Sliding Filament Theory

Myosin

Thick filaments in muscle that interact with actin to cause contraction.

T-Tubule

A structure that conducts action potentials deep into muscle cells.

Ratchet Mechanism

The mechanism by which myosin heads pull actin filaments inward during muscle contraction.

What molecule is released from the nerve to initiate muscle contraction?

Acetylcholine, which crosses the gap between the nerve and the muscle.

What happens during the 'Action Potential on T-Tubule' phase?

The muscle becomes more positively charged after acetylcholine binding, carrying the message to the T-Tubule.

What triggers the release of calcium into the muscle?

The action potential spreading through the T-Tubules.

What is the role of Troponin in muscle contraction?

Calcium binds to Troponin, which then signals Tropomyosin to move off the actin binding site.

Describe the 'Powerstroke' in muscle contraction.

It's the rotation of the energized myosin head after a cross bridge forms, causing actin to slide past myosin and shortening the muscle.

What causes Actin-Myosin Detachment?

A new ATP molecule attaching to the myosin head, releasing it from the actin binding site.

What are actin filaments?

They are the thin filaments in muscle fibers to which myosin heads bind.

What are myosin filaments?

They are the thick filaments in muscle fibers that possess heads which bind to actin.

What are Z lines?

Z lines are regions where actin filaments are connected.

What are M lines?

M lines are regions that connect the myosin filaments in the middle of a sarcomere.

What is a cross bridge in muscle contraction?

It is the bond formed when an energized myosin head connects to a binding site on actin.