Vision

Question 1

Visual memory is associated with these lobes of the telencephalon:

Answer 1

Parietal and temporal

Question 2

This layer of the globe of the eye is the protective layer for the choroid and retina:

Answer 2

Sclera

Question 3

This is the vascular bed of the outer retina. It actually has the most BF compared to any organ of the body for size.

Answer 3

Choroid

Question 4

Describe the retinal blood supply in terms of percentages from what sources.

Answer 4

20% - central retinal artery (in CNII)

80% - choroid

Question 5

What is it called when BVs invade the fovea, distorting vision?

Answer 5

Macular degeneration

Question 6

These cells make up the 1st layer of the retina. Their primary job is to separate the photoreceptors and other superficial layers of the retina from the choroid and, secondarily, to phagocytize portions of the upper projections of the photoreceptors every 10 days adn provide them with nutrients/support.
Also, they have melanin pigment, that absorbs excess light to prevent the photoreceptors from being damaged by it.

Answer 6

Retinal Pigmented Epithelium (RPE)

Question 7

The outer nuclear layer (layer 4) of the retina contains cell bodies of these cells:

Answer 7

Photoreceptors. Their processes (dendrites) are found in the outer plexiform layer (layer 5).

Question 8

The inner nuclear layer (layer 6) of the retina contains cell bodies of these cells:
The axonal projections of these cells collect information from photoreceptors in this layer:

Answer 8

Bipolar cells. Axonal projections collect photoreceptor signals from outer plexiform layer (layer 5)

Question 9

Describe the types, layers, and functions of the interneurons of the retina.

Answer 9

Horizontal cells (outer plexiform layer) and amacrine cells (inner plexiform layer) function to integrate millions of signals from photoreceptors to the comparatively few ganglion cells that will carry that information to the brain.

Exception: in the fovea of the retina, there is a 1:1 photoreceptor:ganglion cell ratio, providing for the sharp images seen at the focal point of vision.

Question 10

What is drusen?

Answer 10

As people age, the RPE doesn’t do as good of a job of phagoctizing the photoreceptors as it used to. Proteins build up in that layer of the retina resulting in autofluorescence. (important in dry MD)

Question 11

Damage to the RPE, compromising the blood/retina barrier, may lead to invasion of the retina by BVs, resulting in this disease characterized by distorted vision:

Answer 11

Macular Degeneration

Question 12

Rods have 1 of this type of pigment responsible for black and white vision:

Answer 12

Rhodopsin

Question 13

Cones have 3 of these types of pigments, each responsible for green, red, and blue pigments:

Answer 13

Opsins

Question 14

Explain why color blindness is more common in males than females.

Answer 14

The genes for the red and green opsins are found on X chromosomes. Because males only have one X chromosome, they are more likely to have those genes disturbed and absent (no back-up copy), resulting in red-green color blindness.

Question 15

The three types of cones representing blue, green, and red are called S, M, L respectively. Why are they called that?

Answer 15

S = small wavelength (blue) -think ultraviolet is short WL
M = medium wavelength
L = large wavelength (red)

Question 16

The photoreceptors undergo hyper or depolarization in response to light stimulation?

Answer 16

HYPERPOLARIZATION- different from any neuronal signaling anywhere else in body

Question 17

Outline the process of transduction of light to electrical signals.

Answer 17

Process for rods/cones similar
light enters rod:
11-cis-retinal—> all-trans-retinal—> activation of rhodopsin
Active rhodopsin activates GTP–> ^ cGMP PDE –> v cGMP
—> hyperpolarized cell
hyperpolarized cell—> v Na/Ca conductance —> visual response

To reset:
Na/Ca excess in cell—> Ca pumped out via Na/Ca exch.
–> ^ cGMP levels
–> cell REpolarization
Rhodopsin is dephosphorylated and all-trans-retinal—> 11-cis-retinal

Question 18

In the light–>electrical signal transduction pathway, something phosphorylated rhodopsin. What was it and what inhibits it from keeping rhodopsin phosphorylated at all times?

Answer 18

Rhodopsin kinase phosphorylates rhodopsin.

Arrestin prevents this from occurring before the next light stimulus arrives (photon)

Question 19

Outline the transmission of the light signal from photoreceptor to occipital cortex.

Answer 19

Photoreceptor—> bipolar cell (convergence by horizontal interneuron)
Bipolar cell—> ganglion cell (convergence by amacrine interneuron)
Gangion cell axons are in the optic nerve–> chiasm–> tract–> LGN—> optic radiations–> synapse on cortical cells in occipital cortex

Question 20

Alpha gangion cells receive their primary input from rods in this area of the retina:

Answer 20

Periphery - mostly rods found in periphery

Question 21

Beta ganglion cells receive their primary input from cones in this area of the retina:

Answer 21

Central retina- cones found in highest concentration in central retina for focal clarity

Question 22

Alpha and Beta ganglion cells each project to different layers of the lateral geniculate nuclei. Which goes to which?

Answer 22

Alpha—> magnocellular layer (1-2)- “where in space is the object?”
Beta—> Parvocellular region (3-6)- “what is the form of the object?”

Question 23

These layers of the retina are displaced in the fovea centralis so that the cones can achieve maximal acuity:

Answer 23

Layers 6 (bipolar cell bodies) and up (they are still there, just layed down like grass by rotor wash)

Question 24

What is the MCC of blindness in working age adults?

Outline its pathophysiology.

Answer 24

Diabetic retinopathy

^ Glu—> ^ angiogenesis, v photoreceptors, v ganglion cells –> shitty vision everywhere

Question 25

What is the MCC of blindness in the elderly?

Outline its pathophysiology.

Answer 25

Macular degeneration
^ damage to choroidal vessels—> BVs invade through RPE—> obscure light from entering retinal layers—> Loss of central vision.

Question 26

Describe the difference between wet and dry macular degeneration:

Answer 26

Dry= ^ drusen due to v RPE phagocytosis of photoreceptors ==> protein buildup (age)
- affects 1 eye

Wet= ^ BVs in retinal layers of macula
-affects BOTH eyes

Question 27

How do you tx WET MD?

Answer 27

anti-VEGFs (Avastin- bevacizumab, Mucagen- a “-nib”)