Electrolytes and Body Fluids Practice Questions

Q: Major ions in ECF are:

Sodium and chloride. ***Sodium and chloride*** - **Sodium (Na+)** is the primary cation, and **chloride (Cl-)** is the primary anion in the extracellular fluid (ECF). - These ions play crucial roles in maintaining **osmotic pressure**, **fluid balance**, and **nerve impulse transmission**. *Potassium and phosphate* - **Potassium (K+)** is the major intracellular cation, while **phosphate (PO43-)** is a major intracellular anion. - While present in the ECF, their concentrations are significantly lower compared to sodium and chloride. *Sodium and phosphate* - **Sodium** is a major ECF cation, but **phosphate** is predominantly an intracellular anion. - Therefore, phosphate is not considered one of the major extracellular ions. *Potassium and chloride* - **Potassium** is primarily an intracellular ion, not a major ECF cation. - While **chloride** is a major ECF anion, its pairing with potassium does not represent the two major ions in the ECF.

Q: Which of the following is the approximate extracellular fluid volume of a normal individual?

20% of body mass. ***20% of body mass*** - Extracellular fluid (ECF) volume constitutes approximately **20% of total body mass**, or roughly one-third of the total body fluid. - This fluid compartment includes plasma, interstitial fluid, lymph, and transcellular fluid. *40% of body mass* - This percentage represents the approximate volume of **intracellular fluid (ICF)**, not extracellular fluid. - ICF accounts for about two-thirds of the total body fluid, residing within the cells. *5% of body mass* - This percentage is too low for the total extracellular fluid volume. - It more closely approximates the volume of **plasma**, which is a component of ECF, but not the entire ECF. *10% of body mass* - This value is lower than the typical extracellular fluid volume. - It does not accurately represent the combined volume of all fluid outside the cells.

Q: Which of the following is true about ICF?

28 L. ***28 L*** - The **intracellular fluid (ICF)** volume is approximately two-thirds of the total body water, which for a 70 kg individual is around **28 liters**. - This fluid is found within the cells and is crucial for various cellular functions and metabolic processes. *14 L* - This value typically represents the **extracellular fluid (ECF)** volume, which is divided into interstitial fluid and plasma, not the ICF. - The ECF is approximately one-third of the total body water, or about 14 liters. *33% of body weight* - This percentage is **inaccurate for both ICF and ECF**. - ICF accounts for approximately **40% of body weight**, while ECF accounts for about 20% of body weight. - This option does not correctly represent any major fluid compartment. *20% of body weight* - While **20% of body weight** more closely represents the **extracellular fluid (ECF)** volume, it is an underestimate for the intracellular fluid (ICF) volume. - ICF makes up approximately **40% of body weight** in an adult, which is double this value.

Q: Daily loss of water from skin in absence of sweating is:

200-300 ml. ***200-300 ml*** - This range accurately represents the typical daily **insensible water loss** from the skin when **sweating** is not actively occurring. - Insensible water loss is a continuous, unregulated process of water evaporation from the skin and respiratory tract surfaces, essential for thermoregulation and hydration balance. *1.5 litres* - This volume is significantly higher than the insensible water loss from the skin alone and generally reflects the total daily water loss through all routes, including urine, feces, and respiration, in an adult. - Active **sweating**, especially during exercise or in hot environments, would be required to reach this level of total dermal water loss. *1 litre* - While a substantial amount, 1 liter is generally too high for the daily insensible water loss from the skin in the absence of active sweating. - This value might be closer to the total insensible volume when considering both skin and respiratory losses. *500-700 ml* - This range is usually considered the total daily insensible water loss through both the skin and the respiratory tract together. - The skin's contribution alone is typically less than this total amount.

Q: Why is carpopedal spasm seen in hyperventilation?

Increased plasma protein binding of Ca. ***Increased plasma protein binding of Ca*** - **Hyperventilation** leads to respiratory alkalosis due to excessive CO2 exhalation, increasing blood pH. - This elevated pH enhances the binding of **calcium to albumin**, decreasing the amount of free ionized calcium available. *Increased excretion of calcium in urine* - **Hyperventilation** itself does not directly lead to increased urinary calcium excretion; rather, it primarily affects the **distribution of calcium** within the bloodstream. - While prolonged alkalosis can affect renal handling of electrolytes, the immediate cause of carpopedal spasm is not urinary loss. *Increased sequestration of Ca in SER* - **Calcium sequestration** in the sarcoplasmic/endoplasmic reticulum (SER) is a process related to intracellular calcium handling and muscle contraction. - It is not the primary mechanism by which **hyperventilation-induced alkalosis** causes **hypocalcemia** and carpopedal spasm. *Ca utilized in bones* - Calcium is continuously exchanged between bone and the extracellular fluid, but **hyperventilation** does not immediately or significantly increase **bone utilization of calcium** to cause acute carpopedal spasm. - Bone serves as a reservoir, but the rapid onset of spasm points to changes in **circulating ionized calcium**.

Q: Major contributor to plasma osmolarity is:

Sodium. ***Sodium*** - **Sodium (Na+)** is the most abundant extracellular cation and accounts for approximately 90-95% of the **effective plasma osmolarity**. - Its concentration is tightly regulated by hormones like **ADH** and **aldosterone**, making it the primary determinant of water movement between intracellular and extracellular compartments. *Plasma proteins* - While plasma proteins contribute significantly to **oncotic pressure** (colloid osmotic pressure), they have a relatively small direct contribution to the overall **plasma osmolarity** due to their lower molar concentration compared to sodium. - Their primary role is in fluid distribution between the vascular and interstitial spaces, not the total effective solute concentration. *Glucose* - **Glucose** contributes to plasma osmolarity, especially in conditions like **diabetes mellitus** where its levels are high. - However, under normal physiological conditions, the concentration of glucose is much lower than sodium, making its contribution to overall osmolarity less significant. *Urea* - **Urea** is a significant contributor to **total plasma osmolarity**, but it is generally considered an **ineffective osmole** because it can readily cross cell membranes. - While it contributes to the measured osmolarity, it does not exert a significant osmotic force that causes sustained water movement between compartments in the same way sodium does.

Q: Which of the following is hypertonic?

3% normal saline. ***3% normal saline*** - This solution contains a significantly **higher concentration of sodium chloride** (NaCl) than the body's normal plasma osmolality (approximately 154 mEq/L for 0.9% NS). - Its high solute concentration creates an **osmotic gradient**, causing water to move out of cells and into the extracellular space, classifying it as **hypertonic**. *5% dextrose* - While initially isotonic in the bag, dextrose is rapidly metabolized by the body, leaving behind free water. - This makes it functionally a **hypotonic solution** once administered intravenously, as it dilutes plasma and can cause fluid shifts into cells. *0.45% normal saline* - This is also known as **half-normal saline**, meaning it has half the sodium chloride concentration of 0.9% normal saline. - With a lower solute concentration than plasma, it is considered a **hypotonic solution**, causing fluid to shift into cells. *0.9% normal saline (NaCl)* - This solution has an osmolality of approximately 308 mOsm/L, which is **similar to that of human plasma**. - It is therefore considered an **isotonic solution**, meaning it does not cause significant fluid shifts between the intracellular and extracellular compartments.

Q: All of the following are true about potassium, except

Leaves the cell in the presence of insulin. ***Leaves the cell in the presence of insulin*** - Insulin promotes the uptake of **potassium into cells**, primarily by stimulating the Na+/K+-ATPase pump. - Therefore, insulin actually causes potassium to enter the cell, not leave it, which helps to **lower extracellular potassium levels**. *Mostly concentrated inside the cells* - **Potassium (K+)** is the primary intracellular cation, with concentrations approximately 30 times higher inside cells than outside. - This high intracellular concentration is crucial for maintaining **resting membrane potential** and cellular functions. *Plasma concentration increases at time of metabolic acidosis* - In **metabolic acidosis**, hydrogen ions (H+) shift into cells in exchange for potassium ions, which move out of cells into the extracellular fluid. - This H+/K+ exchange mechanism leads to an **increase in plasma potassium concentration**. *Ingestion of acetazolamide results in potassium loss* - **Acetazolamide** is a carbonic anhydrase inhibitor that acts on the proximal tubule of the kidney. - It inhibits bicarbonate reabsorption, leading to increased delivery of sodium and water to the collecting duct, which promotes **potassium secretion and loss**.

Q: Which of the following is NOT true about body fluids:

Synovial fluid is transcellular fluid. ***Synovial fluid is transcellular fluid*** - This statement is **NOT true** according to most standard classifications. - **Synovial fluid** is classified as a component of **interstitial fluid**, not transcellular fluid. - **Transcellular fluid** refers to specialized fluids formed by active transport across epithelial membranes and includes cerebrospinal fluid (CSF), pleural fluid, peritoneal fluid, pericardial fluid, and digestive secretions. - Synovial fluid, while specialized, is formed by ultrafiltration of plasma and secretion by synoviocytes, and is considered part of the interstitial compartment. *ECF volume of 70 kg adult man would be approximately 14 L* - This statement is **TRUE**. - **Extracellular fluid (ECF)** constitutes approximately **20% of total body weight** in adult males. - For a **70 kg man**: 20% × 70 kg = **14 kg ≈ 14 L** of ECF. *The total body fluid per unit body weight is more in infants as compared to adults* - This statement is **TRUE**. - **Infants** have approximately **75-80% total body water (TBW)** compared to adults with **50-60% TBW**. - This is due to higher metabolic rate, less fat tissue, and different body composition in infants. *Intracellular fluid is 40% of total body weight* - This statement is **TRUE**. - **Intracellular fluid (ICF)** represents approximately **two-thirds of total body water**, which equals about **40% of total body weight** in adults. - ICF is the largest fluid compartment in the body.

Q: Which of the following is not a general compartment of body fluid?

Peritoneal. ***Peritoneal*** - The **peritoneal fluid** is a component of the **extracellular fluid**, but it is not considered one of the *general* body fluid compartments in the typical physiological classification. - General compartments refer to the broad categories of **intracellular** and **extracellular fluid**, with extracellular being further divided into **interstitial fluid** and **blood plasma**. *Blood plasma* - **Blood plasma** is a major component of the **extracellular fluid** compartment, specifically the **intravascular fluid** that circulates within blood vessels. - It is crucial for **transporting nutrients**, waste products, hormones, and blood cells throughout the body. *Interstitial* - **Interstitial fluid** is a part of the **extracellular fluid**, located in the spaces between cells. - It acts as an **interface** between blood plasma and intracellular fluid, facilitating the exchange of substances. *Intracellular* - **Intracellular fluid (ICF)** is the fluid found *inside* cells and constitutes about two-thirds of the total body water. - It is a primary compartment, essential for **cellular metabolism** and maintaining cell volume.

Question 1

Major ions in ECF are:

Accepted Answer

Sodium and chloride

Answer

Potassium and phosphate

Answer

Sodium and phosphate

Answer

Potassium and chloride

Question 2

Which of the following is the approximate extracellular fluid volume of a normal individual?

Accepted Answer

20% of body mass

Answer

40% of body mass

Answer

5% of body mass

Answer

10% of body mass

Question 3

Which of the following is true about ICF?

Accepted Answer

28 L

Answer

14 L

Answer

33% of body weight

Answer

20 % of body weight

Question 4

Daily loss of water from skin in absence of sweating is:

Accepted Answer

200-300 ml

Answer

1.5 litres

Answer

1 litre

Answer

500-700 ml

Question 5

Why is carpopedal spasm seen in hyperventilation?

Accepted Answer

Increased plasma protein binding of Ca

Answer

Increased excretion of calcium in urine

Answer

Increased sequestration of Ca in SER

Answer

Ca utilized in bones

Question 6

Major contributor to plasma osmolarity is:

Accepted Answer

Sodium

Answer

Plasma proteins

Answer

Glucose

Answer

Urea

Question 7

Which of the following is hypertonic?

Accepted Answer

3% normal saline

Answer

5% dextrose

Answer

0.45% normal saline

Answer

0.9% normal saline (NaCl)

Question 8

All of the following are true about potassium, except

Accepted Answer

Leaves the cell in the presence of insulin

Answer

Mostly concentrated inside the cells

Answer

Plasma concentration increases at time of metabolic acidosis

Answer

Ingestion of acetazolamide results in potassium loss

Question 9

Which of the following is NOT true about body fluids:

Accepted Answer

Synovial fluid is transcellular fluid

Answer

ECF volume of 70 kg adult man would be approximately 14 L

Answer

The total body fluid per unit body weight is more in infants as compared to adults

Answer

Intracellular fluid is 40% of total body weight

Question 10

Which of the following is not a general compartment of body fluid?

Accepted Answer

Peritoneal

Answer

Blood plasma

Answer

Interstitial

Answer

Intracellular

Electrolytes and Body Fluids — MCQs

Electrolytes and Body Fluids — MCQs

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