Lecture 8 Review Flashcards
What are the properties of light?
It acts as a particle and a wave. The higher the frequency, the shorter the wavelength. Absorption is how the eye transduces light energy. Refraction helps shape detection
Describe the path light takes to get to the retina
Light passes the cornea then to the lens. The size of the pupil determines how much light is allowed into the retina
What is the organization of the retina?
Ganglion cells - first to be hit by light, only one that fires APs
Bipolar cells - with horizontal and amacrine cells, it processes input to the ganglion cells
Photoreceptors - detect light and transduces it.
They are all considered neurons, but ganglion are the ones that fire APs
How does light impact intracellular concentrations?
Exposure to light = decrease in cGMP = decrease in Na conductance = decease in membrane potential
cGMP is needed to open Na channels
Hyperpolarization when light increases
Where does transduction of light occur and what are the proteins involved?
Photopigments contain opsin and retinal.
Retinal - sensitive to light, causes conformational change
Opsin - similar to G protein coupled receptor
Transducin is a G protein similar to Gi (inhibitory - binds cGMP)
What are the two types of photoreceptors and how are they different
Rods - high area of rhodopsin. Extremely sensitive to light, poor color perception. Broadly tuned to wavelengths. Only one type of rod
Cones - Small area of rhodopsin. Insensitive to light, need a lot for color perception. Narrow tuned. Contains differential responsiveness - different types of cone proteins/cones: blue, green, red. respond differentially to different colors
Describe the distribution of photoreceptors of the retina
center: high cones, low rods, low convergence
periphery: high rods, low cones, high convergence
Describe the organization of the fovea
contains mostly cones. lateral displacement of non-photoreceptor cells. high qualitative information
Where do bipolar cells receive input from?
photoreceptors (direct) and horizontal cells (indirect)
horizontal cells produce lateral inhibition
What are the types of ganglion cells?
P cells - small receptive field with high spatial acuity for small area. high stimulation for small area. differential responses to color
M cells - large receptive fields with low spatial acuity for large area. very sensitive, need low level of stimulation. found in the periphery and undergo habituation
What are ganglion cell photoreceptors?
rare ganglion cells that are photosensitive and can carry out transduction. contains a large receptive field. helps mediate unconscious functions (sleepwake)
Where do optic nerves cross over?
At the optic chiasm
What is the visual pathway?
ganglion cells project to the LGN in the thalamus. it crosses the cerebral hemispheres. cortex receives information contra and ipsilaterally. It projects to the striate cortex (V1).
How do V1 cells respond to visual patterns?
Respond depending on specific orientation. cells at different layers of a column respond to the same type of input
Describe cortex layers
6 layers each containing different types of cells. function as columns. either process information or send information.
