Vision Flashcards
Sclera
Most of exposed portion, or whites, of the eye
Does not cover cornea
Choroidal vessels
Supply the eye with nutrients (blood vessel)
Retinal vessels
Supply eye with nutrients (blood vessel)
Retina
Innermost layer and contains actual photoreceptors that transduce light into electrical information the brain can process
Cornea
Light passes first through here
Clear domelike window
Gathers and focuses incoming light
Ant chamber
The front of the eye that lies in front of the iris
Post chamber
between the iris and the lens
Iris
Colored part of the eye
Composed of-
dilator pupillae: opens the pupil under sympathetic stimulation
constrictor pupillae: constricts the pupil under parasympathetic stimulation
Coroid
Continuous with the iris
Surrounds and provides nourishment to the retina
Ciliary body
Continuous with the iris
Produced aqueous humor and drains into the canal of Schlemm
Lens
Behind iris and controls light refraction
Ciliary muscle
Contraction is under parasympathetic control
Pulls on the suspensory ligaments and changes the shape of the lens to focus on an image as the distance varies (accommodation)
Vitreous humor
Behind lens
Transparent gel that supports retina
Retina
Back of the eye and consists of neural elements and blood vessels
Convert incoming photons into electrical signals
Rods and cones
Cones
Color vision and fine details
Best work in brightness
S blue
M green
L red
Rods
Sensitive
Only contain rhodopsin
Only allow sensation of light or dark
Spread over a much larger area of the retina than cones
Macula
Central section of the retina
High concentration of cones
The very center is called the fovea
Visual acuity is best at fovea due to high concentration of cones
Optic disk
Blind spot
Region devoid of photoreceptors
How do rods and cones transmit information to the optic nerve?
Synapse directly onto bipolar cells (in front of rods and cones) which then synapse with ganglion cells the axons of which form the optic nerve
horizontal cells and amacrine cells
modulate the information flow from photoreceptors (PRs) to bipolar cells (BCs) in the outer plexiform layer (OPL) and from BCs to retinal ganglion cells (RGCs)
Visual pathway
An object to your left then photons from it stimulate the right side of retina in each eye
Optic chiasm
Retinal fibers from each eye travel through the optic nerves toward the brain
Nasal fibers from the left and right eyes cross paths
Because temporal fibers are already on the correct side there is no need to cross them
These reorganized pathways are called optic tracts after leaving the optic chiasm
From the optic chiasm the information goes…
to nerves that pass through the LGN of the thalamus where they synapse w nerves that then pass through radiations in the temporal and parietal lobes to the visual cortex in the occipital lobe
other nerves skip this and head directly to superior colliculi in midbrain which control reflexive responses
Parallel processing
The brains ability to analyze information regarding color, form, motion, and depth simultaneously using independent pathways in the brain
