The skeletal muscles and partially the respiratory.
Body swap carries the connotation of being voluntary, whereas switched bodies is more reminiscent of accidental body-swapping.
Voluntary means you have voluntary control, while the involuntary you do not have voluntary control of them.
do voluntary job.
voluntary
voluntary informant
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I played a voluntary on the organ on Sunday. Your response to my request is entirely voluntary.
It is voluntary because your voluntary muscells in the arm are preforming this action.
Voluntary .. you make the choice to for example get a soda can .. blinking, breathing are involuntary you don't have to think about it
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