neck muscles: MA

Question 1

sternocleidomastoid

Answer 1

Unilateral contraction: tilts head to same side (i.e., laterally flexes neck) and rotates it so face is turned superiorly toward opposite side.
Bilateral contraction: (1) extends neck at atlanto-occipital joints, (2) flexes cervical vertebrae so that chin approaches manubrium, or (3) extends superior cervical vertebrae while flexing inferior vertebrae, so chin is thrust forward with head kept level.

Question 2

platysma

Answer 2

Draws corners of mouth inferiorly and widens it as in expressions of sadness and fright;
Draws skin of neck superiorly when teeth are clenched