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Questions and Answers
What is the percentage of total body calcium that is found intracellularly?
What is the percentage of total body calcium that is found intracellularly?
Which compartment contains the largest proportion of total serum calcium?
Which compartment contains the largest proportion of total serum calcium?
What effect can a plasma potassium concentration increase of 3 to 4 mEq/L have?
What effect can a plasma potassium concentration increase of 3 to 4 mEq/L have?
What is the primary mechanism of calcium absorption that is significant when intake is high?
What is the primary mechanism of calcium absorption that is significant when intake is high?
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What is the percentage of total serum calcium that is ionized?
What is the percentage of total serum calcium that is ionized?
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What can cause falsely low serum calcium levels in patients?
What can cause falsely low serum calcium levels in patients?
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Which of the following ions is most sensitive to changes in extracellular fluid concentration?
Which of the following ions is most sensitive to changes in extracellular fluid concentration?
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Which ion can lead to cardiac arrest or fibrillation at higher concentrations?
Which ion can lead to cardiac arrest or fibrillation at higher concentrations?
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What is the primary mechanism of magnesium reabsorption in the nephron?
What is the primary mechanism of magnesium reabsorption in the nephron?
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Which segment of the nephron is responsible for the highest percentage of phosphorus reabsorption?
Which segment of the nephron is responsible for the highest percentage of phosphorus reabsorption?
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Which of the following factors is NOT known to decrease magnesium absorption?
Which of the following factors is NOT known to decrease magnesium absorption?
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What percentage of total serum magnesium is typically free in the bloodstream?
What percentage of total serum magnesium is typically free in the bloodstream?
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What is the role of calbindin in the transport of calcium?
What is the role of calbindin in the transport of calcium?
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Which factor increases magnesium absorption in the body?
Which factor increases magnesium absorption in the body?
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What is the normal concentration range of magnesium in the serum?
What is the normal concentration range of magnesium in the serum?
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Which of the following statements is true regarding renal handling of phosphorus?
Which of the following statements is true regarding renal handling of phosphorus?
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What percentage of total body calcium is found in bones?
What percentage of total body calcium is found in bones?
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Which segment of the nephron is responsible for the majority of calcium reabsorption?
Which segment of the nephron is responsible for the majority of calcium reabsorption?
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Which hormone is primarily produced by the parathyroid glands to regulate calcium levels?
Which hormone is primarily produced by the parathyroid glands to regulate calcium levels?
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What is the function of calbindin in calcium absorption?
What is the function of calbindin in calcium absorption?
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What percentage of filtered calcium is typically excreted in the urine?
What percentage of filtered calcium is typically excreted in the urine?
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Which organs are primarily involved in the actions of hormonal regulation of calcium homeostasis?
Which organs are primarily involved in the actions of hormonal regulation of calcium homeostasis?
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Which mechanism primarily facilitates calcium transport in the thick ascending loop of Henle?
Which mechanism primarily facilitates calcium transport in the thick ascending loop of Henle?
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Which factor directly influences the secretion of parathyroid hormone (PTH)?
Which factor directly influences the secretion of parathyroid hormone (PTH)?
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What role does the Calcium Sensing Receptor play in calcium regulation?
What role does the Calcium Sensing Receptor play in calcium regulation?
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How much of the calcium filtered by the kidneys is actively reabsorbed?
How much of the calcium filtered by the kidneys is actively reabsorbed?
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What is the primary effect of Vitamin D on bone health?
What is the primary effect of Vitamin D on bone health?
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What is the primary role of calcitriol in the body?
What is the primary role of calcitriol in the body?
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Which of the following is a 25-hydroxylated metabolite of vitamin D?
Which of the following is a 25-hydroxylated metabolite of vitamin D?
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What percentage of total body phosphorus is found in bone?
What percentage of total body phosphorus is found in bone?
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Which of the following Vitamin D analogs is NOT a synthetic derivative?
Which of the following Vitamin D analogs is NOT a synthetic derivative?
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What is the normal concentration range of phosphorus in the body?
What is the normal concentration range of phosphorus in the body?
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Which molecule is referred to as 1,25-dihydroxycholecalciferol?
Which molecule is referred to as 1,25-dihydroxycholecalciferol?
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What percentage of extracellular phosphorus exists in the organic form?
What percentage of extracellular phosphorus exists in the organic form?
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What happens to H2CO3 when it ionizes?
What happens to H2CO3 when it ionizes?
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Which of the following is considered a volatile acid?
Which of the following is considered a volatile acid?
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Which compound acts as a base by accepting H+ to form H2CO3?
Which compound acts as a base by accepting H+ to form H2CO3?
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What does alkalosis refer to?
What does alkalosis refer to?
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What are non-volatile acids primarily generated from?
What are non-volatile acids primarily generated from?
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Which of the following amino acids would potentially function as a base in the body?
Which of the following amino acids would potentially function as a base in the body?
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What is the average normal blood pH range?
What is the average normal blood pH range?
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Which of the following acids is categorized as a non-volatile acid?
Which of the following acids is categorized as a non-volatile acid?
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What is the primary mechanism by which acute glomerulonephritis causes kidney injury?
What is the primary mechanism by which acute glomerulonephritis causes kidney injury?
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Which of the following is NOT a common trigger for acute glomerulonephritis?
Which of the following is NOT a common trigger for acute glomerulonephritis?
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In acute tubular necrosis, which type of substances primarily causes damage to renal tubular epithelial cells?
In acute tubular necrosis, which type of substances primarily causes damage to renal tubular epithelial cells?
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A patient presents with oliguria and urine osmolality greater than 500. What condition is most likely affecting the patient?
A patient presents with oliguria and urine osmolality greater than 500. What condition is most likely affecting the patient?
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Which of the following agents is NOT commonly associated with causing acute tubular necrosis?
Which of the following agents is NOT commonly associated with causing acute tubular necrosis?
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What is the typical FeNa+ level in patients suffering from acute glomerulonephritis?
What is the typical FeNa+ level in patients suffering from acute glomerulonephritis?
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Which of these symptoms is typically associated with a decreased renal function due to acute tubular necrosis?
Which of these symptoms is typically associated with a decreased renal function due to acute tubular necrosis?
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What pH value indicates alkalosis in the context of acid-base balance?
What pH value indicates alkalosis in the context of acid-base balance?
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Study Notes
Renal Regulation of Electrolytes
- Extracellular fluid potassium (K+) is seldom more than 0.3 mEq/L different from normal.
- Many cell functions are sensitive to changes in extracellular fluid potassium concentration.
- A 3 to 4 mEq/L increase in plasma potassium can cause cardiac arrhythmias.
- Higher concentrations can cause cardiac arrest or fibrillation.
- Normal potassium intake is about 100 mEq/day.
- Extracellular fluid potassium is 4.2 mEq/L and intracellular is ~140 mEq/L.
- Potassium is reabsorbed in the proximal tubule and ascending loop of Henle, resulting in only about 8 percent of the filtered load being delivered to the distal tubule.
- Normal total body calcium is 1,000 to 1,200 g.
- 99% of body calcium is in bone with 1% being freely exchangeable in extracellular fluids.
- Total serum calcium (8.4-10.2 mg/dl) is composed of ionized (48%), protein bound (46% albumin), and complexed inorganic compounds (7%).
Factors Affecting Potassium Distribution
- Table 30-1 details factors shifting potassium into and out of cells, impacting extracellular concentrations.
- Insulin, aldosterone, and beta-adrenergic stimulation shift K+ into cells, lowering extracellular levels.
- Insulin deficiency (diabetes), aldosterone deficiency (Addison's disease), beta-adrenergic blockade, acidosis, and cell lysis shift K+ out of cells, increasing extracellular levels.
- Strenuous exercise and increased extracellular fluid osmolarity also shift K+ out of cells.
Calcium Flux
- Calcium flux between body compartments is shown in a diagram.
- Oral calcium intake is 1,000 mg/day.
- Calcium in soft tissue and intracellular calcium are depicted with amounts.
- Calcium in extracellular fluid and plasma are shown, as well as in the intestines, bones, and kidneys.
- Calcium in the feces and urine are also shown in the diagram.
- Two main mechanisms for intestinal calcium absorption are between cells (paracellular) and through cells (transcellular).
Calcium Absorption
- Paracellular absorption is passive.
- Transcellular absorption is active and influenced by calcitriol.
- Calbindin acts as an intracellular calcium sink in the intestines.
Renal Handling of Calcium
- Different segments of the nephron have specific roles in calcium reabsorption.
- Proximal convoluted tubule: absorbs 60-70% of calcium.
- Loop of Henle: absorbs 20%
- Distal convoluted tubule: absorbs ~10%
- Collecting duct: absorbs 5%
Calcium Regulation Hormones
- Parathyroid hormone (PTH) and calcitriol regulate calcium homeostasis.
- PTH and calcitriol affect bone, intestine, and kidneys.
Vitamin D
- 25-Hydroxyvitamin D (ercalcidiol or calcidiol) are metabolites of vitamin D.
- Calcitriol (1,25-dihydroxycholecalciferol) is a derivative used clinically.
- Vitamin D analogs are synthetic derivatives, including doxercalciferol, paricalcitol, alfacalcidol, and falecalcitriol, and 22-oxacalcitriol (maxacalcitol).
Clinical Consequences
- Hypocalcemia has symptoms like neuromuscular changes (muscle spasms).
- Hypercalcemia causes gastrointestinal issues and weakness.
Phosphorus
- Phosphorus stores are primarily in bone (85%).
- Extracellular phosphorus is 70% organic and 30% inorganic with 15% bound to proteins.
- Normal extracellular concentration of phosphorus is 2.5-4.5 mg/dL.
- Phosphate absorption is via two main mechanisms.
Magnesium
- Total body magnesium stores are 24 grams; 99% is intracellular, and 1.7-2.6 mg/dL is the normal concentration in serum.
- 70% of serum magnesium is unbound to proteins.
- Magnesium has multiple enzymatic functions in the body.
Magnesium Absorption
- Magnesium absorption ranges from 25% to 75%, with typical absorption of 120 mg/day.
- Magnesium is absorbed via paracellular or transcellular mechanisms, using TRPM6/7 channels, with mutations related to hypomagnesemia and hypocalcemia.
Magnesium Handling in the Kidney
- Kidneys filter 2000-4000 mg/day of magnesium.
- 70% of serum magnesium is filterable.
- Distribution of magnesium reabsorption across different nephron segments is noted.
Acid-Base Balance
- pH of arterial blood is in the 7.35-7.45 range.
- Volatile acids (e.g., carbonic acid) are eliminated via the lungs, while non-volatile acids (e.g., sulfuric and phosphoric acids) are eliminated by kidneys.
- Buffers (bicarbonate, ammonia, phosphate, proteins) regulate pH.
Renal Acid-Base Regulation
- Kidneys eliminate non-volatile acids and reabsorb bicarbonate.
- Bicarbonate is the most important extracellular buffer, and phosphate and ammonia are important renal buffer systems.
- Buffers in the body help maintain pH balance.
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Description
Test your knowledge on the renal regulation of electrolytes, focusing on potassium and calcium dynamics within the body. Explore how various factors influence potassium distribution and the implications of abnormal levels on cardiac function. This quiz will help deepen your understanding of electrolyte management in physiology.
