Question

Unilateral contraction of the ______ results in lateral flexion and rotation of the head to the opposite side; bilateral contraction flexes the head and neck.

a. sternocleidomastoid
b. splenius capitis and cervicis
c. longissimus capitis
d. superior oblique
e. splenius

Answer 1

The sternocleidomastoid muscle is responsible for the unilateral rotation of the head to the opposite side and lateral flexion. Bilateral contraction of this muscle leads to flexion of the head and neck.

Step-by-step explanation:

Unilateral contraction of the sternocleidomastoid muscle results in lateral flexion and rotation of the head to the opposite side; bilateral contraction flexes the head and neck. The sternocleidomastoid is the major muscle responsible for these movements. When it contracts on one side, it causes the head to rotate to the opposite side, and when both sides contract together, they act as flexors of the head and neck. To feel this muscle in action, you can place your fingers on both sides of your neck and turn your head from side to side, the movement can be felt originating in the sternocleidomastoid.