The Relation Between the Structure and Innervation of Small Arteries and Arterioles and the Smooth Muscle Membrane Potential Changes Expected at Different Levels of Sympathetic Nerve Activity

The membrane potential changes in arterial smooth muscle due to natural sympathetic nerve activity have been calculated. The electrical properties of the smooth muscle syncytium were taken into account and various assumptions made concerning the release of noradrenaline by the perivascular nerves. The depolarization that would result from asynchronous nerve activity at various mean frequencies was calculated for arterioles and small arteries of various diameters up to 150 micron. The calculations suggested that the depolarization would be irregular and that discrete excitatory junction potentials as evoked by synchronous nerve stimulation would not be recorded during natural nerve activity. The irregularity of the depolarization would be greater in small arterioles and would cause them to reach threshold for action potential generation at lower frequencies of nerve activity than larger arteries.