SandP2.2: Vision Flashcards
Anatomy of the Eye
- Sclera
- Two sets of blood vessels that supply eye with nutrition
- Retina
-Thick structural (outermost) layer that covers most of the exposed eye, does not cover the frontmost part (cornea)
- Chorodial Vessels (middle layer): blood vessels between sclera and the retina
Retinal Vessels (inner layer)
-The inner most layer of the eye, contains the actual photorecepetors that traduce light for CNS
Anatomy of the Eye
- Front of the eye is divided into two chambers
- Lens
-Anterior Chamber: Lies in front of the iris
Posterior Chamber: Lies between the iris and the lens
–Lies right behind the Iris and helps control the refraction of the incoming light.
Anatomy of the Eye
- Cornea
- Iris
- two muscles of the Iris
- Continuous parts of the Iris
-Where light passes through, it is a domelike window in the front of the eye, which gathers and focuses light
-Colored part of the eye
-Dilator Pupillae (opens the pupil with sympathetic stimulation) and Constrictor Pupillae (closes or constricts the pupil with parasympathetic stimulation)
-Choroid
Ciliary Body: Produces Aqueous Humor that bathes the front part of the eye before draining into the Canal of Schlemm.
Anatomy of the Eye
- Ciliary Muscle (part of the Ciliary body)
- How does it work
- Contraction of this muscle is under parasympathetic control
- As the muscle contracts, it pulls on Suspensory Ligaments and changes the shape of the lens (Accommodation)
Anatomy of the Eye
- What is a Retina
- What is function of Retina
- Retina CNS or PNS?
- Vitreous
- The back of the eye and is like a screen consisting of neural elements and blood vessels.
- Its function is to convert incoming photons of light into electrical signals.
- Considered part of the CNS and develops as an outgrowth of brain tissue
- A transparent gel, behind the lens, that supports the retina
Duplexity or Duplicity Theory of Vision
-States that retina contains two kinds of photoreceptors: those specialized for light/dark and those specialized for color detection
Retina
- Cones
- 3 forms of Cones
- Rods (What pigment?)
- How many Cones and how many Rods?
- Mnemonic
- Used for color vision and to sense fine details, most effective in bright light.
- Named for wavelengths of light they best absorb. S (Short, 440, Blue), M(Medium, 540, Green), and L (Long, 560, Red)
- Allow sensation of light and dark because they all contain a single pigment called Rhodopsin. Low sensitivity and most effective in reduced illumination. Are not involved in color vision, but permit night vision.
- 6 million Cones and 120 Million Rods in Retina
- Rods function in RODUCED light
Retina
- Macula
- Fovea
- Blind Spot
- Central Section of Retina that has high concentration of Cones.
- Center part of the Macula and contains only cones, this is where visual acuity is at its best, it is most sensitive in normal daylight.
- Where the optic nerve leaves the eye, there are no photoreceptors here
Explain the cell pathway of the retina?
-Rods and Cones connect with Bipolar Cells, which synapse with Ganglion Cells, which group together to form the Optic Nerve.
- Ganglion Cell Issues
- Is the problem the same for both cones and rods?
- There are far more receptors (cones and rods) than ganglion cells, therefore one ganglion cell represents the combined activity of many rods and cones. This results in a loss of details as information from photoreceptors is combined. More cells less resolution.
- No on average the number of converging cells is smaller for cones than rods, therefore Color vision is more sensitive than black and white vision.
- Bipolar Cell function
- Ganglion Cell function
- Exist to transmit information between the photoreceptor cells (cones and Rods) to the Ganglion Cells.
- Take information from Bipolar Cells. They group together to from the optic nerve.
Amacrine and Horizontal Cell Function
-Detect slight differences between the visual information in each bipolar cells. These cells are important for edge detection, as the increase our perception of contrast. See the edge of a building or square.
- Optic Chiasm
- Optic Tracts
- The place where Optic Nerves (fibers) from the nerves closer to the nose cross paths. Vision on far right and far left say on their corresponding sides. Vision on near right and near left (next to nose) cross paths at the Optic Chiasm.
- These recognized pathways
- Lateral Geniculate Nucleus (LGN) of the Thalamus
- Where else does it go?
- Superior Colliculus
- First place visual information reaches in the brain, after the optic chiasm.
- It then goes to the temporal, parietal, and visual cortex in the occipital.
- There also inputs here, which controls some responses to visual stimuli and reflexive eye movements (deer in headlights in startle response)
-What is Parallel Processing (Feature Detection)
-The ability to take information (color, shape, and motion) and compare it to our memories to determine what it is we are looking at. This is also Called Feature Detection.
