Ball and socket joints: rotate until constrained either by the pelvis or the shoulder blade and clavicle.
Hinge joints: arc until constrained by the particular end of the joint which locks into place and does not allow over movement.
Vertebrae: is held in place by sheaths of muscle i.e. torso and neck which keeps the vertebrae in place while allowing the column to pivot.
If you want more study into the Anatomy of the Muscles of the Head and Neck check out the lecture by John Simmons only 7 minutes long, well worth watching for any animator. Click Here