4.3: Introduction to Electrolytes
In humans, electrolytes play a vital role in various physiological processes. Balancing electrolyte levels is essential for normal body functions; their imbalance can be life-threatening. The major electrolytes include sodium, potassium, chloride, calcium, phosphate, and bicarbonate. They are primarily involved in physiological processes, such as nerve signal transmission, membrane trafficking, muscle contraction, buffering body fluids, and balancing water levels in the body.
Role of Sodium
One of the most important electrolytes is the sodium cation. It functions in regulating membrane potential in electrically active cells, and plays a role in active transport of ions across cell membranes. Sodium is reabsorbed in the kidneys via the sodium-chloride symporters. Decreased reabsorption can lead to the condition called hyponatremia that presents with symptoms such as nausea, confusion, and headaches. Conversely, too much sodium, or hypernatremia causes restlessness and muscle spasms, breathing issues, and sleeping difficulties.
Role of Potassium
Potassium ions are the intracellular counterparts to the extracellular sodium. Potassium is actively transported into the cell in exchange for sodium by the sodium-potassium ATPase pumps. These ions are essential for muscle activity and any imbalance can cause weakness, fatigue, and cardiac arrhythmias.
Role of Chloride
Chloride is the primary extracellular ion that plays a vital role in maintaining an osmotic pressure gradient between intracellular and extracellular fluids and, therefore, appropriate water levels in the body. The most common source of chloride in food is table salt. When the levels of chloride ions in the blood rise above normal due to dehydration or excessive salt intake, the resulting state is called hyperchloremia. In case of vomiting, diarrhea, and metabolic acidosis, the chloride level in the blood drops below normal. This resulting state is called hypochloremia.
Role of Calcium
Calcium ions are essential in blood coagulation, muscle contraction, and nerve signal transmission. In addition, calcium and its salts provide tensile strength to bones and teeth. Calcium food sources include dairy products like milk and cheese, while some drinks like soy milk are also fortified with calcium. For successful absorption of calcium in the intestine, vitamin D is necessary. Vitamin D deficiency can affect calcium absorption leading to rickets in children and osteomalacia— softening of bones in adults.
Role of Phosphate
Phosphate is an important electrolyte in the body and constitutes 1% of the total body weight in humans. Approximately 85% of phosphate in humans is present in the form of calcium phosphate salts in bones and teeth. The dietary sources of phosphate are poultry, egg, meat, milk, cereal, grains, and peanuts. Frequent use of antacids and malnourishment contributes to reduced levels of phosphate in the body, called hypophosphatemia. Hyperphosphatemia — abnormally high levels of phosphates — results in declined renal function and is usually observed in acute lymphocytic leukemia.
Role of Magnesium
Magnesium is a rather abundant intracellular cation that regulates many enzymes by serving as a cofactor. Of importance are many protein kinases, helicases, cyclases and topoisomerases. It is also involved in ATP metabolism and glycolytic pathways. Magnesium deficiency can present as neurological issues, cardiovascular irregularities, and neuromuscular alterations.
Role of Bicarbonate
Bicarbonate is crucial to the human body's physiological pH buffering mechanism. In the blood plasma, carbon dioxide is converted into bicarbonate, which is alkaline and helps maintain the body's acid-base balance. Any drastic rise or fall in the bicarbonate level indicates an acid-base imbalance in the body.
