In some situations the of the
skeletal striated does not
depend upon of the superior
motor , i.e., it is not
by volition.

Involuntary movements those
muscles may happen sensory
fibers that make or indirect
connection with motor neurons
are unexpectedly in
situations that suggest to the
body. This , for example, in the
reflex, or knee jerk , when
a sudden percussion the knee patella
(kneecap) an involuntary
contraction of quadriceps (the
extension muscle the thigh). Another
example the arch reflex occurs
someone steps on a object: one
leg retracts the other, by the
reflex, distends to maintain
equilibrium of the body.