A&P: Chapter 12 SB

What two benefits do humans gain by having their eyes on the front of their face, unlike animals such as rabbits who have eyes on the side of their head?

-allows stereoscopic vision -allows depth perception

3 compnents of the middle layer (tunic) of the eye

-choroid coat -iris -ciliary body

The posterior cavity is the largest compartment of the eye and is bound by what three structures?

-ciliary body -lens -retina

3 characteristics of the iris of the eye

-contains smooth muscle -controls amount of light coming into eye -colored portion of the eye

3 structures of the eye that refracts light rays

-lens -vitreous humor -cornea

Rods following exposure to light (in order)

1.Rhodoposin Breaks down, releasing option which acts as an enzyme 2.Transducin is activated 3.Phosphodiesterase is activated 4. cGMP is broken down 5.Sodium and calcium channels close 6.cell membrane hyperpolarizes

Light passing through as it enters eye (in order)

1.cornea 2.aqueous humor 3.lens 4.vitreous humor 5.retina

Unlike in rods which all contain the same rhodopsin pigment, there are _____ different types of opsin and proteins present in cones.

3

Approx. ___% of the fibers in the optic nerve cross over to the other side of the brain.

50

A fluid called ____ humor is found in the anterior cavity of the eye.

Aqueous

True or False: Accommodation of the lens occurs in order to view objects that are a distance away.

False

The process of changing the shape of the lens to view a close object is called _______.

accommodation

The ______ chamber is located between the cornea and the iris

anterior

Within the eye, what fluid is secreted into the posterior chamber, circulates into the anterior chamber, and leaves through the sclera venous sinus (canal of Schlemm)?

aqueous humor

highly vascular and darkly pigmented layer

choroid coat

In the bright light, the _____ set of contractile cells of the iris will contract, causing the pupil to ______ in diameter.

circular; decreases

The lens is rounder when viewing _______ objects so that it can cause greater bending of the incoming divergent light rays.

close

The photoreceptors called cones are responsible for______ vision.

color

Each type of ____ responds to different wavelengths of light. This is because each type contains a different type of _____.

cone; iodopsin

The fovea centralis is the area of the sharpest vision because it contains only ______ which do not have converging fibers.

cones

When light passes through the convex surface, the light rays band, resulting in ______ of the light.

converge

Light coming into the eye _________ as it passes through the cornea and lens, focusing the image on the retina.

converges

Which part of the eye is made up of transparent connective tissue, has no blood vessels, but has abundant pain receptors?

cornea

the clear, anterior-most structure of the eye, part of the fibrous tunic, is called the ______.

cornea

oculo-

eye

True or false: if a bright light was flashing into an eye, the people were dilate.

false

True or false: with exposure to light, rods respond by releasing an increased amount of neurotransmitter.

false

An individual who is hyperopic can see ______ but cannot see _______.

far; near

Light from distant objects (more than 20 feet) travels in parallel lines. Thomas, the lens needs to be _______ in order to focus the image on the retina

flatter

The portion of the retina that produces the greatest visual activity (sharpness of image) is the _______. It is located within a patch of cells posterior to the center of the lens called the ______.

fovea centralis; macula lutea

The axons of which retinal to cell type form the optic nerve?

ganglion cells

therm-

heat

When light stimulates photoreceptor cells, it eventually result in a(n) ________ in action potentials in nearby retinal neurons.

increase

The neurotransmitter released by rods in response to light exposure is _______.

inhibitory

Rods and cons are found in the _______ tunic of the eye.

inner

As light passes through the retinal layers, the photoreceptors are in the ________ layer light passes through

last

The _______ is a transparent, elastic structure; its shape is modified by ciliary muscles.

lens

the ciliary body is attatched to the _____ via suspensory ligaments.

lens

Astigmatism results from an irregularity in either the _______ or _______ of the eye.

lens; cornea

photo-

light

The iris has color due to the amount of, and distribution of, _______.

melanin

the posterior portion of the vascular tunic is pigmented due to the presence of the pigmented-producing cells called _______.

melanocytes

After passing through the optic nerves, fibers from the ________ half of each retina cross over to the other side of the brain as a structure called the optic chiasma.

nasal (medial)

A myopic individual can see _____ but cannot see ______.

near; far

When one perceives the color black, it is because _____ cone photoreceptor type(s) have/has been stimulated.

no

Presbyopia is common in ______ individuals, and causes the loss of ______ vision.

older; near

In the dark, the sodium and calcium channels and cell membranes of rods are ______ , resulting in the release of a neurotransmitter that inhibits generation of action potentials along the optic nerve.

open

When the visual pigment rhodopsin is exposed to light, it breaks down into _____ and _____.

opsin; retinal

What is the name of the X shaped structure that consist of fibers of the optic nerves that crossover?

optic chiasma

Area of retina lacking photoreceptors

optic disc

what structure exits the back of the eye, carrying nerve fibers and blood vessels?

optic nerve

After visual signals pass through the thalamus, they form _______, which go to the visual cortex. Other fibers go to the brainstem to stimulate _______.

optic radiations; visual reflexes

The sclera and the cornea make up the _____ tunic, or layer, of the eye.

outer

Reduced ability to accommodate for near vision that commonly occurs with aging.

presbyopia

Found within the ciliary body are two structures: the ciliary _________ and ciliary ________.

processes; muscle

The _______ is a circular opening in the center of the iris.

pupil

Within the iris, the pupillary dilator muscles are arranged as a ________ set of smooth muscle cells. The pupillary constrictor muscles are arranged as a ______ set of smooth muscle cells.

radial; circular

The process called ______ involves the bending of light rays as they pass though objects of different density.

refraction

The _____ forms the inner, or nervous, tunic of the eye. It contains the photo receptors.

retina

Light-sensitive pigment found in rods of the retina

rhodopsin

Images from which type of photoreceptor are less precise because their nerve fibers tend to converge?

rods

The photoreceptors called _______ are responsible for the vision in Des Moines

rods

What type of photoreceptor provide black/white/gray vision?

rods

Which type of photoreceptor is more abundant in the retina?

rods

the "white" of the eye, forming the posterior portion of the fibrous (outer) tunic, is called the ______.

sclera

the outer layer (tunic) of the eye includes a posterior portion called the _____ and the anterior portion called the ______.

sclera;cornea

When looking at a close object, the lens ________ as the ciliary muscle fibers contract; when looking at a distant object, the lens ________ as the ciliary muscles relax.

thickens; thins

olfact-

to smell

Each optic ______ is composed of fibers from the nasal half of one eye and the temporal half of the contralateral eye.

tract

True or false: the images detected at the right now are upside down and reversed from left to right.

true

The ________ humor is a jelly-like substance located between the lens and the retina of the eyeball.

vitreous