Question:
Choose the correct statements regarding muscle contraction.
A. A motor neuron carries a signal sent by the Central Nervous System (CNS) to the sarcolemma of the muscle fibre.
B. The neural signal generates an action potential which causes the release of $Ca^{++$ into sarcoplasm.
C. Increase in $Ca^{++}$ inactivates the actin for breaking cross bridges.
D. Actin binds to the myosin head to form a cross bridge.
E. Shortening of sarcomere takes place, by pulling actin filaments towards the centre of 'A' band.
Choose the correct answer from the options given below:}
Choose the correct statements regarding muscle contraction.
A. A motor neuron carries a signal sent by the Central Nervous System (CNS) to the sarcolemma of the muscle fibre.
B. The neural signal generates an action potential which causes the release of $Ca^{++$ into sarcoplasm.
C. Increase in $Ca^{++}$ inactivates the actin for breaking cross bridges.
D. Actin binds to the myosin head to form a cross bridge.
E. Shortening of sarcomere takes place, by pulling actin filaments towards the centre of 'A' band.
Choose the correct answer from the options given below:}
A. A motor neuron carries a signal sent by the Central Nervous System (CNS) to the sarcolemma of the muscle fibre.
B. The neural signal generates an action potential which causes the release of $Ca^{++$ into sarcoplasm.
C. Increase in $Ca^{++}$ inactivates the actin for breaking cross bridges.
D. Actin binds to the myosin head to form a cross bridge.
E. Shortening of sarcomere takes place, by pulling actin filaments towards the centre of 'A' band.
Choose the correct answer from the options given below:}
Show Hint
Logic Tip: Calcium is the universal "Go!" signal for muscle contraction. It exposes binding sites (activates), it never inactivates them. Knowing Statement C is false instantly eliminates options 1 and 4.
Updated On: May 3, 2026
- C and E only
- A, B and E only
- A and B only
- C and D only
Show Solution
Verified By Collegedunia
The Correct Option is B
Solution and Explanation
Concept:
The sliding filament theory explains muscle contraction. It states that contraction of a muscle fibre occurs by the sliding of the thin (actin) filaments over the thick (myosin) filaments, driven by cross-bridge formation and ATP hydrolysis.
Step 1:
Muscle contraction is initiated by a neural signal sent by the CNS via a motor neuron. This signal reaches the neuromuscular junction and ultimately depolarizes the sarcolemma. Statement A is correct.
Step 2:
The action potential spreads along the sarcolemma and down the T-tubules, triggering the sarcoplasmic reticulum to release stored calcium ions ($Ca^{++}$) into the sarcoplasm. Statement B is correct.
Step 3:
An increase in $Ca^{++}$ levels leads to calcium binding to troponin on the actin filaments. This binding removes the masking of active sites on actin, activating it for cross-bridge formation, rather than inactivating it or breaking bridges. Statement C is incorrect.
Step 4:
During cross-bridge formation, it is the energized myosin head that actively binds to the exposed active sites on the actin filament, not the other way around. Statement D is incorrect.
Step 5:
Once attached, the myosin heads pivot, pulling the attached actin filaments inwards towards the center of the 'A' band (the M-line). This inward pulling shortens the sarcomere, causing contraction. Statement E is correct.
Step 6:
Since only statements A, B, and E represent accurate physiological events during muscle contraction, Option (2) is the correct choice.
The sliding filament theory explains muscle contraction. It states that contraction of a muscle fibre occurs by the sliding of the thin (actin) filaments over the thick (myosin) filaments, driven by cross-bridge formation and ATP hydrolysis.
Step 1:
Muscle contraction is initiated by a neural signal sent by the CNS via a motor neuron. This signal reaches the neuromuscular junction and ultimately depolarizes the sarcolemma. Statement A is correct.
Step 2:
The action potential spreads along the sarcolemma and down the T-tubules, triggering the sarcoplasmic reticulum to release stored calcium ions ($Ca^{++}$) into the sarcoplasm. Statement B is correct.
Step 3:
An increase in $Ca^{++}$ levels leads to calcium binding to troponin on the actin filaments. This binding removes the masking of active sites on actin, activating it for cross-bridge formation, rather than inactivating it or breaking bridges. Statement C is incorrect.
Step 4:
During cross-bridge formation, it is the energized myosin head that actively binds to the exposed active sites on the actin filament, not the other way around. Statement D is incorrect.
Step 5:
Once attached, the myosin heads pivot, pulling the attached actin filaments inwards towards the center of the 'A' band (the M-line). This inward pulling shortens the sarcomere, causing contraction. Statement E is correct.
Step 6:
Since only statements A, B, and E represent accurate physiological events during muscle contraction, Option (2) is the correct choice.
Was this answer helpful?
0
0
Top NEET Biology Questions
- Chordae tendineae are found in
- Glycolysis takes place in
- All the components of the nodal tissue are autoexcitable. Why does the SA node act as the normal pacemakar?
- All vertebrates are chordates but all chordates are not vertebrates, why ?
- The blood calcium level is lowered by the deficiency of
View More Questions
Top NEET Muscle Questions
- Identify the substances having glycosidic bond and peptide bond, respectively in their structure :
Match List I with List II :
List I List II A. Tetany I. Inflammation of joints B. Arthritis II. Autoimmune disorder affecting neuromuscular junction C. Myasthenia gravis III. Wild contraction in muscle due to low Ca++ in body fluid D. Muscular dystrophy IV. Progressive degeneration of skeletal muscle
पेशी संकुचन के संबंध में सही कथनों का चयन कीजिए।
A. प्रेरक तंत्रिका केंद्रीय तंत्रिका तंत्र (CNS) से प्राप्त संकेत को पेशी तंतु के सार्कोलेमा तक ले जाती है।
B. तंत्रिक संकेत एक क्रिया विभव उत्पन्न करता है जिसके कारण सार्कोप्लाज्म में Ca\(^{2+}\) मोचित होते हैं।
C. Ca\(^{2+}\) की वृद्धि ऐक्टिन को क्रॉस सेतु तोड़ने के लिए निष्क्रिय कर देती है।
D. ऐक्टिन, मायोसिन के शीर्ष से जुड़कर क्रॉस सेतु बनाता है।
E. ऐक्टिन तंतुओं का 'A' बैंड के मध्य की ओर खिंचने से सार्कोमियर छोटा हो जाता है।
नीचे दिए गए विकल्पों में से सही उत्तर का चयन कीजिए :
Top NEET Questions
- A coil of inductive reactance $31\, \Omega$ has a resistance of 8 $\Omega$. It is placed in series with a condenser of capacitative reactance $25 \,\Omega$. The combination is connected to an a.c. source of 110 V. The power factor of the circuit is :-
- A liquid compound (x) can be purified by steam distillation only if it is
- In an a.c. circuit with phase voltage V and current I, the power dissipated is
- A bubble in glass slab $ (\mu = 1.5) $ when viewed from one side appears at 5 cm and 2 cm from other side, then thickness of slab is
- A bulb is located on a wall. Its image is to be obtained on a parallel wall with the help of convex lens. If the distance between parallel walls is 'd' then required focal length of lens placed in between the walls is : -
View More Questions