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.
Muscles of the Neck: Head Movements. Head is moved by muscles originating from the axial skeleton. Major head flexor is the sternocleidomastoid muscles. Synergists to head flexion are the suprahyoid and infrahyoid. Lateral head movements are accomplished by the sternocleidomastoid and. scalene muscles.