B.2.1 Define total lung capacity, vital capacity, tidal volume and ventilation rate
Total lung capacity: Volume of air in the lungs after a maximum inhalation
Vital capacity: Maximum volume of air that can be exhaled after a maximum inhalation
Tidal volume: Volume of air taken in or out with each inhalation or exhalation
Ventilation rate: Number of inhalations or exhalations per minute
Overview of Different Types of Lung Capacity for a Typical Healthy Male
B.2.2 Explain the need for increases in tidal volume and ventilation rate during exercise
- During exercise, oxygen is consumed by the respiring muscles and carbon dioxide is produced as a by-product
- Thus the rate of gas exchange within alveoli needs to increase in order to maintain the concentration gradients needed to continue cell respiration
- Increasing levels of CO2 in the blood are detected by chemosensors in the walls of the arteries which trigger the breathing centre of the brainstem
- Fresh air (high O2 levels, low CO2 levels) is exchanged with stale air (low O2 levels, high CO2 levels) in the lungs
- Increasing the rate of gas exchange may be achieved in one of two ways:
- Increasing tidal volume (deeper breaths allows more air into the lungs to be exchanged)
- Increasing ventilation rate (a greater frequency of breaths allows a more continuous exchange of gases)
B.2.3 Outline the effects of training on the pulmonary system, including changes in ventilation rate at rest, maximum ventilation rate and vital capacity
- Ventilation rate at rest can be reduced from about 14 to 12 bpm (breaths per minute)
- Maximum ventilation rate can be increased from about 40 to 45 bpm or more
- Vital capacity may increase slightly
- General dilation of blood capillaries around the alveoli resulting in increased efficiency of gas exchange
- Strengthening of the muscles used for ventilation (diaphragm and intercostals)