Muscular System Health Article

Mechanical injury

Disorders of the muscular system can result from genetic, hormonal, infectious, autoimmune, poisonous, or neoplastic causes. But the most common problem associated with this system is injury from misuse. Sprains and tears cause excess blood to seep into skeletal muscle tissue. The residual scar tissue leads to a slightly shorter muscle. Muscular impairment and cramping can result from a diminished blood supply. Cramping can be due to overexertion. An inadequate supply of blood to cardiac muscle causes a sensation of pressure or pain in the chest called angina pectoris. Inadequate ionic supplies of calcium, sodium, or potassium can also affect most muscle cells adversely.

Immune system disorders

Muscular system disorders related to the immune system include myasthenia gravis and tumors. Myasthenia gravis is characterized by weak and easily fatigued skeletal muscles, one of the symptoms of which is droopy eyelids. Myasthenia gravis is caused by antibodies that a person makes against their own ACh receptors; hence, it is an autoimmune disease. The antibodies disturb normal ACh stimulation to contract skeletal muscles. Failure of the immune system to destroy cancerous cells in muscle can result in muscle tumors. Benign muscle tumors are called myomas, while malignant muscle tumors are called myosarcomas.

Disorders caused by toxins

Muscular disorders may also be caused by toxic substances of various types. A bacterium called Clostridium tetani produces a neurotoxin that causes tetanus, which is a disease characterized by painful repeated muscular contractions. In addition, some types of gangrene are caused by clostridial toxins produced under anaerobic conditions deep within a muscle. A poisonous substance called curare, which is derived from tropical plants of the genus Strychnos blocks neuromuscular transmission in skeletal muscle, causing paralysis. Prolonged periods of ethanol intoxication can also cause muscle damage.

Genetic disorders

The most common type of muscular genetic disorder is muscular dystrophy, of which there are several kinds. Duchenne's muscular dystrophy is characterized by increasing muscular weakness and eventual death. Becker's muscular dystrophy is a less severe disorder than Duchenne's, but both can be classified as X-linked recessive genetic disorders. Other types of muscular dystrophy are caused by a mutation that affects a muscle protein called dystrophin. Dystrophin is absent in Duchenne's and altered in Becker's muscular dystrophies. Other genetic disorders, including glycogen storage diseases, myotonic disorders, and familial periodic paralysis, can affect muscle tissues. In glycogen storage diseases, the skeletal muscles accumulate abnormal amounts of glycogen due to a biochemical defect in carbohydrate metabolism. In myotonic disorders, the voluntary muscles are abnormally slow to relax after contraction. Familial periodic paralysis is characterized by episodes of weakness and paralysis combined with loss of deep tendon reflexes.