Final answer:
The statement that the internal intercostals and abdominal muscles are used during normal, quiet breathing is false. The diaphragm and external intercostal muscles are primarily responsible for quiet breathing, with the internal intercostals and abdominal muscles being recruited during forceful exhalation.
Step-by-step explanation:
The internal intercostals and abdominal muscles are not typically used during normal, quiet breathing. This is false. During quiet breathing, primarily the diaphragm and external intercostal muscles are responsible for the process. The diaphragm contrasts and flattens, increasing thoracic cavity volume and decreasing pressure, which allows air to flow into the lungs. The external intercostal muscles assist by raising the rib cage, thus expanding it and helping in inspiration.
When deeper breaths, called diaphragmatic breathing, are taken, it requires the diaphragm to contract significantly. Upon relaxation, the air is passively exhaled. Shallow breathing, or costal breathing, involves the contraction of the intercostal muscles. During a forceful expiration, such as when we cough or during vigorous exercise, the internal intercostals and abdominal muscles may be utilized to expel air actively from the lungs.