Question

multiple choice question

contraction of the right sternocleidomastoid turns the head toward the left. what type of movement is this?

ipsilateral
bilateral
contralateral

Explanation:

Analyze the muscle action

Using the Sternocleidomastoid Muscle knowledge point
The right sternocleidomastoid muscle originates on the right sternum/clavicle and inserts on the right mastoid process. When it contracts unilaterally, it pulls the right mastoid process anterolaterally, rotating the face/head to the opposite side (the left).

Define directional terms

• Ipsilateral: Refers to a movement or structure on the same side of the body as the stimulus or muscle contraction.
• Bilateral: Refers to both sides of the body acting together (e.g., when both sternocleidomastoid muscles contract, they flex the neck forward).
• Contralateral: Refers to a movement or structure on the opposite side of the body from the stimulus or muscle contraction.

Determine the movement type

Since contraction of the muscle on the right side causes rotation of the head toward the left (the opposite side), this is a contralateral movement.

Answer:

• Ipsilateral
• Bilateral
• Contralateral (Correct answer)