splenius: either of two flat muscles that extend from the upper vertebrae to the base of the skull and serve to rotate or flex or extend the head and neck
skeletal muscle: a muscle that is connected at either or both ends to a bone and so move parts of the skeleton; a muscle that is characterized by transverse stripes
classical conditioning: conditioning that pairs a neutral stimulus with a stimulus that evokes a reflex; the stimulus that evokes the reflex is given whether or not the conditioned response occurs until eventually the neutral stimulus comes to evoke the reflex