An irregular heartbeat, medically referred to as an arrhythmia, is common during pregnancy. Approximately 50 percent of pregnant women experience some kind of irregularity in their heart rhythm, according to Cleveland Clinic.

The internal carotid artery provides blood supply to most of the brain's cortex on one side, including the frontal, parietal and temporal lobes. Only the posterior parts of the brain are supplied by different arteries.

Methylsulfonylmethane, or MSM, is organic sulfur used by the body to grow bone, hair and nails. Drugs.com reports that MSM may be useful in elevating conditions such as arthritis or allergies. It is also used as a combatant against some parasitical infections.

Several years before menopause, you may begin to experience a variety of symptoms that your ovaries are failing. Premenopausal women may experience such a wide range of symptoms -- headaches, joint aches, hot flashes, sleep disturbances -- that one woman's journey may be completely different from that of her friends.

Vitamins play a vital role in sustaining a healthy respiratory system and reducing your risk of diseases, such as chronic obstructive pulmonary disease, emphysema, bronchitis, tuberculosis, pneumonia and asthma. Chronic lower respiratory diseases are the fourth leading cause of death in the United States.

Pressure in the ears, also known as aural fullness, can be caused by a number of reasons, most of which are temporary and disappear on their own. According to Dr. Douglas Hoffman in his column AllHealth.

Proteins are important structural and functional biomolecules that are a major part of every cell in your body. There are 2 nucleic acids -- DNA and RNA. Your cells make proteins by following the instructions encoded in your DNA, which is genetic material and a type of nucleic acid.

Throughout development from infancy to adulthood, normal vital signs change. Due to anatomical differences, what is normal for one age group could be abnormal for another. Normal pulse rate changes substantially from infancy to middle childhood. By age 12, the normal pulse rate approximates that of an adult.

Your body's muscle tissue contains several enzymes, which are catalysts that cause chemical reactions. Your muscles require chemical reactions to supply them with energy, help them repair damage and help them function. High muscle enzymes in your blood can mean that muscle cells have been damaged.

You've no doubt experienced a muscle cramp before. It's extremely painful but usually doesn't last long. Sometimes you get them while you exercise or right after your workout. Or you might get them in the middle of the night.

Cramps are painful muscle spasms that can occur after intense exercise or competition. Cramps are not usually dangerous, but can be extremely painful. Besides overuse, muscle cramps can stem from dehydration, diuretic medications or an imbalance of the minerals calcium, magnesium and potassium.

Breathing can be a conscious or unconscious act. We can hold our breath or breathe deep even while the rest of our body is asleep. Without the respiratory system our body could not get the vital oxygen it needs to function. Lungs themselves are made of a soft, spongy material that contain no muscle at all.