1. Ventilation Inspiration: inhaling Expiration: exhaling
Respiratory cycle: one complete inspiration and expiration

2. Muscle of Ventilation
External intercostals: the contractions of these muscles cause a lifting of the rib cage.
This increases volume in the chest cavity letting the lungs expand lowering pressure in the lung
Pressure outside the lung is higher then in the lung causing air to flow in and fill lung

3. Muscle of Ventilation
Internal intercostals: contractions of these muscles pull down the rib cage
The ribcage pushes on the lungs decreasing volume and increasing pressure
Pressure in the lung is higher then outside the lung causing air to flow out of lung

4. Muscle of Ventilation
Diaphragm: is a band of muscle that rests above the liver and separates the thoracic cavity into upper and lower
The diaphragm is the primary mover of air with the intercostals as synergist
Diaphragm contracts and descends during inspiration and relaxes and ascends during expiration
Why?

5. Neural Control of Ventilation
The brainstem has several respiratory centers that control certain parts of the breathing process
Regulation is based on CO2 levels in the blood by chemoreceptors
As CO2 and waste products of metabolism increase the pH of blood becomes more acidic causing AP’s in chemoreceptors and increase in respiration

6. Measurements of ventilation
Voluntary control: respiration can be changed by the use of the motor cortex to a “breaking point” where the autonomic system takes over
Know the respiratory volumes and capacities in table 22.2 Pg 874