Excitation - Contraction Coupling
Sarcoplasmic reticulum are specialized cell organelles that concentrate Calcium ions [2000x]
Channels between the sarcoplasmic reticulum are called T-tubules - carry action potential to sarcoplasmic reticulum [sr]
SR releases calcium into sarcoplasm of fibers, surrounding the myofibrils
Calcium binds to troponin. Causes the troponin / tropomyosin complex to swivel off actin’s bind site
Myosin heads seize opportunity and bind with actin = Cross Bridge