Sliding Filament Theory

Definition

The sliding filament theory is a model that explains the mechanism of muscle contraction, describing how the thin and thick filaments in muscle fibers interact to generate force and shorten the muscle. This theory is central to understanding how skeletal muscles produce movement in the body.

5 Must Know Facts For Your Next Test

1. The sliding filament theory proposes that muscle contraction occurs when the thin actin filaments are pulled inward towards the center of the sarcomere by the thick myosin filaments.
2. This movement is driven by the cyclic attachment and detachment of the myosin heads to the actin binding sites, powered by the hydrolysis of ATP.
3. As the myosin heads pull the actin filaments, the sarcomere shortens, resulting in the overall contraction of the muscle fiber.
4. The sliding of the filaments does not change the length of the individual filaments, but rather the overlap between them, which is what causes the muscle to shorten.
5. The sliding filament theory explains how skeletal muscles are able to generate force and produce movement, which is essential for locomotion, posture, and other bodily functions.

Review Questions

• Describe the role of the sarcomere in the sliding filament theory of muscle contraction.
  • The sarcomere is the basic functional unit of a skeletal muscle fiber and is central to the sliding filament theory. Within the sarcomere, the overlapping thick myosin filaments and thin actin filaments slide past each other during muscle contraction. As the myosin heads attach to the actin binding sites and pull the thin filaments towards the center of the sarcomere, the overall length of the sarcomere decreases, causing the muscle fiber to shorten and contract.
• Explain how the hydrolysis of ATP powers the sliding of the filaments during muscle contraction.
  • The sliding filament theory proposes that the cyclic attachment and detachment of the myosin heads to the actin binding sites is driven by the hydrolysis of ATP. When ATP binds to the myosin heads, it causes a conformational change that allows the heads to detach from the actin. The hydrolysis of ATP then provides the energy for the myosin heads to re-attach to the actin, pulling the thin filaments inward and causing the sarcomere to shorten. This ATP-powered sliding of the filaments is the fundamental mechanism that generates the force and movement of muscle contraction.
• Analyze how the sliding filament theory explains the ability of skeletal muscles to generate force and produce movement.
  • The sliding filament theory provides a comprehensive explanation for how skeletal muscles are able to generate the force and movement necessary for locomotion, posture, and other bodily functions. By describing the cyclic interaction between the thick myosin filaments and thin actin filaments within the sarcomeres of muscle fibers, the theory demonstrates how the hydrolysis of ATP powers the sliding of the filaments, causing the sarcomeres to shorten and the muscle as a whole to contract. This sliding of the overlapping filaments, without a change in their individual lengths, is the key mechanism that allows skeletal muscles to produce the force required for diverse movements and physical activities.

Related terms

Sarcomere:

The basic functional unit of a skeletal muscle fiber, consisting of overlapping thick and thin filaments that slide past each other during contraction.

Actin:

A globular protein that forms the thin filaments in the sarcomere, which interact with the thick filaments of myosin to generate muscle contraction.

Myosin:

A motor protein that forms the thick filaments in the sarcomere, with heads that can bind to actin and use ATP hydrolysis to generate the force for muscle contraction.