484
Chapter 13
Chapter 13 Answers to Physiological Inquiries
Figure 13–23
The increase in cardiac output with exercise greatly
increases pulmonary blood fl ow and decreases the amount of
time erythrocytes are exposed to increased oxygen from the
alveoli. In a normal region of the lung, there is a large safety
factor such that a large increase in blood fl
ow still allows normal
oxygen uptake. However, even small increases in the rate of
capillary blood fl ow in a diseased portion of the lung will
decrease oxygen uptake due to a loss of this safety factor.
Figure 13–29
Less O
2
will be unloaded in peripheral tissue as the
blood is exposed to increased
P
CO
2
and decreased pH because
the oxygen dissociation curve will not shift to the right as it
does in real blood. Also, less O
2
will be loaded in the lungs as
P
CO
2
diffuses from blood into the alveoli because the oxygen
dissociation curve will not shift to the left as it normally would
with removal of CO
2
and decreased acidity.
Figure 13–43
These receptors might facilitate the increase
in alveolar ventilation that occurs during exercise because
pulmonary artery
P
O
2
will decrease and pulmonary artery
P
CO
2
will increase.
Figure 13–13
P
tp
P
alv
P
ip
(
P
alv
P
ip
)
Change in Lung Volume
1
0
–4
4
>
P
tp
is increasing
lung volume
2
–1
–6
5
>
P
tp
is increasing
lung volume
3
0
–7
7
>
P
tp
is decreasing
lung volume
4
1
–5
6
>
P
tp
is decreasing
lung volume
1
0
–4
4
Note: The actual volume increase or decrease in ml is
determined by the compliance of the lung (see Figure 13 –16).
Figure 13–16
Anything that increases
P
tp
during inspiration will,
theoretically, increase lung volume. This can be done with
positive airway pressure generated by mechanical ventilation,
which will increase
P
alv
. This approach can work but also
increases the risk of pneumothorax by inducing air leaks from
the lung into the intrapleural space.
4. Why must a person fl oating on the surface of the water and
breathing through a snorkel increase his tidal volume and/or
breathing frequency if alveolar ventilation is to remain normal?
5. A healthy person breathing room air voluntarily increases alveolar
ventilation twofold and continues to do so until reaching new
steady-state alveolar gas pressures for oxygen and carbon dioxide.
Are the new values higher or lower than normal?
6. A person breathing room air has an alveolar
P
O
2
of 105 mmHg
and an arterial
P
O
2
of 80 mmHg. Could hypoventilation due to,
say, respiratory muscle weakness produce these values?
7. A person’s alveolar membranes have become thickened enough
to moderately decrease the rate at which gases diffuse across
them at any given partial pressure differences. Will this person
necessarily have a low arterial
P
O
2
at rest? During exercise?
8. A person is breathing 100 percent oxygen. How much will the
oxygen content (in milliliters per liter of blood) of the arterial
blood increase compared to when the person is breathing
room air?
9. Which of the following have higher values in systemic venous
blood than in systemic arterial blood: plasma
P
CO
2
, erythrocyte
P
CO
2
, plasma bicarbonate concentration, erythrocyte
bicarbonate concentration, plasma hydrogen ion concentration,
erythrocyte hydrogen ion concentration, erythrocyte
carbamino concentration?
10. If the spinal cord were severed where it joins the brainstem,
what would happen to respiration?
11. Which inspired gas mixture leads to the largest increase in
minute ventilation?
a. 10% O
2
/ 5% CO
2
b. 100% O
2
/ 5% CO
2
c. 21% O
2
/ 5% CO
2
d. 10% O
2
/ 0% CO
2
e. 0.1% CO / 5% CO
2
12. Patients with severe uncontrolled diabetes mellitus produce
large quantities of certain organic acids. Can you predict the
ventilation pattern in these patients and whether their arterial
P
O
2
and
P
CO
2
would increase or decrease?
13. Why does an inspired O
2
of 100 percent increase arterial
P
O
2
much more in a patient with ventilation-perfusion mismatch
than in a patient with pure anatomical shunt?
previous page 512 Vander's Human Physiology The Mechanisms of Body Function read online next page 514 Vander's Human Physiology The Mechanisms of Body Function read online Home Toggle text on/off