can have an accommodation of about 14 diotpers