Sliding filament theory can be best explained as :a)When myofilaments slide pass each other, Myosin filaments shorten while Actin filaments do not shortenb)When myofilaments slide pass each other Actin filaments shorten while Myosin filament do not shortenc)Actin and Myosin filaments shorten and slide pass each otherd)Actin and Myosin filaments do not shorten but rather slide pass each otherCorrect answer is option 'D'. Can you explain this answer?

Question

Answer

According to sliding filament theory, muscle contraction is brought about by sarcomere contraction. This is result of sliding of actin and myosin filaments past each other leading to shortening of I band and disappearance of the H zone. Options B, C and D are incorrect as the sarcomere shortens while both the filaments remain the same length. Correct answer is option D

Answer

Correct option is B as in ncert it is written that A band is not shortened

Answer

Sliding Filament Theory Explained

The sliding filament theory is a widely accepted explanation for how muscles contract. It describes the mechanism by which myofilaments, specifically actin and myosin, interact to generate force and cause muscle contraction.

1. Introduction
The sliding filament theory states that during muscle contraction, actin and myosin filaments slide past each other, resulting in the shortening of the sarcomere, which is the basic contractile unit of muscle. This process occurs in response to a nerve impulse, which triggers the release of calcium ions from the sarcoplasmic reticulum into the muscle cell.

2. Myofilament Structure
To understand how the sliding filament theory works, it's important to understand the structure of actin and myosin filaments. Actin filaments are thin filaments composed of globular actin proteins, while myosin filaments are thick filaments made up of myosin protein molecules.

3. Cross-Bridge Formation
The sliding filament theory begins with the interaction between actin and myosin filaments. When calcium ions are released into the muscle cell, they bind to troponin, a regulatory protein on the actin filaments. This binding causes tropomyosin, another regulatory protein, to shift its position, exposing the myosin-binding sites on the actin filaments.

The myosin heads, which are part of the myosin filaments, then form cross-bridges with the exposed myosin-binding sites on the actin filaments. This attachment is facilitated by the hydrolysis of ATP to ADP and inorganic phosphate, providing the energy required for cross-bridge formation.

4. Power Stroke
Once the cross-bridges are formed, the myosin heads undergo a conformational change known as the power stroke. During this process, the myosin heads pivot, pulling the actin filaments towards the center of the sarcomere. This sliding of the actin filaments past the myosin filaments is what causes muscle contraction.

5. Cross-Bridge Detachment
After the power stroke, the myosin heads need to detach from the actin filaments to reset for another cycle of contraction. ATP binds to the myosin heads, causing them to detach from the actin filaments. The ATP is then hydrolyzed to ADP and inorganic phosphate, providing the energy for the myosin heads to return to their original position.

6. Repeated Cycling
The process of cross-bridge formation, power stroke, and cross-bridge detachment repeats as long as there is sufficient ATP and calcium present. This repeated cycling of myosin heads pulling actin filaments towards the center of the sarcomere leads to the shortening of the sarcomere and muscle contraction.

Conclusion
In summary, the sliding filament theory explains how muscle contraction occurs by the sliding of actin and myosin filaments past each other. This process is driven by the formation and detachment of cross-bridges between actin and myosin filaments. The shortening of the sarcomere, resulting from this sliding filament mechanism, is what ultimately leads to muscle contraction.

Similar NEET Doubts

Sliding filament theory can be best explained as: [2015]

Sliding filament theory can be best explained as

Assertion (

Assertion: Mechanism of muscle contraction is explained by sliding-filament theory.Reason: Contraction of muscle fibre takes place by the sliding of thick filaments over the thin filaments

During muscle contraction in humans, the

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