Changes in Voltage of the Resting Membrane Potential. In addition to the slow waves
and spike potentials, the baseline voltage level of the smooth muscle resting membrane potential can
also change. Under normal conditions, the resting membrane potential averages about −56 millivolts,
but multiple factors can change this level. When the potential becomes less negative, which is
called depolarization of the membrane, the muscle fibers become more excitable. When the
potential becomes mor negative, which is called hyperpolarization, the fibers become less excitable.
