Anatomy And Physiology

Anatomy Physiology



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Electrolytes in the body are special ions and cations that each have a specific role in the body.  These electrolytes are physiologically essential for the normal function of the body tissues.  Electrolytes are soluble in water due to the presence of the charge on them.  They are distributed in the body between the extracellular and intracellular spaces.  This distribution is based on active transport of these ions across the cellular membrane that uses enzymes for this purpose. 

Certain electrolytes such as sodium ions control osmosis of water between the body compartments.  For example, excess sodium in the body can cause an osmotic effect on water increasing its re-absorption in the kidney tubules. Also when administering diuretics that decrease the re-absorption of sodium in the kidney tubules, the increased amount of sodium ions in the renal tubules exert an osmotic effect on water causing its diuresis in the urine. 

This osmotic effect of ions on water is not restricted to ions but also is observed with molecules which can also exert osmotic effect such as glucose and mannitol.  For example, in diabetes mellitus in which there is a state of hyperglycemia there is increased filtration of glucose in the glomeruli of the kidney.  The filtered glucose exerts an osmotic effect on water leading to its diuresis in the urine. 

Other functions of ions in the body act as buffers.  Especially notable here are the ions, phosphates and bicarbonates in addition to hydrogen ions.  Bicarbonate is the major buffer in the blood and the extracellular space.  While phosphate ions are the major buffers inside the cell.  In addition to phosphates also intracellular proteins usually function as buffers such as the hemoglobin molecules.  Other buffers in the body include the ammonia molecule which is the degradation product of amino acids.  It is obtained from the deamination process of certain amino acids. Protons or hydrogen ions are also present in the body.  They are also a type of electrolyte which can function as a buffer for bases. 

Acids are usually obtained in the body as a result of metabolic reactions such as anaerobic respiration in the case of ischemia which leads to the accumulation of lactic acids.  Also in diabetes mellitus the accumulation of ketonic acids in diabetic ketoacidosis can lead to the accumulation of acids in the body.  These cases can predispose to metabolic acidosis in the body that can be corrected partially by the function of the buffers in the body especially the bicarbonate buffer. 

Bicarbonate ions are normally obtained in the body as basic solutions that are administered either orally or intravenously.  It is obtained metabolically from the reaction between carbon dioxide and water which forms carbonic acid that dissociates to bicarbonate ions and hydrogen ions.  This reaction is catalyzed by a special enzyme that is called carbonic anhydrase. 

Certain electrolytes in the body function as electric charge carriers.  Especially notable here are the sodium and potassium ions.  These ions are the main contributors of the cellular membrane electric potential in nerve and muscle cells.  There is a concentration gradient of these ions across the cellular membrane in neurons and muscle cells.  This concentration gradient leads to the formation of resting electric potential across the cellular membrane.  This concentration gradient is maintained using special mechanisms which are called ion pumps that use enzymes that are called ATPases because they use ATP molecules.  These enzymes catalyze the transport of these ions against their concentration gradient across the cellular membrane. 

The presence of the concentration gradient of these ions has an enormous effect on the neurons and the muscle cells.  Depolarization of neurons and muscle cells by the process of sodium ions flow inside the cell leads to the formation of action potential that can spread electrical information between adjacent neurons.  In addition, the depolarization of muscles can lead to the contraction of the muscle cells.  Sodium ions are the major extracellular cation while chloride ions are the major extracellular ions.  Potassium cation is the major electrolyte in the intracellular space while phosphate ions are the major ions inside the cell.

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