The jaw muscles assist the jaw's complex three-dimensional movements. The physical makeup of the masticatory muscles reflects the type of activity required. Jaw muscles work to open and close in coordination with the cerebellum in the brain. The jaw muscle sequencing of opening and closing is “rhythm pattern generated”. Consider this pattern the harmonized motion of the jaw. When the openers are engaged, the closers are silenced. When the jaw is strained, the lateral pterygoids (jaw opening muscles) fatigue, the opener/closer muscles fire out of sequence. The jaw closing muscles are the masseter, temporalis and medial pterygoid. When jaw muscles get overstretched, the natural rhythms are interrupted and protective muscle guarding is often triggered, causing a state of sustained contraction and hypertonicity. Temporomandibular joints and associated muscles, tendons and ligaments are in continuous use and are difficult to immobilize for healing.