The accessory motor innervation of the diaphragm.

Abstract

AbstractIn cats, dogs, monkeys and rabbits, the section of the two phrenic nerves in the thorax does not lead to a paralysis of the diaphragm; inspiratory and expiratory discharges may be recorded (fig. 1). The corresponding motor fibers leave the spinal cord through the ventral roots T5 to T13.The diaphragm is innervated by the intercostal nerves 4 to 9, mainly by the 8th (fig.s 2 and 3). These motor fibers do not share in the respiratory activity but in reflex responses (fig. 2).The spinal control of the diaphragm includes thus three sets of motor fibers. Two of them are respiratory: from C4 to C7 (the phrenics) and from T5 to T13 (the accessory respiratory pathways). The third (T4 to T9) is involved in spinal reflexes and travels with the corresponding intercostal nerves.