Vision Flashcards
Refraction
Bending of light rays
Vision Process
- Light is focused through the lens
- The cornea bend light rays and focuses the image on the retina
- Focus is adjusted by changes in the shape of the lens
- Rods and Cones are activated, releasing NT molecules
- Triggers Bipolar Cells that connect with Ganglion Cells
- Axons form the optic nerve that carry information to the brain
- Either the Scotopic or Photopic System is activated
- Scotopic (Rods): Rhodpsin is hit by light it triggers G protein transducin, causing sodium ion channels to close creating a hyperpolarization
Ciliary Muscles
Control the shape of the lens
Pupil
Controls the amount of light that enters the eye
Extraocular Muscles
Extend from the outside of the eyeball.
Fixating still or moving targets require control of these muscles
Bipolar Cells
Located in the retina and receive information from rods and cones and pass the information to retinal ganglion cells.
Ganglion Cells
A class of cells in the retina whose axons form the optic nerve
Horizontal Cells
Contact both the receptor cells and the bipolar cells
Amacrine Cells
Contact both the bipolar cells and the ganglion cells
Especially significant in inhibitory interactions within the retina
Rods, Cones, Bipolar Cells, and Horizontal Cells generate…
Local potentials
Ganglion Cells generate…
Action potentials
Scotopic System
Operates with rods and works in dim light
Photopic System
Operates at high levels of light, shows sensitivity to color and involves the cones
Rods
Work in dim light
Contain Rhodopsin
Concentrated in the periphery of the retina
Cones
Work to distinguish colors
Contain Opsin
Concentrated in the fovea
The size of the hyperpolarizing photoreceptor potential determines…
how much less synaptic transmitter will be released
The process required to stimulate the visual receptors helps account for…
Sensitivity
Integration
Adaption
Photoreceptor adaptation factors
Varying concentration of calcium ions
The recombination of retinal and opsin
There are no photoreceptors in the..
Optic Disc
Rods provide…
High sensitivity with limited acuity
Cones provide…
High acuity with limited sensitivity
Lateral Inhibition
Interconnected neurons inhibit their neighbors, producing contrast at the edges of regions
Optic Chiasm
The point at which the two optic nerves meet
Lateral Geniculate Nucleus
The part of the thalamus that receives information from the optic tract and sends it to visual areas in the occipital cortex
Scotoma
Blindness
On-Center Bipolar Cells
Turning a light on in the center of an on-center cell excites the cell because it receives less glutamate which otherwise inhibits on-center bipolar cells
Off-Center Bipolar Cells
Turning off light in the center of an off-center bipolar cell’s receptive field excites the cell because it receives more glutamate which depolarizes off-center bipolar cells
Bipolar cells also release…
Glutamate.
Therefore, when a light is turned on, on-center bipolar cells depolarize on-center ganglion cells and when a light is turned off, off-center bipolar cells depolarize (excite) off-center ganglion cells
On-center/Off-surround
Referring to a concentric receptive field in which the center excites the cell of interest while the surround inhibits it
Off-center/On-surround
Referring to a concentric receptive field in which the center inhibits the cell of interest while the surround excites it
Parvocellular vs Magnocellular
Small vs. Big
Hubel and Wiesel
Reported that visual cortical cells require more specific elongated stimuli than those that activate LGN cells.
Simple Cortical Cells
A cell in the visual cortex that responds best to an edge or a bar that has a particular width, orientation and location
Complex Cortical Cells
A cell in the visual cortex that responds best to a bar of a particular size and orientation anywhere within a particular area of the visual field
Trichromatic Hypothesis
There are three different types of cones, each excited by a different region of the spectrum and each having a separate pathway to the brain
Opponent-Process Hypothesis
The theory that color vision depends on systems that produce opposite responses to light of different wavelengths
Hemoltz
Trichromatic Hypothesis
Hering
Opponent-Process Hypothesis
