Calcium is one of the most common minerals in the human body, and 99 percent of the calcium in your body is stored in your bones and teeth, according to the Office of Dietary Supplements. Calcium serves several vital functions within your body. It plays a role in nerve conduction, constriction and relaxation of blood vessels, and hormone secretion. Calcium also plays a vital role in muscle contraction, including your cardiac and skeletal muscles.
Structure of Muscle
Muscle cells form the bundles of muscle fibers that make up individual muscles. Muscle fibers are divided into sections called sarcomeres, and each sarcomere contains tiny structures called myofilaments, which cause muscle contractions by sliding across each other, which shortens the length of the muscle fiber.
Myofilaments and Contractions
Some myofilaments contain a protein called actin, while other myofilaments contain a protein called myosin. Actin and myosin are naturally attracted to each other; when exposed to each other, they pull the opposing filaments toward each other, which causes them to slide across each other. Two other proteins, troponin and tropomyosin, are chained together and act as a barrier across the filament. Troponin and tropomyosin keep the actin and myosin apart so that your muscles do not remain perpetually contracted.
Calcium and Muscle Contractions
When the brain signals the muscle to contract, the body pulls calcium from the blood into the muscle cells. The calcium binds with the troponin and draws it out of position. The tropomyosin follows the troponin because the two proteins are linked together. When the troponin and tropomyosin move, this activates the actin and myosin to move toward each other and contract the muscle. When the calcium dissipates, the troponin and tropomyosin move back into position, the myosin and actin separate, and the filaments slide apart to relax the muscle.
If you do not get enough calcium from your diet, your body will pull calcium from your bones to fuel muscle contractions and other vital functions. Initially, calcium-deficient individuals might not experience any symptoms, but prolonged deficiencies can cause bone loss. If the deficiency becomes more severe, such as with a chronic eating disorder, it can adversely affect all the muscles in your body. Individuals with severe calcium deficiencies will experience muscle weakness, numbness and tingling in the fingers, and abnormal heart rhythms. Severe calcium deficiencies can also lead to cardiac arrest and death.