What is the primary neurotransmitter used at the neuromuscular junction?

What is the primary neurotransmitter used at the neuromuscular junction?

• A. Glutamate
• B. Acetylcholine
• C. GABA
• D. Dopamine

Answer: (B)

At the neuromuscular junction the signal from the motor neuron is transmitted mainly by acetylcholine. When an action potential arrives, acetylcholine is released into the synaptic cleft and binds to nicotinic acetylcholine receptors on the muscle endplate. These receptor channels are ligand-gated ion channels, so their opening lets sodium (and a bit of calcium) into the muscle cell, depolarizing the endplate enough to trigger a muscle action potential and, ultimately, contraction. The signal is quickly terminated by acetylcholinesterase, which breaks down acetylcholine in the cleft, with choline recycled for reuse. Glutamate, GABA, and dopamine are important neurotransmitters in the brain and other systems, but they are not the primary transmitter at the neuromuscular junction.

At the neuromuscular junction the signal from the motor neuron is transmitted mainly by acetylcholine. When an action potential arrives, acetylcholine is released into the synaptic cleft and binds to nicotinic acetylcholine receptors on the muscle endplate. These receptor channels are ligand-gated ion channels, so their opening lets sodium (and a bit of calcium) into the muscle cell, depolarizing the endplate enough to trigger a muscle action potential and, ultimately, contraction. The signal is quickly terminated by acetylcholinesterase, which breaks down acetylcholine in the cleft, with choline recycled for reuse. Glutamate, GABA, and dopamine are important neurotransmitters in the brain and other systems, but they are not the primary transmitter at the neuromuscular junction.