588
UNIT 3
Regulation and Integration of the Body
becomes the retina. Overlying ectoderm folds to form the lens
vesicle, which gives rise to the lens. Te remaining eye tissues and
the accessory structures are formed by mesenchyme.
4.
Te eye is foreshortened at birth and reaches adult size at the age of
8–9 years. Depth perception and color vision develop before age 3.
5.
With age, the lens loses its elasticity and clarity, there is a decline
in the ability of the iris to dilate, and visual acuity decreases. Te
elderly are at risk for eye problems resulting from dry eyes and
disease.
Hearing and Balance
(p. 585)
6.
Te membranous labyrinth develops from the otic placode, an
ectodermal thickening lateral to the hindbrain. Mesenchyme
forms the surrounding bony structures. Pharyngeal pouch
endoderm, in conjunction with mesenchyme, forms most
middle ear structures; the external ear is formed largely by
ectoderm.
7.
Congenital ear problems are fairly common. Maternal rubella can
cause deafness.
8.
Response to sound in infants is reflexive. By the fourth month, an
infant can locate sound. Critical listening develops in toddlers.
9.
Te spiral organ deteriorates throughout life as noise, disease,
and drugs destroy cochlear hair cells. Age-related loss of hearing
(presbycusis) occurs in the 60s and 70s.
the cerebellum. Tese centers initiate responses that fix the eyes
on objects and activate muscles to maintain balance.
Homeostatic Imbalances of Hearing and Equilibrium
(p. 584)
17.
Conduction deafness results from interference with conduction
of sound vibrations to the fluids of the internal ear. Sensorineural
deafness reflects damage to neural structures.
18.
±innitus is an early sign of sensorineural deafness; it may also
result from inflammation or certain drugs.
19.
Ménière’s syndrome is a disorder of the membranous labyrinth.
Symptoms include tinnitus, deafness, and vertigo. Excessive
endolymph accumulation is the suspected cause.
Developmental Aspects of the Special Senses
(pp. 584–585)
Taste and Smell
(pp. 548–585)
1.
Te chemical senses are sharpest at birth and gradually decline
with age as receptor cells are replaced more slowly.
Vision
(p. 585)
2.
Congenital eye problems are uncommon, but maternal rubella
can cause blindness.
3.
Te eye starts as an optic vesicle, an outpocketing of the
diencephalon that invaginates to form the optic cup, which
Multiple Choice/Matching
(Some questions have more than one correct answer. Select the best
answer or answers from the choices given.)
1.
Accessory glands that produce an oily secretion are the
(a)
conjunctiva,
(b)
lacrimal glands,
(c)
tarsal glands.
2.
Te portion of the fibrous layer that is white and opaque is the
(a)
choroid,
(b)
cornea,
(c)
retina,
(d)
sclera.
3.
Which sequence best describes a normal route for the flow of
tears from the eyes into the nasal cavity?
(a)
lacrimal canaliculi,
lacrimal sacs, nasolacrimal ducts;
(b)
lacrimal ducts, lacrimal
canaliculi, nasolacrimal ducts;
(c)
nasolacrimal ducts, lacrimal
canaliculi, lacrimal sacs.
4.
Activation of the sympathetic nervous system causes
(a)
contraction of the sphincter pupillae muscles,
(b)
contraction
of the dilator pupillae muscles,
(c)
contraction of the ciliary
muscles,
(d)
a decrease in ciliary zonule tension.
5.
Damage to the medial recti muscles would probably affect
(a)
accommodation,
(b)
refraction,
(c)
convergence,
(d)
pupil
constriction.
6.
Te phenomenon of dark adaptation is best explained by the fact
that
(a)
rhodopsin does not function in dim light,
(b)
rhodopsin
breakdown occurs slowly,
(c)
rods exposed to intense light need
time to generate rhodopsin,
(d)
cones are stimulated to function
by bright light.
7.
Blockage of the scleral venous sinus might result in
(a)
a sty,
(b)
glaucoma,
(c)
conjunctivitis,
(d)
a cataract.
8.
Nearsightedness is more properly called
(a)
myopia,
(b)
hyperopia,
(c)
presbyopia,
(d)
emmetropia.
9.
Of the neurons in the retina, the axons of which of these form the
optic nerve?
(a)
bipolar cells,
(b)
ganglion cells,
(c)
cone cells,
(d)
horizontal cells.
10.
Which sequence of reactions occurs when a person looks at a
distant object?
(a)
pupils constrict, ciliary zonule (suspensory
ligament) relaxes, lenses become less convex;
(b)
pupils dilate,
ciliary zonule becomes taut, lenses become less convex;
(c)
pupils
dilate, ciliary zonule becomes taut, lenses become more convex;
(d)
pupils constrict, ciliary zonule relaxes, lenses become more
convex.
11.
During embryonic development, the lens of the eye forms
(a)
as part of the choroid coat,
(b)
from the surface ectoderm
overlying the optic cup,
(c)
as part of the sclera,
(d)
from
mesodermal tissue.
12.
Te blind spot of the eye is
(a)
where more rods than cones are
found,
(b)
where the macula lutea is located,
(c)
where only cones
occur,
(d)
where the optic nerve leaves the eye.
13.
Olfactory tract damage would probably affect your ability to
(a)
see,
(b)
hear,
(c)
feel pain,
(d)
smell.
14.
Sensory impulses transmitted over the facial, glossopharyngeal,
and vagus nerves are involved in the sensation of
(a)
taste,
(b)
touch,
(c)
equilibrium,
(d)
smell.
15.
±aste buds are found on the
(a)
anterior part of the tongue,
(b)
posterior part of the tongue,
(c)
palate,
(d)
all of these.
16.
Gustatory epithelial cells are stimulated by
(a)
movement of
otoliths,
(b)
stretch,
(c)
substances in solution,
(d)
photons of
light.
17.
Cells in the olfactory bulb that act as local “integrators” of
olfactory inputs are the
(a)
hair cells,
(b)
amacrine granule cells,
(c)
olfactory stem cells,
(d)
mitral cells,
(e)
supporting cells.
18.
Olfactory nerve filaments are found
(a)
in the optic bulbs,
(b)
passing through the cribriform plate of the ethmoid bone,
(c)
in the optic tracts,
(d)
in the olfactory cortex.
19.
Conduction of sound from the middle ear to the internal ear
occurs via vibration of the
(a)
malleus against the tympanic
Review Questions
15
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