When you hold your breath the urge to inhale first results from
1. rising PCO₂
2. falling PCO₂
3. rising PO₂
4. falling PO₂

The conversion of carbon dioxide into carbonic acid in the red blood cells is catalyzed by the enzyme:

The efficiency of a respiratory system is enhanced by all the following except:

The most efficient respiratory system amongst the following would be:
1. mammal lungs
2. reptile lungs
3. bird lungs
4. fish gills

The Bohr effect is a physiological phenomenon first described in 1904 by the Danish physiologist Christian Bohr. It explains why
1. hemoglobin binds carbon monoxide more readily than oxygen
2. hemoglobin unloads its oxygen when it encounters low pH
3. diffusion occurs so slowly over long distances
4. oxygen is present in the atmosphere in relatively low concentrations

The division of the circulatory system involved in the exchange of gases between interstitial fluid and the blood are:
1. arteries
2. arterioles
3. capillaries
4. venules

Dyspnea in an asthmatic patient is due to the constriction of the
1. trachea.
2. larynx.
3. terminal bronchioles.
4. alveoli.

Which of the following is most likely to take place during quiet expiration?
1. abdominal muscles relax.
2. diaphragm moves inferiorly.
3. external intercostal muscles contract.
4. thorax and lungs passively recoil.

The lungs are always inflated and do not normally collapse even during expiration because of
1. surfactant.
2. pleural pressure.
3. elastic recoil.
4. both 1 and 2.

The pulmonary function of a person reveals the following values:
a. tidal volume = 500 mL
b. residual volume = 1000 mL
c. inspiratory reserve volume = 2500 mL
d. expiratory reserve volume = 1000 mL
His vital capacity is