When a muscle is not contracting, actin and myosin are prevented from reacting by:
When a muscle is not contracting, actin and myosin are prevented from reacting by troponin-tropomyosin. Tropomyosin covers the active sites on actin filaments which prevents myosin heads from attachment. Troponin must bind with Ca++ in order to cause the tropomyosin to move off the active sites. Phosphocreatine has a high energy phosphate bond which is used to reconstitute ATP. Heavy meromyosin refers to the heavy chains in the myosin filament. Acetylcholinesterase and acetylcholine are at the neuromuscular junctions and do not directly affect actin and myosin crossbridge formation. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 5. Excitable Tissue: Muscle. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds),Ganong's Review of Medical Physiology, 24e.
Troponin-tropomyosin
Phosphocreatine
Heavy meromyosin
Acetylcholinesterase