HL Paper 3
The graph shows the ventilation rate and tidal volume of a well-trained runner during exercise on a treadmill. The tidal volume is the volume of air being moved in and out of the lungs in each breath.
State the apparatus used to measure the tidal volume.
Calculate the total volume of air inhaled during one minute during the highest velocity of the treadmill in this test, giving the units.
Compare and contrast the effect of increasing treadmill speed on the ventilation rate and tidal volume in this runner.
Markscheme
spirometer
a. tidal volume x ventilation rate
OR
litres breath-1 × breath min-1
b. 186 L (min-1)
a. both ventilation rate and tidal volume increase with increase in treadmill speed/ intensity of exercise
b. at low treadmill speed/below 14.2 km h-1, the tidal volume increases more steeply than ventilation rate
OR
at high treadmill speed, ventilation rate increases more steeply than tidal volume
OR
tidal volume plateaus while ventilation rate does not
Examiners report
Measurements of the lung capacity of a student were recorded using a spirometer and displayed with a data logger. Initially the student was at rest, then changed to carrying out strenuous exercise. The results are displayed in the graph.
Calculate the ventilation rate at rest, giving the units.
Explain the changes in ventilation after 35 seconds.
Suggest how the total lung volume at rest would differ for a patient with emphysema.
Outline the function of pneumocytes in the lungs.
Markscheme
12 breaths per minute/6 litres per minute ✔
Accept answers from 11 to 12 breaths per minute.
Accept answers from 5.5 to 6 litres per minute.
Answer must include breaths or litres and a standard unit of time.
Correct:
eg: 12 breaths / minute
eg: 0.1 L sec–1 or 6 L min–1
Incorrect:
eg: but 12 breaths = 0 marks
a. the volume of air per breath increases
OR
the volume of each breath reaches a maximum/levels off
OR
frequency of ventilation/breaths per minute increases ✔
b. exercise increases «rate of cellular» respiration/energy use/blood CO2/acidity ✔
c. exercise causes increased demand for oxygen/removal of carbon dioxide ✔
d. maximum rate/depth of ventilation is determined by the capacity of the student ✔
«total resting lung volume» would be greater ✔
a. type I pneumocytes carry out gas exchange ✔
OWTTE
b. type II pneumocytes secrete surfactant/fluid OWTTE
OR
type II pneumocytes create a moist surface inside the alveoli
OR
type II pneumocytes reduce surface tension between alveoli
OR
type II pneumocytes prevent the sides of the alveolus adhering to each other ✔