Vision I+II

Question 1

What are the 4 stages of vision?

Answer 1

Light collection by eye, transduction b photreceptor, info proecessing by retina and visual cortex.

Question 2

What are the advantages (2) for compound eye? How about refractive eye?

Answer 2

Compound eyes have ebtter sensitivity to mevement and detects wider range of waevlengths (polarized light); Refractive eye is optimized resolving power (acuity).

Question 3

What does ommatidia mean?

Answer 3

the single unit of a compound eye. Increase visual acuity.

Question 4

Name the three layers of the eye.

Answer 4

Outer layer: sclera (same layer of the cornea; sclera:white); coroid layer (blood vessel, pigmented layer); innermost: neural retina (photoreceptor and neurons)

Question 5

What is the major refractory part of the eye?

Answer 5

Cornea

Question 6

What is the adjustable refractory part of the eye?

Answer 6

Lens

Question 7

If going under water, which part of eye is equivalent to not being functional?

Answer 7

Cornea

Question 8

What is the borders for the anterior chamber? Is it fluid-filled or not?

Answer 8

Between cornea and iris; yes, aqueous humor.

Question 9

Where is the aqueous humor produced?

Answer 9

by ciliary epithelium, which is dorsal to the iris. It is continuously produced; in order to reach the anterior chamber, it leaves the trabecular meshwork. Absorption is at canal of schlemm.

Question 10

What if the anterior chamber fluid is over produced or not properly drained?

Answer 10

pressure building up leads to Glaucoma: result in blockage of blood flow into retina and damage to the neural retina. Second leading cause of blindness.

Question 11

Define the concept of “accommodation”

Answer 11

Change in the refractive power of the lens due to changes in its shape. For far vision, the ciliary muscle is relaxed, suspensory ligament taut, and lens flattened.

Question 12

Describe the accommodation process for seeing near object.

Answer 12

Ciliary muscle contracted, suspensory ligament relexed, lens thickened and focused.

Question 13

How does age has to do with accommodation

Answer 13

lens becomes less elastic with aging

Question 14

What happened with myopia/nearsighted? What lens to use?

Answer 14

focal plane is in front of the retina; too much refractive power (concentrate too quickly); correction is concave lens (refract the light a bit).

Question 15

How about farsighted/hyperopia?

Answer 15

the focal plane falls behind the retina; use the convex lens to focus the light

Question 16

What are cataracts?

Answer 16

Opacities in the lens of the eye that interfere with vision and can result in loss of parts of the visual field. Often developed with aging. The crystallins protein, which is filled inside the lens fiber cells, becomes sort of old and denatured.

Question 17

What is fovea?

Answer 17

The point where majority of the light will hit in retina with fewest neuron cells. Light can travel directly hit the photoreceptor, detecting the light. Fovea is responsible for sharp central vision (also called foveal vision), which is necessary in humans for reading, driving, and any activity where visual detail is of primary importance.

Question 18

What cell is the photoreceptor synapsing with? How about the next cell?

Answer 18

Rods synapse with bipolar cells; bipolar cells synapse with ganglion cells.

Question 19

Is it possible for living being having more than one fovea in each eye?

Answer 19

Yes, some birds have two! The other fovea is locating near the top part of the retina, allowing light coming from the ground below to focus and obtain acuity.

Question 20

What is the pigment in the pigmented epithelium? What is the function?

Answer 20

Melanin (black pigment); absorb light that was not absorbed by the photoreceptor.

Question 21

What is tapetum? What is for?

Answer 21

another layer in the pigmented epithelium in some animals.The tapetum consists of a layer of GUANINE CRYSTALS. This layer helps reflect light that has not been absorbed upon the first pass through the photoreceptor layer of the retina, so that there is a second chance for the photons to be absorbed by the photoreceptors. Thus, it INCREASES SENSITIVITY of the eye to light and ENHANCES NIGHT VISION, but because it involves the absorption of light which has been reflected/scattered, it however decrease acuity.

Question 22

Why retinal detachment happens?

Answer 22

Because the retina and pigmented epithelium are from separate embryological layers. The junction between the two layers are not mechanically strong.

Question 23

What is macular degeneration

Answer 23

Loss of pigmented epithelial cells, then photoreceptors. Mos common cause of vision loss in the elderly (6 mil in U.S.).

Question 24

Where is macula?

Answer 24

Oval-shaped, yellowish pigmented spot surrounding the fovea

Question 25

What is the "wet" form of macular degeneration?

Answer 25

Growth of tissue or blood vessel separates the pigmented epithelium from the retina.

Question 26

What is the "dry" form of macular degeneration?

Answer 26

accumulation of "drusen" – yellow or white extracellular accumulations of proteins and lipids.

Question 27

Name the major types of cells in the retina

Answer 27

Photoreceptor, horizontal, bipolar, amacrine, and ganglion

Question 28

What does horizontal cell do?

Answer 28

Connecting the photoreceptor

Question 29

Does ganglion cell have myelin?

Answer 29

No. they don't. They are the "output" of visual signal. Only ganglion cells fire AP.

Question 30

What are some distinct feature of the rods and cones cells?

Answer 30

Shape of outer segment; stack of disks; cilium; lots of mitochondria; at synapse, filled with glutamate.

Question 31

How is the disk produced?

Answer 31

Constantly, 3-4/hour. Disks added at the base. Pigmented epithelial cells phagocytosize the disks, removing them.

Question 32

What are the features of the rods?

Answer 32

high sensitivity; good for night vision; low temporal resolution, low acuity, achromatic.

Question 33

What are the features of the cones?

Answer 33

Lower sensitivity, good for day vision, high temporal resolution, high acuity, and chromatic.

Question 34

Which one is better at catching scattered light? axial light?

Answer 34

Rods - scattered light; cones - axial light rays

Question 35

Which is concentrated at fovea - rods or cones?

Answer 35

cones

Question 36

What the difference between the M and P type of ganglion cells in the retina

Answer 36

M - magnocelluar type, arger receptive field, involved in motion detection; P ; parvocellular, smaller receptive field, color vision.

Question 37

Reponse properties of On center and Off center.

Answer 37

Life in the center of the field, increase in firing of on center ganglion in the center, Light in the surrounding increase the firing of the off center.

Question 38

What is the W type of ganglion cell?

Answer 38

1-2% of all ganglion cell. It contains melanopsin and are photosensitive. Do not have center-surround receptive field.

Question 39

What is the function of hypthalamuc in terms of vision

Answer 39

regulation of carcadian rhythms

Question 40

What is the function of pretectum in terms of vision?

Answer 40

reflex control of pupil and lens

Question 41

What is the function of superior colliculus?

Answer 41

Orienting movements of head and eyes.

Question 42

Describe the path of pupillary reflex

Answer 42

Optic never in -> pretectum -> Edinger-Westphal nucleus (2) -> oculomotor nerve ->ciliary ganglion -> motor function on both sides (consensual).

Question 43

What is the function of lateral geniculate nucleus of thalamus?

Answer 43

relay the information to cortex. P type: layers 3-6, color vision. M type: 1,2, layers, movement information.