Firing of the Intercostal and Phrenic Nerves

Question

Firing of the intercostal and phrenic nerves
A) activates the respiratory control center in the medulla oblongata.
B) causes relaxation of the muscles of respiration.
C) causes a skeletal muscle response that increases thoracic volume.
D) dilates the bronchioles.

Accepted Answer

Firing of the intercostal and phrenic nerves causes the contraction of the muscles of respiration, increasing thoracic volume and causing inhalation. In their absence, the muscles relax, decreasing thoracic volume and causing exhalation. Activation of the respiratory control center in the medulla oblongata is necessary for controlling the rate and depth of breathing, but this is not directly related to the firing of these nerves. Dilating the bronchioles is controlled by the sympathetic nervous system and is not directly related to the firing of these nerves.