Electrolytes and Body Fluids Practice Questions

Q: Insensible water loss per day is ?

1000 ml. ***1000 ml*** - **Insensible water loss** occurs through the skin (evaporation) and respiratory tract (exhalation) without conscious perception. - The typical daily insensible water loss in an adult is approximately **800-1000 ml/day**. - **Breakdown**: Skin evaporation (~400-500 ml) + Respiratory tract (~300-400 ml) = **~900-1000 ml total**. - **1000 ml** is the standard value cited in major physiology textbooks (Guyton & Hall, Ganong) and is the most commonly accepted answer for NEET PG examinations. *100 ml* - This value is significantly **lower** than the actual insensible water loss, which occurs continuously throughout the day. - Such a low volume would imply negligible evaporation and respiratory loss, which is not physiologically accurate. *300 ml* - While greater than 100 ml, 300 ml is still **far below** the typical range for daily insensible water loss. - This amount represents only about one-third of the actual insensible losses from the skin and respiratory system combined. *700 ml* - Although this value is sometimes mentioned in literature, it is at the **lower end** of the physiological range. - The more widely accepted standard value for insensible water loss in a healthy adult under normal conditions is **900-1000 ml/day**. - 700 ml would underestimate the normal daily insensible losses.

Q: What electrolyte imbalance is commonly associated with laxative abuse?

Hypokalemia. ***Hypokalemia*** - Chronic laxative abuse, particularly with stimulant laxatives, can lead to significant **potassium loss** through increased fecal excretion and altered colonic fluid and electrolyte transport. - **Hypokalemia** can manifest with symptoms like muscle weakness, cramps, fatigue, and even cardiac arrhythmias. *Hypomagnesemia* - While laxative abuse can occasionally contribute to **magnesium depletion**, it is not as consistently or significantly associated as potassium loss. - Primarily, **hypomagnesemia** is related to malabsorption syndromes, chronic alcoholism, or certain medications. *Hyponatremia* - **Hyponatremia** is not typically a direct consequence of laxative abuse; rather, it can be associated with excessive fluid intake in an attempt to alleviate constipation or with certain diuretic use. - Laxative abuse primarily causes loss of water and electrolytes from the gut, not a primary dilution of plasma sodium. *Hyperkalemia* - **Hyperkalemia** (high potassium) is the opposite of what occurs with laxative abuse, which causes potassium loss. - It is more commonly associated with kidney failure, certain medications (e.g., ACE inhibitors, potassium-sparing diuretics), or acidosis.

Q: Intracellular water constitutes what percentage of total body water?

60%. ***60%*** - **Intracellular fluid (ICF)** makes up approximately **two-thirds (67%)** of the total body water. - Among the given options, **60% is the closest approximation** to the actual value. - ICF refers to the fluid contained within cells, crucial for mediating cellular reactions and maintaining cell volume. - ICF comprises about **40% of total body weight** (67% of 60% TBW). *40%* - This represents the approximate percentage of **total body weight** that is intracellular water, not the percentage of total body water. - As a proportion of total body water, ICF is much higher (approximately 67%). *25%* - This value is significantly lower than the actual proportion of intracellular water. - No major fluid compartment accounts for 25% of total body water. *80%* - This percentage is much higher than the actual proportion of intracellular water. - An 80% proportion would be physiologically inconsistent with normal fluid distribution between ICF and ECF compartments.

Q: Among the following gastrointestinal compartments, maximum K+ concentration is seen in which one?

Colon. ***Colon*** - The **colon** exhibits the highest potassium (K+) concentration among gastrointestinal compartments, with levels reaching **75-90 mEq/L** in the distal colon. - This high concentration is due to active **K+ secretion**, which is regulated by aldosterone and increases with high dietary K+ intake. - The colonic epithelium actively secretes K+ to maintain systemic electrolyte balance. *Saliva* - **Saliva** has a K+ concentration of approximately **20-30 mEq/L**, which is lower than colonic fluid. - While relatively high compared to plasma (3.5-5 mEq/L), it is still significantly less than the colon. - Its primary functions are lubrication, initial digestion, and buffering. *Small intestine* - The **small intestine** has a relatively low K+ concentration of approximately **5-10 mEq/L**. - It is primarily involved in **K+ absorption**, particularly in the jejunum and ileum. - Net K+ movement is towards absorption rather than secretion. *Stomach* - The **stomach** has a K+ concentration of approximately **10-15 mEq/L**, similar to plasma levels. - Its main function is secretion of **hydrochloric acid (HCl)** for digestion. - K+ handling is not a primary gastric function.

Q: What is the typical amount of insensible water loss per day?

800 ml. ***800 ml*** - The typical amount of **insensible water loss** per day in an adult is approximately **800-1000 ml**, with **800 ml** being a commonly cited average value. - This loss occurs primarily through the **skin** (~500-600 ml via evaporation) and **respiratory tract** (~300-400 ml via exhaled moist air). - Insensible losses occur **without conscious awareness** and are not visible like sweat or urine. *100 ml* - This amount is **far too low** for daily insensible water loss. - Even in cool, resting conditions, insensible losses are several times higher than this value. - This would not account for the continuous evaporation from skin and respiratory surfaces. *600 ml* - This is **below the typical range** for total daily insensible water loss. - While skin alone may contribute ~500-600 ml, this doesn't account for **respiratory losses** (~300-400 ml). - Total insensible loss is the sum of both skin and respiratory components. *1000 ml* - This represents the **upper end of the normal range** for insensible water loss. - While physiologically accurate in many contexts, **800 ml** is more commonly cited as the **typical average** in standard physiology references. - Actual losses vary with temperature, humidity, activity level, and metabolic rate.

Q: All of the following are present in sweat, except which of the following?

Uric acid. ***Uric acid*** - **Uric acid** is the **best answer** because it is present in sweat in only **trace/negligible amounts** (approximately 20-30 μmol/L), significantly lower than other waste products. - While technically present, its concentration is so minimal that it is often considered clinically insignificant in sweat composition. - The primary excretory routes for uric acid are the **kidneys (urine)** and, to a lesser extent, the gastrointestinal tract. - Among the given options, uric acid has the **lowest concentration** in sweat. *Calcium* - **Calcium** is present in sweat in measurable concentrations (0.2-1.0 mmol/L). - Significant calcium loss can occur through sweating, especially during prolonged physical activity. *Lactic acid* - **Lactate** is present in substantial amounts in sweat (5-25 mmol/L). - Concentration increases significantly during **intense physical activity** due to anaerobic metabolism. - Important for pH buffering and thermoregulation. *Urea* - **Urea** is abundantly present in sweat (5-25 mmol/L). - One of the major waste products in sweat, contributing to its characteristic odor. - Provides an important alternative excretory route, especially relevant in patients with renal impairment.

Q: Which ion is considered the chief intracellular ion in the human body?

K+. ***K+*** - **Potassium (K+)** is the most abundant cation **within cells**, playing a critical role in cellular function, particularly in nerve impulse transmission and muscle contraction. - Its high intracellular concentration is maintained by the **Na+/K+ ATPase pump**, which actively transports K+ into the cell. *Na+* - **Sodium (Na+)** is the primary cation of the **extracellular fluid**, rather than the intracellular fluid. - It is crucial for maintaining **osmotic pressure**, fluid balance, and electrical potentials across cell membranes. *Ca2+* - **Calcium (Ca2+)** is important for bone formation, muscle contraction, and neurotransmitter release, but its concentration is typically **low within the cytoplasm** of cells. - Most intracellular calcium is stored in organelles like the **endoplasmic reticulum** or mitochondria. *Mg2+* - **Magnesium (Mg2+)** is an important intracellular ion and a cofactor for many enzymes, but it is **not the chief (most abundant)** intracellular ion. - Its concentration is substantially lower than that of potassium within the cell.

Q: What percentage of body weight is total body water (TBW) in a one-year-old child?

70%. ***70%*** - In a one-year-old child, **total body water (TBW)** constitutes approximately **70%** of their body weight. - This represents a decrease from the **75-80%** seen in newborns but remains significantly higher than the **60%** seen in adult males. - This high TBW percentage is crucial for understanding **fluid balance**, **medication dosing**, and **dehydration risk** in pediatric patients. *90%* - This percentage is **too high** for a one-year-old child. - Values around 90% are seen in **extremely premature infants** or the **fetus**. - TBW decreases progressively with age and development. *80%* - This value is typically associated with **full-term newborns** and **young infants (0-3 months)**. - By one year of age, the TBW percentage has declined significantly from the newborn level. *50%* - This percentage represents the TBW found in **adult females**, which is the lowest among all age groups. - A one-year-old child has a much higher proportion of body water compared to adults due to higher metabolic rate and greater extracellular fluid volume.

Q: Maximum concentration of plasma calcium exists as

Ionized form. ***Ionized form*** - Approximately **50% of plasma calcium** exists as **free, ionized calcium (Ca2+)**, which is the biologically active form regulating various physiological processes. - This form is not bound to proteins or complexed with organic anions, allowing it to easily interact with target cells and receptors. *Complexed to phosphate* - Only a **small percentage (around 5-10%)** of plasma calcium is complexed with anions like phosphate, citrate, and bicarbonate. - Phosphate complexation is less significant than protein binding or the ionized form in terms of overall plasma calcium concentration. *Complexed to citrate* - **Citrate** also forms complexes with calcium, but like phosphate, this accounts for a minor fraction of total plasma calcium. - While important in specific contexts (e.g., blood storage due to anticoagulant effect), it is not the dominant form in vivo. *Bound to plasma albumin* - Roughly **40-45% of plasma calcium** is bound to plasma proteins, primarily **albumin**. - While a significant fraction, it is still less than the ionized form, which is the functional component that is tightly regulated.

Q: QT shortening is associated with which electrolyte imbalance?

Hypercalcemia. ***Hypercalcemia*** - **Elevated calcium levels** lead to a shortened **plateau phase of the cardiac action potential**, which manifests as a **shortened QT interval** on an ECG. - This imbalance increases the risk of ventricular arrhythmias, although profound shortening can lead to **QRS widening** with further increase in calcium. *Hypokalemia* - **Low potassium** levels typically cause **QT prolongation**, usually due to prominent U waves and T wave flattening. - It does not cause QT shortening; instead, it is associated with an **increased risk of Torsades de Pointes**. *Hypocalcemia* - **Low calcium** levels cause **QT prolongation** by lengthening the **plateau phase of the cardiac action potential**, increasing the duration of ventricular repolarization. - ECG findings include prolonged ST segment and can increase the risk of arrhythmias, including Torsades de Pointes. *Hyperkalemia* - **High potassium** levels primarily cause **peaked T waves**, a **widened QRS complex**, and a **prolonged PR interval**, potentially leading to asystole or ventricular fibrillation. - It does not cause QT shortening; instead, severe hyperkalemia can lead to **loss of P waves** and a **sine wave pattern**.

Question 1

Insensible water loss per day is ?

Accepted Answer

1000 ml

Answer

100 ml

Answer

700 ml

Answer

300 ml

Question 2

What electrolyte imbalance is commonly associated with laxative abuse?

Accepted Answer

Hypokalemia

Answer

Hypomagnesemia

Answer

Hyponatremia

Answer

Hyperkalemia

Question 3

Intracellular water constitutes what percentage of total body water?

Accepted Answer

60%

Answer

25%

Answer

80%

Answer

40%

Question 4

Among the following gastrointestinal compartments, maximum K+ concentration is seen in which one?

Accepted Answer

Colon

Answer

Saliva

Answer

Small intestine

Answer

Stomach

Question 5

What is the typical amount of insensible water loss per day?

Accepted Answer

800 ml

Answer

600 ml

Answer

100 ml

Answer

1000 ml

Question 6

All of the following are present in sweat, except which of the following?

Accepted Answer

Uric acid

Answer

Calcium

Answer

Urea

Answer

Lactic acid

Question 7

Which ion is considered the chief intracellular ion in the human body?

Accepted Answer

K+

Answer

Na+

Answer

Ca2+

Answer

Mg2+

Question 8

What percentage of body weight is total body water (TBW) in a one-year-old child?

Accepted Answer

70%

Answer

90%

Answer

80%

Answer

50%

Question 9

Maximum concentration of plasma calcium exists as

Accepted Answer

Ionized form

Answer

Complexed to phosphate

Answer

Complexed to citrate

Answer

Bound to plasma albumin

Question 10

QT shortening is associated with which electrolyte imbalance?

Accepted Answer

Hypercalcemia

Answer

Hypokalemia

Answer

Hypocalcemia

Answer

Hyperkalemia

Electrolytes and Body Fluids — MCQs

Electrolytes and Body Fluids — MCQs

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