The human body is comprised of over 600 muscles. The muscular system makes up nearly half of a person's body weight. There are three different types of muscles in the body: skeletal muscles, cardiac muscles and smooth muscles. All three types of muscles contract, but each type of muscle is responsible for different functions.
Skeletal Muscles
Skeletal muscles, also known as striated muscles, give the body its shape, generate heat, maintain posture and allow the body movement. Skeletal muscles cover the skeleton and are attached to the bone by tendons. Bending the arms, holding the head up and walking are all examples of using skeletal muscles. Skeletal muscles also produce heat through movement, allowing the body to regulate and maintain normal body temperature. Skeletal muscles are voluntary and can be controlled. Body builders target skeletal muscles by lifting heavy weights, causing the targeted muscle to gain mass. Skeletal muscles work together in pairs. When one muscle contracts, allowing the arm to bend, another muscle must extend allowing the arm to straighten.
Cardiac Muscles
Cardiac muscles are involuntary muscles of the heart. The only place cardiac muscles can be found in the body are in the heart. The rest of the muscles in the body are skeletal and smooth muscles. The primary functions of cardiac muscles are to contract and release. When the cardiac muscles contract, blood is pumped out of the heart and circulated throughout the body. When the cardiac muscles release, blood is moved back into the heart. Cardiac muscles have to last the body a lifetime and are highly resistant to fatigue.
Smooth Muscles
Smooth muscles are found inside the organs of the body. Smooth muscles are involuntary muscles, meaning they can not be controlled. In the intestines, smooth muscles contract to push food through the body. The smooth muscles of the bladder contract to expel urine. The smooth muscles located inside the uterus are used in childbirth, helping to push a baby out of the womb. A person who suffers from asthma or allergic reactions will experience narrow airways due to the smooth muscles of the bronchi contracting. Alleviating the condition requires inhalants and drugs to relax to the smooth muscles.
