Neuromuscular Junction Labeled Diagram

Where a motor neuron meets a muscle fibre, placed and then enlarged: 12 parts to name.

Neuromuscular Junction Labeled Diagram

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Write the name of each numbered part.Answer key

  1. Motor neuron axon
  2. Skeletal muscle fiber
  3. Neuromuscular junction
  4. Axon terminal
  5. Synaptic vesicles
  6. Acetylcholine (ACh)
  7. Synaptic cleft
  8. Acetylcholinesterase (AChE)
  9. Acetylcholine receptors
  10. Junctional folds
  11. Sarcolemma
  12. Motor end plate

Drawn for this site on 2026-10-05 by script. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: the neuron the signal comes from

All 12 parts on the diagram

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Start here: 8 main parts 8

  1. Motor neuron axon The long process of a motor neuron. It carries the action potential from the spinal cord or brainstem to the muscle and branches to its fibres.
  2. Neuromuscular junction Where a motor neuron's terminal meets the muscle fibre. Here the fibre first responds to the neuron's signal.
  3. Axon terminal The swollen end of the axon branch. It releases acetylcholine into the synaptic cleft.
  4. Synaptic vesicles Sacs of acetylcholine that fuse with the terminal's membrane when calcium enters. This releases their contents into the cleft.
  5. Acetylcholine (ACh) The neurotransmitter released at the junction. It diffuses across the cleft and binds to receptors on the muscle fibre.
  6. Synaptic cleft The tiny space between the nerve ending and the muscle fibre. It is about 30 nanometres.
  7. Acetylcholine receptors Receptors in the motor end plate. When ACh binds, a channel opens and positive ions enter, depolarising the fibre.
  8. Motor end plate The part of the sarcolemma that holds the acetylcholine receptors. Formed by the junctional folds.

Where it is: 3 1

  1. Skeletal muscle fiber A single skeletal muscle cell. Every one is supplied by a motor neuron at a neuromuscular junction.

Nerve side and cleft: 5 1

  1. Acetylcholinesterase (AChE) The enzyme in the cleft that breaks down acetylcholine. That stops it keeping the channels open.

Muscle side: 4 2

  1. Junctional folds Infoldings of the sarcolemma under the terminal. They increase the surface facing the cleft.
  2. Sarcolemma The cell membrane of the muscle fibre. The action potential sweeps along it after the end plate is stimulated.

How this list was compiled: Read 2026-09-26. OpenStax Anatomy and Physiology 2e, section 10.2 Skeletal Muscle, https://openstax.org/books/anatomy-and-physiology-2e/pages/10-2-skeletal-muscle : the NMJ as where a motor neuron's terminal meets the muscle fibre, every fibre supplied at one; motor neurons from the spinal cord and brainstem with long axons; the axon terminal releasing acetylcholine, which diffuses across the synaptic cleft to ACh receptors in the motor end-plate of the sarcolemma, opening a channel for positive ions and depolarising the fibre; the action potential spreading along the sarcolemma; acetylcholinesterase degrading ACh in the cleft. Wikipedia, Neuromuscular junction, https://en.wikipedia.org/wiki/Neuromuscular_junction : calcium entry triggering synaptic vesicle fusion and release; the postjunctional folds of the sarcolemma increasing its surface and forming the motor endplate, studded with nicotinic receptors; terminal boutons; the 30 nanometre cleft holding acetylcholinesterase. Licence: own work

The drawing: Drawn for this site on 2026-10-05 by script. Own work, nothing traced. The junctional folds follow the form seen in the public domain electron micrograph of a neuromuscular junction in cross-section by the National Institute of Mental Health (https://commons.wikimedia.org/wiki/File:Electron_micrograph_of_neuromuscular_junction_(cross-section).jpg); the nerve branching onto muscle fibres is drawn from the general form of a teased nerve and muscle preparation. Licence: own work

How it works

A neuromuscular junction labeled diagram in two figures: a motor axon reaching a muscle fibre, then the junction enlarged from the axon terminal down to the motor end plate. Start with the 8 main parts.

Read the full guide

From nerve to muscle

An action potential reaches the axon terminal, synaptic vesicles release acetylcholine, and it crosses the synaptic cleft to receptors in the motor end plate. Positive ions flow in, and an action potential sweeps along the sarcolemma.

Why the folds and the enzyme

Junctional folds give the end plate more surface facing the cleft. Acetylcholinesterase in the cleft breaks acetylcholine down, so it cannot keep reopening the channels and prolong the contraction.

  • Nerve side on top, muscle side below: vesicles and terminal belong to the neuron; receptors, folds and end plate to the muscle.

Questions and answers

What happens at the neuromuscular junction?

The axon terminal releases acetylcholine, which crosses the synaptic cleft and binds receptors in the motor end plate. That opens channels, depolarises the muscle fibre and starts the action potential that leads to contraction.

What is the motor end plate?

The part of the muscle fibre's sarcolemma under the axon terminal that holds the acetylcholine receptors, folded into junctional folds.

What does acetylcholinesterase do?

It breaks down acetylcholine in the synaptic cleft, so the signal stops and the muscle is not kept excited.

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