![]() An absolute loss of sodium may be due to a decreased intake of the ion coupled with its continual excretion in the urine. Hyponatremia is a lower-than-normal concentration of sodium, usually associated with excess water accumulation in the body, which dilutes the sodium. Sodium is freely filtered through the glomerular capillaries of the kidneys, and although much of the filtered sodium is reabsorbed in the proximal convoluted tubule, some remains in the filtrate and urine, and is normally excreted. Excretion of sodium is accomplished primarily by the kidneys. ![]() This excess sodium appears to be a major factor in hypertension (high blood pressure) in some people. People eating a typical Western diet, which is very high in NaCl, routinely take in 130 to 160 mmol/day of sodium, but humans require only 1 to 2 mmol/day. It is responsible for one-half of the osmotic pressure gradient that exists between the interior of cells and their surrounding environment. Sodium is the major cation of the extracellular fluid. Electrolyte and Ion Reference Values (Table 26.1) Bicarbonate is the one ion that is not normally excreted in urine instead, it is conserved by the kidneys for use in the body’s buffering systems. Urine values reflect the rates of excretion of these ions. In contrast, calcium and phosphate analysis requires a collection of urine across a 24-hour period, because the output of these ions can vary considerably over the course of a day. ![]() In a clinical setting, sodium, potassium, and chloride are typically analyzed in a routine urine sample. Table 26.1 lists the reference values for blood plasma, cerebrospinal fluid (CSF), and urine for the six ions addressed in this section. Adjustments in respiratory and renal functions allow the body to regulate the levels of these ions in the ECF. Severe vomiting or diarrhea will cause a loss of chloride and bicarbonate ions. Excessive sweating may cause a significant loss, especially of sodium and chloride. Phosphate is a normal constituent of nucleic acids hence, blood levels of phosphate will increase whenever nucleic acids are broken down.Įxcretion of ions occurs mainly through the kidneys, with lesser amounts lost in sweat and in feces. In the event that calcium and phosphate are needed for other functions, bone tissue can be broken down to supply the blood and other tissues with these minerals. More than 90 percent of the calcium and phosphate that enters the body is incorporated into bones and teeth, with bone serving as a mineral reserve for these ions. These ions enter the body through the digestive tract. These six ions aid in nerve excitability, endocrine secretion, membrane permeability, buffering body fluids, and controlling the movement of fluids between compartments. In terms of body functioning, six electrolytes are most important: sodium, potassium, chloride, bicarbonate, calcium, and phosphate. All of the ions in plasma contribute to the osmotic balance that controls the movement of water between cells and their environment.Įlectrolytes in living systems include sodium, potassium, chloride, bicarbonate, calcium, phosphate, magnesium, copper, zinc, iron, manganese, molybdenum, copper, and chromium. Still others aid in releasing hormones from endocrine glands. Other ions help to stabilize protein structures in enzymes. Some ions assist in the transmission of electrical impulses along cell membranes in neurons and muscles. The body contains a large variety of ions, or electrolytes, which perform a variety of functions.
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