846
UNIT 4
Maintenance of the Body
3.
In emphysema, alveoli enlarge permanently and disintegrate.
Te lungs lose their elasticity, and expiration becomes an active
process.
4.
Chronic bronchitis is characterized by excessive mucus
production in the lower respiratory passageways, which severely
impairs ventilation and gas exchange.
Asthma
(p. 840)
5.
Asthma is a reversible obstructive condition caused by an
immune response that causes its victims to wheeze and gasp for
air as their inflamed respiratory passages constrict. It is marked
by acute episodes and symptom-free periods.
Tuberculosis (TB)
(pp. 840–841)
6.
±uberculosis, an infectious disease caused by an airborne
bacterium, mainly affects the lungs. Although most infected
individuals remain asymptomatic by walling off the bacteria
in nodules (tubercles), symptoms appear when immunity is
depressed. Some patients’ failure to complete drug therapy has
produced multidrug-resistant ±B strains.
Lung Cancer
(p. 841)
7.
Lung cancer, promoted by free radicals and other carcinogens, is
extremely aggressive and metastasizes rapidly.
Developmental Aspects of the Respiratory System
(pp. 841–844)
1.
Te superior respiratory system mucosa develops from the
invagination of the ectodermal olfactory placodes. Te mucosa
of the inferior passageways develops from an outpocketing of
the endodermal foregut lining. Mesoderm forms the walls of the
respiratory conduits and the lung stroma.
2.
Cystic fibrosis (CF), the most common fatal hereditary disease in
North America, results from an abnormal CF±R protein that fails
to form a chloride channel. Te result is thick mucus, which clogs
respiratory passages and invites infection.
3.
With age, the thorax becomes more rigid, the lungs become
less elastic, and vital capacity declines. In addition, sleep apnea
becomes more common, and respiratory system protective
mechanisms are less effective.
5.
Hypocapnia depresses respiration and results in decreased
ventilation and, possibly, apnea.
6.
Arterial P
O
2
levels below 60 mm Hg strongly stimulate peripheral
chemoreceptors.
7.
Decreased pH and a decline in blood P
O
2
act on peripheral
chemoreceptors and enhance the response to CO
2
.
8.
Emotions, pain, body temperature changes, and other stressors
can alter respiration by acting through hypothalamic centers.
Respiration can also be controlled voluntarily for short periods.
9.
Dust, mucus, fumes, and pollutants initiate pulmonary irritant
reflexes.
10.
Te inflation (Hering-Breuer) reflex is a protective reflex initiated
by extreme overinflation of the lungs; it acts to terminate
inspiration.
Respiratory System; Topic: Control of Respiration, pp. 6–14.
Respiratory Adjustments
(pp. 838–839)
Exercise
(p. 838)
1.
As exercise begins, there is an abrupt increase in ventilation
(hyperpnea) followed by a more gradual increase. When exercise
stops, there is an abrupt decrease in ventilation followed by a
gradual decline to baseline values.
2.
P
O
2
, P
CO
2
, and blood pH remain quite constant during exercise
and hence do not appear to account for changes in ventilation.
Inputs from higher centers and proprioceptors may contribute.
High Altitude
(pp. 838–839)
3.
At high altitudes, arterial P
O
2
and hemoglobin saturation levels fall
because of the decrease in atmospheric pressure compared to sea
level. Increased ventilation helps restore P
O
2
to physiological levels.
4.
Long-term acclimatization involves increased erythropoiesis.
Homeostatic Imbalances of the Respiratory
System
(pp. 839–841)
1.
±wo major respiratory disorders are COPD (emphysema and
chronic bronchitis) and lung cancer; smoking is a significant
cause. A third major disorder is asthma. Multidrug-resistant
tuberculosis may become a major public health problem.
Chronic Obstructive Pulmonary Disease
(pp. 839–840)
2.
COPD is characterized by an irreversible decrease in the ability to
force air out of the lungs.
Multiple Choice/Matching
(Some questions have more than one correct answer. Select the best
answer or answers from the choices given.)
1.
Cutting the phrenic nerves will result in
(a)
air entering the
pleural cavity,
(b)
paralysis of the diaphragm,
(c)
stimulation of
the diaphragmatic reflex,
(d)
paralysis of the epiglottis.
2.
Which of the following laryngeal cartilages is/are not paired?
(a)
epiglottis,
(b)
arytenoid,
(c)
cricoid,
(d)
cuneiform,
(e)
corniculate.
3.
Under ordinary circumstances, the inflation reflex is initiated
by
(a)
noxious chemicals,
(b)
the ventral respiratory group,
(c)
overinflation of the alveoli and bronchioles,
(d)
the pontine
respiratory centers.
4.
Te detergent-like substance that keeps the alveoli from
collapsing between breaths because it reduces the surface tension
of the water film in the alveoli is called
(a)
lecithin,
(b)
bile,
(c)
surfactant,
(d)
reluctant.
5.
Which of the following determines the direction of gas
movement?
(a)
solubility in water,
(b)
partial pressure gradient,
(c)
temperature,
(d)
molecular weight and size of the gas
molecule.
6.
When the inspiratory muscles contract,
(a)
the size of the
thoracic cavity increases in diameter,
(b)
the size of the thoracic
cavity increases in length,
(c)
the volume of the thoracic cavity
decreases,
(d)
the size of the thoracic cavity increases in both
length and diameter.
Review Questions
22
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