Muscular System

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The muscular system is responsible for the movement of the human body.

Explain how skeletal muscle contracts, including the release of calcium ions from the sarcoplasmic reticulum, the formation of cross-bridges, the sliding of actin and myosin filaments and the use of ATP.

The myosin filaments have heads which form cross-bridges when they are attached to binding sites on acting filaments. ATP binds to the myosin heads and causes them to break the cross bridges by detaching from the binding sites. ATP is hydrolyzed to ADP and phosphate, causing the myosin heads to change their angle. The heads attach to binding sites on actin that are further from the center of the sarcomere than the previous sites.


Disorders in the muscular system

Muscular dystrophy is a group of diseases that cause progressive weakness and loss of muscle mass. Some who have muscular dystrophy can lose their ability to walk. Some may have trouble breathing or swallowing. There is no cure for muscular dystrophy but medications and therapy can help maintain symptoms and slow down the disease.

You have flatfeet when the arch on the inside of your feet is flattened, allowing the entire sole of your foot to touch the floor when you stand up. A common and painless condition, flatfeet occur when the arches don't develop during childhood. Most people have little to no signs or symptoms associated with flatfeet. Your family doctor may refer you to a doctor specializing in foot disorders or sports medicine.