Respiratory Physiology and Lung Capacity

Inhalation Diaphragm contracts Ribs move up and out, chest cavity enlarges and pressure decreases Air rushes in from higher pressure environment

Exhalation Diaphragm relaxes Ribs compress, chest cavity gets smaller and pressure increases Air escapes to lower pressure environment

Breathing Involuntary inhalation and exhalation Delivers O 2 to alveoli and removes CO 2 Medulla oblongata –Brain region that controls breathing

Gas Exchange

Control of Breathing Chemoreceptors detect change in blood pH –Blood high in CO 2 has lower than normal pH Drop in pH causes medulla oblongata to stimulate breathing

Breathing is a Negative Feedback Loop

Human Lung Capacity Influenced by many factors: –Age –Gender –Body position –Strength of diaphragm –Strength of chest muscles –Illness / disease The average human breathes times per minute.

Measurements Tidal Volume (TV): the amount of air inhaled and exhaled in a normal breath. Inspiratory Reserve Volume (IRV): the amount of air that can be inhaled after a normal inhalation. Expiratory Reserve Volume (ERV): the amount of air that can be forcefully exhaled after a normal exhalation. Vital Capacity (VC): the maximum amount of air that can be exhaled. (VC = TV + IRV + ERV)

Residual Volume (RV): the amount of air remaining in the lungs after a forceful exhalation. Without this “leftover” air in our lungs, they would collapse!

Average Lung Volumes for Young Adult Males

Measuring Lung Capacity Displacement Method –Air is breathed through a tube into a bottle of water. –Air displaces the water (water leaves the bottle into the surrounding tub). –Litres of air are measured from markings on side of bottle.

Measuring Lung Capacity Balloon Method –Air is breathed into balloon. –Circumference (C) of balloon is measured. –Volume is calculated with the following formula:

Measuring Lung Capacity Spirometer –Air is breathed into the mouthpiece of the spirometer. –The spirometer’s gauge needle moves. –The gauge’s measurement is read in mL.

Comparing Average Lung Capacities Males tend to have larger vital capacities than females. Athletes and musicians tend to have larger VC. Smokers tend to have a smaller VC.

How do we measure up to other mammals?