Contraction and Relaxation of the Diaphragm and Intercostal Muscles

Question

Contraction and relaxation of the diaphragm and intercostal muscles
A) change thoracic volume.
B) close the glottis.
C) occur in response to firing of the vagus nerve.
D) All of the above are true.

Accepted Answer

Contraction and relaxation of the diaphragm and intercostal muscles change the thoracic volume, which is necessary for breathing. The glottis is closed during swallowing, not during normal breathing, and firing of the vagus nerve can contribute to breathing regulation, but it is not the only factor involved.