Table 1 Selected differences between skeletal muscle cells, smooth muscle cells and their respective motoneurons.

Discharge frequency

Rather high and modulated over wide range, e.g. around 40 Hz for full activation of upper extremity muscles²³

Rather low and discontinuous, maximum around 10 Hz²⁴

Nerve-muscle-interface

Direct: neuromuscular synapse (chemical) between motoaxon and muscle fiber^25,26

Indirect: chemical synapse between motoneuron and ICC, electrical synapse between ICC and SMC^20,27,28

Neurotransmitters

Acetylcholine, possibly modulated by glutamate (no human data)^29,30,31

Acetylcholine, purines, and neuropeptides, e.g. substance P, complex local network with even more transmitters and mediators^22,32,33

Muscle cell acetylcholine receptor

Nicotinic receptor (α₁)₂β₁δε³⁴

Muscarinic receptors (M_2, M₃), nicotinic receptors of α3β2-, α3β4- and/or α7-subtype^35,36

neuronal action potential

carried by sodium channels, most likely NaV 1.6^37,38

carried by sodium channels, most likely NaV 1.5, NaV 1.9³⁹