Functions of Major Physiological Ions

A substance that forms ions when dissolved in water is an electrolyte. An ion can have either a positive charge (cation) or a negative charge (anion).

The human body contains several electrolytes, including:
Calcium (Ca++)
Magnesium (Mg++)
Bicarbonate (HCO3-)
Potassium (K+)
Chloride (Cl-)
Sodium (Na+)
Sulfate (SO4--)
Phosphate (HPO4--)

There are similarities in the electrolyte makeup of blood plasma and interstitial fluid. Major electrolytes are sodium and chloride. Electrolytes such as K+ and HPO4- are primarily found in the intracellular fluid.

The physiological role of sodium

Associated with muscle and nerve excitability, this plays an essential role. Furthermore, it also plays a crucial role in controlling fluid balance. A kidney's function is critical for regulating sodium levels. Most sodium is reabsorbed in the kidney tubules after it is filtered into the glomerular filtration system. Additionally, other factors, such as blood pressure at the glomerulus and sympathetic nervous system stimulation of the renal arterioles, affect GFR. The proximal convoluted tubule reabsorbs as much sodium as possible, and this proportion generally remains around 67%.

The hormone also stimulates the adrenal glands to release aldosterone. Water and sodium are chemically linked so that the kidney will reabsorb a more significant amount of water. Ultimately, this will result in improved blood pressure. During an elevated arterial blood pressure, the left and right atria of the heart will release the atrial natriuretic factor (ANF). Hormones like this inhibit aldosterone and renin production. Through this decrease in aldosterone stimulated reabsorption, the kidneys can lose more sodium by losing more sodium. Due to sodium's ability to be followed by water, water is lost from the body, causing the blood pressure to drop to an average level.

The physiological role of potassium

The intracellular fluid contains a large amount of potassium. Between the inside and outside of cells, the concentration varies by eighty-two times. Muscles, neurons, sensory receptors, and other excitable cells require sodium to function correctly, as do neurons. Furthermore, it is essential for maintaining the correct pH balance of the body and maintaining the right amount of fluid within each cell. The potassium output generally matches the potassium input. Aldosterone usually reabsorbs sodium by exchanging hydrogen ions or potassium ions. Therefore, reabsorbing sodium ions will result in a loss of potassium as well. In this way, high potassium levels in the interstitial fluid stimulate the release of aldosterone.

Hypokalaemia (low potassium levels which cause loss of blood pressure, weakness, or cardiac arrhythmia) may occur due to Cushing's disease (overproduction of ACTH) or hyperaldosteronism (overproduction of aldosterone). Acidosis results in increased potassium excretion (leading to hyperkalemia, higher than normal potassium levels), while alkalosis causes the opposite.

Physiology of calcium

The majority of calcium is contained in extracellular fluids; most phosphorus is contained in intracellular fluids. They are both critical for maintaining bone and tooth health. Besides transmitting nerve impulses across synapses, calcium is essential for clotting blood and contracting muscles. In terms of muscles and nerves, calcium deficiency causes them to become more excitable.

Physiology of phosphate

Nucleic acids and high-energy molecules such as ATP require phosphorus for synthesis. Furthermore, it contributes to maintaining the pH balance of the body.

Physiology of magnesium

Most of the magnesium in the body is found in intracellular fluid and bones. Among the functions of magnesium within cells are to assist sodium-potassium pumps and aid enzymes. It has an important role in muscle contraction, conduction of action potentials, and the production of bone and teeth. Adolescents' levels of aldosterone are influenced by magnesium levels in the extracellular fluid. When Mg++ levels are low, aldosterone secretion increases and the renal reabsorption of Mg++ is accelerated as a result.

Physiology of chloride

Its cellular concentration is 26 times greater than its extracellular concentration, which makes it the most abundant extracellular anion. Ions of chlorine can easily diffuse across plasma membranes, and sodium movement is closely associated with chloride transport, which also explains how aldosterone indirectly regulates chlorine levels. Passively, chlorine is reabsorbed along with sodium. The osmotic pressure difference between compartments is essential for regulating pH balance and regulating osmotic pressure. Bicarbonate ions are transported to the plasma as a result of the chloride shift within the blood. As chlorine and hydrogen combine with hydrogen in the gastric mucosa, hydrochloric acid is produced.

Physiology of bicarbonate

The human body's pH buffering system (which maintains acid-base balance) is a compound of alkali (as bicarbonate is alkaline). As much as 70% of carbon dioxide is transformed in the body into carbonic acid (H2CO3), which is then quickly converted into bicarbonate (HCO3). Water, hydrogen ions, carbon dioxide, bicarbonate, and carbonic acid all form a buffering system that prevents pH changes by maintaining the needed volatile equilibrium. pH changes exceeding the normal range in either direction is especially dangerous for tissue in the central nervous system, where too far deviation could be devastating. The small intestine can also be kept at a proper pH level by bicarbonate. Pancreatic acid is produced by secretin, which is a hormone produced by the pancreas in order to neutralize the acidic contents of the stomach.

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