The Eye Flashcards
Dark current channels close and less Ca is entering. Ca inhibits the synthesis of cGMP by guanylyl cyclase and thus with less unerring guanylyl cyclase is more active and cGMP synthesis inc. Dark channel currents gradually open and depolarize cones so that they have a range through white they can function in the light
Light adaptation
Neural tissue at the back of the eye
Retina
Carry red-green and blue-yellow info
P and nonm-nonp ganglion cells
Respond to the opposite way the photoreceptors communicating with them do. Metabotropic glutamate receptors (light is preferred stimulus)
On type (sign inverting) bipolar cells
Fewer disks, contain red, blue, or green pigments
Cones
Only output cells, fire APs
Ganglion cells
The cornea uses this since there is air in front and fluid behind (aqueous humor)
Refraction
Bending of light when traveling from one medium to another
Refraction
What does it mean when we say our visual system doesn’t detect differences in absolute values?
Not great in uniformly light/dark environments
SLIDE 45
SLIDE 45
More sensitive to light bc rods more sensitive to low light, more photoreceptors per ganglion cell
Peripheral retina
What does the G protein (transducin) do when rhodopsin is hit by light?
Activates phosphodiesterase and reduces the level of cGMP
All the complex data we need to construct our perception of the world is gathered by this
Retina
How does light activate rhodopsin?
Light strikes retinal and changes its shape to linear and the color of rhodopsin changes
Distance between peaks
Wavelength
Are red on center, green off surround or green on center, red off surround. Red and green are opponent colors
P type cells
Release GABA as a NT
Horizontal cells
Transfer of light energy, compounds do this with light of specific wavelengths and reflect others
Absorption
Used in daylight (photopic) to detect color. Many more photons are required to activate these photoreceptors. Not very active in the dark
Cones
SLIDE 59
SLIDE 59
What happens when Na and Ca stop flowing into rhodopsin?
The cell is hyper polarized (more negative)
These photoreceptors and 1000x more sensitive to the others and are thus used for night vision (scotopic) and shut down in bright light
Rods
90% of the ganglion cells. Contact one to a few cone bipolar. They have, small concentric receptive fields, produce sustained slowly adapting responses, with a weak response to movement. Good at analyzing SHAPES
P type
Respond to light at 560 nm (l)
Red cones