eye lectures Flashcards
What is lysozyme in tears?
protective bactericidal enzyme
where is the retina located?
the posterior three-quarters of the inner layer of the eyeball
what is the tarsal plate?
a fold of connective tissue that gives form to the eyelids
what is the function of tarsal glands?
elongated, modified sebaceous glands that secrete a fluid that helps keep the eyelids from adhering to each other
what does intraocular pressure do?
maintains shape of eye and prevents it from collapsing
an infection of the tarsal gland causes what?
a chalazion
what is the cause of hyperopia (farsightedness)?
the eyeball is shorter than normal and the image converges behind the retina
what is the shape of the eyeball in cases of myopia (nearsightedness)?
longer than normal and the image converges in front of the retina.
Do cone pigments or rhodopsin regenerate faster?
cones pigments
what is the shape of the lens when focusing on a distant object?
flat
when focusing on a distant object, what is the state of the zonular fibers?
taut
when focusing on a close object, what is the state of the ciliary muscles?
contracted
how is hypertropia treated?
with a convex lens
what are the two chambers of the eye and what divides them?
the anterior and posterior chamber are separated by the iris
how do distance and convergence connect? does this change overtime?
the nearer the object, the greater the degree of convergence needed
the ability to converge goes down over time
what is function of the neural layer of the retina?
send nerve impulses into axons that form the optic nerve
function of aqueous humor
nourishes the lens and cornea
what is light adaption and how fast does it take?
when you go from dark to light, seconds
what causes blood shot eyes?
dilation and congestion of the blood vessels of the bullbar conjunctiva
what is the shape of the lens when focusing on something close?
more spherical
function of the retina
receives light and converts it into receptor potentials and nerve impulses. output to the brain via axons of ganglion cells which form the optic nerve
what is the most common form of color blindness
red-green
what do the pretectal nuclei control?
pupillary and accomadation reflexes
what is an astigmatism caused by?
the cornea or the lens or both have an irregular curve. causes blurred or distorted vision
function of the cornea
admits and refracts light, also protection
function of the choroid
provides blood supply and absorbs light
in what way are images projected into the eye?
inverted and left to right reversed
function of the vitreous chamber
contains vitreous body that helps maintain the shape of the eyeball and keeps retina attached to the choroid
what are the two types of conjunctiva and where are they located?
palpebral conjunctiva-inside of the eyelids
bulbar conjunctiva- covers the sclera
what does the fibrous tunic contain?
the cornea and the sclera
what is the function of the cornea?
focus light on the retina
function of the anterior cavity
contains aqueous humor that helps maintain the shape of the eyeball and supplies oxygen and nutrients to the lens and cornea
what do rods contain?
rhodopsin
what is the function of glutamate?
inhibits bipolar cells from transmitting signals to ganglion cells
what two structure is the posterior chamber between?
behind the iris and in front of the lens
what is the function of the iris?
controls the size of the pupil based on autonomic reflexes
What are the 5 accessory structures of the eye?
eyelids, eyelashes, eyebrows, lacrimal apparatus, and extrinsic eye muscles
where do the axons of the eye’s ganglion cells exit?
the axons exit as the optic nerve
What is the direction of the nerve impulse in the layers of the retina
photoreceptors->outer synaptic layer->bipolar cells->inner synaptic layer->ganglion cells->optic disc->optic nerve
what does the lacrimal caruncle contain?
sebaceous glands and sweat glands
what is the function of the extrinsic eye muscles
moving the eyeball in all directions
what are the six extrinsic eye muscles?
superior rectus. inferior rectus, lateral rectus, medial rectus, superior oblique, and inferior oblique
what are the two parts of the ciliary body?
ciliary processes and ciliary muscle
what is convergence?
the medial movement of the two eyeballs so that both are directed toward the object being viewed
What are three common retinal diseases in the elderly?
macular degeneration, detached retina, and glaucoma.
cataracts is also common in the elderly
what is the function of tarsal/meibomian glands and where are they located?
keeps the eyelids from sticking together
the tarsal plate
Describe the cyclical process of photopigment response to light
- in darkness retinal has a bent shape called cis-retinal which fits in the opsin portion of the photopigment
- When cis-retinal absorbs a photon, it straightens out to trans-retinal
This change in shape is called isomerization and is the first step in visual transduction - After this isomerization, some chemicals form and then disappear which lead to the production of a receptor potential
- after about a minute, the trans-retinal completely separates from opsin. It becomes colorless (bleaching)
- an enzyme called retinal isomerase converts trans to cis
6.the cis retina binds to optin again and reforms a function photopigment (regeneration)
Why does crying produce a runny nose?
tears flowing down through the nasolacrimal duct into the nose
what is the iris and what determines it’s color?
colored portion of the eyeball
the amount of melanin in it
function of the lens
refracts light
what is the other name for the vascular tunic?
uvea
functions of choroid
provides nutrients to posterior surface of retina and contains melanocytes that produce melanin that make the layer seem dark brown. The melanin absorbs stray light rays and prevents reflection and scattering of light within the eyeball.
what is the function of the vitreous humor
holds retina against choroid giving the retina an even surface
what is the name for a normal eye?
emmetropic
What happens when bright light stimulates the eye?
parasympathetic fibers of the oculomotor nerve stimulate the circular muscles of the iris to contact and decrease the size of the pupil
how often is aqueous humor replaced?
every 90 minutes
What cranial nerve supplies the lacrimal glands?
parasympathetic fibers of the facial nerve (7)
What is contained in the fibrous tunic?
anterior cornea
posterior sclera
the function of the suprachiasmatic nucleus?
patterns of sleep
function of the lacrimal apparatus?
production of tears
what is the pathway of visual impulses through the brain?
optic nerve->optic chiasm (cross over)->optic tract->lateral geniculate nucleus of the thalamus->optic radiation->primary visual area in occipital lobe
functions of the sclera
covers the entire eyeball except the cornea
gives shape to the eyeball
protects its inner parts
serves as a site for attachment for eye muscles
what is the pigmented layer
a sheet of melanin-containing epithelial cells which help the retina absorb stray light
What two structures is the anterior chamber between?
the iris and the cornea
function of horizontal and amacrine cells
modify the signals being transmitted along the pathway from photoreceptors to bipolar cells to ganglion cells
contents of vitreous humor
water, collagen fibers, and hyaluronic acid. also contains phagocytic cells that remove debris
what is the center of the retina?
macula lutea
when focusing on a distant object, what state are the ciliary muscles?
relaxed
where is the image projected?
fovea centralis, vision is the sharpest there
what is the function of the eyebrows and the eyelashes?
Protect the eyes from perspiration, foreign objects, and direct rays of the sun
what is the anterior chamber filled with?
aqueous humor
what is the tarsal plate?
a thick fold of connective tissue that forms and supports the eyelids
where does information go after the photoreceptors?
flows through the outer synaptic layer to bipolar cells through the inner synaptic layer to ganglion cells
function of the ciliary muscle
alters the shape of the lens for adaption to near or far vision by pulling on the zonular fibers
what volume of tears does a lacrimal gland produce per day?
1 mL
how does light pass through the retinal cell layers
ganglion cell layer->inner synaptic layer->bipolar cells-> outer synaptic layer-> photoreceptor layer
what is the first step of visual transduction?
absorption of light by a photopigment which leads to the production of a receptor potential
what is the posterior chamber filled with?
aqueous humor
what is the science name for the eyelid?
palpebrae
what do the superior colliculi control?
extrinsic eye muscles
what are the functions of the palpebrae?
shade eyes during sleep, protect eyes from excessive light and foreign objects, and spread lubricating secretions over eyeballs
what do cones contain?
red, blue, and green photopigments
what are the two photoreceptors?
rods and cones
what is dark adaption and how long does it take?
moving from light to dark area, takes minutes
what does the blind spot not contain
rods or cones
what are the three systems that process visual signals?
processing shape
processing color
processing movement, location, and spatial organization
what do all photopigments contain?
a glycoprotein called opsin and a vitamin A derivative called retinal
what three structures make up the vascular tunic?
choroid, ciliary body, and iris
What types of tissue make up the three layers of the cornea?
Outer layer: nonkeratinized stratified squamous epithelium
middle layer (stroma): collagen fibers and fibroblasts
inner layer: simple squamous epithelium
What do rods release in darkness?
glutamate
what causes a stye?
infection in the ciliary glands
what is the function of horizontal cells?
assist in the differentiation of various colors
What is the size of an adult eyeball?
2.5cm
how is myopia corrected?
with a concave lens
What is the sclera made of?
dense connective tissue made of collagen fibers and fibroblasts
what is dacryocystitis?
infection of the lacrimal sacs
how does convergence happen?
coordinated action of the extrinsic eye muscles
What wavelengths are visible to the eye?
400-700nm
explain the path of light into the eye
cornea->anterior chamber->pupil->posterior chamber->lens->vitreous humor_> projected onto the retina
what is the posterior CAVITY filled with?
vitreous humor
does the ciliary body contain melanin?
yes
what does the fovea centralis contain?
only cones
functions of tears
cleans, protects, lubricates, and moistens the eyeball
function of ciliary processes?
secretes aqueous humor
function of canal of schlemm
aqueous humor drains into it
how are images projected onto the retina?
images are inverted and right to left reversed due to refraction; the brain corrects the image
where is the poster CAVITY/vitreous chamber located?
behind the lens
when focusing on a close object, what is the state of the zonular fibers?
loose
what is the name for the point which the optic nerve exits the eye
optic disc or blind spot
what are the two (3?) tunics
fibrous tunic
vascular tunic
nervous tunic? (in the lab slides)
what does the vascular tunic contain
the choroid, ciliary body, and iris
why is cone vision sharper?
cones only synapse with one bipolar cell
in the fetus, what does the hyaloid canal hold?
hyaloid artery
What does the pigmented layer of the retina near the photoreceptors store?
vitamin A which contributes to regeneration in rods
function of the sclera
provides shape and protects inner parts
More than half of the sensory receptors in the human body are located in the eye? True or false
true
what is in the center of the macula lutea
fovea centralis, the area of the highest visual acuity
what is the function of amacrine cells?
synapse with ganglion cells and transmit excitatory signals to ganglion cells to initiate nerve impulses
what is the function of rods?
see in dim light
what is the conjuntiva?
A thin, protective mucous membrane made of non-keratinized stratified squamous epithelium with numerous goblet cells that is supported my areolar connective tissue
describe vitreous humor
a transparent, gelatinous substance
what do horizontal cells do?
transmit inhibitory signals to bipolar cells in the areas lateral to excited rods and cones
what are the two layers of the retina/nervous tunic?
pigmented layer and neural layer
what is the function of cones?
see in color
function of the ciliary body
secretes aqueous humor and alters the shape of the lens for near or far visions (accommodation)
Function of ciliary glands?
Release lubricating fluid into the follicles (sebaceous)
What should the pressure in the eye be?
16mmHg
function of the iris
regulates the amount of light that enters the eyeball
what is the funtcion of the palpebral muscles?
control eyelid movement
describe aqueous humor
a clear, watry liquid
How does visual information travel in terms of sides?
right half of each visual field goes to the left side of the brain and vice versa