UPSC-CMS 2024 — Physiology
5 Previous Year Questions with Answers & Explanations
Which of the following are approximate daily requirements of the common electrolytes in an adult? 1. Sodium 50-90 mM/day 2. Calcium 25-30 mM/day 3. Potassium 90 mM/day 4. Magnesium 15-17 mM/day Select the correct answer using the code given below.
Distributive shock is described by which of the following patterns of cardiovascular responses? 1. Vasodilation 2. Reduced peripheral vascular resistance 3. Inadequate 'afterload' 4. Low cardiac output Select the correct answer using the code given below.
Which one of the following statements is correct regarding foetal physiology?
Which of the following are advantages of state of haemodilution during pregnancy? 1. Optimum gaseous exchange between maternal and foetal circulation due to decreased blood viscosity 2. Protection against adverse effect of blood loss during delivery 3. Increased oxygen carrying capacity of blood Select the correct answer using the code given below.
Onset of labour is initiated by which of the following?
UPSC-CMS 2024 - Physiology UPSC-CMS Practice Questions and MCQs
Question 1: Which of the following are approximate daily requirements of the common electrolytes in an adult? 1. Sodium 50-90 mM/day 2. Calcium 25-30 mM/day 3. Potassium 90 mM/day 4. Magnesium 15-17 mM/day Select the correct answer using the code given below.
- A. 2, 3 and 4
- B. 1, 3 and 4 (Correct Answer)
- C. 1, 2 and 3
- D. 1, 2 and 4
Explanation: ***1, 3 and 4*** - The approximate daily requirements for **sodium** are indeed within the range of **50-90 mM/day** (typical maintenance: 1-2 mEq/kg/day) - **Potassium** is around **90 mM/day** (typical maintenance: 1 mEq/kg/day or ~70 mEq/day) - **Magnesium** is typically **15-17 mM/day** (typical maintenance: 0.2-0.3 mEq/kg/day or ~7-10 mM/day) - These values are essential for maintaining proper physiological functions, including fluid balance, nerve impulse transmission, and muscle contraction *2, 3 and 4* - This option incorrectly includes the daily requirement for **calcium** as **25-30 mM/day**, which is approximately **3-4 times higher** than the typical maintenance requirement - Actual adult calcium requirement is approximately **0.1-0.2 mEq/kg/day** or **3.5-7 mM/day** - While potassium and magnesium values are close to accurate, the calcium value makes this option incorrect *1, 2 and 3* - This option incorrectly states the daily requirement for **calcium** as **25-30 mM/day** - The value of **25-30 mM/day** appears to confuse dietary calcium intake (1000-1200 mg/day ≈ 25-30 mmol) with maintenance electrolyte requirements - Although sodium and potassium requirements are correctly stated, the error in calcium makes this choice incorrect *1, 2 and 4* - This combination is incorrect because it includes the inaccurate daily requirement for **calcium** as **25-30 mM/day** - While sodium and magnesium requirements are generally accurate, the inclusion of the incorrect calcium value (should be ~3.5-7 mM/day) invalidates this option
Question 2: Distributive shock is described by which of the following patterns of cardiovascular responses? 1. Vasodilation 2. Reduced peripheral vascular resistance 3. Inadequate 'afterload' 4. Low cardiac output Select the correct answer using the code given below.
- A. 1, 2 and 4
- B. 1, 3 and 4
- C. 1, 2 and 3 (Correct Answer)
- D. 2, 3 and 4
Explanation: ***1, 2 and 3*** - Distributive shock is characterized by **widespread vasodilation** (1), leading to a significant **reduction in peripheral vascular resistance/SVR** (2). - The reduced vascular resistance causes **inadequate afterload** (3) on the heart, as afterload is determined by SVR. - Cardiac output is typically **normal or elevated** in early distributive shock as the heart compensates for the low SVR, so statement 4 is NOT characteristic. - Classic examples include septic shock, anaphylactic shock, and neurogenic shock. *1, 2 and 4* - While **vasodilation** (1) and **reduced peripheral vascular resistance** (2) are correct, **low cardiac output** (4) is NOT a defining feature of distributive shock. - In distributive shock, cardiac output is often elevated in the hyperdynamic phase as the heart compensates for decreased SVR. - Low cardiac output is more characteristic of cardiogenic or hypovolemic shock. *1, 3 and 4* - **Vasodilation** (1) and **inadequate afterload** (3) are correct features, but **low cardiac output** (4) is incorrect. - Distributive shock typically presents with normal or increased cardiac output, not decreased. - This combination incorrectly includes low CO while missing the reduced peripheral vascular resistance (2). *2, 3 and 4* - **Reduced peripheral vascular resistance** (2) and **inadequate afterload** (3) are correct, but this option misses the fundamental mechanism of **vasodilation** (1). - Additionally, **low cardiac output** (4) is not a defining characteristic of distributive shock. - Without mentioning vasodilation, the underlying pathophysiology is incomplete.
Question 3: Which one of the following statements is correct regarding foetal physiology?
- A. Foetal pancreas secretes insulin as early as 20 weeks.
- B. Haematopoiesis is demonstrated first in the yolk sac by 14th day. (Correct Answer)
- C. Meconium appears at 16 weeks.
- D. Breathing movements are identified at 26 weeks.
Explanation: **Haematopoiesis is demonstrated first in the yolk sac by 14th day.** - **Hematopoiesis** (blood cell formation) begins as early as the 14th day of gestation within the **yolk sac**, which is the primary site for this process during the initial weeks. - This early development is crucial for meeting the oxygen and nutrient demands of the rapidly growing embryo. *Foetal pancreas secretes insulin as early as 20 weeks.* - The fetal pancreas begins to secrete some insulin as early as **10-12 weeks** of gestation, although significant secretion and functional maturity develop later. - By **20 weeks**, the fetal pancreas is well-differentiated, but insulin production starts earlier than this specific time point. *Meconium appears at 16 weeks.* - **Meconium** typically begins to form around **10-14 weeks** of gestation, but its appearance at the anus (often indicating a bowel movement) is usually noted later in the third trimester or at birth. - The formation at 16 weeks is too late for its initial appearance and too early for its common clinical observation. *Breathing movements are identified at 26 weeks.* - Fetal **breathing movements** can be identified much earlier, often by **18-20 weeks** of gestation using ultrasound. - These movements are intermittent and contribute to lung development, although they do not involve air exchange.
Question 4: Which of the following are advantages of state of haemodilution during pregnancy? 1. Optimum gaseous exchange between maternal and foetal circulation due to decreased blood viscosity 2. Protection against adverse effect of blood loss during delivery 3. Increased oxygen carrying capacity of blood Select the correct answer using the code given below.
- A. 1, 2 and 3
- B. 1 and 3 only
- C. 2 and 3 only
- D. 1 and 2 only (Correct Answer)
Explanation: ***1 and 2 only*** - **Haemodilution** during pregnancy, characterized by a disproportionate increase in plasma volume relative to red blood cell mass, leads to decreased blood **viscosity**. - A lower blood viscosity facilitates more efficient **gaseous exchange** (oxygen and carbon dioxide) between the maternal and fetal circulations at the placenta, and also offers a degree of protection against the effects of **blood loss during delivery** by maintaining circulating volume. *1, 2 and 3* - While haemodilution promotes efficient gaseous exchange and protects against blood loss, it does **not increase the oxygen carrying capacity** of the blood. - In fact, the relative decrease in red blood cell concentration leads to physiological anemia of pregnancy, which reduces the oxygen-carrying capacity (though total oxygen delivery may be maintained by increased cardiac output). *2 and 3 only* - This option correctly identifies protection against blood loss but incorrectly states an **increased oxygen carrying capacity**. - The primary mechanism for improved oxygen delivery is enhanced blood flow due to reduced viscosity and increased cardiac output, not an increased concentration of oxygen carriers. *1 and 3 only* - This option correctly identifies improved gaseous exchange but incorrectly suggests an **increased oxygen carrying capacity**. - Protection against blood loss is a significant benefit of pregnancy-induced haemodilution, which is overlooked in this choice.
Question 5: Onset of labour is initiated by which of the following?
- A. Increased level of progesterone immediately before labour
- B. Uterine distension
- C. Increased synthesis of myometrial receptors for oxytocin due to effect of oestrogen (Correct Answer)
- D. Increased CRH and ACTH from foetal hypothalamic-pituitary-adrenal axis
Explanation: ***Increased synthesis of myometrial receptors for oxytocin due to effect of oestrogen*** - **Estrogen** plays a crucial role in initiating labor by increasing the number of **oxytocin receptors** in the myometrium, making the uterus more sensitive to oxytocin's contractile effects. - **Oxytocin** then stimulates strong, coordinated uterine contractions essential for cervical dilation and expulsion of the fetus. *Increased level of progesterone immediately before labour* - During pregnancy, **progesterone** maintains uterine quiescence and prevents premature contractions. - The withdrawal or decrease in the inhibitory effect of progesterone, not an increase, is thought to be involved in the onset of labor. *Uterine distension* - While **uterine distension** contributes to uterine irritability and can trigger some contractions, it is not the primary initiator of true labor. - It is a physical factor that complements hormonal changes but doesn't independently start the complex cascade of labor. *Increased CRH and ACTH from foetal hypothalamic-pituitary-adrenal axis* - An increase in **fetal corticotropin-releasing hormone (CRH)** and **adrenocorticotropic hormone (ACTH)** leads to increased fetal cortisol. - Fetal cortisol then signals the placenta to produce more estrogen and less progesterone, thereby indirectly contributing to labor initiation, but it's not the direct trigger for contractions.