Chapter 17, Exam 4

macula lutea and fovea centralis

-center of visual axis FC: contains only cones. In addition, the layers of bipolar and ganglion cells, which scatter light to some extent, do not cover the cones here; these layers are displaced to the periphery of the fovea centralis. As a result, the fovea centralis is the area of highest visual acuity or resolution (sharpness of vision)

Photopigment process

1. Isomerization. In darkness, retinal has a bent shape, called cis-retinal, which fits snugly into the opsin portion of the photopigment. When cis-retinal absorbs a photon of light, it straightens out to a shape called trans-retinal. This cis-to-trans conversion is called isomerization and is the first step in visual transduction. After retinal isomerizes, chemical changes occur in the outer segment of the photoreceptor. These chemical changes lead to the production of a receptor potential 2. Bleaching. In about a minute, trans-retinal completely separates from opsin. Retinal is responsible for the color of the photopigment, so the separation of trans-retinal from opsin causes opsin to look colorless. Because of the color change, this part of the cycle is termed bleaching of photopigment. 3. Conversion. An enzyme called retinal isomerase converts trans-retinal back to cis-retinal. 4. Regeneration. The cis-retinal then can bind to opsin, reforming a functional photopigment. This part of the cycle—resynthesis of a photopigment—is called regeneration.

Which of the cells listed below is/are components of the pigmented layer of the retina?

1. amacrine cells 2. bipolar cells 3. cones 4. epithelial cells (correct) 5. rods

Perilymph is located in the

1. scala tympani 2. cochlear duct 3. bony labyrinth of the semicircular ducts 1 and 3

tongue chart

A- vallate papilla B- Fungiform papilla C- Filiform papilla D- Foliate papilla

Crystallins (lens)

Behind the pupil and iris, within the cavity of the eyeball, is the lens. Within the cells of the lens, proteins called crystallins. The lens helps focus images on the retina to facilitate clear vision.

Which of the following are responsible for producing new olfactory receptors?

Bowman's glands basal cells (correct) supporting cells olfactory bulbs

Which of the following statements is correct?

Bowman's glands are located in connective tissue beneath taste buds. Taste buds are found only on the tongue A gustatory hair is a microvillus projecting from each gustatory receptor through a taste pore. (correct) Supporting cells are squamous epithelial cells of the mucous membrane lining the nose. Gustatory receptor cells have a life span of 60 days

Which of the following is a TRUE statement?

Cone pigments regenerate much more slowly than rod pigments. Rhodopsin absorbs blue and green light, retinal absorbs orange and red light, and opsin absorbs yellow light. Rods are involved in color vision. Rods contain three different kinds of photopigments, each of which absorbs light at different wavelengths. The retina contains three different types of cones, each with a different kind of photopigment. (correct)

otholiths

Crystals found in the otholitic membrane of utricle and saccule. the otolithic membrane sits on top of the macula

The optic chiasm is a complete decussation of the left and right optic nerves. T/F

False

Conjunctivitis (pink eye)

Infection/inflammation of the outer lining of the eye, known as the conjunctiva

Which of the following pathways is the correct olfactory pathway? (Some steps may be omitted.)

Olfactory hairs on olfactory receptors are stimulated by an odorant molecule; the impulse travels to olfactory nerves; it moves through olfactory bulbs to the primary olfactory area of cerebral cortex (orbitofrontal area of the frontal lobe).

taste papillae

Projections from the tongue where taste buds are embedded. 12 very large, circular vallate papillae form an inverted V-shaped row at the back of the tongue. Each of these papillae houses 100-300 taste buds. Fungiform papillae are mushroom-shaped elevations scattered over the entire surface of the tongue that contain about five taste buds each. Foliate papillae are located in small trenches on the lateral margins of the tongue, but most of their taste buds degenerate in early childhood. The entire surface of the tongue has filiform papillae These pointed, threadlike structures contain tactile receptors but no taste buds. They increase friction between the tongue and food, making it easier for the tongue to move food in the oral cavity.

Rods and cones specialization

Rods can function in dim light, but cones need good amount of light. Rods are responsible for black and white vision while cones are for color vision.

extrinsic eye muscles

Six extrinsic eye muscles move each eye: the superior rectus, inferior rectus, lateral rectus, medial rectus, superior oblique, and inferior oblique

optic disc

The optic disc is the site where the optic (II) nerve exits the eyeball.

olfactory epithelium

The receptors for the sense of smell or olfaction are located in the olfactory epithelium of the nose. olfactory epithelium consists of three kinds of cells: olfactory receptor cells, supporting cells, and basal cells

Cranial nerves that innervate inner ear

The vestibular nerve innervates the vestibular system of the inner ear, which is responsible for detecting balance. The cochlear nerve travels to cochlea of the inner ear, forming the spiral ganglia which serve the sense of hearing.

Cranial nerves that innervate tastebuds

Three cranial nerves contain axons of the first-order gustatory neurons that innervate the taste buds. The facial (VII) nerve serves taste buds in the anterior two-thirds of the tongue; the glossopharyngeal (IX) nerve serves taste buds in the posterior one-third of the tongue; and the vagus (X) nerve serves taste buds in the throat and epiglottis

Light sensitivities of rods and cones

Three different cone photopigments are present in the retina, one in each of the three types of cones, green cones, and red cones). Color vision results from different colors of light selectively activating the different cone photopigments. The single type of photopigment in rods is rhodopsin. The most common type is red-green color blindness

Sound waves are converted to mechanical energy and transmitted to the inner ear. T/F

True

The lacrimal apparatus assist in protecting cleaning, lubricating, and moistening the eyeball. T/F

True

Vestibular input into the cerebellum provides us with conscious awareness of the position and movements of the head. T/F

True

Lens: divides the interior of the eyeball into two cavities: the anterior cavity and vitreous chamber.

anterior cavity—the space anterior to the lens—consists of two chambers. The anterior chamber lies between the cornea and the iris. The posterior chamber lies behind the iris and in front of the zonular fibers and lens. Both chambers of the anterior cavity are filled with aqueous humor

external ear

auricle (or pinna)-flap of elastic cartilage shaped like the flared end of a trumpet and covered by skin. rim of the auricle is the helix; the inferior portion is the lobule. external acoustic meatus- curved tube about 2.5 cm (1 in.) long that lies in the temporal bone and leads to the eardrum. tympanic membrane- eardrum is a thin, semitransparent partition between the external auditory canal and middle ear. The tympanic membrane is covered by epidermis and lined by simple cuboidal epithelium. Between the epithelial layers is connective tissue composed of collagen, elastic fibers, and fibroblasts. Tearing of the tympanic membrane is called a perforated eardrum. It may be due to pressure from a cotton swab, trauma, or a middle ear infection, and usually heals within a month. The tympanic membrane may be examined directly by an otoscope

There is a white outer covering of the eye known as the

choroid conjunctiva cornea sclera (correct)

When considering the arrangement of rods and cones in the retina, there is a central location where only cones are found. As we move farther away from this point there are increasing amounts of rods and fewer cones so, as some point we are only able to see black and white. This central location of only cones is known as the

choroid posterior chamber optic disc fovea centralis (correct)

Ciliary muscle (in body)

ciliary muscle is a circular band of smooth muscle. Contraction or relaxation of the ciliary muscle changes the tightness of the zonular fibers, which alters the shape of the lens, adapting it for near or far vision.

Which of the following structures is correctly matched with its layer of the eyeball?

ciliary muscle; vascular (correct) optic disc; fibrous iris; inner sclera; retina

Which is NOT part of the vascular tunic of the eye?

ciliary process ciliary body ciliary ganglion (correct) ciliary muscle iris

cataract

common cause of blindness is a loss of transparency of the lens known as a cataract. The lens becomes cloudy (less transparent) due to changes in the structure of the lens proteins. Cataracts often occur with aging but may also be caused by injury, excessive exposure to ultraviolet rays, certain medications (such as long-term use of steroids), or complications of other diseases. sight can usually be restored by surgical removal of the old lens and implantation of a new artificial one.

Correcting myopic and hyperopic vision

concave glasses/convex glasses

Inner ear also called the labyrinth

consists of two main divisions: an outer bony labyrinth that encloses an inner membranous labyrinth. The bony labyrinth is a series of cavities in the petrous portion of the temporal bone divided into three areas: (1) the semicircular canals, (2) the vestibule, and (3) the cochlea. The bony labyrinth is lined with periosteum and contains perilymph. This fluid, which is chemically similar to cerebrospinal fluid, surrounds the membranous labyrinth, a series of epithelial sacs and tubes inside the bony labyrinth that have the same general form as the bony labyrinth and house the receptors for hearing and equilibrium. The epithelial membranous labyrinth contains endolymph. The level of potassium ions (K+) in endolymph is unusually high for an extracellular fluid, and potassium ions play a role in the generation of auditory signals

Pathway of light in eye

cornea, aqueous humor, pupil, lens, vitreous humor, retina, optic nerve

Which structure within the ampulla contains hair cells that are involved in dynamic equilibrium?

cupola macula otolithic membrane crista (correct) vestibular apparatus

The aqueous humor

develops during the embryonic period and is not replaced. is found only in the posterior chamber of the eye. accumulates "floaters" as a person ages. nourishes the cornea and the lens. (correct) holds the retina against the choroid.

Select the correct pathway of sound waves from the auricle to the spiral organ of Corti?

external auditory canal → tympanic membrane → maleus → incus → stapes → oval window → perilymph (correct) external auditory canal → tympanic membrane → stapes → incus → maleus → secondary tympanic membrane → endolymph eustachian tube → tympanic membrane → incus → maleus → stapes → oval window → endolymph internal auditory canal → tympanic membrane → eustachian tube → maleus → incus → stapes → secondary tympanic membrane → perilymph internal auditory canal → tympanic membrane → maleus → incus → stapes → secondary tympanic membrane → Perilymph

There are two structures of the eye which help to focus light on the retina. They are the

iris and cornea cornea and lens (correct) optic disc and lens choroid and iris

Cataracts refer to loss of transparency of the ___.

lens (correct) cornea sclera vitreous body

vascular tunic (eye)

middle layer of the eyeball. It is composed of three parts: choroid, ciliary body, and iris. Melanin in the choroid absorbs stray light rays, which prevents reflection and scattering of light within the eyeball. As a result, the image cast on the retina by the cornea and lens remains sharp and clear. The iris regulates the amount of light entering the eyeball through the pupil. In the anterior portion of the vascular tunic, the choroid becomes the ciliary body it contains melanin-producing melanocytes. ciliary processes contain blood capillaries that secrete aqueous humor.

myopic/Hyperopic vision

nearsightedness, which occurs when the eyeball is too long relative to the focusing power of the cornea and lens, or when the lens is thicker than normal, so an image converges in front of the retina. Myopic individuals can see close objects clearly, but not distant objects./ Farsightedness. the eyeball length is short relative to the focusing power of the cornea and lens, or the lens is thinner than normal, so an image converges behind the retina. Hyperopic individuals can see distant objects clearly, but not close ones

The point of greatest visual acuity is the

optic disk utricle optic chiasm central fovea (correct)

Cones

outnumber rods. function only at low light levels. allow color vision. (correct) are concentrated at the periphery of the retina. are most critical for night vision.

olfactory (I) nerves

pass through the olfactory foramina of the cribriform plate of the ethmoid bone and extend to parts of the brain known as the olfactory bulbs, which contain ball-like arrangements called glomeruli. The sense of smell sleeps as the person sleeps. It is only sense which bypasses thalamus.

An age-related change where an individual has a ringing sensation in the ears is called:

presbyopia cataracts presbycusis tinnitus (correct) glaucoma

The most common type of color blindness is

red-blue color blindness red-green color blindness (correct) blue-green color blindness total color blindness

Axons of which cells make up the optic nerve?

rods and cones bipolar cells amacrine cells ganglion cells (correct) none of these choices

fibrous tunic (eye)

superficial layer of the eyeball and consists of the anterior cornea and posterior sclera. The sclera is the "white" of the eye, is a layer of dense connective tissue made up mostly of collagen fibers and fibroblasts. it gives shape to the eyeball, makes it more rigid, protects its inner parts, and serves as a site of attachment for the extrinsic eye muscles. At the junction of the sclera and cornea is an opening known as the scleral venous sinus or (canal of Schlemm). A fluid called aqueous humor, which will be described later, drains into this sinus

Which of the following is not a primary taste sensation?

sweet salty pungent (correct) bitter

The thin, protective mucous membrane composed of nonkeratinized stratified squamous epithelium with numerous goblet cells that is supported by areolar connective tissue is known as the...

tarsal plate chalazion lacrimal caruncle conjunctiva (correct)

Which of the following does not pertain to the lacrimal apparatus?

tears are produced by the sebaceous glands (correct) tears contain a bactericidal enzyme tears exit the eye vicinity via two small lacrimal puncta lacrimal fluid ultimately ends up in the nasal cavity lacrimal ducts empty tears onto the conjunctiva of the upper lid

The hair cells responsible for hearing are located on the ________; their hair bundles are embedded in the ________

tectorial membrane; tympanic membrane tympanic membrane; basilar membrane basilar membrane; tectorial membrane (correct) vestibular membrane; tectorial membrane basilar membrane; vestibular membrane

vitreous chamber

the main interior portion of the eye, filled with vitreous humor. A transparent jellylike substance that holds the retina flush against the choroid, giving the retina an even surface for the reception of clear images.

The blind spot is the area where

there are more rods than cones there are more cones than rods the optic nerve exits the eye (correct) the iris attaches to the cornea

semicircular canals and cochlea

three bony semicircular canals. named the anterior, posterior, and lateral semicircular canals. help you keep your balance. When your head moves around, the liquid inside the semicircular canals sloshes around and moves the tiny hairs that line each canal. cochlea- a bony spiral canal. divided into three channels: cochlear duct, scala vestibuli, and scala tympani. transform the vibrations of the cochlear liquids and associated structures into a neural signal

Middle ear

three smallest bones in the body, the auditory ossicles malleus, incus, and stapes. The "handle" of the malleus attaches to the internal surface of the tympanic membrane. The head of the malleus articulates with the body of the incus. The incus, the middle bone in the series, articulates with the head of the stapes. The base or footplate of the stapes fits into the oval window. Directly below the oval window is another opening, the round window, which is enclosed by a membrane called the secondary tympanic membrane.

What is the function of the iris?

to provide nutrients to the posterior retina to control the amount of light entering the eye (correct) to convert light to an action potential to focus light on the retina