Q.152 Zoology ⭐ 360° Option Elimination Active

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NEET 2026 Zoology Question 152 Solution

Topic: Locomotion and Movement · Official NTA Booklet Code 50

Question

Muscle contraction is initiated by a signal sent by the central nervous system by the release of.

✓

Verified Against NTA Final Answer Key

Option (1) : Acetyl choline

📚 Locomotion and Movement Easy

📋 Given Parameters & Problem Setup

Site of Action Neuromuscular Junction (Motor End Plate)

Trigger CNS motor neuron action potential

Target Effect Action potential generation in sarcolemma

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The 30-Second Exam Hall Shortcut: ⚡ Motor End Plate Gold Standard

⏱️ Save ~40 seconds

Skeletal Neuromuscular Junction = Always Acetylcholine (ACh)!

1 Identify target synapse: Motor neuron junction with skeletal muscle sarcolemma.

2 Recall the primary excitatory neurotransmitter of the vertebrate motor end plate: Acetylcholine.

3 When action potential arrives at axonal terminal, voltage-gated Ca²⁺ influx causes exocytosis of ACh vesicles into the synaptic cleft.

4 ACh binds nicotinic receptors on the sarcolemma, opening Na⁺ channels.

5 Select Option (1): Acetyl choline in 5 seconds.

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Why You Can 100% Trust This Shortcut: NCERT Biology · Locomotion and Movement (Sliding Filament Theory: Actin filaments slide over myosin during muscle contraction).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Neuromuscular Junction Organization

A neural signal reaching the neuromuscular junction (the junction between a motor neuron and the sarcolemma of the muscle fibre) releases a neurotransmitter (acetylcholine) which generates an action potential in the sarcolemma.

\text{Axon Terminal Action Potential} \xrightarrow{\text{Ca}^{2+} \text{ Influx}} \text{Exocytosis of ACh} \xrightarrow{\text{Synaptic Cleft}} \text{Sarcolemma Depolarization}

• Vesicles in synaptic knobs fuse with presynaptic membrane and release ACh into synaptic cleft.

Step 2

Excitation-Contraction Coupling

This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm from the sarcoplasmic reticulum, initiating sliding filament contraction.

\text{Action Potential} \xrightarrow{\text{T-tubules}} \text{Sarcoplasmic Reticulum} \xrightarrow{\text{Release of Ca}^{2+}} \text{Troponin C Binding}

• Acetylcholinesterase subsequently degrades ACh to terminate muscle stimulation.

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360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. Acetylcholine is the universal neurotransmitter at vertebrate neuromuscular junctions.

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Why this is airtight: None; standard textbook knowledge.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Adrenaline (epinephrine) is an adrenal medullary hormone and sympathetic neurotransmitter, not the motor end plate neurotransmitter.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing sympathetic fight-or-flight hormones with somatic motor neurotransmitters.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Noradrenaline is the postganglionic sympathetic neurotransmitter for smooth muscles and cardiac tissue.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing autonomic nervous system with somatic skeletal motor innervation.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Dopamine is a central nervous system neurotransmitter (involved in reward and basal ganglia motor control), not released at the peripheral neuromuscular junction.

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Student Fallacy (Why candidates pick this trap): Associating dopamine with motor coordination and wrongly placing it at muscle end plates.

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NTA Trap Alert: Autonomic vs. Somatic Neurotransmitter Mix-up

Students sometimes confuse sympathetic neurotransmitters (adrenaline/noradrenaline) with somatic motor neuron transmitters. Somatic motor neurons exclusively release acetylcholine onto nicotinic receptors.

🛡️ How to avoid the -1 mark: Remember: Somatic motor neuron -> Skeletal muscle ALWAYS equals Acetylcholine (ACh).

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Core NEET Syllabus Standard

NEET Biology Core Syllabus · Locomotion and Movement Standard Benchmark

Core Scientific Principle Tested:

"Neuromuscular junction releases acetylcholine to generate an action potential in the sarcolemma."

Syllabus Focus: Mechanism of Muscle Contraction

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

ACh = Action of Contraction Happens!

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NEET 2026 Zoology Question 152 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Motor End Plate Gold Standard

Step-by-Step Rigorous Workflow & Mathematical Proof

Neuromuscular Junction Organization

Excitation-Contraction Coupling

360° Option Elimination Engine Key Feature

NTA Trap Alert: Autonomic vs. Somatic Neurotransmitter Mix-up

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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