Analyzing a SpirogramThe volume of air in the lungs increases as a person inhales and decreases as aperson exhales. A spirogram is a graph of the volume of air in a person’s lungsover time. Look at the spirogram shown below. Where the line of the graphmoves upward the person is inhaling, and where the line of the graph movesdownward the person is exhaling.The first three breaths on the spirogram show normal breathing. During thefourth breath, however, the person inhaled as much air into the lungs as possible.The next two breaths show normal breathing again. Then, during the seventhbreath, the person exhaled as much air from the lungs as possible.

Answer the following questions on a separate sheet of paper.1. During one cycle of breathing, a person begins to inhale, finishes inhaling,then begins to exhale, and finally finishes exhaling. What part of this cycle doesa peak on the graph represent? What part of this cycle does a low point on thegraph represent?2. What is the total volume of air in the lungs after the person inhales during anormal breath? What is the volume after the person exhales during a normalbreath?3. What volume of air does the person inhale during a normal breath? Thisvolume is represented by the line AB on the spirogram.4. What is the maximum volume of air that can be inhaled after a normal exhalation? This volume is represented by the line CD on the spirogram.5. What is the maximum volume of air that can be exhaled after a normal inhalation? This volume is represented by the line EF on the spirogram.6. How would the spirogram change if the person began breathing faster?7. What would happen to the line of the graph if the person inhaled and thenheld his or her breath?

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Time (seconds)5

AB

C

D

E

F

10 15 20 25 30 35 40 45 50

5700

Volume

of air in

lungs (

mL)

92 Unit 3 Resources Science Explorer Grade 7

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S E C T I O N 1 3 - 1 E N R I C H