Retinal Transduction Lec11 Flashcards by brittany gouse

what is the fovea? the small depression at center of macula with the ___

highest spatial acuity

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what enters and leaves the optic disk?

blood vessels enter and retinal axons leave the eye

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: ant. ciliary and long post. ciliary arteries supply blood to the

iris and ciliary body

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Uveal tract consists of three structures:

choroid, the ciliary body and the iris.

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Delivery of metabolic substrates and oxygen to the retina is accomplished by (2)

the inner retinal and choroidal.

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what is the posteriro chamber

Region between the vitreous and the lens.

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what produces aqueous humor?

the vascular component of the ciliary body.

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where is the vitreous humor

the space between the back of the lens and the surface of the retina.

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what pigment does the macula contain?

a yellowish pigment (xantophyl). Supports high acuity.

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The ocular vessels are derived from the

all from the ophthalmic artery (OA),

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what are the two distinct vasciualr systems that supply the eye

a) the anterior segment (iris and ciliary body)
b) the retinal systems.

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Focusing Power of a lens =

Curvature of surface + differences in Refractive Indexes

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focal length - how strongly a lens ___

converges light.

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Greater lens curvature = Greater converging power = __ focal length

Shorter

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diopters - measure of

optical power.

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dipopeter =

1/focal length

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emmetropic eye - is

elaxed, unaccommodated, focused on object at “infinity”

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what is responsible for most of the refraction in the eye

Cornea - 80%

lens does 20%

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Refractive index of cornea =

1.37

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accommodation - the___ to focus on near objects

curvature of the lens increases

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what muscles contract to increase the curvature of the lens? which relax?

ciliary muscles contract, zonule fibers relax

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when the curvature of the lens increases the focal length

decreases

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Accommodative triad/near reflex:

eye accomm. + pupil constriction + eye convergence

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eye accomm. + pupil constriction is mediated by the

parasymp. nerves from Edwin Westphal nucleus of pretectum

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The ___ lens is transparent, has crystallins, with high refractive index of 1.42,

crystalline

• cataract - disorder of\_\_\_ that destroys lens transparency,

lens cell fibers or aggregation of crystallin

\_\_\_ is the leading cause of blindness worldwide.

cataracts

risk factors for cataracts

aging, diabetes, sunlight, smoking

sx of cataracts

hazy vision, poor night vision, glare, faded colors

tx of cataracts includes

surgical replacement with an artificial lens

presbyopia - inability to focus on _____ objects

near

Refractive errors prevent light from

focusing on the retina

myopia / nearsightedness is caused by the

cornea too curved or eyeball too long

with myopia the light is focused \_\_\_

in front of the retina

nearsightedness is called

myopia

with -hyperopia / farsightedness the cause is the

cornea not curved enough or eye too short

with hypoerpopnia the light is focused

behind the retina

you correct hyperopia with

(+)/convex lens

you fix myopia with a

concave lens

Aqueous humor nourishes the\_\_ and \_\_\_

cornea and lens

aqueous fumor is secreted by the

epihtelium

Aqueous humor flows from anterior chamber angle of eye to...

Leaves the eye by passive flow at the anterior chamber angle

Flow of aqueous humor against resistance generates \_\_\_.

intraocular pressure (IOP) of ~15 mmHg

Glaucomas = damage to the ___ that can result in vision loss and blindness

optic nerve

risk factors for glycoma

high IOP, thin cornea, abnormal optic nerve, HTN, cardiovascular disease, diabetes

glaucoma causes loss of ___ fields

peripheral

tx of gluacoma?

treat with 1. eyedrops to **decrease aqueous production** or **increase drainage** or 2. surgery

where are photoreceptor cell bodies found?

outer nuclear layer

order light passes through to get to the photoreceptor

1. ganglion cell layer 2. inner plexiform laer 3. inner nuclear layer 4. outer plexiform layer 5. out nuclear layer

cells in inner plexiform layer

bipolar / amacrine / ganglion cells synapse

cells in inner nuclear layer

bipolar / amacrine / horizontal cell bodies

cells in outer plexiform layer

photoreceptor / bipolar / horizontal cells

function of pigment epithelium?

backstop for light, regenerate pigment, nourish and regenerate photoreceptors

pigment epithelium in the back of the eye contains ___ pgiment

melanin

a lens with a short focal length has ___ focal power

greater

Focal distance is ___ proportional to the curvature of the lens.

inversely

loss of ___ with cage causes presbyopia

lens elasticity

A diopter of accommodation is defined as

1/distance to the object

. A near object at 1 m requires accommodation of \_\_\_

1 D 1/ ( distance to object)

\_\_\_ requires a positive lense

hypermetropia (positive is a convex lens)

Myopic correction using the excimer laser is based on a graded removal of\_\_\_\_ tissue to decrease the central anterior corneal curvature.

central anterior corneal

\_\_\_ correction is based on a graded removal of a **peripheral and paracentral anterior corneal** curvature.

Hyperopic

glaucoma Open angle: Slow development of pathology caused by obstruction of the\_\_\_

drainage canals

glaucoma Close angle: Sudden increase in intraocular pressure. Closed or\_\_\_

narrow angle between the iris and cornea.

where does phototransduction occur

in the outer photoreceptor segments

photic input is transmitted to the brain by **the spiking discharge pattern** of the\_\_\_\_ via the optic nerve.

ganglion cells

Retinal glia cells include

astrocytes microglioa mueller cells

Vertical information flow:

photoreceptorsbipolar cellsganglion cells

Lateral information flow: Is mediated by

horizontal cells and amacrine cells

Cells along the vertical path (photoreceptors, bipolar and ganglion cells) release \_\_\_

glutamate

Cells mediating lateral information transmission (horizontal and amacrine cells) release mostly

GABA or glycineric

rods and cones are \_\_\_

photoreceptors

rods and cones use what NT

glutamate

Photoreceptors in the ___ have a standing/circulating current

Dark

Dark \_\_ and ___ influx at outer segment: depolarization

Ca and Na

Dark \_\_\_ at inner segment: hyperpolarization

K efflux

in the dark, the photoreceptor is constantly

staying depoalrized and -40 and releasing glutamate

Photoreceptors respond to Light by suppressing the \_\_\_

inward, cationic current

rhodopsin = pigment in \_\_\_

rods

cone opsin = pigment in \_\_\_

cones

Photon absorption makes 11-cis retinal to

all-trans

11-cis retinal to all-trans, activates --\>

rhodopsin (rods) or opsin (cones)

Rhodopsin\* initiates signal cascade (via transducin and PDE) that\_\_\_

decreases cGMP

1 Rhodopsin ___ lots of cGMP --\> closes 200+ cGMP channels

hydrolyzes

↓ cGMP in outer segment --\>

Na and Ca gates close

how does light cuase less Glu release?

Rhodopsin dec cGMP \> Na and Ca gates close - -\> ↓ Na and Ca influx (but K efflux continues) --\> h yperpolarization --\> ↓ Glu release & ↓ intracellular Ca

\_\_\_\_ is the ability of photoreceptors to adjust to the ambient level of light

Light Adaptation

light adaption occurs in Occurs in __ and \_\_\_

photoreceptors & in postsynaptic retinal cells

what happens at saturation?

all cGMP-gated channels are closed, photoreceptors cannot respond to further light

rods are cones are very senstiive to light

rods

mutation in rod proteins causes \_\_\_

retinitis pgimentosa

night blindess, tunnel vision, often legally blind by 40 are sx of

retinitis pgimentosa

1 cone to __ bipolar cell

1 rods have a much higher convergence

rods or cones mediate high acuity vision?

cones

wet blood vessels behind retina grow and leak dry degeernation of epithelium and photorceptors, causing dursen build

age related macular degeration

lose: central vision and acuity

age related macular degeration

LGN enters V1 and terminates in\_\_\_

layer 4

Ouputs to higher areas of v1 is by \_\_\_

pyramidal cells

Retinal Transduction Lec11 Flashcards

(99 cards)