Intro and Duplex (Midterm I)

Question 1

What are the main reasons that the optic nerve is more like a tract of the CNS than PNS?

Answer 1

1. development from diencephalon
2. myelin produced by oligodendrocytes
3. vasculature with blood-retinal barrier
4. narrow and completely ensheathed retinal synapses
5. regeneration is rare

Question 2

What are the three principle functions of the retina?

Answer 2

1. transduce visual images to electrochemical signals
2. perform initial processing of signal
3. convert signal into signal to be sent and interpreted by brain

Question 3

What is the order of layers in the retina from anterior to posterior?

Answer 3

1. inner limiting membrane
2. nerve fiber layer
3. ganglion cell layer
4. inner plexiform layer
5. inner nuclear layer
6. outer plexiform layer
7. outer nuclear layer
8. outer limiting membrane
9. photoreceptors (rods and cones)
10. retinal pigment epithelium (RPE)

Question 4

What are specialized glial cells that span nearly all of the retinal layers? 1. What do they form? 2

Answer 4

1. muller cells

2. OLM and ILM

Question 5

What cells convert light energy into an electrical signal?

Answer 5

photoreceptors

Question 6

What cells receive visual info from photoreceptors and transmit this signal to retinal ganglion cells?

Answer 6

bipolar cells

Question 7

What cell are the output neurons of the retina?

Answer 7

ganglion cells

Question 8

What are the retinal neuron cells that modulate the transmission between the photoreceptors, bipolar cells, and ganglion cells?

Answer 8

horizontal and amacrine cells

Question 9

Why does the optic nerve have a white look?

Answer 9

RGC axons become myelinated as they pass the lamina cribosa

Question 10

What is it called when RGCs become myelinated before reaching the ONH? 1. What is the effect on vision? 2

Answer 10

1. MRNF

2. none

Question 11

Where do ganglion cells from the retina project to? 1. What is this collection of axons called? 2

Answer 11

1. lateral geniculate nucleus (in thalamus)

2. optic nerve (before optic chiasm) and optic tract (after optic chiasm)

Question 12

Where do cells of the lateral geniculate nucleus project to? 1. What is this collection of axons called? 2

Answer 12

1. primary visual cortex

2. optic radiations

Question 13

What portion of the axons from the retina cross at the optic chiasm?

Answer 13

the axons from the nasal retina

Question 14

What is the name for the optic radiations that loop temporally around the lateral ventricle and synapse below the calcarine fissure? 1. What area of the visual field are these from? 2.

Answer 14

1. Meyer’s loop

2. superior visual field (inferior retina)

Question 15

Does the superior or inferior visual field have a more direct route to synapse from the LGN to the primary visual cortex?

Answer 15

inferior field (superior retina)

Question 16

What is the detection of a stationary light target displayed on uniform white background called?

Answer 16

static perimetry

Question 17

What is the main indication of a prechiasm lesion?

Answer 17

visual field defect that crosses the midline

Question 18

What kind of visual field defect is associated with damage to Meyer’s loop radiations?

Answer 18

superior quadrantanopia

Question 19

What kind of visual field defect is associated with damage to non-Meyer’s loop radiations?

Answer 19

inferior quadrantanopia

Question 20

Where is the lesion locate is there is a homonymous hemianopia with macular sparing?

Answer 20

at the calcarine fissure or striae cortex

Question 21

What anatomical finding is responsible for a junctional scotoma when there is a pituitary adenoma?

Answer 21

knee of Willebrand

Question 22

What is a clear sign in a visual field that a lesion has occurred prechiasmally?

Answer 22

defect crosses the midline

Question 23

Where do the thermal and chemical injuries occur on the retina with intense sun exposure?

Answer 23

outer retina (bilateral)

Question 24

For scotopic vision: what are the photoreceptors that mediate this? 1. Are threshold detection levels high or low? 2. Is it associated with good or poor visual acuity? 3. Is there a high or low amount of saturation? 4

Answer 24

1. rods
2. low (more sensitive)
3. poor VA
4. high saturation at high luminances

Question 25

For photopic vision: what are the photoreceptors that mediate this? 1. Are threshold detection levels high or low? 2. Is it associated with good or poor visual acuity? 3. Is there a high or low amount of saturation? 4

Answer 25

1. cones
2. high (less sensitive)
3. good VA
4. little saturation

Question 26

What are the photoreceptors that mediate mesopic vision?

Answer 26

rods and cones

Question 27

Where does visual pigment reside in the photoreceptor? 1. What is its responsibility? 2

Answer 27

1. discs in outer segment

2. capturing photons

Question 28

Do cones or rods have encapsulated discs in the outer segment?

Answer 28

rods

Question 29

Where is visual pigment first formed? 1. What area does the pigment pass to end up in its final location? 2

Answer 29

1. inner segment

2. cilium

Question 30

About how many rods are there in a human retina? 1. How many cones? 2

Answer 30

1. 120 million

2. 6 million

Question 31

What is the cause of the foveal light reflex?

Answer 31

concave shape of fovea

Question 32

What is the location of the axon terminals of the pushed aside cones in the fovea called?

Answer 32

Henle fiber layer

Question 33

What is the retinal vasculature found in the fovea?

Answer 33

there is none

Question 34

Human vision is capable of operating over a large range of light intensities. Of the roughly 11 log units that this range encompasses, how much range of adaptation is due to pupil constriction?

Answer 34

1 log unit