A&P Vision

What happens in cataracts?

a clouding of the lens from the aqueous humor not draining properly

what the duplicity theory?

a single type of receptor cell is incapable of providing high sensitivity and high resolution: it has to be on or the other, sensitive night vision is one type of cell and neural circuitry, whereas high resolution daytiem vision is different cell type and neuronal circuitry

what is the purpose of pigment epithelium

absorb stray light and prevent reflection

what is perrla

accomodation of the eyes (may be specific to pupil--double check)

what are typical causes of cataracts?

aging, diabetes, smoking, ub light

How do your eyes integrate images via bipolar cells?

as your eyes scan scene light vs. dark creates changing patterns of bipolar cones in excitation vs. inhibition which topographically translates to nerve signals

why can't you see too well in dark?

because of large amount of convergence

Why do rods react even in dim light?

because of the neuronal convergence, 600 rods converge on one bipolar cell, many bipolar neurons converge on each ganglion cell--->spatial summation, one ganglion cell receives info from 1 mm2 of retina producing only coarse image

characteristics of conjunctiva

covers the inside of the eyelids and the sclera making it like a fine gel, transparent mucous membrane, ichly innervated and vascular (heals quickly)

what causes dark adapation?

dilation of the pupil occurs, 20 to 30 minutes for regneration of rhodopsin, the rods are sensitive and require a high degree of spatial summation

what is opthalmoscopic exam of the eye for?

direct evaluation of blood vessels with a talmoscope

what causes high resolution vision during the day?

each foveal cone has their own private line and room service. There is no neuronal convergence, and little spatial summation so there is less sensitivity to dim light

tarsal plates are another word for...

eyelids

do primates have colorvision?

hull ya

what are cones mostly made of? how do they absorb wave lengths?

photopsin (iodopsin): opsin moieties contain different amino acids that determine different wave lengths of light absorb: 3 dif. kinds of cones absorb 3 dif. wavelengths producing color vision

where is the reina in relation to the eye? what does it grow out of and attach to?

retina and optic nerve: retina forms an outgrowth of diencephalon, attaches at optic disc and at ora serrata, pressed against rear of eyeball by vitreous humor

what is within the internal layer?

retina and the optic nerve (the most deep)

What are rod cells comprised of? What can it absorb up to?

rhodopsin that has peak abosrption of wavelength at 500nm

What is called when the tarsal plate gets infected?

schlasion

What is the most common type of color blindness?

sex linked 8% of males are incapable of distinguishing red from greed: hereditary lack of one photopsin

What are the four optical components and what is meant by 'optical components'

structures that refract light to focus on retina: cornea, aqueous humor: serous fluid posterior to cornea anterior to lens, lens changes shape to focus light via ciliary muscles, vitreous humor: jelly fills space between lens and retina

what do tarsal galnds do?

tarsal glands secrete oil that reduces tears evaporation

what is the physiology of crying

tears drain flow across eyeball and drain into lacrimal sac from lacrimal puntum along lacrimal canal and into the nasolacrimal duct in the inferior meatus of the nasal cavity, when you're ability to drain is exceeded that is when you shed tears

What is the function of tears

tears flow across eyeball to help wash away foreign particles, help with diffusion of O2 and Co2 and contain baceticidal enzymes

Where are the two chambers of the eye? What type of fluid are they filled with?

the anterior chamber is anterior to the pupil, the posterior chamber is deep to pupil. Filled with humerous: hydrophillic/aqeous

what is wiithin the vascular layer?

the choroid (innervates retina and sclera), the ciliary body, and the iris

what suspends the lens of the eye?

the ciliary body

when you get pink eye what is infected?

the conjunctiva: the whole thing can swell up

what is covering the pupil and iris?

the cornea

What are the three layers of the eye ball?

the fibrous layer vascular layer internal layer

what focuses light on the eye?

the lens

what is the blind spot?

the optic disc (it does not contain photoreceptors)

what is within the fibrous layer?

the sclera and the cornea

what are the two types of bipolar cells and how do they respond to light?

there are those that are inhibited and excited by glutamate: those inhibited by gluatamate are excited by rising light intensity, those depolarized by gluatamate are excited by falling light intensity

when people say they have 'over active tear ducts' what is actually occuring?

they have underactive tear ducts: the nasolacrimal duct is comprimized this can happen in maxillary cancer: than the eyes can't drain properly and you end up crying all the time

what nerve opens your eyes?

trochlear nerve

what are consequences of galucoma?

when the scleral venous sinus in anterior chamber is not absorbed it can cause halos and dimness of vision, causes death of retinal cells due to elevated pressure within the in vitreous humor

What causes light adaptation ?

when you walk out into sunlight you can't see because your pupil constricts and there is pain from overstimulated retinas, causing color vision and acuity below normal for 5-10 min

What are the motion detectors of the eye?

widely spaced rod cells at the edge of the retina

how does the pupil work?

parsympathetic system narrows pupil with the pupillary constrictor is smooth muscle encircling the pupil: , sympathetic widens pupil with spokelike myoepithelial cells

howmany receptors are there converging on one optic nerve?

114

When do blue, green, and red cones peak?

420 nm, 531 nm, 558nm

After the 2nd order neurons form _____nerve where do they go?

CNII, optic nerve, hemi dessucation in optic chaism, 1/2 of fiber decussate so that images of all object in left visual field fall on right half of each retina-->3rd order neurons in lateral geniculate nucleus of thalamus form optic radiation to 1st visual cortex where conscious visual sensation occurs & a few fibers project to superior colliculi and midbrain for visual reflexes

Wchich neurons in retinal layers are 1st order and 2nd order neurons? What other cells are there? What do they do?

bipolar cells are first order neurons that synapse on ganglion cells with large amount of convergence--->the 2nd order neurons are the ganglion cells whose axons form optic nerve there are also horizontal and amacrine cells that enhance perception of contrast, edges of objects, and changes in light intensity

What happens to generate visual signals in the light?

bleached rhodopsin molecules act like an enzyme and break down cGMP-->no na influx-->no dark current-->no inhibition-->disinhibition

what is photopuillary reflex?

both pupils constrict if one eye is illuminated, its a consensual reflex, active if light intensity changes or gaze shifts from distant object to nearby object

What is the macula lutea

cells on the visual axis of eye: contains fovea centralis, center of macula, finely detailed imaged duee to packed receptor cells,

What is the aqueous humor produced by?

ciliary body, ciliary part of the eye there is thicker fluid called vitrious body, aqueous body

aqueous humor

ciliary processes make aqueous humor, flows to posterior champer through pupil to anterior chamber, rabdorbed into schlem canal

what cells are responsible for photopic vision?

cone cells do day vision, outer segment tapers to point

What are the two different types of cells in the eye? What type of vision are they for?

cones and rods: rods are for scotopic vision and cones are for photopic vision

What type of cells does the fovea contain?

cones/photopic system, there are 4000 cone cells adn NO RODS,

when you're gaze shifts from nearby object three things happen:

convergence of eyes orienting visual axis toward object-->constriction of pupil blocking peripheral light rays and reduces spherical aberation/blurry edges-->accommodation of lens where ciliary muscle contracts and lens takes convex shape-->light is refracted more strongly and focused onto retina

When you experience emmetropia does the ciliary muscle increase contraction or decrease? the suspensory ligaments ligaments?

in distance vision i.e. emmetropia the muscle relaxes the diameter of the muscle increases pulling the suspensory ligaments on the lens taught and making it thinner (wider-->pulls more light in)

How do rods generate visual signals?

in the dark rods exhibit a dark signal flow of sodium through cGMP gated sodium channel, sodium influx/depolarization leads to release glutamate-->stimulate the bipolar cell to have inhibitory post synaptic potential which results in no firing

what is papilledma

increased ocular pressure that is a sign of an intracranial event/increased intracranial pressure -also happens in pregnant women

What is the purpose of the nasal lacrimal puncta?

it's the hole for tears

What are the 6 muscles of the eye and what cranial nerves are they innervated by?

lateral, medial, superior, inferior rectus, and superior and inferior oblique -lateral rectus is innervated by cranial nerve 6 (abducens) -superior oblique in innervated by cranial nerve IV (trochlear) -everything else is innervated by oculomotor nerve

What is ptosis? What muscle insites ptosis?

levator palpebrae superios muscle on top of superior rectus muscle dysfunctions and your eye droups

by what pathway do you form images in the eye?

light passes through pupil, then through the lens to form an inverted image on the retina

What is color perception based on?

mixtures of nerve signals

which photoreceptor has scotopic vision

night vision is by rod cells: stack of coinlike membranous discs studded with rhodopsin pigment colecules

What is the muscle of the eye on the external and interior part of the eye?

obicularis oculi muscle and tarsal plate covered with skin on the outside and the conjunctiva is inside

what causes glaucoma?

obstruction of the scleral veinous sinus (schlem canal)

what nerve closes your eyes?

oculomotor nerve

What type of cells do nocturnal vertabrates have in their eyes?

only rods

what are the two parts of rhodopsin?

opsin: protein portion, retinal: vitamin A derivative

what is myosis vs mdriasis

parasympathetic constriction vs. mdriasis is sympathetic widening/relaxing