Electrolytes and Body Fluids Practice Questions

Q: The second most abundant intracellular cation is

Magnesium. ***Magnesium*** - **Magnesium** is the **second most abundant intracellular cation** after potassium. - It plays a crucial role in over 300 enzymatic reactions, including **ATP metabolism**, protein synthesis, and nucleic acid synthesis. *Calcium* - **Calcium** is primarily concentrated **extracellularly** and in intracellular stores like the endoplasmic reticulum, rather than being a highly abundant free intracellular cation. - Its main roles are in **bone mineralization**, muscle contraction, and neurotransmitter release. *Iron* - While **iron** is essential for cellular functions like **oxygen transport** (hemoglobin) and enzyme activity, it is not considered a bulk intracellular cation. - Its intracellular concentration is carefully regulated due to its potential toxicity. *Sodium* - **Sodium** is the **most abundant extracellular cation**, with a significantly lower concentration inside cells. - The **sodium-potassium pump** actively maintains this gradient, which is vital for nerve impulse transmission and osmotic balance.

Q: What is the percentage of water in adult human being?

60%. ***60%*** - The human body is composed of approximately **60% water** by weight in adult males. - This percentage can vary slightly based on age, sex, and body composition, but 60% is a widely accepted average. *40%* - 40% is generally considered too low for the average total body water content in an adult human. - While certain tissues have lower water content, the overall average is significantly higher. *50%* - 50% is below the typical average for most adult humans, although it might be seen in individuals with a higher percentage of **adipose tissue**, as fat contains less water than lean tissue. - This figure is more common in older adults or individuals with a higher body fat percentage. *70%* - 70% is generally considered on the higher side for the average adult human, more characteristic of infants and young children whose bodies have a higher water content. - While some lean individuals may approach this percentage, it is not the typical average for adults.

Q: Major portion of body water lies in:

Intracellular. ***Intracellular*** - Approximately **two-thirds (60%)** of the total body water is located **inside cells** (intracellular fluid, ICF). - In a 70 kg adult male, out of ~42L total body water, approximately **28L is intracellular**. - This fluid is crucial for maintaining **cell volume**, metabolic processes, and overall cell function. - The ICF contains high concentrations of potassium, magnesium, and phosphate. *Extracellular* - The **extracellular fluid (ECF)** compartment accounts for about **one-third (40%)** of the total body water (~14L in a 70 kg adult). - While vital for nutrient and waste transport, it is a smaller volume compared to the intracellular compartment. - ECF is further divided into interstitial fluid (~75% of ECF) and plasma (~25% of ECF). *Interstitial fluid* - Interstitial fluid is a **component of extracellular fluid**, not a major body water compartment on its own. - It accounts for only about **10-11L** in a typical adult, which is less than the intracellular volume. - It surrounds tissue cells and facilitates exchange between plasma and cells. *Plasma* - Plasma is the **smallest fluid compartment**, representing only about **3-3.5L** (~8% of total body water). - While essential for circulation and transport, it contains far less water than the intracellular compartment. - Plasma is the liquid component of blood, excluding cellular elements.

Q: Which of the following is true about body fluid osmolarity?

Major contributor is Na+. ***Major contributor is Na+*** - **Sodium (Na+)** and its associated anions (chloride and bicarbonate) are the primary determinants of **extracellular fluid (ECF) osmolarity** due to their high concentration and inability to freely cross cell membranes. - The concentration of effective solutes like Na+ dictates the **osmotic movement of water** between fluid compartments. *Measured by dilution method* - **Dilution methods** are typically used to measure **body fluid volumes**, such as total body water or ECF volume, by tracking the distribution of a known tracer. - **Osmolarity** is measured by an **osmometer**, which determines the number of solute particles per unit of solvent, often based on freezing point depression. *Major contributor is proteins* - While proteins are present in body fluids, their contribution to **total osmolarity** is relatively small compared to electrolytes, especially in the **extracellular fluid**. - Proteins exert an **oncotic pressure**, which is important for fluid distribution between plasma and interstitial fluid, but not the primary determinant of overall osmolarity. *ECF osmolarity is 250 mOsm/L* - The normal range for **ECF osmolarity** in humans is approximately **280-295 mOsm/L**, with an average of around 285-290 mOsm/L. - A value of 250 mOsm/L would indicate **hypoosmolality**, which is a deviation from the normal physiological range.

Q: Normal amount of sodium in plasma is (in mEq/L)

143. ***Correct: 143 mEq/L*** - The normal physiological range for **sodium concentration in plasma** is typically between **135 and 145 mEq/L**. - Therefore, **143 mEq/L** falls right within the healthy range and represents a normal value. *Incorrect: 95 mEq/L* - A plasma sodium concentration of **95 mEq/L** would indicate severe **hyponatremia**. - This level is significantly below the normal range and would be associated with severe neurological symptoms such as **seizures or coma**. *Incorrect: 120 mEq/L* - A plasma sodium concentration of **120 mEq/L** would indicate **hyponatremia**. - While not as severe as 95 mEq/L, it is still below the normal range and could lead to symptoms like **nausea, malaise, and headache**. *Incorrect: 175 mEq/L* - A plasma sodium concentration of **175 mEq/L** would indicate severe **hypernatremia**. - This is significantly above the normal range and could cause symptoms such as **thirst, lethargy, seizures, or even brain damage**.

Q: Factors that decrease insensible water losses are all, except –

Prematurity. ***Prematurity*** - **Premature infants** have **thinner skin** and a larger surface area to body weight ratio, leading to **increased insensible water losses** compared to full-term infants. - Their immature skin barrier function allows for greater evaporative water loss. *Sedation* - **Sedation** can **decrease metabolic rate** and activity, leading to a reduction in insensible water losses. - It reduces ventilation rate and skin blood flow, both contributing to decreased water evaporation. *Humidified air* - Using **humidified air**, particularly with mechanical ventilation, **decreases the gradient for water evaporation** from the respiratory tract. - This directly reduces pulmonary insensible water loss. *Hypothermia* - **Hypothermia** (low body temperature) **reduces metabolic rate** and peripheral blood flow. - A decreased metabolic rate leads to lower heat production and, consequently, reduced evaporative water loss from the skin and respiratory tract.

Q: Which of the following methods is NOT used for measurement of body fluid volumes? (March 2013)

Creatinine clearance for blood volume. ***Creatinine clearance for blood volume*** - **Creatinine clearance** is a measure of **glomerular filtration rate (GFR)** and kidney function. - It is **not used** to measure blood volume; rather, blood volume is typically measured using indicator dilution methods. *Evans blue for plasma volume* - **Evans blue** is a dye that binds to **plasma albumin** and remains within the intravascular space. - Its concentration can be used in the **indicator dilution method** to accurately determine plasma volume. *Inulin for extracellular fluid* - **Inulin** is freely filtered by the glomeruli but **neither reabsorbed nor secreted** by the renal tubules. - It is used to measure **extracellular fluid volume** because it distributes throughout this compartment but does not enter cells. *Antipyrine for total body water* - **Antipyrine** is a lipid-soluble substance that diffuses readily across cell membranes and distributes uniformly throughout **total body water**. - Its concentration is used in the **indicator dilution method** to determine the total water content of the body.

Q: Daily water loss in sweat during high physical activities is approximately:

1000-1200ml. ***1000-1200ml*** - During **high physical activities**, the body significantly increases **sweat production** to regulate body temperature. - This level of activity can lead to a substantial daily water loss through sweat, typically in the range of 1 to 1.2 liters (1000-1200 ml). *200-400ml* - This range represents a relatively **low level of sweat loss**, which might occur during mild activity or in cooler environments. - It seriously underestimates the water loss during **high physical activities**, where metabolic heat production is much greater. *50-100ml* - This amount is typical for **insensible water loss** through the skin in a sedentary state, not related to active sweating. - It is far too low for any physical activity, let alone **high physical activity**, which demands significant thermoregulation. *500-700ml* - This range might be closer to sweat loss during **moderate physical activity** or in less demanding conditions. - However, for **high physical activities**, especially those sustained over time, this amount is generally an underestimate of the total water loss.

Q: Which of the following is NOT true about osmotic adaptation?

Due to urea and glucose mainly. ***Due to urea and glucose mainly*** - Osmotic adaptation primarily involves organic osmolytes like **myoinositol**, **taurine**, **sorbitol**, and **glutamate**, not primarily urea and glucose. - While urea and glucose contribute to osmotic pressure, they are not the main adaptive osmolytes used by cells for long-term osmotic balance. - This statement is **NOT true** about osmotic adaptation. *Due to osmolytes* - Osmotic adaptation depends on the cell's ability to regulate intracellular concentration of specific **organic osmolytes** (e.g., polyols, amino acids, methylamines). - These osmolytes help fine-tune intracellular osmotic pressure without disrupting **protein function**. *Occurs in brain cells* - Brain cells are particularly vulnerable to changes in osmolality due to the skull's rigid confines, making **osmotic adaptation** critical for maintaining brain volume. - They actively regulate intracellular osmolytes to protect against **swelling or shrinking** in response to plasma osmolality changes. *Protects against large water shift* - By adjusting internal osmolyte concentrations, cells counteract osmotic gradients, thereby preventing **excessive water influx or efflux**. - This mechanism is crucial for maintaining **cell volume and function** in environments with fluctuating external osmolality.

Q: Which of the following is considered the active form of calcium?

Ionised calcium. ***Ionised calcium*** - **Ionized calcium** (approximately 50% of total serum calcium) is the physiologically active form of calcium, responsible for most calcium-dependent bodily functions. - It directly participates in processes like **muscle contraction**, **nerve impulse transmission**, **blood coagulation**, and serves as a **second messenger** in cellular signaling. - This is the **free, unbound form** that exerts biological effects. *Albumin bound calcium* - **Albumin-bound calcium** (approximately 40% of total serum calcium) is a storage and transport form of calcium, but it is not metabolically active. - Albumin is the **primary protein** that binds calcium in the blood. - Its concentration can be affected by **albumin levels**, making corrected calcium calculations necessary in hypoalbuminemia. *Phosphate bound calcium* - **Phosphate-bound calcium** represents calcium that is complexed with phosphate and other anions (approximately 10% of total serum calcium). - Often found as insoluble salts in bone or as soluble complexes in body fluids. - While essential for bone mineralisation, this form is **not directly active** in signaling or metabolic processes. *Protein bound calcium* - **Protein-bound calcium** refers to calcium attached to various proteins, primarily **albumin** (80% of protein-bound fraction), and other proteins like globulins. - This is a **broader category** that encompasses albumin-bound calcium. - This fraction serves as a **reservoir** but is not the free, unbound calcium that performs cellular functions.

Question 1

The second most abundant intracellular cation is

Accepted Answer

Magnesium

Answer

Calcium

Answer

Iron

Answer

Sodium

Question 2

What is the percentage of water in adult human being?

Accepted Answer

60%

Answer

40%

Answer

50%

Answer

70%

Question 3

Major portion of body water lies in:

Accepted Answer

Intracellular

Answer

Extracellular

Answer

Interstitial fluid

Answer

Plasma

Question 4

Which of the following is true about body fluid osmolarity?

Accepted Answer

Major contributor is Na+

Answer

Measured by dilution method

Answer

Major contributor is proteins

Answer

ECF osmolarity is 250 mOsm/L

Question 5

Normal amount of sodium in plasma is (in mEq/L)

Accepted Answer

143

Answer

95

Answer

120

Answer

175

Question 6

Factors that decrease insensible water losses are all, except –

Accepted Answer

Prematurity

Answer

Sedation

Answer

Humidified air

Answer

Hypothermia

Question 7

Which of the following methods is NOT used for measurement of body fluid volumes? (March 2013)

Accepted Answer

Creatinine clearance for blood volume

Answer

Evans blue for plasma volume

Answer

Inulin for extracellular fluid

Answer

Antipyrine for total body water

Question 8

Daily water loss in sweat during high physical activities is approximately:

Accepted Answer

1000-1200ml

Answer

200-400ml

Answer

50-100ml

Answer

500-700ml

Question 9

Which of the following is NOT true about osmotic adaptation?

Accepted Answer

Due to urea and glucose mainly

Answer

Due to osmolytes

Answer

Occurs in brain cells

Answer

Protects against large water shift

Question 10

Which of the following is considered the active form of calcium?

Accepted Answer

Ionised calcium

Answer

Albumin bound calcium

Answer

Phosphate bound calcium

Answer

Protein bound calcium

Electrolytes and Body Fluids — MCQs

Electrolytes and Body Fluids — MCQs

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