Chapter 6: More Vision Flashcards
Law of Specific Nerve Energies
Johannes Muller; regardless of the type of stimulus, activity in the nerve always leads to the same psychological experience.
Photons
packets of energy with oscillating electromagnetic fields that travel through space at 3.0e8 m/s. Brightness of a light source depends on how many photons it emits
Wavelength
based on the frequency of electromagnetic oscillation taking into account the speed of light. Color of a light source depends on wavelengths of the photons
Electromagnetic Spectrum
light makes up small portion; x-rays to radio waves
Choroid Coat
found behind retina; heavily pigmented to absorb scatteredlight; provides oxygen and nutrients for parts of retina; maintains photoreceptors
Cornea
main refractive surface of the eye; bends the light; fluid filled
Lens
Does bend light; provides visual accommodation; siscilary muscles contract and pull the ligament and make lens thinner, relax to make it more round
Visual accommodation
provides fine focus by changing thickeness
Presbyopia
condition in which the lens lose resiliency with age
Iris
radial muscle tissue which constricts or expands the size of the pupil. Determines eye color
Humors
provide structural and functional support for the eye
Aqueous Humor (fluid)
in anterior chamber. Behind the cornea, in front of the lens
Vitreous humor
in posterior chamber. located behind the lens; helps eye maintain shape (thicker)
Retina
contains the visual photoreceptors and neurons that process and transmit visual information to the brain
Fovea
indentation in the retina, contains only cones (point of central focus)
Macula
has a lot of cones, surrounds the fovea
Photoreceptors
hyperpolarize in response to light (depolarize in response to dark), and synapse with horizontal cells and bipolar cells (RODS AND CONES)
Horizontal cells
have large dendritic trees that make inhibitory contaact with many nearby photoreceptors; responsible for phenomena of lateral inhibition (no action potentials)
Bipolar Cells
each stimulated by a group of surrounding photoreceptors forming a receptive field. synapse with ganglion cells (no action potentials)
ganglion cells
each stimulated by a group of surrounding bipolar cells forming a receptive field; convergence of input through the visual pathway; axons form optic nerve
amacrine cells
modulate the output of bipolar cells
Trichromatic Theory of Color Vision
color vision is based on ratio of responses from 3 different types of cones that have peak absorption of light at different wavelengths
Opponent Process Theory of Color Vision
the way the information is organized in the visual system appears to be based on two opponent processes: Red vs. Green; Yellow vs. Blue
Psychological evidence
no reddish-green or blueish-yellow color perceptions
Electrophysiological evidence
Some bipolar cells, ganglion cells, LGN cells, and cortical cells have center-surround receptive fields that are organized in opponent process way
Retinex THeory
suggests the cortex compares information from various parts of the retina to determine the brightness and color for each area. Better explains color constancy
magnocellular pathway
named after the large cell bodies of the retinal ganglion cells and LGN cells of the pathway
Parvocellular pathway
named after the small cel bodies of the retinal ganglion cells and LGN cells of the pathway
Parvocellular ganglion cells
have small cell bodies, small receptive fields, are dense and near fovea
Magnocellular ganglion cells
large cell bodies, large receptive field, and are uniformly distributed in the retina
koniocellular ganglion cells
small cell bodies, mixed receptive field size, and are distributed uniformly throughout retina
simple cells
small receptive fields, bar or edge shaped, excitatory and inhibitory zones, spots of light can produce weak excitatory or inhibitory responses
complex cells
larger receptive fields, no clear cut inhibitory zones, spots of light are relatively ineffective, responds to bars of light of a specific orientation anywhere in receptive field
occular dominance
cells in particular column respond best to input from left eye and from right eye
