Â© 2000 John Wiley & Sons, Inc. An inverse relationship between household income and violence exposure in youth hasbeen reported in numerous studies (e.g., Garbarino & Crouter, 1978; Gelles, 1992; Gelles& Straus, 1979; Steinberg, Catalano, & Dooley, 1981).
The head, attached to the top of the vertebral column, is balanced, moved, and rotated by the neck muscles (). When these muscles act unilaterally, the head rotates. When they contract bilaterally, the head flexes or extends. The major muscle that laterally flexes and rotates the head is the sternocleidomastoid.
The sternocleidomastoid is a long muscle in the side of the neck that extends up from the thorax to the base of the skull behind the ear. When the sternocleidomastoid on one side contracts, the face is turned to the opposite side. When both muscles contract, the head is bent toward the chest. If the immovable end is fixed in position by other muscles, it can raise the sternum (breastbone) - an action which aids in forceful inhalation of air. The sternocleidomastoid is a long muscle in the side of the neck that extends up from the thorax to the base of the skull behind the ear.