Editing Anatomy and Physiology (section)

=== Spinal Cord ===

The spinal cord transmits motor commands down and sensory information up, and mediates reflexes. Injury above T6 risks '''autonomic dysreflexia''', an exaggerated sympathetic response to a stimulus below the level of injury (most often a distended bladder or impacted bowel) causing severe hypertension, pounding headache, bradycardia, flushing above the injury, and pallor below it. The nursing response is to sit the patient upright first, then find and remove the stimulus.

Injury at or above C3 to C5 threatens diaphragm innervation by the phrenic nerve, which is why the memory aid "C3, 4, 5 keeps the diaphragm alive" matters clinically.