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76 Cards in this Set
- Front
- Back
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foveola relies on...for nutritional support
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choriocapillaris
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why is the fovea yellow
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contains xanthophyll carotenoid pigments (lutein & zeaxanthin) in the cone axons
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what does area centralis contain and where is it located
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area centralis: contains macula and fovea
located sup. and inf. temporal arteries |
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how is the optic disc formed
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ganglion cell axons from the retina pierce the sclera here to form the optic nerve
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what are the three principle neural cell types
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photoreceptors, bipolar cells, ganglion cells
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what are the layer of the retina
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retinal pigment epithelium
photoreceptor layer* outer limiting membrane outer nuclear layer* outer plexiform layer* inner nuclear layer* inner plexiform layer* ganglion cell layer* nerve fiber layer* inner limiting membrane *7 neural layer |
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ribbon synapse uses...as the primary neurotransmitter
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glutamate
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ribbon synapses are made up of...
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photoreceptors with bipolar terminal endings
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neural network convergence
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many sensory receptors all form synapses with a single neuron at an upper stage
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neural network divergence
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a single neuron may contribute to multiple parallel neural pathways.
each pathway focuses on a different visual function |
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what are some types of synapses
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ribbon
chemical synapses flat/basal junction electrical synapses |
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what are three types of retinal neuroglia
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Muller cells
Astrocytes Microglia |
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photoreceptors use what type of potential
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graded membrane potential
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ganglion cells use what type of potential
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action potential
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function of Muller cells
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structural support for neurons
environmental K+ homeostasis oxidative stress protection (free radicals) |
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where are Muller cells located
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from inner limiting membrane to outer limiting membrane
outer limiting membrane: junction of Muller and photoreceptors (separates inner photoreceptors from their nuclei) |
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astrocytes are derived from...
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cells OUTSIDE of the retina (not Retinal Neuroepithelium)
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purpose of astrocytes in optic nerve
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forms nerve sheath
part of blood brain barrier provides glucose for nerves regulate K+ regulate neurotransmitter metabolism |
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microglia are derived from...
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myeloid progenitor cells (bone marrow)
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microglia are located...
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ALL LAYERS OF RETINA
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purpose of microglia cells
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functions as IMMUNE CELLS
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microglia at resting?? activated??
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resting: not phagocytic
activated: ameboid shape and engulf apoptotic (dying) cells |
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neurotransmitter for the vertical pathway (feed-forward)
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Glutamate:
excitatory photoreceptors bipolar cells ganglion cells |
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neurotransmitter for the horizontal pathway (lateral)
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GABA
Glycine Acetylcholine Dopamine |
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blood supply to the choroid
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ophthalmic artery->posterior ciliary arteries
2 long posterior ciliary arteries supply anterior choroid |
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venous drainage system for Choriocapillaris
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choriocapillaris
larger choroidal veins 4-6 vortex veins sup. & inf. ophthalmic veins |
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venous drainage system for retinal capillary network
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retinal capillary network
central retinal vein sup/inf ophthalmic vein or cavernous sinus |
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what are the visual pigments
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chromophores: retinal, derived from retinol (vit. A)
opsin: integral membrane protein with 7 transmembrane helices that enclose binding pockets for 11-cis retinal |
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what is dark current
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in the absence of light
non selective cation binds to cGMP and opens Na+ influx and K+ efflux DEPOLARIZATION maximal glutamate release |
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chromophore in LIGHT?? DARK??
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dark: 11-cis configuration
light: all-trans configuration |
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what is light current
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11-cis retinal -> all-trans form
(rhodopsin -> metarhodopsin) GDP-bound transducin exchange GDP for GTP GTP-bound transducin increase activity of cGMP phosphodiesterase (decrease level of cGMP in cytoplasm) decrease level of cGMP, closes cGMP ion gate HYPERPOLARIZATION |
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rhodopsin renewal process
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all-trans retinal converted to all-trans retinol (retinal dehydrogenase)
all-trans retinol export to IPM (interphotoreceptor matrix) |
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describe horizontal cell and photoreceptor (ROD) synapse
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rod spherules: one or two ribbon synapse. with two or more bipolar cells
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describe horizontal cell and photoreceptor (CONE) synapse
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cone pedicle: many synaptic ribbons. with two or more bipolar cell at each synapse
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horizontal cells connect with neighboring horizontal cells via...
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gap junctions
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type of horizontal cell in humans and its function
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Luminosity (L-type): hyperpolarize to light of any wavelength in the visible range
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horizontal cells before and after light
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dark: depolarized from glutamate release from photoreceptor
light: photoreceptor (HYPERPOLARIZATION) release less glutamate HYPERPOLARIZATION SIGN CONSERVING!!! |
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describe photoreceptor to h-cell relationship at the onset of light
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Light
hyperpolarization of photorecp. decreased glutamate release hyperpolarization of h-cell feedback from to h-cell to photorecp photoreceptor relative depolarized compared to h-cell then go to bipolar cell |
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gain is the ratio between...
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gain=output/input
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what type of auto gain control does low ambient light need?? high ambient light?
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low light: needs HIGH gain
high light: need LOW gain (to avoid saturation) |
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what is lateral inhibition
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H-cells extending across a large retinal area
sending opposite signs compared to photoreceptor input alone. able to see "edges of thing" |
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different types of bipolar cells
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rod bipolar cells: most numerous
cones: diffuse bipolar (DB), blue cone-specific (BB), midget (invaginating midget, flat midget) |
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describe horizontal cell and photoreceptor (ROD) synapse
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rod spherules: one or two ribbon synapse. with two or more bipolar cells
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describe horizontal cell and photoreceptor (CONE) synapse
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cone pedicle: many synaptic ribbons. with two or more bipolar cell at each synapse
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horizontal cells connect with neighboring horizontal cells via...
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gap junctions
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type of horizontal cell in humans and its function
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Luminosity (L-type): hyperpolarize to light of any wavelength in the visible range
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horizontal cells before and after light
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dark: depolarized from glutamate release from photoreceptor
light: photoreceptor (HYPERPOLARIZATION) release less glutamate HYPERPOLARIZATION SIGN CONSERVING!!! |
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describe photoreceptor to h-cell relationship at the onset of light
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Light
hyperpolarization of photorecp. decreased glutamate release hyperpolarization of h-cell feedback from to h-cell to photorecp photoreceptor relative depolarized compared to h-cell then go to bipolar cell |
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gain is the ratio between...
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gain=output/input
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what type of auto gain control does low ambient light need?? high ambient light?
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low light: needs HIGH gain
high light: need LOW gain (to avoid saturation) |
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what is lateral inhibition
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H-cells extending across a large retinal area
sending opposite signs compared to photoreceptor input alone. able to see "edges of thing" |
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different types of bipolar cells
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rod bipolar cells: most numerous
cones: diffuse bipolar (DB), blue cone-specific (BB), midget (invaginating midget, flat midget) |
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describe horizontal cell and photoreceptor (ROD) synapse
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rod spherules: one or two ribbon synapse. with two or more bipolar cells
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describe horizontal cell and photoreceptor (CONE) synapse
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cone pedicle: many synaptic ribbons. with two or more bipolar cell at each synapse
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horizontal cells connect with neighboring horizontal cells via...
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gap junctions
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type of horizontal cell in humans and its function
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Luminosity (L-type): hyperpolarize to light of any wavelength in the visible range
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horizontal cells before and after light
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dark: depolarized from glutamate release from photoreceptor
light: photoreceptor (HYPERPOLARIZATION) release less glutamate HYPERPOLARIZATION SIGN CONSERVING!!! |
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describe photoreceptor to h-cell relationship at the onset of light
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Light
hyperpolarization of photorecp. decreased glutamate release hyperpolarization of h-cell feedback from to h-cell to photorecp photoreceptor relative depolarized compared to h-cell then go to bipolar cell |
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gain is the ratio between...
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gain=output/input
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what type of auto gain control does low ambient light need?? high ambient light?
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low light: needs HIGH gain
high light: need LOW gain (to avoid saturation) |
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what is lateral inhibition
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H-cells extending across a large retinal area
sending opposite signs compared to photoreceptor input alone. able to see "edges of thing" |
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different types of bipolar cells
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rod bipolar cells: most numerous
cones: diffuse bipolar (DB), blue cone-specific (BB), midget (invaginating midget, flat midget) |
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how are bipolar cells classified
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by where the axons terminate in the IPL
OFF: outermost half of IPL (sublamina A) ON: innermost half of IPL (sublamina B) |
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rod bipolars excitation results in...
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depolarization
ON-BIPOLAR |
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what happens when light hits ON-bipolar cells
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DEPOLARIZATION
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what happens when light hits OFF-bipolar cells
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HYPERPOLARIZATION
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difference between midget and diffuse bipolar cells
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midget: receive info from ONE cone
diffuse: spread lateral and receives info from multiple cones |
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what do midget and diffuse bipolars have in common
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both ON and OFF bipolar cells
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where are amacrine cells found
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majority in INNER NUCLEAR LAYER
some in ganglion cell layer (displaced) |
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function of amacrine cells
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information integration and modulation
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in amacrine cells what is reciprocal synapse
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synaptic feedback from an amacrine cell to the same bipolar
IMMEDIATE INPUT NO RIBBON SYNAPSE |
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A2 Amacrine Cells
Morphology Neurotransmitter Receptive Field |
Morphology: small field, bi-stratified
Neurotransmitter: GLYCINE Receptive Field: ON center/OFF surround stimulation of surround gives HYPERPOLARIZATION |
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A17 Amacrine Cells
Morphology Neurotransmitter Receptive Field |
Morphology: wide field, diffuse
Neurotransmitter: GABA Receptive Field: ON center (no surround) |
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Function of A2
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major carrier of rod signals to ganglion cells
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Function of A17
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modifying signal transmission from rod bipolar to A2 amacrine cells
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Function of A18
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control Inner Plexiform Layer gap junction through Dopamine release
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