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 The excitation-contraction coupling of uterine smooth muscle is also very similar to that of other smooth muscle in general, with intracellular increase in calcium (Ca2+) leading to contraction. Restoration to resting state Removal of Ca2+ after contraction induces relaxation of the smooth muscle, and restores the molecular structure of the sarcoplasmic reticulum for the next contractile stimulus. References Pelvis Mammal female reproductive system