Figure 1. Overview of calcium dynamics in vascular smooth muscle.

Ca²⁺ influences the state of vascular smooth muscle contraction directly and indirectly. Direct mechanisms include changes (Δ) in Ca²⁺ influx and release from intracellular Ca²⁺ stores leading to increased Ca²⁺ within the cell, binding of Ca²⁺ to calmodulin (CaM), and activation of myosin light chain kinase (MLCK). Indirect mechanisms include changes in Ca²⁺ influx via alterations in plasma membrane potential (Vm), Ca²⁺ release from intracellular stores, Ca²⁺ sequestration, and Ca²⁺ sensitization of the contractile apparatus.