Splenius capitis acts unilaterally to produce which motion?

Splenius capitis acts unilaterally to produce which motion?

• A. Ipsilateral flexion and rotation
• B. Contralateral rotation
• C. Bilateral head extension
• D. Neck flexion of the trunk

Answer: (A)

Unilateral contraction of the Splenius capitis pulls the head toward the same side and bends the neck to that side. Because the muscle crosses from the spine to the back of the skull, it shortens on one side to rotate the face to that same side and to produce lateral flexion (ipsilateral flexion) of the head. This matches the chosen option, which describes ipsilateral flexion and rotation. Bilateral contraction would extend the head, and motions like contralateral rotation or trunk flexion aren’t produced by the Splenius capitis when acting on one side.

Unilateral contraction of the Splenius capitis pulls the head toward the same side and bends the neck to that side. Because the muscle crosses from the spine to the back of the skull, it shortens on one side to rotate the face to that same side and to produce lateral flexion (ipsilateral flexion) of the head. This matches the chosen option, which describes ipsilateral flexion and rotation. Bilateral contraction would extend the head, and motions like contralateral rotation or trunk flexion aren’t produced by the Splenius capitis when acting on one side.