Mechanisms of Ventilation Learning Targets: Define the process of ventilation. (knowledge) Determine how certain factors affect breathing rate. (reasoning)

Ventilation- movement of air into and out of lungs 1

2

Structures 3-4 Also refer to the next page

3-4

Inhalation 1.Contraction of external intercostal muscles pulls ribs upward and outward. 2.Diaphragm contracts. 3.Volume of thoracic cavity increases. 4.Pressure in pleural cavity decreases. 5.Lungs inflate as air rushes in. 5-9

5-9 Image

Inhalation (a) Maximum Inhalation (b) 10-11

Expiration (Exhalation) 1.Muscles of inhalation relax due to elastic recoil. 2.Volume of thoracic cavity decreases. 3.Pressure in pleural cavity increases. 4.Lungs deflate

Exhalation (a) Maximum Exhalation (b) 16

Please watch by clicking on the illustration. Summary animation for questions 5-16.

There’s more to it Like a new balloon, a new lung has a lot of elastic recoil. It is difficult to inflate. The first breath for an infant is 20 times more difficult than any breath after that.

Also, elastic recoil can also cause a balloon or alveoli to completely collapse. Alveoli cannot completely collapse. It would take too much energy to breath. So the body produces surfactant which decrease elastic recoil. Premature babies may not produce surfactant and need to have it administer artificially.

Surfactant 1.A phospholipid 2.Reduces elastic recoil 3.Prevents complete deflation of our lungs 17-19

Measuring Breathing Intensities A respiratory therapist uses a peek flow meter to measure the patient’s breathing intensities.

Breathing intensities graph

Homework How do each of these factors affect breathing rate? 1. Respiratory areas of the brain. a. Medullary respiratory center b. Neurons of the pons 2.Chemoreceptors 3.Inflation reflex 4.Emotions 5.Physical fitness.