Splenius capitis and Splenius cervicis share which bilateral action?

Splenius capitis and Splenius cervicis share which bilateral action?

• A. Head and neck extension
• B. Head and neck flexion
• C. Ipsilateral rotation
• D. Shoulder elevation

Answer: (A)

Bilateral contraction of splenius capitis and splenius cervicis extends the head and neck. These muscles run from the spine up to the skull and upper cervical region, so when both sides pull, they act to straighten and tilt the head backward, increasing the angle at the front of the neck. This extension is the defining bilateral action for these muscles. When they contract on one side only (unilaterally), they cause ipsilateral rotation and lateral flexion, which is why that action is not the bilateral one in question. Shoulder elevation isn’t produced by these muscles, since they attach to the skull and cervical spine rather than the shoulder girdle.

Bilateral contraction of splenius capitis and splenius cervicis extends the head and neck. These muscles run from the spine up to the skull and upper cervical region, so when both sides pull, they act to straighten and tilt the head backward, increasing the angle at the front of the neck. This extension is the defining bilateral action for these muscles. When they contract on one side only (unilaterally), they cause ipsilateral rotation and lateral flexion, which is why that action is not the bilateral one in question. Shoulder elevation isn’t produced by these muscles, since they attach to the skull and cervical spine rather than the shoulder girdle.