Resting state The resting membrane potential (Vrest) of<unk>  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. This resting potential undergoes rhythmic oscillations, which have been termed slow waves, and reflect intrinsic activity of slow wave potentials. These slow waves are caused by changes in the distribution of Ca2+, Na+, K+ and Cl− ions between the intracellular and extracellular spaces, which, in turn, reflects the permeability of the plasma membrane to each of those ions. K+ is the major ion responsible for such changes in ion flux, reflecting changes in various K+ channels. Excitation-contraction As the uterus becomes essentially denervated during gestation, it is unlikely that any coordinated nervous regulation of the myometrium is centrally orchestrated. Excitation The excitation-contraction coupling of<unk>  smooth muscle is also very similar to that of other smooth muscle in general, with intracellular increase in calcium (Ca2+) leading to<unk> . Nitric oxide (NO) is particularly effective in relaxing the myometrium and in fact has a lower inhibitory concentration 50% (Ki) in human than guinea pig or non-human primate myometrium. Restoration to resting state<unk>  smooth muscle mechanisms of relaxation differ significantly from those of other human smooth muscles. Removal of Ca2+ after<unk>  induces relaxation of the smooth muscle, and restores the molecular structure of the sarcoplasmic reticulum for the next contractile stimulus.
Uterine contraction
Vaginal contraction
Placental expulsion
Ovulation
Ovulation induction
Uterine inversion
Uterine hyperstimulation
Cervical dilation