What is the volume of tears produced everyday?1 mLWhat is the flow of tears?-lacrimal gland -excretory lacrimal duct -superior or inferior lacrimal canal -lacrimal sac -nasolacrimal duct - nasal cavitywhat is the bactericidal enzyme is tears called?lysozymeWhat are the 3 layers of the eye ball from superficial to deep?Fibrous tunic Vascular tunic Nervous tunicWhat makes up the fibrous tunic of the eye?Cornea, scleraWhat is the cornea? What does it do?tranparent and colourless covering of eye helps to focus light (refraction)Is the cornea vascular or avascular? What nourishes the tissue?Avascular (thus why is a good transplant candidate), nourished by tears and aqueous humorWhat is the sclera? What does it do?White part of eye provides shape and supportWhat is the scleral venous opening?opening at the junction of the sclera and corneaWhat pierces the posterior portion of the sclera?the optic nerve (CN II)What makes up the vascular tunic?Choroid Ciliary Body Ciliary Processes Iris LensWhat makes up the Choroid, what is its purpose?pigmented epithelial cells (melanocytes and blood vessels) provides nutrients to retina black pigment in melanocytes absorb scattered lightWhat does the ciliary body do?contains ciliary mm, changes lens shapeWhat does the ciliary process do?fold in the ciliary body that secrete aqueous humorWhat is the iris?colored portion of eye shape of flat donut suspended between cornea and lens contains mm fibers, pigment, CT and epithelial tissueWhat is the pupil? What is its function?hold in center of iris, function is to regulate the amount of light entering the eyeExplain how the ANS functions in controlling how much light enters the eye?under PNS- circular mm fibers contract in bright light to constrict pupil under SNS- radial muscle fibers contract in dim light to enlarge the pupilWhat is the lens? What is its purpose?acts like cornea, lets light in (cornea does more refraction) focuses light on retinaWhat is presbyopia?age related loss of elasticity of the lensWhat holds the lens in place?suspensory ligaments, attach lens to ciliary process (ciliary mm) Ciliary mm controls tension on ligaments and lensWhere is the nervous tunic found?posterior 3/4 of eyeballWhat is the optic disc?area where optic nn exits back of eyeball- has no photoreceptors (Blind spot)Where is the central retinal blood vessel found?fans out to supply retina, exits out optic discWhy do optometrists check the central retinal blood vessel?can indicate hypertension or diabetesWhat are rods?specialized for dim light discrimination between shades of dark and light see shapes and mvmt 120 million rod cells distributed along peripheryWhat are cones?specialized for bright light, sharpness of vision (acuity) most densely concentrated in central fovea sharp, colour vision 6 millionWhere is the fovea? What is found here?a small depression in the macula lutea (exact visual axis of eye) that has a high concentration of conesWhat is the macula lutea?found in posterior portion of the retina, almost in the centre, corresponds to visual axis of eyeAre rods found in the fovea and macula lutea?NOWhat is macular degeneration?degeneration of the macula lutea, which causes loss of visual acuity and centered visionWhat part of the eye absorbs stray light?retinaWhat are the 3 layers of neurons in the eye?photoreceptor layer bipolar neuron layer ganglion neuron layerWhat cells modify the neuronal signal in the eye?horizontal cells amacrine cellsWhat is the basic visual pathway?- light penetrates retina - rods and cones transduce light into action potentials - rods and cones excite bipolar cells - bipolars excite ganglion cells - axons of ganglion cells form optic nn leaving the eyeball at the optic disc (blind spot) - goes to thalamus (LGN) - third order neurons end a the primary visual cortexWhere is the anterior cavity? What does it contain?cavity found anterior to the lens filled with aqueous humour continually drained, repleced every 90 minutesHow many chambers does the anterior cavity have?2 chambers anterior (between cornea and iris) posterior (between iris and lens)What produces aqueous humor?ciliary bodyWhere does the aqueous humor drain to?the blood stream via the canal of Schlemm (junction of cornea and sclera)Where is the posterior cavity? What does it contain?posterior to lens contains vitreous humour (jelly like)What are floaters?debris in vitreous body of older individuals (floaters= vitreous fluid that was formed at back of eye and became dislodged)What is intraocular pressure? What produces it?pressure in the eye, produced mainly by aqueous humor.What does intraocular pressure do?maintains shape of eyeball, keeps retina smoothly applied to the choroid so the retina forms clear imagesWhat is glaucoma?increased intraocular pressure- problem with drainage of aqueous humor- may produce degeneration of retina and eventual blindnessWhat 3 things help with image formation?1) refraction of light by cornea and lens 2) accommodation of the lens 3) constriction of the pupilWhat is refraction?bending of light- occurs when light moves through substances with different refractive indices at non-perpendicular anglesWhat is the refractive index?degree to which a substance can bend light (a number value).How many refractive surfaces does the eye have? What are they? Where does the most refraction occur?4 (lens, cornea, air, aqueous humor) most refraction occurs at the corneaWhat part of the eye can change its refractive power? How does this occur?Lens- can change shape to keep things in focus and therefore changes its refractive powerWhat is a diopter?measure of the refractive power of a lens (reciprocal of the focal length of the lens)What is the focal point of a lens?the point of convergence of parallel light rays after passing through a lensWhere is 75% of refraction done? Where does the rest occur?75% at cornea, rest at lensAt what length are light rays nearly parallel so therefore don't require much refraction?20 feetWhat is accommodation?increase in convexity of lens, initiated by ciliary mm contractions to allow lens to refract light "harder"What does the ability to focus on a near object involve?1) increasing refractive power of the lens (more convex) 2) eyes converging via medial rectus mm 3) pupils constrictIs the lens of the eye convex or concave?biconvexWhen are suspensory ligaments most taut?when viewing distant objects- lens is nearly flatWhat happens to the lens as an object moves closer to you?the ciliary mm contracts and decreases tension of suspensory ligaments, making lens more elasticWhat is the near point of vision?minimum distance from the eye that an object can be clearly focused using maximum effort (holding your finger as close as possible while still being able to see fingerprint clearly)What is the mechanism that causes rounding of the lens?PNS fibers from the oculomotor nerve stimulate the ciliary mm to contract, relaxing suspensory ligaments, allowing lens to become more roundWhat is binocular vision?2 eyes at the front of the head (like humans) which allows for depth perceptionWhat does constricting the pupil do?allows for improved depth of focus also constricts in bright lightWhat does the PNS do to the pupil?causes constrictionWhat does the SNS do to the pupil?causes it to dilateWhat is emmetropia?normal visionWhat is hyperopia? How is it corrected?far sightedness (light converges behind retina) - correct with convex contact/glasses lensesWhat is myopia? How is it corrected?nearsightedness *(can't see far away- light converges before the retina) Concave lenses fix thisWhat is a normal near point in a young adult? Middle aged person? 80 year old?YA= 4 inches 40 y/o= 8 inches 80 y/o= 31 inchesWhat is an astigmatism?irregular curvature of the cornea or lens, which causes light to be refracted in differing amounts (halos around street lights at night) each plane requires a different amount of accommodation so they eye can't compensate- if it focuses on one plane, other planes go out of focusWhat is nearpoint stress?a condition in which the ciliary muscles become unable to completely relaxWhat is open angle glaucoma?inadequate drainage of aqueous humor despite normal sized opening between iris and cornea (d/t clogging of trabecular meshwork)What is closed angle glaucoma?angle between the iris and cornea is too narrow for adequate flow and drainage of aqueous humorExplain transduction of vision?- photopigments found in rods and cones absorb light - light energy transduced to a receptor potentialWhat is a photopigment?integral membrane protein that chemically changes when it absorbs light energy (membrane is folded into discs or folds)What are photopigments made up of?opsin (protein) + retinal (derivative of vitamin A)What is the light absorbing part of photopigment?retinalHow many different opsins are there?4 (3 for cones, 1 for rods)What are the 3 types of photopigments contained in cones?opsins for red, blue or greenWhat photopigment is contained in rods?rhodopsinVisual acuity poor, good night vision, no color visionrodsgood visual acuity, poor night vision, colour visionconesWhat happens when you see something in your peripheral vision?image is hitting the rods (which are overly sensitive to light), so they can detect it (if bright/moving)At night, if you stare directly at a dim light, why can't you see it?central vision, light is only hitting the fovea which has no rods, therefore you can't detect the light (b/c cones are not light sensitive)What are the three designations of cones?S, M and L for short, medium and long wavelengthIs blue a short or long wave length?shortWhat is bleaching and regeneration?accounts for sensitivity change during light and dark adaptationWhat is nyctalopia?night blindnessWhat is cooperative eye hypothesis?idea that distinct appearance of human eye (with so much white) may have evolved so that it is easier for humans to follow one anothers gaze while communicating or while working together on tasksWhat innervates the constrictor pupillae (circular)?parasympathetic nerve fibersWhat innervates the dilator pupillae (radial)?sympathetix nerve fibers

Neuro- Vision Quiz 1

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