Description of neurotransmitter of neuromuscular junction

Question

Give a brief description of neurotransmitter of neuromuscular junction? How does nervous system trigger the muscle contraction?

Answer 1

Nervous cells which trigger muscle contraction are motor neurons. Neurotransmitter of motor neurons is acetylcholine. When a motor neuron is stimulated depolarizing current flows along the membrane of its axon till reaching the synapse at neuromuscular junction (neural impulse passage zone between axon extremity and sarcolemma). Near the axonal extremity depolarization permits entrance of calcium ions in the axon (note that calcium also has a relevant function here). The calcium ions excite the neuron to liberate acetylcholine in synapse.

Acetylcholine then binds to special receptors into outer surface of sarcolemma, permeability of this membrane is changed and an action potential is created. The depolarization is then conduced along sarcolemma to sarcoplasmic reticulum that thus liberates calcium ions for sarcomere contraction.