Class NEET 2026 ALL Q #2064
COMPETENCY BASED
APPLY
4 Marks 2026 NTA-RE-NEET-2026 MCQ SINGLE
Muscle contraction is initiated by a signal sent by the central nervous system by the release of
(A) cyclic adenine monophosphate
(B) acetyl choline
(C) acetyl coenzyme A
(D) cyclic guanine monophosphate
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Correct Answer: B

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Detailed Solution

Step 1: Understanding the Neuromuscular Junction

Muscle contraction begins when a motor neuron sends an action potential to the neuromuscular junction, which is the site of communication between a motor neuron and a muscle fiber.

Step 2: Identifying the Neurotransmitter

Upon the arrival of the action potential at the axon terminal, synaptic vesicles fuse with the plasma membrane and release a neurotransmitter into the synaptic cleft. In the case of skeletal muscle contraction, this specific neurotransmitter is acetylcholine.

Step 3: Evaluating the Options

The released acetylcholine binds to receptors on the sarcolemma, generating an action potential in the muscle fiber, which eventually leads to the release of calcium ions from the sarcoplasmic reticulum. Other options like cyclic AMP or cyclic GMP are secondary messengers in different signaling pathways, and acetyl coenzyme A is involved in cellular respiration.

Final Answer: acetyl choline

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because it requires the student to recall specific physiological mechanisms and apply that knowledge to identify the correct chemical mediator in a biological process.
Knowledge Dimension: FACTUAL
Justification: The question tests the recall of specific terminology and biological facts regarding neurotransmission in the muscular system as defined in the NCERT curriculum.
Syllabus Audit: In the context of NEET, this is classified as KNOWLEDGE (Textbook). This question directly assesses the student's grasp of the 'Locomotion and Movement' chapter, which is a high-yield topic in the NEET biology syllabus.

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