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 :
This question was previously asked in
NEET UG Re-Exam 2026 Question Paper (21-Jun-2026)
The correct answer is
A, B, D and E only
Muscle Contraction: Statement Analysis
This section analyzes the statements related to the mechanism of muscle contraction to identify the correct ones.
Analyzing Statement A: Motor Neuron Signal
- Statement: "A motor neuron carries a signal sent by the Central Nervous System (CNS) to the sarcolemma of the muscle fibre."
- Analysis: This statement is correct. Motor neurons are responsible for transmitting nerve impulses from the CNS to muscle fibres, initiating muscle contraction at the neuromuscular junction on the sarcolemma.
Analyzing Statement B: Action Potential and Calcium Release
- Statement: "The neural signal generates an action potential which causes the release of Ca$^{++}$ into sarcoplasm."
- Analysis: This statement is correct. The arrival of a nerve impulse triggers an action potential in the muscle fibre membrane (sarcolemma) and T-tubules, leading to the release of calcium ions (Ca$^{++}$) from the sarcoplasmic reticulum into the sarcoplasm.
Analyzing Statement C: Calcium and Actin Interaction
- Statement: "Increase in Ca$^{++}$ inactivates the actin for breaking cross bridges."
- Analysis: This statement is incorrect. Calcium ions (Ca$^{++}$) bind to troponin, causing tropomyosin to shift away from the myosin-binding sites on actin. This process *activates* actin, allowing myosin heads to bind and form cross bridges, rather than inactivating it.
Analyzing Statement D: Actin-Myosin Binding
- Statement: "Actin binds to the myosin head to form a cross bridge."
- Analysis: This statement is correct. The interaction between the myosin heads and the actin filaments forms the cross bridges, which are essential for generating force during muscle contraction.
Analyzing Statement E: Sarcomere Shortening
- Statement: "Shortening of sarcomere takes place, by pulling actin filaments towards the centre of 'A' band."
- Analysis: This statement is correct. According to the sliding filament theory, during contraction, the actin filaments slide past the myosin filaments towards the M-line (center of the A band), causing the sarcomere to shorten.
Conclusion: Correct Statements
Based on the analysis, the correct statements are A, B, D, and E.
Therefore, the option that includes all these correct statements is the right choice.
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Similar Questions
- Which of the following statements are correct with reference to human endoskeleton ?
A. Human skull is monocondylic.
B. The joint between any two adjoining vertebrae is a cartilaginous joint.
C. In human beings the number of cervical vertebrae is seven.
D. All ribs except the last 2 pairs are bicephalic.
E. The occipital bone of skull is articulated with atlas vertebra.
Choose the correct answer from the options given below : - Match List I with List II related to muscular/skeletal system :
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
Choose the correct answer from the options given below : - Which of the following statements about the reabsorption process in Henle's loop are correct ?
(a) The descending limb of Henle's loop is permeable to water but almost impermeable to electrolytes.
(b) Urine gets concentrated in Henle's loop.
(c) Reabsorption of Na$^+$ and water takes place in Henle's loop.
(d) Active or passive transport of electrolytes occurs in the ascending limb of Henle's loop.
Choose the correct answer from the options given below :
Important Questions from Human Anatomy and Physiology-IV
- Which of the following statements are correct with reference to human endoskeleton ?
A. Human skull is monocondylic.
B. The joint between any two adjoining vertebrae is a cartilaginous joint.
C. In human beings the number of cervical vertebrae is seven.
D. All ribs except the last 2 pairs are bicephalic.
E. The occipital bone of skull is articulated with atlas vertebra.
Choose the correct answer from the options given below : - Match List I with List II related to muscular/skeletal system :
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
Choose the correct answer from the options given below : - Which of the following statements about the reabsorption process in Henle's loop are correct ?
(a) The descending limb of Henle's loop is permeable to water but almost impermeable to electrolytes.
(b) Urine gets concentrated in Henle's loop.
(c) Reabsorption of Na$^+$ and water takes place in Henle's loop.
(d) Active or passive transport of electrolytes occurs in the ascending limb of Henle's loop.
Choose the correct answer from the options given below :
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