Are all motor units in facial muscles always activated when muscle is used?

[jjylonen]

I'm making Master's Thesis in university, relating to neuroscience.

From following issue I have found contradictory information, so can you confirm is it correct or not.

 

"In facial muscles (or in all muscles innervated by cranial nerves) all motor units are always activated when muscle is used, and only action potential rate changes when used force changes."

 

If there's differences in muscles innervated by different cranial nerves, how it goes in muscles innervated by facial nerve and in muscles innervated by trigeminal nerve.

Edited April 20, 2015 by jjylonen

[Cubbly]

yes and no certain muscles in your face activate and some do not