with exposure to light.
A tumor in the right visual cortex would aﬀect
the lef visual ﬁeld. A tumor compressing the right optic nerve would
aﬀect both the lef and right visual ﬁelds From the right eye only.
ﬁve taste modalities are sweet, sour, bitter, salty, and umami. Te Fun-
giForm, vallate, and Foliate papillae contain taste buds.
Te cilia and
hairs oF these receptor cells greatly increase the surFace area For sensory
Te tympanic membrane separates the external From the
middle ear. Te oval and round windows separate the middle From the
Te basilar membrane allows us to diﬀerentiate sounds oF
You would not be able to locate the origin oF a sound
iF the brain stem did not receive input From both ears.
apply to a macula: “contains otholiths,” “responds to linear acceleration
or deceleration,” and “inside a saccule.” Te Following apply to a crista
ampullaris: “inside a semicircular canal,” “has a cupula,” “responds to
rotational acceleration and deceleration.”
Te “Fullness” in Moham-
med’s ears is likely due to an accumulation oF ﬂuid in the middle ear as
a result oF his upper respiratory inFection (“cold”) spreading into his ear.
He has a Form oF conduction deaFness.
With age, the lens discolors
and loses its clarity and the dilator pupillae muscles become less eﬃcient,
decreasing the amount oF light that reaches the retinas at night.
Review Questions 1.
Case Study 1.
Te ear is divided into three major areas: external ear, mid-
dle ear, and internal ear. Te portion oF the internal ear, or labyrinth, as-
sociated with balance and equilibrium is the part oF the ear aﬀected in Mr.
Maintaining balance and equilibrium requires multiple
sources oF sensory input. Te three main sources oF sensory input are the
vestibular apparatus oF the ear, visual input, and input From the proprio-
ceptors oF the skin, muscles, and joints.
Te two Functional divisions are
the vestibule and semicircular canals. Te vestibule’s sensory receptors are
the maculae, which sense linear (straight line) acceleration and decelera-
tion. Te semicircular canals’ receptors are the cristae ampullares, which
detect rotational acceleration and deceleration.
Mr. Rhen’s vertigo is
brought on by rotational movements oF the head, suggesting that the cris-
tae ampullares oF the semicircular canals are aﬀected.
Te added mass
oF the displaced otoliths pushes on a cupula oF a semicircular canal when
the head is rotated during the Dix-Hallpike maneuver. Te otoliths either
stick to the gelatinous cupula, or swirl through the canals during head
movement and drif against the cupula like snow. In both cases, the bend-
ing oF the cupula is prolonged and vertigo persists. As a result, vestibular
nystagmus is observed when it would ordinarily be absent.
Check Your Understanding 1.
Te endocrine system is more closely
associated with growth and development, and its responses tend to be
long-lasting, whereas nervous system responses tend to be rapid and
Te thyroid and parathyroid glands are Found in the neck.
Hormones are released into the blood and transported throughout
the body, whereas paracrines act locally, generally within the same
Te two major chemical classes oF hormones are amino
acid–based hormones and steroids. Steroids are all lipid soluble. Ty-
roid hormones are the only amino acid–based hormones that are lipid
Water-soluble hormones act on receptors in the plasma
membrane coupled most ofen via regulatory molecules called G pro-
teins to intracellular second messengers. Lipid-soluble hormones act on
intracellular receptors, directly activating genes and stimulating synthe-
sis oF speciﬁc proteins.
Hormone release can be triggered by humoral,
neural, or hormonal stimuli.
Te hypothalamus communicates with
the anterior pituitary via hormones released into a special portal sys-
tem oF blood vessels. In contrast, it communicates with the posterior
oles, stimulates the adrenal medulla to release its hormones, and causes
You would ﬁnd nicotinic receptors on skeletal muscle and
the hormone-producing cells oF the adrenal medulla, but not on smooth
muscle or glands. Virtually all types oF receptors (including nicotinic re-
ceptors) are also Found in the CNS (see ±able 11.3 on p. 415).
integration center oF the ANS is the hypothalamus, although the most di-
rect inﬂuence is through the brain stem reticular Formation and the reﬂex
centers in the pons and medulla oblongata.
Jackson’s doctor may have
prescribed a beta-blocker because Jackson has hypertension. (Chronic
stress is a Factor in causing hypertension.) Te beta-blocker will decrease
blood pressure by blocking beta-adrenergic receptors in the heart, thereby
decreasing heart rate and Force oF contraction, and by decreasing renin
release From the kidneys.
Te neural crest gives rise to both autonomic
ganglia and the adrenal medulla.
Review Questions 1.
(1)S, (2)P, (3)P, (4)S, (5)S, (6)P, (7)P, (8)S,
(9)P, (10)S, (11)P, (12)S;
Case Study 1.
Te location oF Jimmy’s lacerations and bruises and his in-
ability to rise led the paramedics to suspect a head, neck, or back injury.
Tey immobilized his head and torso to prevent any Further damage to
the brain and spinal cord.
Te worsening neurological signs indicate a
probable intracranial hemorrhage. Te blood escaping From the ruptured
blood vessel(s) will begin to compress Jimmy’s brain and increase his
intracranial pressure. Jimmy’s surgery will involve repair oF the damaged
vessel(s) and removal oF the mass oF clotted blood pressing on his brain.
Loss oF motor and sensory Function below the level oF the nipples in-
dicates a lesion at ±
. See ²igure 13.13.
Jimmy is suﬀering From spinal
shock, which occurs as a result oF injury to the spinal cord. Spinal shock
is a temporary condition in which all reﬂex and motor activities caudal
to the level oF spinal cord injury are lost, so Jimmy’s muscles are para-
lyzed. His blood pressure is low due to the loss oF sympathetic tone in his
Jimmy’s exaggerated reﬂexes are caused by damaged up-
per motor neuron axons in the spinal cord. Tese upper motor neurons
normally inhibit spinal reﬂexes. He is incontinent because there are no
longer pathways to support voluntary control oF bowel and bladder emp-
Tis condition is called autonomic dysreﬂexia (or autonomic
hyperreﬂexia). Tis is a condition in which a normal stimulus triggers
a massive activation oF autonomic neurons.
Extremely high arterial
blood pressure can cause a rupture oF the cerebral blood vessels (as well
as other blood vessels in the body) and put Jimmy’s liFe at risk.
Check Your Understanding 1.
±ears (lacrimal ﬂuid) are a dilute sa-
line secretion that contains mucus, antibodies, and lysozyme. Tey are
secreted by the lacrimal glands.
Te blind spot oF the eye is the optic
disc. It is the part oF the retina where the optic nerve exits the eye and it
is “blind” because it is a region oF the retina that lacks photoreceptors.
An increase in intraocular pressure is called glaucoma and is due to
an accumulation oF aqueous humor, usually because oF impaired drain-
age oF the ﬂuid.
Light passes through the cornea, aqueous humor,
lens, vitreous humor, ganglion cells and bipolar cells beFore it reaches
Te ciliary muscles and sphincter pupillae relax
For distant vision. (IF you said the medial rectus muscles also relax, this is
true, but remember that the rectus muscles are extrinsic eye muscles, not
Te near point moves Farther away as you age because the
lens becomes less ﬂexible (presbyopia), so that it is unable to assume the
more rounded shape required For near vision.
Te Following are char-
acteristics oF cones: “vision in bright light,” “color vision,” and “higher
acuity.” Te Following are characteristics oF rods: “only one type oF visual
pigment,” “most abundant in the periphery oF the retina,” “many Feed
into one ganglion cell,” and “higher sensitivity.”
Breakdown oF the
retinal-opsin combination is called bleaching oF the pigment. It occurs