FIGURE 5.

Hierarchical organization of central and peripheral noradrenergic and cholinergic neurons that potentially regulate skeletal muscle innervation. Relationship between LC and the spinal cord dorsal horn sensory neurons. Ventrally located A5 noradrenergic neurons ① project to cholinergic pre‐ganglionic neurons located at the spinal cord IML ②. The sympathetic pre‐ganglionic neurons at the IML synapse with paravertebral sympathetic post‐ganglionic neurons ③, which in turn innervate the myofiber ④. Sympathetic neuron axons display periodic bulbous enlargements also known as varicosities. The diagram shows both the sympathetic and motor innervation of the skeletal muscle fiber. Adapted from Ref. [45]