UPSC-CMS 2013 — Physiology
5 Previous Year Questions with Answers & Explanations
Non-cardiac causes of raised central venous pressure include all of the following except:
Pregnancy is characterized by the following physiological changes except :
The ferning of cervical mucus is due to the high concentration of :
Which one of the following statements is not correct about fetal circulation?
Which of the following is X-linked dominant trait?
UPSC-CMS 2013 - Physiology UPSC-CMS Practice Questions and MCQs
Question 1: Non-cardiac causes of raised central venous pressure include all of the following except:
- A. Hyper-volemia (Correct Answer)
- B. Abdominal compartment syndrome
- C. Positive pressure ventilation
- D. Tension pneumothorax
Explanation: **IMPORTANT NOTE:** This question as originally presented is medically problematic because **hypervolemia is actually a NON-CARDIAC cause** of elevated CVP. All four options listed are non-cardiac causes, making this question flawed. However, if this represents the original UPSC-CMS-2013 answer key, the intended distinction may have been between **systemic/volume-related causes** versus **mechanical/obstructive causes**. ***Hypervolemia (Marked as answer)*** - Hypervolemia (fluid overload) is technically a **non-cardiac, systemic cause** of elevated CVP, not a cardiac cause - It increases CVP by increasing **circulating blood volume** and venous return, without primary cardiac dysfunction - True **cardiac causes** would include right heart failure, tricuspid regurgitation, cardiac tamponade, or constrictive pericarditis - If this was the intended answer, the distinction may be: hypervolemia is a **systemic/volume cause** while the others are **mechanical/obstructive causes** *Abdominal compartment syndrome* - Increases **intra-abdominal pressure** which transmits to the thorax - Mechanically compresses the **inferior vena cava**, impeding venous return - This is clearly a **non-cardiac, mechanical cause** of elevated CVP *Positive pressure ventilation* - Increases **intrathoracic pressure** during mechanical ventilation - Directly opposes venous return to the right atrium - This is a **non-cardiac, mechanical cause** of elevated CVP *Tension pneumothorax* - Causes severe increase in **intrathoracic pressure** from trapped air - Compresses the **vena cavae** and impedes venous return - This is a **non-cardiac, mechanical/obstructive cause** of elevated CVP **Clinical Pearl:** When evaluating elevated CVP, distinguish between cardiac causes (right heart failure, tamponade), mechanical causes (tension pneumothorax, positive pressure ventilation), obstructive causes (SVC syndrome), and volume-related causes (hypervolemia).
Question 2: Pregnancy is characterized by the following physiological changes except :
- A. Dilatation of ureters
- B. Delayed gastric emptying time
- C. Decreased glomerular filtration rate (Correct Answer)
- D. Increased tidal volume
Explanation: ***Decreased glomerular filtration rate*** - During **pregnancy**, there is a significant **increase in glomerular filtration rate (GFR)**, typically by 30-50%, due to increased renal blood flow and vasodilation. - A decreased GFR would be an abnormal finding, indicating renal dysfunction, not a normal physiological change of pregnancy. *Dilatation of ureters* - **Physiological hydronephrosis** and **utereral dilation** are common in pregnancy, primarily due to the relaxed smooth muscle effects of **progesterone** and mechanical compression by the gravid uterus. - This dilation occurs as early as the first trimester and can persist until after delivery. *Delayed gastric emptying time* - **Progesterone** acts as a smooth muscle relaxant, leading to decreased gastrointestinal motility and a **delayed gastric emptying time** during pregnancy. - This can contribute to common pregnancy symptoms like **nausea, vomiting**, and **heartburn**. *Increased tidal volume* - **Tidal volume (TV)** increases during pregnancy, primarily driven by hormonal changes, specifically **progesterone**. - This increase in TV leads to a greater minute ventilation, helping to meet the increased oxygen demands of both the mother and the fetus.
Question 3: The ferning of cervical mucus is due to the high concentration of :
- A. Sodium chloride (Correct Answer)
- B. Sodium bicarbonate
- C. Potassium chloride
- D. Potassium bicarbonate
Explanation: ***Sodium chloride*** - The characteristic **ferning pattern** observed in cervical mucus is primarily due to the crystallization of **sodium chloride** under the influence of estrogen. - This crystallization occurs as the mucus dries on a slide, forming a fern-like pattern that indicates high estrogen levels and often signifies the periovulatory period. *Sodium bicarbonate* - While present in bodily fluids, **sodium bicarbonate** does not directly contribute to the characteristic fern-like crystallization seen in cervical mucus. - Its primary role is buffering, maintaining pH balance, rather than forming crystal patterns. *Potassium chloride* - Although potassium ions are present in cervical secretions, **potassium chloride** does not specifically form the classic fenestrated pattern observed in ferning. - The unique crystallization properties of sodium chloride distinguish it from other salts in this context. *Potassium bicarbonate* - Similar to sodium bicarbonate, **potassium bicarbonate** does not contribute to the fern phenomenon of cervical mucus. - It plays a role in pH regulation but not in the distinct crystallization pattern associated with estrogen and fertility.
Question 4: Which one of the following statements is not correct about fetal circulation?
- A. Umbilical artery carries deoxygenated fetal blood to the placenta
- B. Two umbilical arteries and one umbilical vein traverse through the fetus and placenta
- C. Umbilical vein carries oxygenated blood to the fetus
- D. Umbilical artery carries oxygenated blood to the fetus (Correct Answer)
Explanation: ***Umbilical artery carries oxygenated blood to the fetus*** - This statement is incorrect because the **umbilical arteries** carry **deoxygenated blood** and waste products away from the fetus to the placenta. - Oxygenated blood is carried *to* the fetus by the **umbilical vein**. *Umbilical artery carries deoxygenated fetal blood to the placenta* - This statement is correct. The **umbilical arteries** are responsible for transporting **deoxygenated blood** and metabolic waste products from the fetal circulation back to the placenta for exchange with the maternal blood. - This is a key component of the fetoplacental circulation. *Two umbilical arteries and one umbilical vein traverse through the fetus and placenta* - This statement is correct. The **umbilical cord** typically contains **two umbilical arteries** and one **umbilical vein**. - This arrangement facilitates efficient nutrient and gas exchange between the mother and fetus. *Umbilical vein carries oxygenated blood to the fetus* - This statement is correct. The **umbilical vein** carries **oxygenated blood** rich in nutrients from the placenta to the fetus. - This is the main conduit for essential substances required for fetal growth and development.
Question 5: Which of the following is X-linked dominant trait?
- A. Colour blindness
- B. Haemophilia-A
- C. Duchenne muscular dystrophy
- D. Vitamin D resistant rickets (Correct Answer)
Explanation: ***Vitamin D resistant rickets*** - This condition is characterized by **impaired kidney reabsorption of phosphate** and **defective bone mineralization**, leading to rickets, and it is inherited in an **X-linked dominant pattern**. - In X-linked dominant traits, an affected father will pass the trait to **all his daughters**, but none of his sons. An affected mother has a 50% chance of passing the trait to **each child**, regardless of sex. *Colour blindness* - **Color blindness** is an **X-linked recessive** disorder, meaning it is more common in males. - Affected individuals have **difficulty distinguishing certain colors**, usually red and green. *Haemophilia-A* - **Hemophilia A** is an **X-linked recessive** disorder caused by a deficiency in **Factor VIII**, leading to uncontrolled bleeding. - Males are predominantly affected, while females are typically carriers. *Duchenne muscular dystrophy* - **Duchenne muscular dystrophy** is an **X-linked recessive** disorder characterized by progressive muscle degeneration and weakness due to a mutation in the **dystrophin gene**. - It primarily affects males, with symptoms often appearing in early childhood.