Ch. 15 Special Senses

fibrous layer of the eye

Outermost layer; dense avascular connective tissue Two regions: sclera and cornea

eyebrows

Overlie supraorbital margins Function Shade eye from sunlight Prevent perspiration from reaching eye

lacrimal apparatus

consists of the lacrimal gland and a number of ducts that drain the lacrimal secretions into the nasal cavity

During close vision, what actions must the eye take to bring an object into focus? contract the ciliary body dilate the pupil relax the ciliary body change the curvature of the cornea

contract the ciliary body

What term refers to the eyes moving medially to track items close at hand?

convergence

As light travels through the eye, it passes through several structures or chambers before reaching the retina. Which list below gives those structures in the correct order? cornea, lens, pupil, anterior chamber, posterior segment cornea, pupil, anterior chamber, lens, posterior segment cornea, anterior chamber, pupil, lens, posterior segment cornea, pupil, lens, anterior chamber, posterior segment

cornea, anterior chamber, pupil, lens, posterior segment

Nerve fibers from the medial aspect of each eye ________. pass posteriorly without crossing over at the chiasma cross over to the opposite side at the chiasma go to the superior colliculus only divide at the chiasma, with some crossing and some not crossing

cross over to the opposite side at the chiasma

superior oblique moves [...] and is controlled by

depresses eye and turns it laterally; IV (trochlear)

inferior rectus moves [...] and is controlled by

depresses eye and turns it medially ; III (oculomotor)

strabismus

disorder where external eye muscles rotates eye medially or laterally

inferior oblique moves [...] and is controlled by

elevates eye and turns it laterally; III (oculomotor)

superior rectus moves [...] and is controlled by

elevates eye and turns it medially; III (oculomotor)

levator palpebrae

elevates upper eyelid

orbicularis oculi

encircles the eyelid Closes eyelids; used in blinking, winking, and squinting

Seventy percent of all sensory receptors are located in the ________. skin ears eye nose

eye

lateral rectus moves [...] and is controlled by

eye laterally; VI (abuducens)

accessory structures of the eye

eyebrows, eyelids, conjunctiva, lacrimal apparatus, extrinsic eye muscles

The structure that allows equalization of the pressure in the middle ear with the atmospheric pressure is the external auditory meatus. True or False

false; pharyngotymapnic (auditory) tube is what equalizes the ear pressure

The neural layer of the retina prevents excessive scattering of light within the eye. True or False

false; pigmented layer prevents excessive scattering of light

eyeball consists of three layers

fibrous, vascular, and inner layers

sclera

forming the posterior portion and the bulk of fibrous layer, white and opaque anchoring site for extrinsic eye muscles pierced by the optic nerve (cranial nerve II) and it is continuous with the dura mater of the brain

common tendinous ring (annular ring)

four rectus muscles originate from here at the back of the orbit and run straight to their insertion on the eyeball. superior, inferior, lateral and medial rectus muscles

the internal cavity of the eye contains

humors; fluids that help maintain the eyeball shape

The ability to clearly see objects at a distance but not close up is properly called ________. myopia presbyopia hypopia hyperopia

hyperopia

Which part of the visual pathway is responsible for our daily biorhythms? superior colliculus visual cortex pretectal area suprachiasmatic nucleus

suprachiasmatic nucleus The suprachiasmatic nucleus in the hypothalamus receives innervation from the visual pathways. Exposure to light helps set our daily biorhythms.

inferior oblique muscle

originates from the medial orbit surface and runs laterally and obliquely to insert on the inferolateral eye surface Elevates eye and turns it laterally and is controlled by the oculomotor nerve

eyelids are separated by

palpebral fissure

the extrinsic eye muscles are among the most precisely and [...] controlled skeletal muscles in the entire body

rapidly

lacrimal carnucle

reddish elevation at the medial angle of eye; produces gritty "eye-sand"

You want to look up and to your right. Which extrinsic eye muscles would be the most active in each eye? right eye: superior oblique left eye: superior rectus right eye: superior rectus left eye: superior rectus right eye: inferior oblique left eye: superior rectus right eye: superior rectus left eye: inferior oblique

right eye: inferior oblique left eye: superior rectus The right eye requires both elevation and lateral movement. The inferior oblique would accomplish both of these. The left eye requires both elevation and medial movement. The superior rectus, because it approaches the eye from the medial side, turns the eye medially as it elevates.

tarsal glands

secretors of an oily substance; located in the eyelids lubricates eye and eyelid prevents eyelid from sticking together

special senses

vision, hearing, taste, smell, equilibrium

tarsal plates

connective tissue within the eyelids

only the anterior [...] of the eye is visible

1/6th

hyperopia

A condition in which visual images come to a focus behind the retina of the eye and vision is better for distant than for near objects -- called also farsightedness.

Color vision has much greater resolution than night vision (vision that is mostly in shades of gray). Which of the following is the best explanation for why this is so? A larger proportion of the brain's visual cortex is active during the day when our cone photoreceptors are most active. A single cone photoreceptor often connects to a single bipolar cell and a single ganglion cell while as many as 100 rods will converge to a single ganglion cell. There are many more cone photoreceptors in the eye than rod photoreceptors. There are several types of cone photoreceptors, each of which enrich the clarity and resolution of vision.

A single cone photoreceptor often connects to a single bipolar cell and a single ganglion cell while as many as 100 rods will converge to a single ganglion cell.

special sensory receptors

Are distinct receptor cells localized in the head region

superior oblique muscle

Depresses eye and turns it laterally and is controlled by the trochlear nerve.

Choose the FALSE statement about the olfactory epithelium.' It is coated with mucus at the air interface. It is located in the roof of the nasal cavity. It is made of simple squamous epithelium. It contains olfactory sensory neurons.

It is made of simple squamous epithelium. The olfactory epithelium is made of pseudostratified (not simple squamous) epithelium.

Paralysis of which eye muscle would prevent the right eye from looking to the left? Superior rectus Medial rectus Inferior rectus Lateral rectus

Medial rectus

Eyelids (palpebrae)

Protection, Shade eyes for sleep, Spread lubricant, Anchor orbicularis oculi

Which of the following is true about photoreceptors? Three types of color-sensitive photoreceptors exist: red, green, and yellow. Rods absorb light throughout the visual spectrum but confer only gray tone vision. In dim light, images are focused directly on the rods in the fovea centralis. If all cones are stimulated equally, all colors are absorbed by the cones and the color perceived is black.

Rods absorb light throughout the visual spectrum but confer only gray tone vision.

extrinsic eye muscles

Six muscles attach to the outer surface of the eye and produce eye movements

Which of the following is a characteristic of the lens? The lens focuses light on the retina. The lens of the human eye has a concave shape. In a healthy eye, the lens will be opaque. The lens is vascularized.

The lens focuses light on the retina. The lens is a biconvex, transparent, flexible structure that can change shape to precisely focus light on the retina. It is enclosed in a thin, elastic capsule and held in place just posterior to the iris by the ciliary zonule. Like the cornea, the lens is avascular; blood vessels interfere with transparency.

nyctalopia

a condition in which an individual with normal daytime vision has difficulty seeing at night; also known as night blindness

In a person who is color-blind, which of the following would you most expect to see? a loss of functions in the rods of their retina a loss of their peripheral vision absence of green or red cones in their foveae an inability to regenerate 11-cis-retinal after bleaching

absence of green or red cones in their foveae

cornea

anterior sixth of the fibrous layer, lets light enter the eye, bulges anteriorly from its junction with sclera epithelial sheet covers both faves of the cornea: - external sheet, stratified squamous to protect from abrasion - deep corneal endothelium composed of simple squamous epithelium lines the inner face of the cornea contains active sodium pumps to keep water level low

intrinsic eye muscles

ciliary body and the iris - controlled by autonomic nervous system

Dark adaptation ________. is much faster than light adaptation involves accumulation of rhodopsin primarily involves improvement of acuity and color vision results in inhibition of rod function

involves accumulation of rhodopsin

What structure regulates the amount of light passing to the visual receptors of the eye? iris lens cornea aqueous humor

iris

Damage to the medial portion of the optic chiasm, cause by a pituitary tumor, would lead to __________. loss of peripheral vision blindness in the left half of the visual field loss of central vision blindness in the right half of the visual field

loss of peripheral vision If you look at the diagram of the visual pathway on page 568, images from your right peripheral visual field land on the left medial retina and vice versa. The ganglion cells from the medial retina of each retina cross over at the optic chiasm. If there were damage at the medial portion of the chiasm, it would block the flow of this peripheral field of view.

bulbar conjunctiva

membrane that covers white of eyes (not cornea) Small blood vessels found in this membrane; seen easily in "bloodshot" eyes

ciliary glands

modified sweat glands between the eyelashes

medical recuts moves [...] and is controlled by

moves eye medially; III (oculomotor)

conjunctiva

mucous membrane that lines the eyelids and outer surface of the eyeball lines the eyelids as the palpebral conjunctiva and folds back over the anterior surface of the eyeball as the bulbar conjunctiva

lacrimal fluid contains

mucus, antibodies, and lysozyme

orbicularis and levator palpebrae superiorsis

muscles that run within the eyelid

myopia

nearsighted

Conscious perception of vision probably reflects activity in the ________. thalamus occipital lobe of the cortex superior colliculus chiasma

occipital lobe of the cortex

Which of the following could NOT be seen as one looks into the eye with an ophthalmoscope? optic chiasma fovea central ismacula lutea optic disc

optic chiasma

diplopia

the perception of two images of a single object; also known as double vision

suprachiasmatic nucleus

timer for daily biorhythms a pair of cell clusters in the hypothalamus that responds to light-sensitive retinal proteins; causes pineal gland to increase or decrease production of melatonin, thus modifying our feelings of sleepiness

conjunctival sac major function

to produce lubricating mucus hat prevents the eye from drying out. where the contact lens lies and eye medication is often administered

Which of the following nerves would you predict is NEVER involved in the development of strabismus? oculomotor (III) trochlear (IV) trigeminal (V) abducens (VI)

trigeminal (V) Strabismus is a condition in which the eyes lack normal alignment, usually due to a lack of control of the extraocular muscles. This nerve functions as the major sensory nerve of the face but also controls the blink reflex. It does not control any of the extraocular eye muscles.

Light passes through the entire thickness of the neural layer of the retina to excite the photoreceptors. True or False

true