A certain amount of potassium is required by all cells, but too much can be harmful and even fatal. Potassium overdose usually causes no symptoms until the blood potassium rises above 6.5 or 7.0 meq/L. When present, symptoms typically involve the nerves, heart or digestive system.

When you exercise, many physiological changes take place to make sure your muscles have enough oxygen to do their job. You blood vessels are able to widen and narrow to redirect the flow of oxygenated blood to your exercising muscles.

Diseases and illnesses target all body systems, such as the circulatory, digestive, reproductive, endocrine, neurological, skeletal and muscular systems. Sources of diseases include genetics, bacteria, poor nutrition, viruses, parasites and fungi.

Bones might be the first thing that comes to mind when you think of calcium, but calcium performs other tasks in the body besides building strong bones. Calcium also helps transmit nerve impulses and regulate muscle contractions.

New studies appear almost daily on the benefits of exercise, from lowering your risk of heart disease to improving memory. Whether you exercise for strength, endurance, or flexibility, the functioning of the body is related to physiological functioning.

The human body has 11 major organ systems, each with specific functions and energy needs. The cardiovascular system, or CVS, serves all of them, delivering vital nutrients, picking up and distributing metabolic products and carrying away waste for elimination.

A powdered-sugar doughnut and a chewy, whole-grain baguette are both carbohydrates, but they are broken down differently by the body. Carbohydrates fall into three basic categories: sugars, starches and cellulose. Simple sugars, or monosaccharies -- such as might be found in your doughnut -- are digested very quickly.

Ten main body systems work in concert to maintain your health. These systems rely on a healthy diet to supply the specific nutrients required for optimum performance. Carbohydrates, lipids, proteins, vitamins and minerals all provide your body systems with the building blocks and fuel required to stay healthy.

Weightlifting for males involves getting stronger and sometimes bigger. A certain level of muscle soreness will come from intense workouts with weights, and that can include discomfort with the nipples. There are several ways nipple soreness can develop.

White dots on the skin can appear on anyone after any type of exercise. People who have certain medical conditions or are taking medications or wearing certain types of fabric may be more likely to develop white spots while exercising.

The body has two lines of natural defense to protect against infection. The first are physical barriers, such as the skin, body secretions and mucous membranes. The second line of defense is the immune system.

AIDS, or acquired immunodeficiency syndrome, is the potentially fatal disease caused by HIV, or human immunodeficiency virus. HIV causes severe damage to the immune system.