| Date | May 2015 | Marks available | 2 | Reference code | 15M.3.SL.TZ2.6 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Define | Question number | 6 | Adapted from | N/A |
Question
Define tidal volume and ventilation rate.
Tidal volume:
Ventilation rate:
Explain the processes that control changes in ventilation rate during exercise.
Markscheme
a. tidal volume: volume of air taken in with each inhalation/out with each exhalation;
b. ventilation rate: number of inhalations/exhalations/breaths per minute;
a. exercise increases aerobic respiration;
b. CO2 concentration in blood increases;
c. drop in pH of blood detected / blood more acidic;
d. breathing centres send impulses to diaphragm and intercostal muscles;
e. increase rate of contraction;
f. increase in ventilation rate increases oxygen uptake/decreases CO2;
Examiners report
N/A
Most candidates knew about the need for exchange of oxygen and carbon dioxide but only the stronger candidates could fully explain the processes changing ventilation rate.
