48.1
What Physical Factors Govern Respiratory
Gas Exchange? 1025
Diffusion is driven by concentration
differences 1025
Fick’s law applies to all systems
of gas exchange 1026
Air is a better respiratory medium
than water 1026
High temperatures create respiratory
problems for aquatic animals 1026
O2 availability decreases with altitude
1026
CO2 is lost by diffusion 1027
48.2 What Adaptations Maximize Respiratory
Gas Exchange? 1028
Respiratory organs have large surface
areas 1028
Transporting gases to and from the
exchange surfaces optimizes partial
pressure gradients 1028
Insects have airways throughout their
bodies 1028
Fish gills use countercurrent flow
to maximize gas exchange 1029
Birds use unidirectional ventilation
to maximize gas exchange 1030
Tidal ventilation produces dead space
that limits gas exchange efficiency
1031
48.3
How Do Human Lungs Work? 1032
Respiratory tract secretions aid ventilation
1034
Lungs are ventilated by pressure changes
in the thoracic cavity 1034
48.4 How Does
Blood Transport Respiratory Gases?
1036
Hemoglobin combines reversibly with
oxygen 1036
Myoglobin holds an oxygen reserve
1037
The affinity of hemoglobin for oxygen
is variable 1037
Carbon dioxide is transported as bicarbonate
ions in the blood 1038
48.5
How is Breathing Regulated? 1039
Breathing is controlled in the brain
stem 1039
Regulating breathing requires feedback
information 1039
