BIO 212 Study Guide - Summer 2018, Comprehensive Midterm Notes -
12 Oct 2018
School
Department
Course
Professor
BIO 212
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Respiratory Physiology Summary
• Lung volumes and capacities are measured with a spirometer (except for
those volumes and capacities that include the residual volume).
Dead space is the volume of the airways and lungs that does not
participate in gas exchange.
Anatomic dead space is the volume of conducting airways.
Physiologic dead space includes the anatomic dead space plus those
regions of the respiratory zone that do not participate in gas
exchange.
• The alveolar ventilation equation expresses the inverse relationship
between PACO2 and alveolar ventilation. The alveolar gas equation
extends this relationship to predict PAO2.
• In quiet breathing, respiratory muscles (diaphragm) are used only for
inspiration; expiration is passive.
• Compliance of the lungs and the chest wall is measured as the slope of
the pressure-volume relationship. As a result of their elastic forces, the
chest wall tends to spring out and the lungs tend to collapse. At FRC,
these two forces are exactly balanced and intra pleural pressure is
negative.
Compliance of the lungs increases in emphysema and with aging.
Compliance decreases in fibrosis and when pulmonary surfactant is
absent.
• Surfactant, a mixture of phospholipids produced by type II alveolar
cells, reduces surface tension so that the alveoli can remain inflated
despite their small radii.
Neonatal respiratory distress syndrome occurs when surfactant is
absent.
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• Airflow into and out of the lungs is driven by the pressure gradient
between the atmosphere and the alveoli and is inversely proportional
to the resistance of the airways.
Stimulation of β2-adrenergic receptors dilates the airways, and
stimulation of cholinergic muscarinic receptors constricts the
airways.
• Diffusion of O2 and CO2 across the alveolar/pulmonary capillary barrier
is governed by Fick’s law and driven by the partial pressure
difference of the gas. Mixed venous blood enters the pulmonary
capillaries and is “arterialized” as O2 is added to it and CO2 is removed
from it. Blood leaving the pulmonary capillaries will become systemic
arterial blood.
• Diffusion-limited gas exchange is illustrated by CO and by O2 in
fibrosis or strenuous exercise.
Perfusion-limited gas exchange is illustrated by N2O, CO2, and O2 under
normal conditions.
• O2 is transported in blood in dissolved form and bound to hemoglobin.
One molecule of hemoglobin can bind four molecules of O2. The
sigmoidal shape of the O2-hemoglobin dissociation curve reflects
increased affinity for each successive molecule of O2 that is bound.
Shifts to the right of the O2-hemoglobin dissociation curve are
associated with decreased affinity, increased P50, and increased
unloading of O2 in the tissues.
Shifts to the left are associated with increased affinity, decreased P50, and
decreased unloading of O2 in the tissues. CO decreases the O2-binding
capacity of hemoglobin and causes a shift to the left.
• CO2 is transported in blood in dissolved form, as carbaminohemoglobin,
and as HCO3−. HCO3− is produced in red blood cells from CO2 and H2O,
catalyzed by carbonic anhydrase. HCO3− is transported in the plasma to
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