The phrenic neuromuscular system

The phrenic neuromuscular system includes the diaphragm muscle, the phrenic nerve, and the phrenic motor nucleus in the spinal cord. This system is critical for breathing and also helps with other actions like coughing and posture. The diaphragm, the main muscle for breathing, contracts rhythmically. This contraction creates pressure changes in the chest, allowing air to fill the lungs. The phrenic nerve sends signals from the brain and spinal cord to the diaphragm, controlling its contractions. It also carries sensory information from the diaphragm back to the brain.

• 1
  The phrenic nerve, which controls the diaphragm, is not uniform; the right and left nerves have differing compositions, with the right nerve containing more total axons.
• 2
  During quiet breathing, only a small percentage (around 20%) of the phrenic motoneuron pool is active. This percentage increases during more intense activities, like exercise, but only approaches 100% during high-force actions like coughing.
• 3
  The recruitment order of phrenic motoneurons during breathing is determined by both intrinsic properties of the motoneurons and the selectivity of synaptic inputs.