8. CNII Optic Nerve

Question 1

What produces aqueous humor? In what chamber? Where is it reabsorbed?

Answer 1

Choroid plexus produces aqueous humor in the posterior chamber. Reabsorbed by trabecular network and canal of schlemm–> venous drainage

Question 2

Rods vs cones

Answer 2

Rods - rhodopsin, dim light (moonlight), monochromatic, more in peripheral retina
Cones - color, bright light, more in fovea

Question 3

What colored photopigments are present in cones? Which color has longest and shortest wavelengths?

Answer 3

Blue (shortest wavelength), green, red (highest wavelength)

Question 4

Protanopia, deuteranopia, tritanopia

Which is most common?

Answer 4

Protanopia - lacks red pigment, MOST COMMON
Deuteranopia - lacks green pigment
Tritanopia - lacks blue pigment

Question 5

What fraction of photons will pass through photoreceptors without colliding with a membrane molecule?

Answer 5

2/3

Question 6

Mechanism for response to light

Answer 6

Photons hit opsin: cis-retinaldehyde –> trans-retinaldehyde –> causes hydrolysis of cGMP –> Na+ channels close –> cells hyperpolarize –> decreased amount of glutamate released –> decreased “noise” captured by eye

Question 7

Mechanism for response to darkness

Answer 7

trans-opsin –> cis-opsin –> increased cGMP –> depolarization –> release of glutamate –> increased noise

Question 8

What eye structure surrounds the fovea?

Answer 8

Macula lutea (cones present here)

Question 9

What is saccadic eye movements?

Answer 9

Quick, simultaneous eye movements involving both eyes moving in the same direction. “Eyes move around, locating interesting parts of scene and building a map. Eye movements stop several times with jerky, saccadic movements, allows for fovea (~1-2degrees of vision) to focus/inc resolution. Also limits head movements to conserve energy

Question 10

Layers of retina

Answer 10

1. Retinal pigment epithelium
2. Rods/cones
3. Outer limiting membrane
4. Outer nuclear layer (cell bodies of rods and cones)
5. Outer plexiform layer (synapses between rods/cones and bipolar/horizontal cells)
6. Inner nuclear layer (cell bodies of horizontal, amacrine, and bipolar cells)
7. Inner plexiform layer (synapses between ganglion cells, amacrine, and bipolar cells)
8. Ganglion cell bodies layer
9. Nerve Fiber layer
10. Inner limiting membrane