Exam 4 Review:  Chapter 26:  Electrolytes II - Specific Examples

sodium = natrium - A soft, light, extremely malleable silver-white metallic element which reacts explosively with water, is naturally abundant in combined forms, especially in common table salt;  symbol Na, atomic number 11; atomic weight 22.99; valence +1; as an electrolyte, the most abundant extracellular cation (90%); important for maintaining the polarized state of cells and a major contributor to the osmolarity of the extracellular fluid; serum reference range:  136-142 mEq/liter; serum sodium levels are regulated by the hormones aldosterone, ADH, and atrial natriuretic peptide.

hyponatremia - An abnormal decrease of sodium ions in the blood; it may occur secondary to inadequate salt intake, water retention (overhydration), solute loss, e.g., excessive sweating or vomiting, or as a drug side-effect; symptoms include muscle weakness, neurologic dysfunction due to cranial edema, and possible coma; serum sodium levels are regulated by the hormones aldosterone, ADH, and atrial natriuretic peptide.

hypernatremia - An abnormal increase of sodium ions in the blood; it may occur secondary to renal disease, dehydration, burns, fever diarrhea; symptoms include altered mental states, muscle twitching, seizures, or coma; serum sodium levels are regulated by the hormones aldosterone, ADH, and atrial natriuretic peptide.

chloride - Any compound containing a chlorine atom or ion; the element chlorine is a greenish-yellow diatomic gas; it is naturally abundant in combined forms, especially in common table salt;  symbol Cl, atomic number 17; atomic weight 70.906; valence -1; as an electrolyte, the most abundant extracellular anion; important for maintaining the polarized state of cells, forms HCL for gastric acidity, and a major contributor to the osmolarity of the extracellular fluid; serum reference range:  95-103 mEq/liter; serum chloride levels are regulated by the hormones aldosterone, ADH, and atrial natriuretic peptide.  [Note:  elevated sweat chloride is diagnostic of Cystic Fibrosis.]

hypochloremia - An abnormal decrease of chloride ions in the blood; it may occur secondary to prolonged vomiting or as a result of diuretic therapy; it usually occurs with hyponatremia; symptoms include alkalosis, muscle spasms and coma; serum chloride levels are regulated by the hormones aldosterone, ADH, and atrial natriuretic peptide.

hyperchloremia - An abnormal increase of sodium ions in the blood; it may occur secondary to metabolic acidosis, hypernatremia, or with the use of carbonic anhydrase inhibitor diuretics; symptoms include altered mental states, muscle twitching, seizures, or coma; serum chloride levels are regulated by the hormones aldosterone, ADH, and atrial natriuretic peptide.

potassium = kalium  - A soft, silver-white, highly or explosively reactive metallic element which occurs in nature only in compounds; symbol K, atomic number 19; atomic weight 39.098;  valence +1; as an electrolyte, the most abundant intracellular cation (90%); important for maintaining the polarized state of cells; serum reference range:  3.8-5.0 mEq/liter; serum potassium levels are regulated by the hormones aldosterone, ADH, and atrial natriuretic peptide.

hypokalemia - An abnormal decrease of potassium ions in the blood; it may occur secondary to renal disease, vomiting and diarrhea, or with the use of certain drugs including many diuretics; symptoms include neuromuscular and cardiac abnormalities, irritability, cardiac fibrillation, and death; serum potassium levels are regulated by the hormones aldosterone, ADH, and atrial natriuretic peptide.

hyperkalemia - An abnormal increase of potassium ions in the blood; it may occur secondary to renal disease, hemolytic anemia, chemotherapy, and various drug side effects; symptoms include cardiac arrhythmias and cardiac arrest; serum potassium levels are regulated by the hormones aldosterone, ADH, and atrial natriuretic peptide.

bicarbonate  - The anion, HCO₃^-, formed from the dissociation of carbonic acid, H₂CO₃, which is an important body fluid buffer; the concentration of bicarbonate ions is regulated by both the respiratory system and the kidneys; the concentration of bicarbonate ions in the blood is the major indicator of the buffering capacity of the blood at any given moment; serum bicarbonate levels are regulated by the ventilation of the lungs and by the kidney under further complex regulation from the hypothalamus and endocrine system.

calcium - A silvery, moderately hard metallic element which occurs widely in nature; symbol Ca,  atomic number 20; atomic weight 40.08; valence +2; as an electrolyte, the most abundant mineral ion in the body (98% stored in the matrix of bone); important for many processes including regulation of depolarization of neurons, muscle cells, and gland cells, and as a trigger for many biochemical pathways including blood clotting and the cortical reaction in a fertilized egg; serum reference range:  4.6-5.5 mEq/liter; serum calcium levels are regulated by the hormones thyrocalcitonin and parathyroid hormone.

hypocalcemia - An abnormal decrease of calcium ions in the blood; it may occur secondary to renal disease, hypoparathyroidism, vitamin D deficiency, pregnancy, and certain bone diseases; symptoms include muscle cramps and spasms, hyperactive reflexes, and convulsions; serum calcium levels are regulated by the hormones thyrocalcitonin and parathyroid hormone.

hypercalcemia - An abnormal increase of calcium ions in the blood; it may occur secondary to hyperparathyroidism, multiple myeloma, excessive vitamin D intake, with diuretic use, and certain cancers, especially if they metastasize to bone; symptoms include vomiting, cardiovascular problems, coma, abnormal calcium deposition in tissues, and stone formation; serum calcium levels are regulated by the hormones thyrocalcitonin and parathyroid hormone.

phosphate - The anions, H₂PO₄^- and HPO₄^-2, and PO₄^-3, which are important intracellular anions as well as being a major constituent of the matrix of bone as calcium phosphate salts, also combined with lipids, proteins, carbohydrates, nucleic acids (DNA and RNA), and high energy phosphate transport compounds, e.g., ATP, and an important body fluid buffer; serum reference range:  1.7-2.6 mEq/liter; serum phosphate levels are regulated by the hormones thyrocalcitonin and parathyroid hormone.

hypophosphatemia - An abnormal decrease of phosphate ions in the blood; it may occur secondary to hyperparathyroidism, bone wasting diseases, vitamin D deficiency, and certain renal tubular diseases; symptoms include hemolysis, weakness, and convulsions; it usually occurs with hypercalcemia; serum phosphate levels are regulated by the hormones thyrocalcitonin and parathyroid hormone.

hyperphosphatemia - An abnormal increase of phosphate ions in the blood; it may occur secondary to hypoparathyroidism, vitamin D deficiency, and certain bone diseases; symptoms include muscle cramps and spasms, hyperactive reflexes, and convulsions; serum phosphate levels are regulated by the hormones thyrocalcitonin and parathyroid hormone.

magnesium - A light, silvery-white, moderately hard metallic element which occurs widely in nature; symbol Mg,  atomic number 12; atomic weight 24.305; valence +2; as an electrolyte, the second most abundant intracellular ion (the majority stored in the matrix of bone); important as an enzyme cofactor and in regulating depolarization events; serum reference range:  1.3-2.1 mEq/liter.

hypomagnesemia - An abnormal decrease of magnesium ions in the blood; symptoms include vomiting and cardiac arrhythmias.

hypermagnesemia - An abnormal increase of magnesium ions in the blood; symptoms include nausea and vomiting.

          sodium (Na⁺), chloride (Cl^-), bicarbonate  (HCO₃^-)

Describe:

2.  the main differences in solute composition between the intracellular versus the extracellular fluid compartments of the body. What is the main difference in solute concentration between the plasma and the interstitial fluid compartments of the body?

Describe the main differences in solute composition between the intracellular versus the extracellular fluid compartments of the body.

Intracellular Fluid Extracellular Fluid Major solutes:  potassium (K+), magnesium (Mg++), phosphate (HPO4-2), sulfate (SO4-2), proteins Major solutes:  sodium (Na+), chloride (Cl-), bicarbonate  (HCO3-), fewer proteins

What is the main difference in solute concentration between the plasma and the interstitial fluid compartments of the body?

Plasma Interstitial Fluid Major solute difference:  many plasma proteins Major solute difference:  few proteins

3.  the hormonal regulation of Na⁺ and K⁺ in body fluids.

          Antagonistic negative feedback control involving:  (1) aldosterone which targets the kidney tubule to reabsorb Na⁺ ions from the filtrate and excrete K⁺ ions into the urine; and (2) atrial natriuretic peptide (ANP) which targets the kidney tubule to reabsorb K⁺ ions from the filtrate and excrete Na⁺ ions into the urine.

4.  the hormonal regulation of Ca⁺⁺ and HPO₄^-2 in body fluids.

          Antagonistic negative feedback control involving:  (1) parathyroid hormone (PTH) = parathormone which targets (a) the intestines to absorb more Ca⁺⁺ and HPO₄^-2 ions from the chyme of digested meals, (b) the osteoclasts in bone to dissolve additional bony matrix liberating more Ca⁺⁺ and HPO₄^- ions into the blood, and (c) the kidney tubule to reabsorb Ca⁺⁺ ions from the filtrate and excrete HPO₄^-2 ions into the urine; and (2) thyrocalcitonin = calcitonin which targets the kidney tubule to reabsorb HPO₄^-2 ions from the filtrate and excrete Ca⁺⁺ ions into the urine.  [Note: the net effect of parathyroid hormone (PTH) = parathormone is to elevate blood calcium levels and decrease blood phosphate levels; the net effect of thyrocalcitonin = calcitonin is to elevate blood phosphate levels and decrease blood calcium levels.]

Explain:

3. the mechanisms used to regulate the Sodium (Na⁺) concentrations in the body. Why is regulation of Na⁺ almost the same as regulating the water concentration of the body?

Explain the mechanisms used to regulate the Sodium (Na+) concentrations in the body.

A.  Primary mechanism:  Antagonistic negative feedback control involving:  (1) aldosterone which targets the kidney tubule to reabsorb Na+ ions from the filtrate and excrete K+ ions into the urine; and (2) atrial natriuretic peptide (ANP) which targets the kidney tubule to reabsorb K+ ions from the filtrate and excrete Na+ ions into the urine. B.  Secondary mechanism:  Regulation of the water concentration of the urine by antidiuretic hormone (ADH) = vasopressin involves some tubular reabsorption of Na+ ions, and, therefore, has an indirect effect on regulate the sodium (Na+) concentration in the body.

Why is regulation of Na+ almost the same as regulating the water concentration of the body?

Water tends to follow passively any of the movements of solutes across body membranes, but it most strongly associates with and follows the movements of sodium (Na+) ions.  Where sodium (Na+) ions move, water follows.

4. why homeostatic imbalances of Na⁺, K⁺, and Ca⁺⁺ all have effects on nerve and muscle function; give specific examples at the molecular level of function.

Differences in the concentrations of Na⁺ ions and K⁺ ions between the cytoplasm and interstitial fluid of all cells influence their ability to maintain and regulate their resting potentials.  Therefore, excitable cells such as neurons and muscle cells can be made to be more or less capable of depolarization if imbalances of Na⁺ ions and K⁺ ions develop between the cytoplasm and interstitial fluid.  Cardiac muscle cells also involve slow calcium channels in their depolarization, so changes in the concentrations of Ca⁺⁺ ions between the cytoplasm and interstitial fluid of cardiac muscle cells influence their ability to maintain and regulate their resting potentials.

In addition, the release of neurotransmitters from storage vesicles in motor neuron axon end bulbs requires the action of Ca⁺⁺ ions, acting as second messengers, to initiate exocytosis of the neurotransmitter vesicles and the sliding filament mechanism of muscle contraction also  requires the action of Ca⁺⁺ ions, acting as second messengers, to initiate myosin-head binding to actin and to initiate ATP hydrolysis to power that binding and the subsequent power stroke (and ratchet effect).  Therefore, neurons and muscle cells can be made to be more or less capable of performing their respective functions of impulse transmission and contraction, respectively, if imbalances of Ca⁺⁺ ions develop between their cytoplasm and the surrounding interstitial fluid.