Myocardial

Cardiac muscle contracts in a similar manner to skeletal muscle, although with some important differences. Electrical stimulation in the form of a cardiac action potential triggers the release of calcium from the cell's internal calcium store, the sarcoplasmic reticulum. The rise in calcium causes the cell's myofilaments to slide past each other in a process called . Diseases of the heart muscle known as cardiomyopathies are of major importance. These include ischemic conditions caused by a restricted blood supply to the muscle such as angina, and myocardial infarction.