Diafragmanärv

The phrenic nerve, known as the diafragmanärv in Swedish, is a mixed motor and sensory nerve that originates in the neck. It plays a crucial role in breathing by innervating the diaphragm, the primary muscle of respiration. The phrenic nerve arises from the cervical spinal cord, specifically from the C3, C4, and C5 nerve roots. These roots converge to form the nerve, which then descends through the neck and thorax to reach the diaphragm. Each side of the body has a phrenic nerve.

The motor function of the phrenic nerve controls the contraction and relaxation of the diaphragm. When the phrenic nerve stimulates the diaphragm, it flattens and moves downward, increasing the volume of the thoracic cavity and drawing air into the lungs (inhalation). When the nerve's stimulation ceases, the diaphragm relaxes and returns to its dome shape, decreasing the thoracic volume and expelling air (exhalation). This continuous, largely involuntary action is essential for life.

In addition to its motor function, the phrenic nerve also carries sensory information from the diaphragm itself. It also provides sensation to the mediastinum, pleura, and pericardium. Damage to the phrenic nerve, whether through injury, surgery, or disease, can lead to diaphragmatic paralysis. This can cause significant breathing difficulties, shortness of breath, and may require mechanical ventilation. In some medical contexts, the phrenic nerve can be intentionally blocked or lesioned to treat conditions like intractable hiccups.