nbeo visual pathway questions.txt
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In what layer of the retina are photoreceptor nuclei and cell bodies?
Outer nuclear layer
Where is the first synapse in the visual pathway?
Outer plexiform layer (where dendrites of bipolar and horizontal cells reside)
Where is the second synapse in the visual pathway found?
Inner plexiform layer
What do bipolar cells do?
- Stimulate ganglion cells
- Relay info from photoreceptors to horizontal, amacrine and ganglion cells
What do amacrine cells do?
Inhibit ganglion cells
In what layer of the retina are the bipolar, horizontal, and amacrine cells found?
Inner nuclear layer
Between what two layers is a retinoschisis found?
Outer plexiform layer and inner nuclear layer
What three classes of neurons are found in the ganglion cell layer?
- Midget cells (80%)
- Parasol cells (10%)
- Small bistratified cells (10%)
Where do retinal ganglion cells synapse?
Lateral geniculate nucleus
What layers of the LGN receive ipsilateral input?
2,3 & 5
What layers of the LGN receive contralateral input?
1,4 & 6
Where do midget cells synapse?
P-cells in the LGN (parvo)
Where do parasol cells synapse?
M-cells in LGN (magno)
What type of information is processed in the parvo cells?
- Color (red/green)
- High spatial frequency (detail)
What type of info is process in the magno cells?
- Low-spatial frequency
What layers of the LGN comprise the magno cells?
1 & 2
What layers of the LGN comprise the parvo cells?
What layer of the LGN receives blue-yellow vision?
Where all do the retinal retinal ganglion cells synapse?
- LGN (majority)
- Pretectal nucleus in midbrain (pupilliary response)
- Hypothalamus (circadian rhythm)
- Superior colliculus tectum (saccadic eye movements)
- Pineal gland (melatonin)
- Pulvinar region in thalamus (visual attention)
What is the superior colliculus responsible for?
- Visual orientation
- Control of saccadic eye movements
- Controls conjugate eye movements
- Voluntary and reflex ocular movements
- Pupil responses to near objects
Where is the cuneus gyrus located?
Occipital lobe superior portion
Where is the lingual gyrus located?
Occipital lobe inferior portion
What do lesions of the parietal lobe cause?
- Abnormal OKN
- Affect visual attention
- Pie on the floor
What do lesions of the temporal lobe cause?
- Olfactory and visual hallucinations
- D?j? vu
- Pie in the sky
What do lesions of the occipitotemporal cortex cause?
Decreased object and facial recognition
Where do vf defects that respect the horizontal midline occur?
Anterior to chiasm ie glaucoma
Where do vf defects that respect the vertical midline occur?
Posterior to the chiasm
Whats the blood supply to the occipital lobe?
Posterior communicating artery
What is the retina derived from?
What are the 10 layers of the retina from most posterior to most anterior?
- External limiting membrane
- Outer nuclear layer
- Outer plexiform layer
- Inner nuclear layer
- Ganglion cell layer
- Nerve fiber layer
- Internal limiting membrane
What is the purpose of the RPE?
- Helps form bruch's membrane
- Prevents scatter
- Phagocytosis of photoreceptor outer segments
- Transport of ions between retina and choroid
What segment of the photoreceptor cell makes disks?
What segment of the photoreceptor cell makes photopigments?
Where does protein synthesis occur within the photoreceptor cell?
At what nanometer is rhodopsin most sensitive?
At what nanometer are cones most sensitive?
What layer of the retina are hard exudates found?
Outer plexiform layer
What is the excitatory neurotransmitter found in the retina
Where along the visual pathway / retina does CRAO cause necrosis?
Ganglion cell layer
What inhibitory neurotransmitters are found in the retina?
In what layer of the retina are cotton wool spots found?
Nerve fiber layer
In what layer of the retina are splinter hemorrhages found?
Nerve fiber layer
In what layer of the retina are epiretinal membranes found?
Internal limiting membrane
What do muller cells do?
- Act as a buffer by regulating [K+ ions]
- Maintain extracellular pH
- Recycle GABA and glutamate
- Metabolize, synthesize and store glycogen
How many photoreceptors feed into a single ganglion cell in peripheral retina?
How many photoreceptors feed into a single ganglion cell in the fovea
Where in the retina are the highest concentration of bipolar cells found?
What is the EOG used to detect?
- Stargardt's disease
- Advanced drusen
- Best's disease
What do the different waves in ERGs mean?
- A- wave
- B- wave
- Bipolar and mueller cells
- C- wave
- OFF bipolar cell signal
What pathology are ERGs used to detect?
What pathologies are VERs used to detect?
- Optic neuritis
- Optic tumors
- Retinal disorders
- Demyelinating disease ie MS
In what part of the macula are the cones at the highest density?
in the foveola, what cells / layers are missing?
- Bipolar and ganglion cells
What is the thickest area of the retina?
What is henle's layer in the retina?
Name of the outer plexiform layer in the foveola
What percentage of information is sent to the pupil response in the visual pathway?
What percentage of information is sent to the LGN from the optic nerve?
What are the 4 segments of the optic nerve?
What purpose does the intraorbital portion of the optic nerve provide ?
Provides for full globe movement without stretching the nerve
What is the afferent pupillomotor pathway?
Photoreceptors >> optic nerve >> superior brachium >> pretectal nucleus (midbrain)
Where do retinal axons terminate?
What types of cells are found in the LGN?
- Magnocellular cells (large)
- Parvocellular cells (medium)
- Koniocellular cells (small)
Where do the optic radiations terminate?
In the striate cortex (Brodmann area 17)
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