Muscle

Muscle is a tissue type found in the bodies of animals . The purpose of muscle is to move a part of the body, often by applying force to the bones. Muscles do this by contracting and relaxing. Contraction is caused by electrical impulses transmitted by the nerves. Muscles and muscular activity account for a lot of the body's energy consumption.

There are three general types of muscle:

• skeletal muscle[?] - often voluntary (over 600 in the human body). These enable movement and locomotion.
• smooth muscle[?] - involuntary, such as in the intestines and blood vessels.
• cardiac muscle[?] - present in the heart.

These three types of cells have many differences, but all use the movement of actin[?] against myosin[?] to produce contraction.

The strength of skeletal muscle is directly proportional to its cross-sectional area. The strength of a body, however, is determined by biomechanical principles (the distance between muscle insertions and joints, muscle size, and so on).

Motor skills are the abilities of proper use of the muscles. They depend also on the proper functioning of the brain, nerves and joints, and the bones being intact. One application of motor skills is locomotion.

Dexterity is the ability of a person to manipulate objects. It relies on good hand to eye coordination[?]. A criminal application is pickpocketing.

See also : myotomy, sphincter, list of muscles in the human body