9.2 Flashcards
The Visual System's Functional Anatomy (70 cards)
What is the retina?
The light-sensitive surface at the back of the eye; consists of neurons and photoreceptor cells
What is a photoreceptor?
A specialized neuron that transduces light into neural activity.
What is the fovea?
Area at the center of the retina that is specialized for high acuity.
Allows for color discrimination and making out details.
Depressed part of the retina
What kind of photoreceptor is abundant in the fovea?
Cones. They are the most dense in the fovea.
There are no rods in the fovea.
What is the lens?
Where light in the eye is flipped upside-down and light-to-left
What is the optic disc?
The area of the retina where axons forming the optic nerve leave the eye and where blood vessels enter and leave.
Where is the blind spot in our eye?
The optic disc. There are no photoreceptors because the axons and blood vessels need to be there.
Slightly off center in both our eyes so we don’t have a hole in our vision.
What is papilledema?
Inflammation of the optic disc. Usually causes vision loss.
Photoreceptors convert light energy into what kind of energy?
Chemical (and then into neural activity)
What are the two types of photoreceptors in the eye?
Rods and cones.
How do rods and cones differ in shape?
Rods are longer and cylindrical on one end. Cones are shorter and have tapered ends.
(hence the names…)
What photoreceptor is used mainly for night vision?
Rods. They are sensitive to low levels of light (cones are responsive to bright light)
What photoreceptor is used for color and visual acuity (fine details)
Cones. (remember that the fovea is where they are concentrated and that’s the place with the most visual acuity)
How many types of pigments do cones have?
- Each cone only has one of these three pigments. (Red, green, and blue)
There are equal numbers of red and green cones but fewer blue cones.
What are the three types of cells in the first layer of retinal neurons? (these connect directly to photoreceptors)
bipolar, horizontal, and amacrine
What does a bipolar cell do?
Receive input from photoreceptors
What do horizontal cells do?
Links photoreceptors and bipolar cells
What do amacrine cells do?
Link bipolar cells and retinal ganglion cells (RGCs)
What are retinal ganglion cells?
One of a group of retinal neurons that form to the optic nerve.
Second neural layer of retinal neurons.
What are the two types of RGCs?
Magnocellular (M-cell) and parvocellular (P-cell)
What do M-cells do and where are they located in the eye?
Receive input from rods (so they are sensitive to light). They are found all over the retina, including periphery (so they are sensitive to moving stimuli).
Where do M-cells input to in the LGN of the Thalamus? (what layers)
Layers 1 and 2
What do P-cells do and where are they located in the eye?
Receive input from cones (so they are sensitive to color and fine detail). They are only found in the fovea.
Where do P-cells input to in the LGN of the Thalamus?
Layers 3-6