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biochemistry of visi

biochemistry of vision

what are the seven layers of the retina RPE, photoreceptor, external limiting membrane, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglion layer, nerve fiber layer, internal limiting membrane
what are the structures of photoreceptor cells outer segment, connecting stalk, inner segment, outer fiber, cell body, inner fiber
what does the outer segment of photoreceptor cell contain? visual pigment molecules for the conversion of light into a neural signal
what does the connecting stalk of photoreceptor cells contain? the cilium
what does the inner segment of the photoreceptor cell contain metabolic apparatus
what does the outer fiber of the photoreceptor cell contain? it extends from the inner segment to the cell body
what does the cell body of the photoreceptor cell contain? the nucleus
what does the inner fiber of the photoreceptor cell contain? ends in a synaptic terminal
what does the membranous discs of the outer segment of the cone contain? vitamin A, which binds light
these cells allow us to take in light and adjust that into a neural signal, turning it into a neurotransmitter rods and cones
how do bipolar cells communicate with each other? via neurotransmitters
what are the three classes of neurotransmitters? small molecule, nuropeptides, gases (ex: NO)
to be classified into a NT, a molecule must have these three characteristics: bust be stored, released, and degraded
what are two classifications of NT receptors? ionotropic (ion channel), metabotropic (G protein coupled receptors)
Dopamine pathway is destructive in what disease? parkinsons
dopamine is made form this amino acid tyrosine
these molecules degrade the NT dopamine after it does its job MAO and COMT
dopamine binds to this after binding to the post-synaptic membrane, causing phosphorylation of the ion channel, resulting in depolarization adenylate cyclase
what is the NT of choice in the retinal neurons? glutamate
how is glutamate formed? it is formed from glutamine via the enzyme glutaminase
which type of cells recycle glutamate afterwards? glial cells
this is a major inhibitory neurotransmitter, and is synthesized from serine glycine
where do glutamate and glycine come from? glutamate comes from TCA cycle, glycine comes from glycolysis
do cells of the retina operate mostly under aerobic or anaerobic processes, and what do they produce a lot of as a result? anaerobic, producing a lot of lactate
the retina is located where? between the vitreous and coroid
how does the retina allow us to see? it takes light (photons) and converts it into a neurological signal to our brain that allows us to see
it the retina, there are no attachments, so how does it stay attached? via intraocular pressure, osmotic pressure, fluid transport across the RPE, and presence of vitreous in microvilli
what are the two types of photoreceptor cells? rods and cones
how is NO made? glutamate is released and binds to its ionotropic receptor and makes NO, which goes in a retrograde fashion, activating pre-synaptic as well as other neurons and eventually the NO is detoxified and broken down by glial cells
what makes NO a special neurotransmitter? it is a gas, and acts as a retrograde NT
these are second order neurons in the visual pathway. they relay information from photoreceptors to horizontal,k amacrine, and ganglion cells and receive extensive synaptic feedback from amacrine cells bipolar cells
what is the NT of choice for bipolar cells? glutamate
these can be either bipolar (single axon and single dendrite) or multipolar (single axon with more than one dendrite) ganglion cells
what is the neurotransmitter of choice for ganglion cells? glutamate
these cells transfer information in a horizontal direction parallel to the retinal surface. they have 1 long axon and several short dendrites with branching terminals. horizontal cell synapse with phootoreceptors, bipolar cells, and other horizontal cells horizontal cells
horizontal cells are throught to modify responses of ________ but not _______ they are thought to modify responses of cones, but not rods
these cells have a large cell body, a lobulated nucleus, a single process with extensive branches and extends into the inner plexiform layer amacrine cells
what are the NTs of choice for amacrine cells? glycine and GABA
this layer of hte retina consists of a single layer of pigmented cells. there are four to six million of these cells and each one interacts with thirty to forty NTs RPE layer
this layer of the retina contains the outer and inner segments of rods and cones, projections from the apical surface of muller cells extend into the PR layer photoreceptor layer
this layer is not a true membrane but is composed of zonula adherence junctions between photoreceptor cells and between photoreceptors external limiting membrane
this layer contains rods and cone cell bodies. cone cell bodies and nucleus are larger than rod cells outer nuclear layer (ONL)
this layer has a wide external band composed of inner fibers of rods and cones and a narrower inner band consisting of synapses between photoreceptor cells and cell from the inner nuclear layer outer plexiform layer (OPL)
this layer consists of cell bodies of horizontal cells, bipolar cells, amacrine cells, interplexiforme neurons, muller cells, and some ganglion cells. inner nuclear layer (INL)
this layer consists of synaptic connections between the axons of bipolar cells and dendrites of ganglion cells. it contains the synapse between the second order and third order neuron in the visual pathway inner plexiform layer
this layer is generally a single cell thick except near the macula whre it might be eight to ten cells thick and the temporal side of the optic disc where it is two cells thick ganglion cell layer
this layer consists of ganglion cell axons nerve fiber layer
this forms the innermost boundary of the retina internal limiting membrane
in this retinal abnormality, there is damage to the RPE, causing bleeding retinopathy
in this retinal abnormality, there is tissue destruction and bundles of blood best's disease
this layer of retina is resp for energy metabolism. the zona occludens which joins the cells is part of hte blood-retinal barrier and is responsible for controlling nutrients and metabolism from the choriocapillaris into the retina and removing waste. RPE layer
what are some funcitons of the RPE layer ion transport, glucose transport, water transport, lactate, energy requirements, growth factor production, lysosomes within the RPE break down parts of the photoreceptor outer segments disc, Vitamin A
what is the primary energy source of retinal metabolism glucose
the retina switches between what two types of metabolism? glycolysis to oxitative metabolism
the retina has a high rate of this metabolic process anaerobic glycolysis
these cells in the retina store glycogen, providing a ready source for glucose muller cells
what is the consumption of energy in retina compared to other CNS neurons? oxygen use by photo receptors is three to four times higher than other CNS neurons.
are photoreceptors more active in the dark or in light? in light
why are photorecepotrs more active in the dark? in the dark, the NT's are depolarzied and are making glutamate, so they are sing a lot of oxygen in the dark
this is considered the main chromophore in the retina vitamin A
this cell in the retina senses light chromophore
this cell in the retina is a membrane spanning protein opsonin
what are the three main forms vitamin A exists in? retinol, retinal, retinoic acid
what are some significant food sources for vitamin A liver, dark green leafy vegetables, yellow-orange vegetables, fruit, and fortified foods.
what are some functions of vitamin A vision, immune function, reproduction, cell proliferation, cell signaling
how is vitamin A stored in the intestinal lumen? as retinol and beta carotene
how is vitamin A stored in intestinal epithelial cells? as beta carotene, or retinyl esters
how is vitamin A stored in the blood retinyl esters in chylomicrons or RBP retinol
how is vitamin A stored in liver parenchymal cells retinyl esters, RBP retinol,
how is vitamin A stored in liver satellite cells? retinyl esters, retinol
this type of reaction allows the photon to be converted into a neurochemical signal, absorbed by a chromophore. cis retinal to trans retinal via the process of phototransduction
phototransduction requires what retinal
what form is retinal in during the dark phase? 11 cis retinal
what form is retinal in during the light phase? 11 trans retinal, which activates a signal transduction pathway
which cell (rods or cones) are more sensitive to light stimulus? rods
which cells are a higher abundence of photosensitive pigments rods
which cell is specialized for day vision cones
which cell is specialized for night vision rods
which cell is more involved in acquity of vision? cones
when do cone cells saturate? when light is very intense
when do rods saturate? in day light
which cells mediate color vision cones
which cell has a higher concentration in the fovea cones (rods are absent in the fovea)
which cell is more numerous rods
what happens when you don't have enough vitamin A? night blindness, ocular functions, depressed immune functions
what populations are mostly affected with vitamin A deficiency? SE asia, africa, central and osuth american populations
what are some diseases associated with vitamin A deficiency? night blindenss, blindness, xeropthalmia, keratomalacia, keratinzation of tracheal epithelium
what are some toxicities associated with vitamin A? teratogenic effects, liver disease, dryness, erythema, scaling and peeling of skin, hair loss, nail problems
Created by: aferdo01