Biology · Locomotion and Movement · NEET
By the nerve. The motor neuron (nerve ending) releases acetylcholine at the neuromuscular junction. The muscle does NOT make it. The muscle's job is to receive this chemical and respond by making an action potential on its sarcolemma. NEET loves to test who releases what, so remember: nerve releases acetylcholine, muscle responds.
Acetylcholine makes it. When acetylcholine binds to the sarcolemma (muscle membrane), it generates an action potential in the sarcolemma. So the order is: motor neuron signal to acetylcholine to action potential to calcium release. The action potential is an electrical wave, and acetylcholine is the chemical that triggers it.
Acetylcholine comes first. Full chain: CNS signal to motor neuron to acetylcholine (at neuromuscular junction) to action potential (on sarcolemma) to release of calcium ions into the sarcoplasm to contraction. Students often jump straight to calcium and forget the two steps before it. Learn the whole ladder because NEET 2026 asked for the correct ordered statements.
It is the meeting point between the tip of a motor neuron and the muscle fibre. It is also called the motor end plate. Here the electrical nerve signal is passed to the muscle as a chemical signal (acetylcholine). It is the exact spot attacked in the disease myasthenia gravis, which is why it appears in NEET disorder questions too.
No. Acetylcholine does not pull the filaments itself. It only starts the chain: it triggers the action potential, which triggers calcium release, and it is the calcium that unmasks the actin active sites so myosin can form cross bridges. Acetylcholine is the starter (trigger), calcium is the switch that allows contraction.
Muscle contraction is initiated by a signal sent by the central nervous system by the release of _____.
Choose the correct statements regarding muscle contraction. A. A motor neuron carries a signal sent by the CNS to the sarcolemma of the muscle fibre. B. The neural signal generates an action potential which causes the release of Ca2+ into sarcoplasm. C. Increase in Ca2+ 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.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
At the neuromuscular junction, also called the motor end plate, which is the junction between the motor neuron and the muscle fibre.
It is an electrical wave that spreads along the sarcolemma (muscle cell membrane) after acetylcholine binds. It travels inward and triggers the release of calcium ions into the sarcoplasm.
The action potential comes first. It is generated in the sarcolemma and it then causes the release of calcium ions into the sarcoplasm.
NEET repeatedly tests the exact ordered sequence (acetylcholine to action potential to calcium) and the trap word acetyl-CoA. Both ReNEET 2026 and NEET 2026 asked questions built on this chain, so knowing the order and the correct chemical earns easy marks.
An enzyme (acetylcholinesterase) at the junction breaks it down so the signal stops. NCERT does not stress this at Class 11 depth, but it explains why the muscle relaxes when nerve signalling stops.
