Vision Flashcards
Sclera
The thick structural layer that covers the exposed portion of the eye (the white of the eye)
Doesn’t cover the cornea
Choroidal vessels and retinal vessels
Blood vessels that supply the eye with nutrients
Retina
The innermost layer of the eye - in the back of the eye
Converts incoming photons of light to electrical signals
Part of the CNS & develops as the outgrowth of brain tissue
Detects images
Cornea
Where the light passes FIRST through
Gathers and focuses the incoming light
(2) chambers th the front eye is divided into:
Anterior chamber
Posterior chamber
Anterior chamber
Lies in front of the iris
Posterior chamber
Between the iris and the lens
Iris
Controls the size of the pupil
Colored part of the eye
The iris has 2 muscles. What are they?
Dilator pupillae
Constrictor pupillae
What is the function of the dilator pupillae (muscle in the Iris)?
Opens the pupil under sympathetic stimulation
OPENS PUPIL
What is the function of the constrictor pupillae (muscle in the Iris)?
Constricts the pupil under parasympathetic stimulation
CLOSES PUPIL
Aqueous humor
Produced by the ciliary body
Bathes the front part of the eye before draining into the canal of Schelemm
Lens
Helps control the refraction of the incoming light
Located right behind the iris
Held in place by suspensory ligaments connected to the ciliary muscle
As the muscle contracts, it pulls on the ..
Suspensory ligaments and changes the shape of the lens
Known as ACCOMODATION
Vitreous
Transparent gel that supports the retina
Located behind the lens
Retina contains:
Rods and cones
Rods
Detect light and dark
Function best in reduced light
Can permit night vision
Cones
Detects colors in 3 forms (short [blue],medium [green], and long [red] wavelengths)
Duplicity theory of vision
States that the retina contains 2 kinds of photoreceptors: those specialized for light & dark detection and those specialized for color detection
Macula
Has high concentration of cones
Central section of the retina
Center most point: fovea
Fovea
Center most point of the macula
Contains only cones
As you move away from the fovea…
Concentration of cones decease and concentration of rods increase
Blind spot
Located where the optic nerve leaves the eye
There are no photoreceptors here
How do rods and cones connect?
Through bipolar cells
Bipolar cells synapse with…
Ganglion cells which group together to form the optic nerve
As the number of receptors that converge through the bipolar neurons onto one ganglion cell increases …
The resolution decreases
Amacrine and horizontal cells
Receives input from multiple retina cells in the same area before the information is passed on to ganglion cells
Important for edge detection as they increase our perception of contrast
What is the visual pathway ? (starting from the eye)
Optic nerve ➡️ optic chiasm ➡️ optic tracts ➡️ lateral geniculate (LGN) of the thalamus ➡️ visual radiations ➡️ visual cortex
Optic chiasm
Contains fibers crossing from the nasal side of the retina (temporal visual fields) of both sides
Visual radiations run through …
Temporal and parietal lobe
Visual cortex is in which lobe
Occipital
Parallel processing
The ability to simultaneously analyze and combine information regarding color, shape and motion
This can be compared to our memories to determine what is being viewed
Example : recognizing a moving car very easily from a distance because they are familiar with the usual motions and shapes of cars
Parvocellular cells
Detect shapes
With high spatial recognition and low temporal resolution
Magnocellular cells
Detects motion
With low spatial recognition and high temporal resolution
Spatial resolution
Permit us to see very fine details when thoroughly examine an object
Pupil
Allows passage of light from anterior to posterior chamber
Ciliary body
produces aqueous humor, accommodation of lens
Canal of Schlemm
Drains the aqueous humor
The eye is used to detect:
Light in the form of photons
