the resting membrane potential (v) of uterine smooth muscle has been recorded to be between -35 and -80 mv. as with the resting membrane potential of other cell types, it is maintained by a na/k pump that causes a higher concentration of na ions in the extracellular space than in the intracellular space, and a higher concentration of k ions in the intracellular space than in the extracellular space. subsequently, having k channels open to a higher degree than na channels results in an overall efflux of positive ions, resulting in a negative potential.