The muscular system is made up of several different types of muscles, each of which performs a different task. These include skeletal, smooth, and cardiac muscles. Other parts of the muscular system include tendons, ligaments, and bones. All of these parts work together to help enact both voluntary and involuntary movements within the body.
The skeletal muscles are the parts of the muscular system that most people think of when they hear the term “muscle.” Each muscle is connected to a corresponding part of the skeleton, and is made up of many fibers bound together. Typically, moving these types of muscles is a voluntary act, although some conditions can cause involuntary movements. Movements are caused by contracting the muscle adjacent to the area that is being moved, rather than the one directly attached to it. For example, the biceps in the upper arm are responsible for bending and releasing the elbow and lower arm.
The skeletal muscles and the bones to which they are connected make up the musculoskeletal system. Tendons, which are similar to a very strong rubber band, attach the muscles to the bones, while ligaments, also strong bands, attach the bones to each other. The tendons and ligaments also help determine how much range of motion a parts of the body have. The joints, junctures where two bones meet, also control range of motion. Although the bones, tendons, ligaments and joints are not actual muscles on their own, they play an important role in how the muscles are used.
Smooth muscle is found throughout the body in many of the vital organs, including the digestive system and the bladder. These components of the muscular system move involuntarily, meaning that people do not have to think about moving them. For example, the stomach empties its contents based on signals from the brain and other parts of the digestive system. Unlike skeletal muscles, which feature a crosshatch pattern created by criss-crossing fibers, smooth muscles are made up of sheets with a smooth surface.
The cardiac muscles, found in the heart, are responsible for the important task of contracting the heart, making them one of the most important parts of the muscular system. The structure of the cardiac muscles is very similar to that of the skeletal muscles, but it is an involuntary muscle like the smooth muscles. The cardiac muscles also contain more energy-producing cells than the skeletal muscles. While people can survive if their skeletal muscles tire out, the cardiac muscles must be able to work at a constant, steady pace.