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Assertion:Action potential passes into t...

Assertion:Action potential passes into the muscle fibre by way T-tubules and Z-line and sarcoplasmic reticulum release calcium ions into the sarcoplasm.
Reason:The released calcium results in sliding of thin myofilaments over the thick myofilaments of the myofibrils, leading to contraction of the muscle

A

if both assertion and reason are true and the reason is correct explanton of Assertion

B

IF both assertion and reason and reason are true but reason is not a correct explanation of assertion

C

IF assertion is true and reason is wrong

D

if both assertion and reason are wrong

Text Solution

AI Generated Solution

The correct Answer is:
**Step-by-Step Solution:** 1. **Understanding the Assertion:** - The assertion states that action potential passes into the muscle fiber through T-tubules and Z-line, and that the sarcoplasmic reticulum releases calcium ions into the sarcoplasm. - T-tubules (transverse tubules) are extensions of the muscle cell membrane that penetrate into the muscle fiber, allowing action potentials to travel deep into the muscle. - The Z-line is a structural feature of the sarcomere, which is the basic unit of muscle contraction. 2. **Understanding the Reason:** - The reason provided explains that the released calcium ions lead to the sliding of thin myofilaments (actin) over thick myofilaments (myosin), resulting in muscle contraction. - This sliding filament theory is fundamental to how muscles contract; when calcium is released, it binds to troponin on the actin filaments, causing a conformational change that allows myosin heads to attach to actin and pull, leading to contraction. 3. **Evaluating the Relationship:** - Both the assertion and the reason are true statements. - The reason provided accurately explains the mechanism by which the assertion occurs. The release of calcium ions is crucial for the sliding of myofilaments, which is the process that leads to muscle contraction. 4. **Conclusion:** - Since both the assertion and the reason are true, and the reason correctly explains the assertion, the correct answer is that both assertion and reason are true, and the reason is the correct explanation of the assertion. **Final Answer:** - Both assertion and reason are true, and reason is the correct explanation of assertion. ---
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