Visual System Flashcards
Perception takes place in
Retina
Retina
Inner most layer of the eye, covered by CT, in contact with vitreous humor
How many layers of cells has the reina
3
Cells within the layers of the reina
Photoreceptors
Bipolar cells
Ganglion cells
Retinal layers
Pigment epithelium
Outer and inner segment layer (cons and rods)
Outer nuclear layer (nucleus of photoreceptors)
Outer plexiform layer (synapsis PR w/ next cell layer)
Inner nuclear layer (bipolar cells)
Inner plexiform layer (synapse bipolar with ganglion cells)
Ganglion cell layer
Nerve fiber layer (axons of the ganglion cell layer)
Part where we don’t find photoreceptors
Optic nerve
Vision is
A cognitive process performed by comparison
Cons perceive
Color - allows to see shapes
Rods perceive
Shades of light (intensity) - allows to see movements
Fovea
Middle part of the macula
Area of the retina that defines what we see
Retinal pigmented epithelium
Tightly bound pigmented cuboidal cells. Unstable
Suplies the retina with glucose and ions. Phagocitosis
Melanin processes elongate to protect from light
Outer segment of the photoreceptors
Stacking membranous discs
Molecules of Rhodopsin (finite reactions to light). Coneopsins
10% phagocitized every morning (by retinal pigment epithelium)
Retinal changes in photoreception
Retina changes its conformation when it interacts with photons
Photoreceptors components
Cilium (microtubules)
Inner segment: mitochondrias
Nucleus
Synapse (feet): rods (spherule), cones (pedicles) and synaptic ribbons
Macula
Central area of the posterior retina that starts lacking retinal layers (there’s only photoreceptors)
Photostimulation
Photon-ops in reaction hyperpolarizes the photoreceptor
In resting conditions, photoreceptors are
Depolarized
Constantly releasing glutamate
Hyperpolarization causes
Reduction of glutamate liberation
Depolarization vs hyperpolarization
Electrons moving towards the neutral point
Electrons moving away from neutral point
Gradient potential
Hyperpolarizes photoreceptors
Bipolar cells
(After hyperpolarization)
On: activated when glutamate is no longer in the synapse (light)
Off: deactivated in light conditions, activate in relax conditions when glutamate get to postsynaptic terminal
Horizontal cells
Inhibits photoreceptors in a center-surround manner
Receptive fields
Created by horizontal cells, which inhibit the peripheral part and activate the center
Colors perceived by retina
Blue (S wavelength), green (M wavelength), red (L wavelength)
Colour theory by which the retina works
Substractive synthesis
Which receptive fields are compared in between?
Green and red
Types of cells
Parallel transmission and processing
Types of ganglion cells
M/Y/alfa —> ON center, OFF center
P/X/beta —> ON center
W/K —> melanopsin
W/K cells relevance
Visual pathway
Each of the eye has a temporal field (to the nasal retina) and nasal field (to the temporal retina)
The cortex controls same hemifields from both eyes (right hemifield form right and left eye, left hemifield from right and left eye) —> some of the fiber has to cross to the other side in the optic quiasm
Optic tract: fibers from the same field
Sinapsis: late geniculate body
Projection: optic radiation
Projections to the visual cortex
Visual hemifields are divided in superior and inferior quadrants. They are caught by the opposite retinal quadrant and reach different banks of the calcarine sulcus
Optic radiation
Visual cortex
Has the largest layer 4
Visual areas are classificated in
Cytoarquitectonic
Functional
Discrepancy of the eye
3D, depth perception
Depth perception
Only with 2 eyes
V1
Blobs
V2
Thick stripes magno
Thin stripes parvo
Cytochrome function
Oxidase blobs and stripes
Complex cells respond to
A line moving
Color
Dominance bands
Direction of lines
Parvo celular pathway
What I am seeing
Magno celular pathway
Where are the things I am seeing
Thick stripes
Motion
Thin stripes
Colours
Interstripes
Depth
V1/V2
