Which nerve supplies the diaphragm?

• A. Vagus nerve
• B. Intercostal nerves
• C. Phrenic nerve (C3–C5)
• D. Accessory nerve

Answer: (C)

The diaphragm is controlled by the phrenic nerve, which comes from the cervical nerves C3 to C5. This nerve travels from the neck into the chest and directly innervates the diaphragm, delivering the motor signals that make it contract during inhalation. It also carries sensory fibers from the central part of the diaphragmatic pleura and pericardium. The other nerves listed don’t provide the diaphragm’s motor innervation: the vagus nerve mostly supplies parasympathetic fibers to thoracic and abdominal organs and some visceral sensation; intercostal nerves serve the intercostal muscles and chest wall; the accessory nerve supplies the trapezius and sternocleidomastoid.