Mecanismo de la contracción muscular

Molecular Mechanism of Muscle Contraction

The discussion delves into the molecular mechanism of muscle contraction, focusing on the sarcomer as the functional unit and detailing the interaction between actin and myosin filaments during contraction.

Sarcomer Structure and Components

• Actin and myosin filaments form the sarcomere, with actin being thin filaments and myosin thick filaments.

• The sarcomer, located between two Z discs, is crucial for muscle contraction.

Calcium Ion Interaction

• Calcium ions released by the sarcoplasmic reticulum bind to troponin, causing a conformational change that displaces tropomyosin.

• This displacement exposes the active site on actin for myosin head binding, initiating muscle contraction.

ATP Activation of Myosin Head

• ATP binds to myosin head, leading to hydrolysis into ADP and inorganic phosphate which activates the myosin head.

• Activated myosin head binds to actin, strengthening their connection before releasing inorganic phosphate for a power stroke.

Repeated Contraction Process

• After power stroke, ATP binds again to myosin head weakening its bond with actin.

• This cycle continues as long as active sites on actins are exposed, driving muscle contraction.