Source of calcium for smooth muscle contraction
Ca2+ plays a prominent role in the initiation of contraction of smooth muscle. Depending on the activating stimulus, Ca2+increase can be due to influx through voltage- or ligand-gated plasma membrane channels, efflux from intracellular stores through the RyR, efflux from intracellular stores through the inositol trisphosphate receptor (IP3R) Ca2+channel, or a combination of these channels.