Smooth muscle physiology, past and future

Abstract

The history of smooth muscle physiology from the work of Engelmann on the ureter (1869) to the introduction of intracellular electrodes by Bülbring (1954) 's outlined. Attempts at classifying smooth muscles are discussed. The observation that passive shortening has an inhibitory effect during twitches and contractures of the turtle aorta indicates the presence of a feedback mechanism like that demonstrated in other muscles, including the heart. This mechanism, which does not involve changes in membrane potential, may play a role in the control of tonus in blood vessels and other organs which are subject to rhythmic mechanical changes.