Sliding Filament Model and Muscle Contraction 1

Myosin Head

A structure on the myosin filament that attaches to active sites on the actin filament and is capable of hydrolyzing ATP into ADP and Pi to release energy.

Actin

A protein that makes up the thin filament in muscle fibers and contains binding sites for myosin heads.

Troponin

A protein bound to both actin and tropomyosin, which binds with calcium ions (Ca++) to facilitate muscle contraction.

Tropomyosin

A protein that winds around actin filaments, blocking the binding sites for myosin heads in a relaxed muscle until calcium binds to troponin.

Neuromuscular Junction

The synapse or junction between a motor neuron and a muscle fiber where action potentials are transmitted.

End Plate Potential

A local depolarization of the sarcolemma triggered by the binding of acetylcholine to its receptors, leading to muscle fiber excitation.

Cross Bridge Cycling

The process in muscle contraction where myosin heads attach to actin, pivot, and detach, leading to muscle shortening.

Excitation-Contraction Coupling

The sequence of events by which an action potential leads to muscle contraction through the release of calcium ions.

Calcium Ions (Ca2+)

Ions that play a key role in muscle contraction by binding to troponin and allowing myosin to attach to actin.

ATP Hydrolysis

The process of breaking down ATP into ADP and Pi to release energy, essential for muscle contraction and myosin head cocking.

Rigor Mortis

A state of muscle stiffness occurring after death due to increased intracellular calcium levels and lack of ATP, preventing myosin detachment from actin.