Lecture 13: Vision Flashcards
1
Q
Light
A
Photons; both energy waves and particles
2
Q
Layers of the Retina
A
Ganglion cells, amicrine cells, bipolar cells, horizontal cells, and photoreceptors (rods and cones)
2
Q
Retinal Ganglion Cells (RGCs)
A
Sends information to the brain
2
Q
Amacrine and Horizontal Cells
A
Lateral interactions (inhibitions) within the retina
2
Q
Bipolar Cells
A
Carry information from photoreceptors to the retinal ganglion cells
3
Q
Photoreceptors
A
Rods and cones; transduce light signals
3
Q
Phototransduction
A
- Occurs in the photoreceptors
- Light strikes a light-absorbing pigment molecule (rhodopsin) in the disc of a photoreceptor
- Rhodopsin breaks into retinal and opsin
- Opsin closes Na+ gates, hyper-polarizing the photoreceptor
- Stops glutamate release
4
Q
Rods vs. Cones
A
- Rods are highly sensitive to light- ideal for vision in dim environments
- Rods have a similar response across wavelength (see in black and white)
- Cones are not sensitive, needs more light to be activated
- Cones come in three types, each sensitive to either red, green, or blue wavelengths
4
Q
Color Blindness
A
A lack in one or more of the cone pigments results in color blindness
5
Q
Honeybee Vision
A
- Humans and bees are both trichromatic, but bees see more ultraviolet light and less red light compared to us
5
Q
Fovea
A
- Sharpest vision, corresponds to center of gaze
- Non-photoreceptor cells are pushed aside in the fovea
- High density of cones, few rods
- Therefore, our focus of gaze is optimized for day
- At night, we are nearly blind in the fovea
5
Q
Receptive Fields of Retinal Ganglion Cells
A
- Light cause photoreceptor to release less glutamate
- This excites bipolar cells, causing them to release more glutamate*
- Excited bipolar cells excite RGCs
- These RGCs are excited by light at center –> “on-center cells”
- APs are fired
- Another class of bipolar cells is inhibited and inhibited RGCs. These RGCs are “off-center cells” because they are inhibited by light, AP rate is reduced in this case
6
Q
Lateral Inhibition
A
Capacity of an excited neuron to reduce the activity of its neighbors
6
Q
On-center off-surround
A
- Light in center excites
- No light in periphery excites
