Visual Part 2

Question 0

What is the fovea centralis? What are two properties of it?

Answer 0

Central focal point of the retina. Has only cones and high acuity

Question 1

What structures doe light pass through before it hits the retina?

Answer 1

Cornea, aq. Humor, lens, vitreous body

Question 2

What is the macula lutea? Why is it yellow?

Answer 2

Yellow area surrounding the fovea. Pigments from carotenoids and lutein and zeaxanthins absorb UV light, protecting the retina from oxidative damage

Question 3

Where does the central artery of the retina come from?

Answer 3

The internal carotid artery

Question 4

What are the four retinal layers- from outer to inner layers

Answer 4

Pigmented epithelium, photoreceptors, neural cells, ganglion cells

Question 5

What are three types of neural cells?

Answer 5

Bipolar, horizontal and amacrine cells

Question 6

What pigment is in cones?

Answer 6

Iodopsin

Question 7

What pigment is in rods?

Answer 7

Rhodopsin

Question 8

What part of the neural layer releases glutamate?

Answer 8

Inner segment of the photoreceptors

Question 9

Where are pigments located within the photoreceptors?

Answer 9

Vesicular discs

Question 10

How does light affect a photoreceptor cell?

Answer 10

11cis retinal –> trans retinal–>opsin activates PDE–> PDE reduces cGMO activity –> cell hyperpolarized–> less glutamate is released

Question 11

What does photopic mean? Which photoreceptors are photopic?

Answer 11

Vision in bright light/ low sensitivity (cones)

Question 12

What is scotopic? What photoreceptors are scotopic?

Answer 12

Vision in dim light/ low sensitivity (rods)

Question 13

Which photoreceptors are chromatic? Which photoreceptors are achromatic?

Answer 13

Cones are chromatic, rods are achromatic

Question 14

Which photoreceptors are better to detect visual motion?

Answer 14

Rods

Question 15

Which photoreceptors are high acuity, sensitive to direct light and impart good spatial resolution?

Answer 15

Cones

Question 16

Which photoreceptors have low acuity, are sensitive to scattered light and impart poor spatial resolution?

Answer 16

Rods

Question 17

What photoreceptors are primarily in the periphery of the retina? Which are primarily in the fovea?

Answer 17

Rods are primarily in the periphery. Cones are primarily in the fovea, but can be spread out thinly in the periphery for general color vision

Question 19

What is one way that cones increase vision acuity in the fovea centralis?

Answer 19

Each cones activates a single ganglion

Question 20

Why is the choroid layer of blood vessels behind the retina?

Answer 20

Because light cant pass through blood vessels well

Question 21

How is it that light can pass through the ganglion and bipolar cells before hitting the retina?

Answer 21

They have the same refractive index as the vitreous humor

Question 22

What are six functions of the retinal pigmented epithelium?

Answer 22

1. visual acuity (limit reflection of light) 2. pigments absorb blue/UV light, as antioxidants 3. recycling of 11-cis retinal to maintain photoreceptor excitability 4. transportation of nutrients/waste from photoreceptors and choroid 5. phagocytosis of UV damaged photoreceptors 6. secretion of PEDF and VEGF

Question 23

What can happen if the RPE no longer phagocytoses photoreceptor fragments?

Answer 23

fragments accumulate and separate from the choroid, causing anoxia and cell death. retinitis pigmentosa

Question 24

How do cells in the fovea centralis get their nutrients?

Answer 24

its avascular, but nutrients are acquired by active transport to and from the choroid- transporters are in the RPE

Question 25

What is macular degeneration, and what can it cause?

Answer 25

rupture of a blood vessel or build-up of cellular waste material. this can cause retinal detachment as the retina separates from the RPE, leading to blindness

Question 26

What three cells in the retina activate the ganglion cells?

Answer 26

bipolar cells, horizontal cells and amacrine cells

Question 27

What three areas of the nervous system do the ganglion cells in the retina transmit information to?

Answer 27

thalamus, superior colliculus and other brain stem areas

Question 28

Is the optic disc myelinated or unmyelinated?

Answer 28

unmyelinated

Question 29

What three things are in the optic tract?

Answer 29

ganglionic axons going to the thalamus, retinal blood vessels, CNS glial clls

Question 30

Why should the optic nerve actually be called an optic ‘tract’?

Answer 30

Because it is surrounded by the three dural layers (dura, arachnoid and pia mater, with CSF fluid)

Question 31

What do oligodendrocytes do in the optic tract?

Answer 31

myelinate the axons

Question 32

What do astrocytes do in the optic tract?

Answer 32

surround cell bodies/dendrites and create structural support

Question 33

What is papilledema? What are characteristics of it that can be viewed with an ophthalmoscope?

Answer 33

increased CSF pressure causes edema underneath the optic disc (due to decreased venous return). visual inspection shows blurred disc margins and dilated tortuous veins

Question 34

Why is the optic disc called the ‘blind spot’?

Answer 34

no photoreceptor cells here, only ganglionic axons

Question 35

How is the blindspot ‘fixed’ in binocular vision?

Answer 35

visual information is interpolated from adjacent areas of the retina during saccadic movements/ by visual cortex activity