Bergmanson- Retina
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Created by:
bustagrill on March 31, 2012
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97 terms
Terms | Definitions |
|---|---|
 Optic Vesicle develops...Optic Vesicle invaginates... | before the 4th week of preg. during the 4th week of preg. |
| Optic Cup is formed by | Optic Vesicle invagination |
| External neuroectoderm becomes Internal neuroectoderm becomes | External- RPE (remains monolayer) Internal- Neural portion of retina |
| Initially, retina obtains blood supply from | Hyaloid circ. |
| What replaces the Hyaloid vessels and when | Retinal Artery and Vein- in the 4th month |
| When is the take-over by the retina arterial and venous systems accomplished by | the 5th month, but final adult vasculature not achieved until AFTER BIRTH |
| Optic nerve becomes progressively myelinated in which direction | proximal to distal, after birth reaches the Lamina Cribosa -myelination usually stops here, but in some people it can continue -post to lamina cribrosa, the axons are myelinates by Oligodendrocytes |
| When is fovea fully developed | not until after birth- 11-15 months it's adult-like, but will continue to mature of the next four to five years |
| Name the 10 Retinal layers | RPE (pigment epith) Outer and Inner Seg (photoreceptors) ELM (ext. limiting memb) ONL (outer nuc) OPL (outer plex) INL (inner nuc) IPL (inner plex) GCL (ganglion cell) NFL (nerve fiber) ILM (int. limiting memb) |
| What type of cells are in the RPE and what do they contain | cuboidal cells- melanin and lipofuscin |
| In retinal detachment, the cuboidal cells remain attached to what | Choroid |
| Function of the RPE | remove H2O- maintain ionic environment Nourish outer ret Phagocytose detached discs from Photorecept. OS and IS |
| Where are the shredded discs from Rod OS broken down | in the cytoplasm of the RPE (bc they are enclosed by it) |
| What happens in Retinal Pigmentosa | the interaction bw receptor cell and RPE fails when RPE phagocytosis of outer discs fails- receptor cells degenerate = blindness as a final outcome |
| RP (ret. pig) is due to mutations in | Visual Pigment **Rhodopsin (point mutations) Rod OS proteins phtotransduction g-protein cascade in rods |
| Mutations of RP are in rods or cones?? | Rods- but cones usually die bc of rod death |
| Cones have high acuity and color vision under | light adapted conditions |
| Where are rods most numerous | 20 degrees oustide the fovea |
| Inner and Outer seg are connected via | Ciliary Stalk = supply channel |
| Proteins and Lipids pass from Inner to Outer seg thru | Cilium |
| How many discs are in OS, and the thickness of one disc | 2000 stacked- 203A |
| Rods contain Cones conatin | Rhodopsin Opsin- tuned to long(R), short(B), med(G) wavelengths |
| What does NOT induce the shedding of discs | LIGHT- but there is a daily rhythm, AND constant darkness OR light can disrupt synchronous shedding |
| When are most discs shed | in the a.m. |
| Are both rods and discs connected to outer seg? | Rod discs become seperated from base of outer seg and cilium, BUT Cone discs are attached to Outer Cell Membrane |
| What is the leading cause of blindness in the ELDERLY | ARMD- age related receptor cell loss in the retina, could be due to failure of interaction between choroid and retina |
| ARMD occurs more in... | females smokers sun exposure FACTOR H |
| 2 stages of ARMD | Dry- early, drusen in macula (precursor), blurry vision Wet- BV form under macular - leaky, Wavy lines |
| What is the precursor to the Dry Stage of ARMD | Drusen in the macula |
| Netting appearance of ELM due to | perofrations by the receptor cells |
| ELM is NOT | a true membrane! |
| ELM is made up of what attachements | desmosomal bw Muller Fibers and Receptor Cells |
| What cells are found in the ELM | Muller Cells |
| The nucleus of Muller cells is found where | INL, because they stretch fro ILM to just beyond ELM |
| Muller cells are important for... | breakdown of glutamate Homeostasis Neuronal survival Storage of glycogen |
| Outer Nuclear Layer is composed of | Cell BODIES of rods and cones, with their nuclei and cytoplasm |
| Difference bw Rod and Cone nuclei | Rod- round, slightly oval (5.5 microns) Cone- oval, larger than rod (5.7 microns), but contain LESS Heterochromatin, and stains fainter |
| Outer Plexiform Layer is composed of | Cell AXONS of rods and cones Contact processes from Bipolar and Horiz. cells |
| Synaptic endings of Rods and Cones | Rods- Sphereules Cones- pedicles |
| 2 types of Cone to Bipolar cell contacts in the OPL | Synaptic Ribbon Sequence Basal (flat) Junction |
| Ribbon synapses in the OPL are found where and are easily identified by what | receptor cell terminal swellings and identified by electron dense ribbon in PRESYNAPTIC CYTOPLASM |
| How is the ribbon oriented and what does it contain | right angles adj to plasma membran- contains GLUTAMATE |
| The processes that lie laterally and deeper in invaginations are | Horizontal cell processes |
| The processes that are more central in the invaginations | Cone bipolar cell dendrite from an ON bipolar cell (depolarize at light onset) |
| In the IPL, where are the syn ribbons located | in Bipolar cells |
| The synaptic Ribbon forms the presyn and postsyn elements and is formed by | Ganglion cell Dendrite Horizontal Cell or Interplexiform Cell Process |
| Basal Junctions are characterized by | thickening of surface membranse on BOTH pre and post synaptic sides |
| What are Basal Junctions missing that makes them not considered as conventional synapses | VESICLES on Presyn side |
| Bipolar cells that make the basal junction contact with cones are | OFF bipolar cells (hyperpolarize at light onset) |
| Why do Horizontal cells mediate a lateral interaction in Basal junctions | because they have much wider spread of processes and contact more photoreceptors than the bipolar cells |
| In the basal junct, how do bipolar cells convey the visual signals | vertically from the outer to inner plexiform layer |
| Nuclei of what cells are found in the INL | Horizontal, Muller, Biplar, Interplexiform, and Amacrin cells |
| How deep is the INL | 8 nuclei in fovea 5 nuclei at Ora Serrata |
| NT of Horizontal cells | GABA |
| NT of Bipolar cells | Glutamate |
| NT of Amacrine cells | Glycine (inhib) GABA- A17 (inhib) Dopamine- A18 ACh |
| NT of Interplexiform cells | Dopamine |
| Order of Genesis of All cells in Retina | Ganglion-Horiz-Cones Amacrine-Muller-Bipolar-Rods |
| Cell bodies of cells in INL are located how, from outermost, to inner | Horiz and Bipoler = outermost Muller - middles Amacrine and Interplex = innermost |
| The dendrites of the rod bipolar cell synapse with | rods |
| The dendrites of the diffuse cone bipolar cells synapse with | large number of cones |
| The dendrites of the midget bipolar cells synapse with | Parafoveal- a few red and green cones Foveal- only ONE cone |
| Where to the 2nd and 3rd order neurons meet | IPL |
| What cells from synapses in the IPL | Bipolar, Amacrine, Interplex, and Ganglion |
| The bipolar terminal in IPL synapse with (postsyn) | a PAIR of Amacrine cell Processes -or- ONE Ganglion cell Dendrite (rarely 2) |
| Synaptic Ribbons of the IPL are diff from OPL because | IPL has no invaginations |
| Synaptic ribbons in the IPL occur in | Bipolar Terminals |
| The direction of conduction | both ways |
| Amacrine cells are involved in what system, and specifically which cell | Local Feedback System- AII = rod to rod bpolar pathway to ganglion cells |
| Intraretinal Centrifugal Pathway | Interplex receives input from amacrine cells and connects the IPL with the OPL |
| Facts about Ganglion cells | multipolar cytoplasm is fibrillar and contains Nissel Granules |
| 3 types of Retinal Ganglion cells | Midget- 70%,( 95% in central, 45% periph ) Parasol- 10% Small Bistratified- 2-8% Other- giant ganglion cells (10%) |
| Where are Melanopsin Ganglion Cells found | plasma membrance, slow response to luminance |
| Melanopsin Ganglion cells project to | Pretectum (pupil diam) Suprachiasmatic Nucleus (circadian rhythms) |
| Melanopsin Ganglion cells are considered Intrinsically Photoreceptive cells because | due to the response of melanopsin to light |
| Nerve Fiber layer consists of | AXONS of Ganglion Cells |
| Nerve fibers radiate towards what and form what | toward optic disc and become optic nerve, myelinated ONLY at the Lamina Cribrosa |
| Origin of a nerve fiber and its location within the NFL explains | the pattern of visual field loss assoc. with particular disesases |
| Glaucoma affects which fibers of the retina | the 1st most external fibers = initial field loss of Periph |
| What is the orientation of thefibers and the horizontal meridian | they DO NOT cross the horizontal meridian i.e. when temporal peripheral fibers are lost, we see an arcuate field loss with a "nasal step" |
| Field loss which respects the horiz meridian is generally due to problem with the | optic nerve |
| What makes the ILM different from the ELM | It is a BASEMENT MEMEBRANE and NOT made up of processes of Muller cells |
| Where is the ILM absent | at the optic disc due to the absense of the Muller cells (which are the secretion of the ILM) |
| Apart from Muller Cells, the retinal neuroglia is made up of | astrocytes, pericascular glia, and microgli |
| Microglia | Phagocytes (increase with inflammation) |
| Astrocytes and Pericascular Glia do what | insulate the vasculature from neural structures |
| Astrocytes also surround what | the Optic Nerve in Prelaminar regions |
| How many cones are found in the foveola vs the fovea | 10,000- foveola, 200,000- fovea |
| Foveola is free of | rods and blue cones (Xanthophil (yellow pig) absorbs blue light) |
| Blue Blind | Tritanopia |
| What is the reason you see a reflex in the ophthalmascope of the foveal pit | because it serves as a CONCAVE mirror |
| What 2 things are NOT modified at the Fovea | the pigment epith (RPE) and the Choriocapillaries |
| Cones in fovea | much longer and thinner, sm diameter allows more per unit which aids in visual resolution |
| Why is the Optic disc the blind spot | it only contains nerve fibers and astrocytes |
| Ora Serrata has reduced resistance to tearing because (is detachments begin here) | general thinning and presence of Vacuoles AND the strong local attachment bw the vitreous base and retina |
| What is the avascular part of th retina | Fovea, dependent of Choroid circulation |
| As arteries branch and emerge from optic nerve, the Muscular sheath is replaced with | incomplete layer of Pericytes = ARTERIOLES, not Arteries |
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