Summary:
- The muscular system consists of all the muscles of the body.
- Muscles are organs composed mainly of muscle cells, which are also called muscle fibers.
- Each muscle fiber is a very long, thin cell that can do something no other cell can do.
- There are three types of human muscle tissue: smooth muscle (in internal organs), skeletal muscle, and cardiac muscle (only in the heart) Contractions of skeletal muscle are voluntary, or under conscious control.
- When cardiac muscle contracts, the heart beats and pumps blood.