Shared Flashcard Set


The Retina and Visual Processing
VCU PHIS 501 September 20, 2010

Additional Physiology Flashcards




Thick region of the retina, which is thick due to a high concentration of photoreceptors and interneurons.  This is where high resolution vision takes place.  The area is pale because the nerves and blood vessels are routed around the area.

a small "pit" in the macula.  The area contains many cones which are oriented so that the outermembrane pigments are bent towards the pit.


Typically has a 1:1 mapping of cones to bipolar cell to ganglion cell.


Virtually no rods are present in the foveal pit.  So, night vision takes place lateral to the fovea.

Peripheral to the fovea

Mixture of rods and cones with more rods than cones.  Cones increase temporally and then drop drastically.  Cones increase nasally and then drop drastically (except for the optic disc location).


Typically a number of receptors and bipolar cells converge onto single ganglion cells.  So, these ganglion cells have larger receptive fields.

Optic Disc
Area located nasally to the foveal pit that does not contain any rods or cones.  This is because the nerve fibers exit the eye and the blood vessels enter the eye.
Layers of the Retina

Remember that light has to pass through all the layers  before it hits the photoreceptors and is transduced through the layers.


1) Pigmented cell layer: adjacent to choroid

2) Photoreceptor layer

3) Outer Nuclear Layer: nuclei and cell body for receptor cells

4) Outer Plexiform Layer: rods and cones synapse onto bipolar cells, horizontal cells also synapse.

5) Inner Nuclear Layer: bipolar cells nuclei and cell body

6) Inner Plexiform:  bipolar cells synapse onto ganglion cells, amacrine cells also synapse

7) Ganglion Cell Layer

8) Optic nerve layer


On-Center, Off-Surround


Off-Center, On-Surround


Ganglion cells have unique receptive fields


On-Center, Off-Surround: results from decreased release of an inhibitory interneuron (on-center) and horizontal cell influence (off-surround)


Off-center, On-Surround: results from decreased release of an excitatory interneuron (off-center) and horizontal cell influence (on-surround)


For max excitation give the cells what they want, for maximum inhibition give them the opposite.

Discuss the different types of ganglion cells

P cells: parvocellular layer of the lateral geniculate ganglion, small receptive fields, slowly adapting, sensitive to different colors


M cells: magnocellular layer of the lateral geniculate nucleus, large receptor fields, rapidly adapting/phasic, sensitive to light intensity


W cells: small cell bodies but extensive dendritic fields, sensitive to light intensity

Discuss visual fields

The nasal retina sees the temporal fields and the temporal retina sees the nasal fields.


The nasal retina crosses at the optic chiasm and goes up contralaterally.  The temporal retina goes up ipsilaterally.


So, R images go to the L brain and L images go to the R brain.



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