Which of the following most accurately describes muscle activity during normal inspiration?
A) Both the internal intercostal muscles and the diaphragm relax.
B) Both the external intercostal muscles and the diaphragm contract.
C) The internal intercostal muscles contract as the diaphragm relaxes.
D) Both the external intercostal muscles and the diaphragm relax.

Question

Quizplus · Accepted Answer

During normal inspiration, the external intercostal muscles and the diaphragm contract to increase the thoracic cavity volume, which leads to a decrease in thoracic pressure and an increase in air flow into the lungs. The internal intercostal muscles are not involved in normal inspiration and are only active during forced expiration. Therefore, options A, C, and D are incorrect.

Which of the Following Most Accurately Describes Muscle Activity During