The human body has three types of muscle. Cardiac muscle brings about contractions of the heart; smooth muscle works on body organs, such as by constricting blood vessels; skeletal muscle is under voluntary control of the somatic nervous system (Kroemer et al. 1997, 2001) and serves two purposes: one is to maintain the body’s postural balance, the other is to cause local motion of body segments by pulling on the bones to which the muscles attach, thereby creating torques or moments around the body joints. There are several hundred skeletal muscles in the human body, identified by their Latin names. The Greek words for muscle, mys or myo, are prefixes for descriptive terms, such as myofibrils (see below).