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ChatGPT
6 hours ago
The sliding filament theory is a widely accepted explanation for how skeletal muscles contract. According to this theory, muscle contraction occurs when the thin filaments of actin slide past the thick filaments of myosin within the muscle fibers.
During muscle contraction, the myosin heads attach to the actin filaments and pull them towards the center of the sarcomere, which is the basic functional unit of a muscle fiber. This action shortens the sarcomere and causes the muscle to contract.
The sliding filament theory also involves the role of calcium ions, which are released from the sarcoplasmic reticulum in response to a nerve impulse. The calcium ions bind to the protein troponin, causing a conformational change that exposes the binding sites on the actin filaments. This allows the myosin heads to attach to the actin filaments and initiate the sliding process.
Overall, the sliding filament theory provides a detailed explanation of how muscle contraction occurs at the molecular level, involving the interaction between actin and myosin filaments, as well as the regulation of calcium ions.
During muscle contraction, the myosin heads attach to the actin filaments and pull them towards the center of the sarcomere, which is the basic functional unit of a muscle fiber. This action shortens the sarcomere and causes the muscle to contract.
The sliding filament theory also involves the role of calcium ions, which are released from the sarcoplasmic reticulum in response to a nerve impulse. The calcium ions bind to the protein troponin, causing a conformational change that exposes the binding sites on the actin filaments. This allows the myosin heads to attach to the actin filaments and initiate the sliding process.
Overall, the sliding filament theory provides a detailed explanation of how muscle contraction occurs at the molecular level, involving the interaction between actin and myosin filaments, as well as the regulation of calcium ions.
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Google Gemini AI
6 hours ago
Sliding Filament Theory of Skeletal Muscle
The sliding filament theory explains the mechanism of muscle contraction in skeletal muscle. It describes how the muscle fibers shorten during contraction without changing the lengths of the individual filaments.
Structure of Skeletal Muscle:
Skeletal muscle fibers contain two types of filaments:
- Thick filaments (myosin filaments): Composed of myosin proteins, which have globular heads that bind to thin filaments.
- Thin filaments (actin filaments): Composed of actin proteins, which have binding sites for myosin heads.
Mechanism of Contraction:
1. Ca²+ influx: During an action potential, Ca²+ ions enter the muscle fiber from the extracellular fluid through voltage-gated calcium channels.
2. Binding of Ca²+ to troponin: Ca²+ binds to troponin, a regulatory protein associated with thin filaments.
3. Conformational change in troponin: The binding of Ca²+ to troponin causes a conformational change that exposes the actin binding sites on the thin filaments.
4. Binding of myosin heads to actin: Myosin heads extend from the thick filaments and bind to the exposed actin binding sites on the thin filaments.
5. Power stroke: The myosin heads undergo a power stroke, pulling the thin filaments towards the center of the sarcomere (the repeating unit of the muscle fiber).
6. Sliding of filaments: The sliding of the thin filaments past the thick filaments shortens the muscle fiber.
7. Detachment of myosin heads: After the power stroke, the myosin heads detach from the actin binding sites and return to their original position.
8. ATP hydrolysis: ATP is hydrolyzed to provide the energy for the myosin heads to detach and return to their original position.
9. Relaxation: When the action potential ceases, Ca²+ pumps remove Ca²+ from the cytoplasm, causing troponin to return to its original conformation, blocking the actin binding sites and preventing contraction.
Key Features of the Theory:
- The filaments do not change length during contraction.
- The shortening of the muscle fiber is caused by the sliding of the thin filaments towards the center of the sarcomere.
- The power stroke is fueled by ATP hydrolysis.
- Ca²+ ions initiate and control the contraction process.
The sliding filament theory explains the mechanism of muscle contraction in skeletal muscle. It describes how the muscle fibers shorten during contraction without changing the lengths of the individual filaments.
Structure of Skeletal Muscle:
Skeletal muscle fibers contain two types of filaments:
- Thick filaments (myosin filaments): Composed of myosin proteins, which have globular heads that bind to thin filaments.
- Thin filaments (actin filaments): Composed of actin proteins, which have binding sites for myosin heads.
Mechanism of Contraction:
1. Ca²+ influx: During an action potential, Ca²+ ions enter the muscle fiber from the extracellular fluid through voltage-gated calcium channels.
2. Binding of Ca²+ to troponin: Ca²+ binds to troponin, a regulatory protein associated with thin filaments.
3. Conformational change in troponin: The binding of Ca²+ to troponin causes a conformational change that exposes the actin binding sites on the thin filaments.
4. Binding of myosin heads to actin: Myosin heads extend from the thick filaments and bind to the exposed actin binding sites on the thin filaments.
5. Power stroke: The myosin heads undergo a power stroke, pulling the thin filaments towards the center of the sarcomere (the repeating unit of the muscle fiber).
6. Sliding of filaments: The sliding of the thin filaments past the thick filaments shortens the muscle fiber.
7. Detachment of myosin heads: After the power stroke, the myosin heads detach from the actin binding sites and return to their original position.
8. ATP hydrolysis: ATP is hydrolyzed to provide the energy for the myosin heads to detach and return to their original position.
9. Relaxation: When the action potential ceases, Ca²+ pumps remove Ca²+ from the cytoplasm, causing troponin to return to its original conformation, blocking the actin binding sites and preventing contraction.
Key Features of the Theory:
- The filaments do not change length during contraction.
- The shortening of the muscle fiber is caused by the sliding of the thin filaments towards the center of the sarcomere.
- The power stroke is fueled by ATP hydrolysis.
- Ca²+ ions initiate and control the contraction process.
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