Muscle contraction

In this module, the processes by which calcium binding triggers actin - myosin interactions and force generation in smooth and striated muscle tissues are annotated. Cardiac conduction, also covered here, depends on coordinated action potentials that spread through tightly coupled cardiac cells to ensure the normal sequence of atrial and ventricular contraction and to allow rapid responses to changes in autonomic tone. The ventricular myocyte action potential consists of five phases: a K⁺-determined resting membrane potential (phase 4), rapid Na⁺-dependent depolarization (phase 0), brief initial repolarization due to outward ion currents (phase 1), a plateau sustained by balanced Ca²⁺ influx and K⁺ efflux that supports contraction (phase 2), and K⁺-mediated repolarization back to the resting potential (phase 3).

Summary from Reactome (R-HSA-397014), read 2026-09-23.