lab two - eyes and ears

how many of the 12 cranial nerves have to do with sight?

5

what receptive layer of the eye is responsible for converting light energy into action potentials, which travel from the eyes through the optic nerves to the brain?

the retina! these action potentials are interpreted as sight in the occipital lobes of the brain!

pupil

opening located in the center of the eye and is surrounded by the colored iris

what part of your eye is colored?

iris

scelera

white part of the eye is covered by a membrane known as the conjunctiva that continues underneath the eye lids

what membrane covers the sclera?

conjuctiva, that continues under the eyelids

where do eyelids join together?

lateral commissure and medial commissure

what is the small piece of tissue near the medial commissure?

lacrimal caruncle

What protects the eyes from material?

upper eyelid and eyelashes and the lower eyelid and eyelashes and reduce visual stimulation when we sleep

in addition to being the white of the eyes, what else does the sclera do?

it is a protective portion of the eye that is an attachment point for the muscles of the eye AND helps maintain the intraocular pressure

what does the intraocular pressure do?

maintains the shape of the eye AND keeps the retina attached to the posterior wall of the eye

what gives the appearance of eyes being “bloodshot”?

if the blood vesicles that traverse the sclera become dilated anteriorly

what forms the fibrous tunic of the eye?

the cornea and sclera

what structure is important in the maintenance of the exterior of the eye?

lacrimal apparatus; made up of the lacrimal gland located superior and lateral to the eye

what do lacrimal glands secrete?

lacrimal secretions (tears) bathe and protect the eye and clean dust from its surface

where are tears (lacrimal secretions) drained?

through the nasolacrimal duct into the nasal cavity

lateral rectus

VI (abducens) - laterally

medial rectus

III (oculomotor) - medially

superior rectus

III (oculomotor) - superiorly

inferior rectus

III (oculomotor) - inferiorly

inferior oblique

III (oculomotor) - superiorly and laterally

superior oblique

IV (trochlear) - inferiorly and laterally

what is the first layer covering the sclera?

conjunctiva - made of epithelial tissue and an important indicator of multiple clinical conditions

cornea*

center of the eye, the structure important fro bending light rays that strike the eye, allowing us to focus light

• composed of dense connective tissue and is avascular

where is the anterior chamber?

behind the cornea, between the cornea and the iris

where is the posterior chamber?

behind the cornea, but between the iris and the lens

what are the two chambers filled with and where is it produced?

aqueous humor produced by the ciliary body

what absorbs aqueous humor produced by ciliary bodies?

scleral venous sinus (canal of Schlemm)

what muscles of the eye constrict in bright light?

sphincter pupillae of the iris

what muscles of the eye constrict in dim light?

dilator pupillae

what is the lens made of?

crystalline protein

how do the eyes focus on an image?

the ciliary muscle of the ciliary body contracts and the suspensory ligaments that attach to the lens loosen, allowing the lens to become more round for focusing on closer images

what is the posterior portion of the eye called?

fundus

vitreous chamber

behind the lens; filled with vitreous humor - a clear, jellylike fluid that maintains the shape of the eyeball

what’s the outermost tunic of the vitreous chamber located behind the lens?

the fibrous tunic (schlera)

what’s the middle tunic of the vitreous chamber located behind the lens?

vascular tunic (choroid, ciliary body and the iris)

• the blood vessels found in this layer nourish the eye and the pigmentation prevents light from scattering and blurring visioin

what’s the innermost tunic of the vitreous chamber located behind the lens?

nervous tunic (retina)

where are light signals sent?

the bipolar neurons that synapse to the ganglion cells

• visual stimulation is transmitted anteriorly toward the vitreous humor to the ganglion cells

• the ganglion cells exit the eye as the optic nerve

what are the three layers of the retina?

ganglionic, bipolar, and photoreceptive (rods and cones)

what do rods and cones do?

rods determine the shape of objects and cones determine the color and visual acuity of objects

where is the concentration of cones the greatest?

fovea centralis; the center of the macula

near point

minimum distance an object can comfortably be held in focus

astagmatism

cornea or lens are not perfectly smooth

what instrument is used to examine the eye?

ophthalmoscope

what’s another name for far-sightedness?

hyperopia (hypermetropic vision)

what’s another name for near-sightedness?

myopia (myopic vision)

what affects color blindness?

red, green or blue cone sensitivity

afterimage

occurs when you look at a bright image against a dark background

negative afterimage

weh nyou can see a dark object against a light background

what is the photosensitive pigment of the eye, rhodopsin, composed of?

retinal and the protein opsin

opic disc

where the retinal nerve fibers exit from the back of the eye and form the optic nerve

what is a blind spot?

small circle at the back of the eye devoid of photoreceptors

consensual reflex

response that happens on one side of the body when the other side is stimulated