The Hering-Sherrington law of reciprocal inhibition of antagonists has been found valid not only in the innervation of striated muscles but in the innervation of some parts of the autonomic nervous system. Stimulation of the depressor nerve, for instance, reflexly decreases the tone of the vasoconstrictors and increases that of the vasodilators (Bayliss1) ; it also induces vagal inhibition and inhibits the accelerator nerves of the heart (Bruecke2). As to the pupil, it is known from animal experiments as well as from clinical experience (Bumke3) that dilatation of the pupil produced by painful stimuli or psychic excitation is brought about not only by stimulation of the dilator but by inhibition of its antagonist, the sphincter of the pupil. It seems, therefore, not unjustified to presume that reciprocal inhibition may also play a part in the mechanism of the light reflex. In fact, such opinions were expressed by Uriarte
SPIEGEL EA, SCALA NP. ROLE OF THE CERVICAL SYMPATHETIC NERVE IN THE LIGHT REFLEX OF THE PUPIL. Arch Ophthalmol. 1940;23(2):371–376. doi:10.1001/archopht.1940.00860130409010
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