Muscles and nerve fibers allow a person to move their body and enable the internal organs to function.
There are more than 600 muscles in the human body. A kind of elastic tissue makes up each muscle, which consists of thousands, or tens of thousands, of small muscle fibers.
Impulses from nerve cells control the contraction of each muscle fiber. A muscle’s strength depends mainly on how many fibers are present.
Humans and other vertebrates have three typesTrusted Source of muscle: skeletal, smooth, and cardiac.
Skeletal muscles move the external parts of the body and the limbs. They cover the bones and give the body its shape.
Skeletal muscles are striated, which means that they consist of thousands of equally sized sarcomeres, or muscle units, which have transverse bands.
Cardiac musclesTrusted Source are responsible for the heartbeat and only exist in the heart.