Eye Anatomy and Accommodation
A ___sighted person with ____opia wears glasses with a convex lens.
farsighted; hyperopia
This type of BPC is metabotropic, and it (depolarizes/hyperpolarizes) in response to light. (two-part answer)
What are 1) ON BPCs; 2) depolarizes?
The mitochondrial enzyme involved in producing ATP.
What is cytochrome oxidase?
Their name comes from the Latin word for "small".
What are parvo cells?
You see what you think is Dr. Stein meditating on the roof of Biomed. As you try to focus on him in the distance, your ciliary fibers _______, and your zonule fibers ______.
Relax; tighten
This G-protein is involved in phototransduction.
Transducin
These cells receive input from surrounding photoreceptors and inhibit center photoreceptors through a process called __. (two-part answer)
What are 1) horizontal cells and 2) lateral inhibition?
This is the process of combining input from both eyes for depth perception. What optical phenomenon does this process rely on? (two-part answer)
What is 1) stereopsis and 2) parallax?
Peter the Horse is competing on American Ninja Warrior. He is extremely nervous because he claims to have a gigantic blind spot in the center of his visual field. Yet somehow, he maneuvers through the entire obstacle course with ease. Peter might have this visual pathology.
What is blindsight?
As light penetrates through the retina, what is the order in which it encounters the cells in the three nuclear layers.
________(cell type), then _______(cell type), then ________(cell type)
Phototransduction occurs in which specific structure within the photoreceptor?
Disks
(outer segment also works)
These RGC cells are most abundant, and they are sensitive to these colors. (two-part answer)
What are 1) parvo cells; 2) B/W and R/G?
This layer of V1 segregates input from the left and right eye. This monocular input is organized into regions known as __. (two-part answer)
What are 1) layer 4C and 2) ocular dominance columns?
Peter isn't very proficient in his swordsmanship and does a number on your your right optic tract instead of the straw mat he was aiming for. In this case, this part of your visual field would be lost.
What is the left visual hemifield.
The Secret Society of Serious Stargazers (SSSS) has deployed a nefarious plot to prevent people form focusing on their phones, books, or anything else up close, while leaving distant vision largely intact. Which component of the eye did they eliminate to achieve this goal?
Lens
Explanation: Lens changes shape to focus light from nearby objects onto the retina. Without it, the eye cant accommodate to focus on close objects at all. Distant objects can still be seen relatively clearly because they don't require as much accommodation to make sure the light hits the retina.
The dark current entering photoreceptors is based on the flow ____ (K+/Na+) at ____(cGMP/transducin) gated channels
b) K+ at transducin-gated channels
c) Na+ at cGMP-gated channels
d) Na+ at transducin-gated channels
Na+; cGMP
In the LGN, layer 2 receives input from the __ eye and __ RGCs.
What is 1) ipsilateral and 2) magno?
Explain the difference between orientation selectivity and directional selectivity. Which layers of the LGN send input to directionally selective neurons? (two-part answer)
1) Directional selectivity involves motion perception, whereas orientation is a static trait.
2) Magno layers (1,2)
Peter the Horse spent a summer abroad in Japan, and came home with a new katana. He's decided to become a student of the blade, but unfortunately, his new dojo is in your retinofugal pathway.
A cut inflicted to your visual system by his lethal blade causes left eye blindness in the temporal visual field and right eye blindness in the temporal visual field. The cut most likely severed this structure in the pathway.
Optic Chiasm
1. Lateral connections between different _________ (cell type) in the retina are made between ______ cells in the _____ plexiform layer.
2. Lateral connections between different _______ (cell type) in the retina are made between _______ cells in the _____ plexiform layer.
6 total answers.
Photoreceptors; horizontal; outer
Bipolar cells; amacrine; inner
Just after light first hits a photoreceptor, Ca++ entry into the photoreceptor ______ (increases/decreases) and this ________ (increases/decreases) cGMP synthesis due to the activation of ________.
decreases; increases; guanylyl cyclase.
It is dark on the entire receptive field of an ON BPC. State whether the following cells depolarize or hyperpolarize: 1) center photoreceptor, 2) surrounding photoreceptors, 3) horizontal cells. Explain the overall effect on the ON BPC using the term “lateral inhibition”.
1) depolarize, 2) depolarize, 3) depolarize.
The horizontal cells are depolarized, so they release more GABA onto the center photoreceptor. As a result of lateral inhibition, the center photoreceptor is only weakly depolarized. The overall effect is weak hyperpolarization of the ON BPC.
Describe the entire pathway of nonM-nonP cells from the retina to parallel streams. What kind of higher-order processing is involved with these cells? (two-part answer)
1) nonM-nonP RGC (retina) -> koniocellular layers (LGN) -> layers 2,3 (V1) ->ventral stream (temporal lobe)
2) recognition and memory (color/form processing)
Akinetopsia and prosopagnosia are two types of blindness. What is the difference between them? In each pathology, which parallel stream is impaired in each? (BONUS: Can you name the specific visual area that is impaired in each pathology?)
Akinetopsia is motion blindness; dorsal stream (area MT) impaired.
Prosopagnosia is face blindness; ventral stream (FFA) impaired.