Effects of Stimulation of Sympathetic and Dorsal Roots on Contraction of Skeletal Muscle

Stimulation of the sympathetic fibers to the smooth muscles of the blood vessels is known to influence their contractile function, notably the degree of shortening (vasoconstriction and vasodilatation). Stimulation of the dorsal roots has been shown to produce vasodilatation. Moreover, in skeletal muscle, stimulation of the sympathetic has been demonstrated to influence contractile function and, as in the case of smooth muscle, chiefly the degree of shortening. Orbeli1showed that effective stimulation of the appropriate sympathetic fibers to the gastrocnemius muscle resulted in an augmentation of the degree of shortening in response to indirect stimulation in about three fourths of his experiments, whereas in another fourth such stimulation produced a depression. Of all the experiments designed to obtain evidence on the influence of the sympathetic nerves on the contraction of skeletal muscle, in few investigations has the isometric technic been employed. In isometric measurements of tetanus Orbeli2showed