<prompt> Sternocleidomastoid muscle is supplied by:Vagus nerveSpinal accessory nerveMarginal mandibular branch of facial nerveNone of the above  <response>: The spinal accessory nerve provides the motor supply. It passes through the muscle.The spinal accessory nerve supplies:The sternocleidomastoid, the chin turningThe trapezius, the shrugging muscle.Cervical nerves provide a proprioceptive sensations to these muscles.Reference: B D Chaurasias Head and Neck anatomy, 6th ed page no 384 