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