Which nerves arise from C3-C5 and control the diaphragm for breathing?

• A. Vagal Nerves
• B. Axillary Nerves
• C. Phrenic Nerves
• D. Brachial Nerves

Answer: (C)

Think about which nerve directly tells the diaphragm to contract during breathing. That signal comes from the phrenic nerve, which receives contributions from the cervical nerve roots C3 through C5. The phrenic nerve travels to the diaphragm and provides the motor input that causes it to contract on inhalation, enlarging the chest cavity and drawing air into the lungs.

Other nerves listed serve different regions or functions: the vagal (parasympathetic) nerves innervate many thoracic and abdominal organs rather than the diaphragm and don’t originate from C3-C5; axillary nerves and other branches of the brachial plexus primarily control shoulder and arm muscles. Thus, the phrenic nerves are the ones that fit the description of arising from C3-C5 and controlling the diaphragm.