AEROSPACE PHYSIOLOGY EXAM
COMPLETE QUESTIONS WITH
VERIFIED ANSWERS
\.Identify which gases are present in the atmosphere and their associated
percentage of the total composition. - ANSWERS-78 percent nitrogen,
21 percent oxygen
1 percent other gases
(including 0.03 percent carbon dioxide). These percentages remain relatively
constant with increased altitude.
\.Recognize the functions of the atmosphere. - ANSWERS-The atmosphere
provides some unique functions that help sustain our existence on Earth.
1. It contains oxygen, essential for animal life and carbon dioxide, essential for
plant life.
2. It is a shield that attenuates cosmic and ultraviolet radiation.
3. Precipitation occurs in the atmosphere, helping maintain the temperature and
climate.
\.Recall the common units of measurement for atmospheric pressure. - ANSWERS-
The weight of the atmosphere can be measured in pounds per square inch (psi),
millimeters of mercury (mmHg), or inches of mercury (inHg). Atmospheric
,pressure readings will vary daily, depending on changing surface temperatures
and high and low pressure areas.
\.Recognize the description and common unit of measure of the U.S. Standard
Atmosphere. - ANSWERS-U.S. Standard Atmosphere was computed by taking the
average pressure and temperature readings for a year at mid-latitude locations. At
sea level, these readings were determined to be +15 °C and 760 mmHg (29.92
inHg) pressure. Figure 1-2 shows the U.S. Standard Atmosphere pressures at
various altitudes. The pressure at 18,000 feet is 379.4 or about one half of the
pressure encountered at sea level. This illustrates that the greatest pressure
change occurs at lower atmospheric levels between sea level and 18,000 feet.
\.Dalton's Law - ANSWERS-The total pressure of a mixture of gases is equal to the
sum of the partial pressures of each gas in the mixture. The pressure exerted by
each gas in a mixture is independent of other gases in the mixture. For example,
the total pressure of the atmosphere at sea level is 760 mmHg this pressure
equals PN2 + PO2 + PCO2 and the partial pressure of other trace gases.
Dalton's Law explains how exposure to a high ambient altitude can reduce the
available oxygen. As ambient altitude increases, the partial pressure of oxygen
(PO2) decreases even though the percentage of oxygen remains the same. For
example, at sea level the PO2 is 21 percent of 760 mmHg or 160 mmHg.
Correspondingly, with a reduction of total pressure, the partial pressure of each
gas will decrease. At 18,000 feet, PO2 is 21 percent of 380 mmHg or 80 mmHg.
\.Boyle's Law - ANSWERS-Boyle's Law
When the temperature remains constant, as in the human body, a volume of gas is
inversely proportional to the pressure surrounding it. This principle explains why a
balloon expands as it ascends and also why a volume of air expands when trapped
in a body cavity when the pressure is reduced around it. Boyle's Law explains for
, the effects of pressure changes in the ears, sinuses, teeth and gastrointestinal
tract.
\.Henry's Law - ANSWERS-Henry's Law
The amount of gas in a solution varies directly with the partial pressure of that gas
over the solution. Therefore, if pressure is reduced above the solution, some gas
will come out of solution. This principle explains why carbon dioxide bubbles are
released when a carbonated beverage container is opened or why nitrogen
bubbles may come out of solution in body tissues during ascent. The nitrogen
bubbles can lead to altitude-induced decompression sickness.
\.List the physiological divisions of the atmosphere. - ANSWERS-Physiological Zone
The physiological zone extends from sea level to approximately 10,000 feet and is
the zone the human body is adapted to. Life above this zone requires considerable
acclimatization. During ascent in the physiological zone, atmospheric pressure
drops from 760 mmHg to 523 mmHg. Even though the oxygen partial pressure
(PO2) falls, the body's compensatory mechanisms keep oxygen delivery within
normal limits. Only at the upper boundary of the physiological zone and in tissues
with very high O2 requirements, e.g., the retina, are symptoms of O2 deficiency
noted. When flying unpressurized above 10,000 feet MSL, the use of
supplemental oxygen is required. Also, trapped gas problems in body cavities can
be a problem if not dealt with effectively.
Physiological Deficient Zone
This zone extends from approximately 10,000 feet to approximately 50,000 feet.
Because of reduced atmospheric pressure, inadequate oxygen is available to
sustain normal physiologic functions. Also, decompression sickness (caused by
evolved gas) can occur in the body tissues and joints. This phenomena will be
covered in later chapters. Atmospheric pressure decreases from 523 mmHg at
10,000 feet to 87 mmHg at 50,000 feet. Pressure suits are required above FL500.
COMPLETE QUESTIONS WITH
VERIFIED ANSWERS
\.Identify which gases are present in the atmosphere and their associated
percentage of the total composition. - ANSWERS-78 percent nitrogen,
21 percent oxygen
1 percent other gases
(including 0.03 percent carbon dioxide). These percentages remain relatively
constant with increased altitude.
\.Recognize the functions of the atmosphere. - ANSWERS-The atmosphere
provides some unique functions that help sustain our existence on Earth.
1. It contains oxygen, essential for animal life and carbon dioxide, essential for
plant life.
2. It is a shield that attenuates cosmic and ultraviolet radiation.
3. Precipitation occurs in the atmosphere, helping maintain the temperature and
climate.
\.Recall the common units of measurement for atmospheric pressure. - ANSWERS-
The weight of the atmosphere can be measured in pounds per square inch (psi),
millimeters of mercury (mmHg), or inches of mercury (inHg). Atmospheric
,pressure readings will vary daily, depending on changing surface temperatures
and high and low pressure areas.
\.Recognize the description and common unit of measure of the U.S. Standard
Atmosphere. - ANSWERS-U.S. Standard Atmosphere was computed by taking the
average pressure and temperature readings for a year at mid-latitude locations. At
sea level, these readings were determined to be +15 °C and 760 mmHg (29.92
inHg) pressure. Figure 1-2 shows the U.S. Standard Atmosphere pressures at
various altitudes. The pressure at 18,000 feet is 379.4 or about one half of the
pressure encountered at sea level. This illustrates that the greatest pressure
change occurs at lower atmospheric levels between sea level and 18,000 feet.
\.Dalton's Law - ANSWERS-The total pressure of a mixture of gases is equal to the
sum of the partial pressures of each gas in the mixture. The pressure exerted by
each gas in a mixture is independent of other gases in the mixture. For example,
the total pressure of the atmosphere at sea level is 760 mmHg this pressure
equals PN2 + PO2 + PCO2 and the partial pressure of other trace gases.
Dalton's Law explains how exposure to a high ambient altitude can reduce the
available oxygen. As ambient altitude increases, the partial pressure of oxygen
(PO2) decreases even though the percentage of oxygen remains the same. For
example, at sea level the PO2 is 21 percent of 760 mmHg or 160 mmHg.
Correspondingly, with a reduction of total pressure, the partial pressure of each
gas will decrease. At 18,000 feet, PO2 is 21 percent of 380 mmHg or 80 mmHg.
\.Boyle's Law - ANSWERS-Boyle's Law
When the temperature remains constant, as in the human body, a volume of gas is
inversely proportional to the pressure surrounding it. This principle explains why a
balloon expands as it ascends and also why a volume of air expands when trapped
in a body cavity when the pressure is reduced around it. Boyle's Law explains for
, the effects of pressure changes in the ears, sinuses, teeth and gastrointestinal
tract.
\.Henry's Law - ANSWERS-Henry's Law
The amount of gas in a solution varies directly with the partial pressure of that gas
over the solution. Therefore, if pressure is reduced above the solution, some gas
will come out of solution. This principle explains why carbon dioxide bubbles are
released when a carbonated beverage container is opened or why nitrogen
bubbles may come out of solution in body tissues during ascent. The nitrogen
bubbles can lead to altitude-induced decompression sickness.
\.List the physiological divisions of the atmosphere. - ANSWERS-Physiological Zone
The physiological zone extends from sea level to approximately 10,000 feet and is
the zone the human body is adapted to. Life above this zone requires considerable
acclimatization. During ascent in the physiological zone, atmospheric pressure
drops from 760 mmHg to 523 mmHg. Even though the oxygen partial pressure
(PO2) falls, the body's compensatory mechanisms keep oxygen delivery within
normal limits. Only at the upper boundary of the physiological zone and in tissues
with very high O2 requirements, e.g., the retina, are symptoms of O2 deficiency
noted. When flying unpressurized above 10,000 feet MSL, the use of
supplemental oxygen is required. Also, trapped gas problems in body cavities can
be a problem if not dealt with effectively.
Physiological Deficient Zone
This zone extends from approximately 10,000 feet to approximately 50,000 feet.
Because of reduced atmospheric pressure, inadequate oxygen is available to
sustain normal physiologic functions. Also, decompression sickness (caused by
evolved gas) can occur in the body tissues and joints. This phenomena will be
covered in later chapters. Atmospheric pressure decreases from 523 mmHg at
10,000 feet to 87 mmHg at 50,000 feet. Pressure suits are required above FL500.
