14102001
Description
Flashcards by Caitlin French, updated more than 1 year ago
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Created by Caitlin French
over 6 years ago
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| Question | Answer |
| Accessory Structures | eyebrows eyelids conjunctiva lacrimal apparatus extrinsic eye muscles |
| Key Structures | Fibrous layer Vascular layer Neural layer Optical chamber Lens and cataracts |
| Eyebrows | UV barrier prevent perspiration from entering eyes orbicularis muscle - depresses corrugator muscle - moves medially |
| Eyelids | Palpabrae fissure - separates upper/lower lids medial/lateral canthus lacrimal caruncle - lubrication, sebaceous/sweat glands tarsal plate - CT structure/support palpabrae superioris - moves upper lid |
| Conjunctiva | palpebral conjunctiva - lines lids bulbar conjunctiva - lines sclera doesnt cover cornea lubrication/protection |
| Lacrimal apparatus | superolateral glands secrete fluid (tears), enters laterally, spreads across eye, exits medially, drains into lacrimal sac, through lacrimal fossa and into nasal cavity - contains mucous, enzymes and antibodies |
| Eyelashes | protection protrudes outwards blinking reflex contains lubricating glands (tarsal glands, sebaceous glands, ciliary/sweat glands) |
| Extrinsic eye muscles | LR = moves lat MR = moves med SR = elevates, moves med IR = depresses, moves med SO = depresses, moves lat IR = elevates, moves med LR6SO4 all surrounded by annular ring (tendonous) |
| Fibrous Layer | Contains clear cornea + cloudy sclera Sclera - post./protects, anchors muscles, cont. with dura mater Cornea - ant./lets light in/aqueous humor behind/ext. stratified + int. simple squamous pain receptors = reflex. blinking |
| Vascular layer | choroid - dark brown, supply blood, post. part of uvea ciliary body - thick ring tissue surr. lens/smooth muscle bundles/anchors susp. lig./zonules holds lens in place iris - cont. with CB/central opening, pupil - 2 muscles (dilator pupillae - symp/distant vis/dim light & sphinter pupillae - parasymp./close vis/bright light) |
| Sensory Layer - Retina | 1. Pigmented epth. layer (outer layer, absorbs light/prevents scattering, engulf dead photorec. cells/ store Vit A 2. Neural layer (transparent inner layer, 3 types; A) photoreceptors = transduce light B) bipolar cells = body in middle C) ganglion cells (generate AP) visual processing via amacrine & horizontal cells |
| Optic Disk | site where optic nerve leaves eye blind spot NOT COVERED BY SCLERA!!! lacks photoreceptors |
| Photoreceptors - Rods and Cones | Rods = resp. dim light (sensitive)/peripheral vision Cones = resp. bright light (less sensitive/high acuity colour vision/posterior lateral to blind spot) Macula lutea = mostly cones Fovea centralis = only cones |
| Optical Chambers (Post. Seg) | vitreous humor forms in embryo lasts lifetime transmits light supports post. surface of lens holds neural retina against pig. layer counteracts pulling force from muscles |
| Optical Chamber (Ant. Seg) | Ant. Chamber = btn cornea & iris Post. Chamber = btwn iris & lens Contains aqueous humor prod. by CB in Post. Chamber, flows up nourishes lens, passes thru pupil, flows back to ant. chamber, drains into canal at edge of cornea supports/nourishes/removes waste! |
| Lens | Transparent, flexible, elastic, avascular, biconvex 2 Regions: 1. Lens Epth. = ant. lens surface + cuboidal cells 2. Lens Fibres = bulk of lens, no nuclei, filled with transparent protein crystallin Optical comp. admits/focus light = humors, cornea, lens! |
| Refraction & Lens | Light passes from one transparent medium to another, changing speed and bending (refracting) Light passes thru convex lens (in eye) is bent so rays converge to one point - retina |
| Pathway for Light | Moves through 1. Cornea 2. Aqueous humor 3. Lens 4. Vitreous humor 5. Thickness of neural layer Light bends when A) entering cornea B) entering lens C) leaving lens |
| Distant Vision Focussing | Lens is thin Ciliary muscles relaxed Little refraction adjustment - light rays are parallel from distance Sympathetic system |
| Close Vision Focussing | Thick lens ACCOMMODATION = Ciliary muscles change lens shape (rounder) to increase refraction power, loosen zonule fibres Pupillary reflex constricts pupils to prevent bright rays entering eye med. rot. of eyeball |
| Problems with Refraction | Emmetropic Vis = normal eye, light focused properly with close vis, lens accomodated Myopic Eye = nearsighted, no distance vis, focal point IN FRONT of retina, corrected with concave lens Hyperopic Eye = shortsighted, no close vis, focal point BEHIND retina, corrected with convex lens Presbyopia = same as hyperopic eye but caused by ageing |
| Photoreception | Eye detects light energy Rods/Cones contain vis. pig./Photo-pigment = Rhodopsin in rods, one for each cone as they respond to diff colours |
| Photopigments in Photoreceptor Cells | Disks parallel to retina, stacked on top of one another Each photopigment contains Opsin (integral protein) Opsin = surrounds and binds chromophore molec, filters light, differs in each type of photopigment, enables diff photopigments to absorb light at diff wavelength Chromophore = light sensitive part of photopigment, same in all four photopigments, retinal - Vit A variant |
| Rods & Cones Comparison | Cones - 3 million/bright light to activate/low sensitivity/pigments for colour vis/each cone synapses with 1 ganglion cell/vision detailed + high res Rods - 100million/sensitive to dim light/night vision/absorb wavelengths of visible light/grey tones only/many rods feed into 1 ganglion cell/fuzzy + indistinct images |
| Excitation of Rods | Rhodopsin breaks down when stim by light Converts cis retinal to all-trans retinal, changing shape, released from opsin + bleaches pigment Dark phase reverses from all-trans retinal/Vit A to cis retinal via ATP enzyme, joins back to opsin to form rhodopsin REGEN - rods = slow 5 mins, cones = fast 90 sec |
| Excitation of Cones | 3 Types of Cones 1. Blue = 420nm wvlth 2. Green = 530nm wvlth 3. Red = 560nm wvlth Intermediate colours are combination of cones Excitation similar to rods |
| Phototransduction | 1. Light converts retinal to trans form 2. Activates G-protein transducin 3. Transducin activates phosphodiesterase (PDE) 4. Converts cGMP to GMP 5. ↓ cGMP = closure of cation channels Results in hyperpolarisation of the photoreceptor |
| Phototransduction Dark | 1. Photoreceptors depolarised from flux of cations thru cGMP channels 2. Open gated Ca2+ channels 3. Cont. release of neurotransmitter 4. Hyperpolarises bipolar cells 5. Inhibits neurotransmitter release 6. No excitation of ganglion cells 7. No AP |
| Phototransduction Light | 1. Light activates molec of retinal, causing it to change shape, ↓cGMP 2. Cation channels close, K+ channels stay open 3. Membrane hyperpolarises + neurotransmitter is released 4. Bipolar cell is disinhibited 5. Depolarises and releases neurotransmitter 6. Depolarises ganglion cell 7. Creates AP |
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