UPSC-CMS 2023 — Physiology
10 Previous Year Questions with Answers & Explanations
The removal of malarial parasites from the blood is called
Stored blood which has been preserved in a blood bank is deficient in which of the following coagulation factors?
The respective hormones responsible for the breast milk secretion and ejection are, in that order:
The absence of fructose in the seminal fluid indicates a defect of
The genetic inheritance of Haemophilia is
The ratio for Type-I to Type-III collagen during maturation of collagen in remodelling phase is :
Which of the following are the functions of larynx ? 1. Fixation of the chest 2. Aids in swallowing of food 3. Phonation 4. Respiration Select the correct answer using the code given below :
Carbohydrate metabolism in normal pregnancy shows :
Smoking is considered to be a modifiable risk factor for Coronary Heart Disease. Consider the following statements with regard to possible mechanisms on the basis of which it acts as a risk factor : 1. Nicotine stimulation of adrenergic drive raises the blood pressure and myocardial oxygen demand. 2. It increases carbon monoxide and induces atherogenesis. 3. It leads to fall in protective high density lipoproteins. 4. It reduces the apolipoprotein-B plasma levels. Which of the statements given above are correct ?
With reference to human body's requirement for proteins, they are essential because they are: 1. an important alternative source for energy during specific metabolic states. 2. the primary molecules responsible for maintenance of osmotic pressure within the extracellular compartment. 3. critical for upkeep of cell mediated immune response. 4. vital for the synthesis of certain hormones. Which of the statements given above are correct?
UPSC-CMS 2023 - Physiology UPSC-CMS Practice Questions and MCQs
Question 1: The removal of malarial parasites from the blood is called
- A. Phagocytosis (Correct Answer)
- B. Binding
- C. Culling
- D. Sequestration
Explanation: ***Phagocytosis*** - **Phagocytosis** is the process by which specialized cells, such as **macrophages** and **neutrophils**, engulf and digest foreign particles, including malarial parasites in the blood. - This is a crucial immune mechanism for clearing infected red blood cells and free parasites from the body. - Phagocytosis occurs primarily in the **spleen, liver, and bone marrow**, where macrophages recognize and destroy parasitized RBCs. *Binding* - **Binding** refers to the initial attachment of parasites or infected cells to host cells or tissues. - While binding is a step in the parasitic lifecycle and influences sequestration, it is not the process of *removal* from the blood. *Culling* - **Culling** refers to the selective removal of damaged, aged, or parasitized red blood cells by the spleen. - In malaria, the spleen does "cull" infected RBCs through mechanical filtration and phagocytic clearance. - However, **phagocytosis** is the broader immunological term that describes the cellular mechanism of engulfment and destruction, making it the more appropriate general answer. *Sequestration* - **Sequestration** is the process by which malarial parasites (specifically *Plasmodium falciparum*) in infected red blood cells adhere to the endothelium of capillaries and venules, especially in vital organs. - This mechanism allows parasites to **avoid clearance** by the spleen, representing a process of *retention* or *hiding* rather than removal from the circulation.
Question 2: Stored blood which has been preserved in a blood bank is deficient in which of the following coagulation factors?
- A. IX and X
- B. II and VII
- C. V and VIII (Correct Answer)
- D. II only
Explanation: ***V and VIII*** - **Factors V and VIII** are **labile coagulation factors** that degrade quickly during blood storage, making them deficient in stored blood. - This lability is due to their protein structure, which is sensitive to breakdown at refrigerated temperatures over time. *IX and X* - **Factors IX and X** are relatively stable and **vitamin K-dependent factors** that maintain their activity well in stored blood. - They are not significantly depleted during standard blood bank storage periods. *II and VII* - **Factors II (prothrombin) and VII** are also **vitamin K-dependent factors** known for their stability in stored blood. - Their levels remain largely preserved for typical blood storage durations. *II only* - **Factor II (prothrombin)** is a **stable, vitamin K-dependent factor**, and its levels are well-preserved in stored blood. - Therefore, stating only factor II is deficient is incorrect, as it is one of the more stable factors.
Question 3: The respective hormones responsible for the breast milk secretion and ejection are, in that order:
- A. Prolactin and Oxytocin (Correct Answer)
- B. Oestrogen and Prolactin
- C. Oxytocin and Prolactin
- D. Prolactin and Oestrogen
Explanation: ***Prolactin and Oxytocin*** - **Prolactin** is the primary hormone responsible for the **synthesis and secretion of milk** from the mammary glands. - **Oxytocin** is responsible for the **milk ejection reflex**, causing contraction of myoepithelial cells around the alveoli and ducts to release milk. *Oestrogen and Prolactin* - **Oestrogen** primarily plays a crucial role in the **development of the mammary glands** during puberty and pregnancy, but it inhibits milk secretion. - While **prolactin** is involved in milk secretion, oestrogen's role is not milk ejection. *Oxytocin and Prolactin* - This option reverses the order of the hormones' functions; **oxytocin** is for ejection, not secretion first. - **Prolactin** is for milk secretion, not ejection. *Prolactin and Oestrogen* - **Prolactin** is responsible for milk secretion. - **Oestrogen** *inhibits* milk secretion and is not involved in milk ejection.
Question 4: The absence of fructose in the seminal fluid indicates a defect of
- A. Seminal vesicles (Correct Answer)
- B. Leydig cells
- C. Hypothalamic-pituitary axis
- D. Testicular tubular epithelium
Explanation: ***Seminal vesicles*** - The **seminal vesicles** are responsible for producing and secreting a significant portion of the seminal fluid, including **fructose**. - **Fructose** serves as the primary **energy source** for sperm motility; its absence indicates a defect in these glands. *Leydig cells* - **Leydig cells** are located in the testes and primarily produce **testosterone**, which is crucial for male sexual development and spermatogenesis. - While important for sperm production indirectly, they do not directly contribute to the **fructose content** of seminal fluid. *Hypothalamic-pituitary axis* - The **hypothalamic-pituitary axis** regulates testicular function by releasing hormones like **GnRH**, **LH**, and **FSH**, which control testosterone production and spermatogenesis. - A defect here would primarily affect hormone levels and sperm production, not directly the **fructose secretion** from seminal vesicles. *Testicular tubular epithelium* - The **testicular tubular epithelium** (Sertoli cells and germ cells) is involved in **spermatogenesis**, the process of sperm formation. - While essential for producing mature sperm, it does not contribute to the production or secretion of **fructose** into the seminal fluid.
Question 5: The genetic inheritance of Haemophilia is
- A. Autosomal recessive
- B. Autosomal dominant
- C. Sex-linked dominant
- D. Sex-linked recessive (Correct Answer)
Explanation: ***Sex-linked recessive*** - Hemophilia, specifically hemophilia A and B, is inherited in an **X-linked recessive** pattern. - Males, having only one X chromosome, are predominantly affected, as a single copy of the mutated gene on the X chromosome leads to the condition. *Autosomal recessive* - Autosomal recessive disorders require **two copies** of the mutated gene (one from each parent) to manifest, and affect males and females equally. - This inheritance pattern does not explain the male predominance and carrier status in females seen in hemophilia. *Autosomal dominant* - Autosomal dominant disorders require only **one copy** of the mutated gene to cause the disease, and also affect males and females equally. - This pattern would mean an affected parent has a 50% chance of passing the condition to each child, which is not characteristic of hemophilia. *Sex-linked dominant* - Sex-linked dominant disorders would affect both males and females, with affected fathers passing the trait to **all their daughters** but none of their sons. - This pattern is not consistent with the inheritance of hemophilia, where affected mothers can pass it to their sons.
Question 6: The ratio for Type-I to Type-III collagen during maturation of collagen in remodelling phase is :
- A. 1 : 1
- B. 2 : 1 (Correct Answer)
- C. 4 : 1
- D. 3 : 1
Explanation: **2 : 1** - During the maturation of **collagen in the remodeling phase**, Type-I collagen replaces Type-III collagen to provide greater tensile strength. - The mature scar tissue predominantly consists of **Type-I collagen**, with a typical Type-I to Type-III ratio around 2:1. *1 : 1* - A 1:1 ratio of Type-I to Type-III collagen is more characteristic of **early granulation tissue formation** rather than the mature remodeling phase. - In the initial stages of wound healing, there is a relatively high proportion of **Type-III collagen** for rapid closure and scaffolding. *4 : 1* - While the ratio does shift towards Type-I collagen, a 4:1 ratio of Type-I to Type-III collagen would imply an **even greater dominance of Type-I**, which is higher than the commonly accepted ratio for mature scar tissue. - This ratio is not typically observed in the normal remodeling process and might indicate a **hypertrophic scar** or keloid, if Type 1 is greatly increased as comparison to Type 3 *3 : 1* - A 3:1 ratio of Type-I to Type-III collagen represents a significant increase in Type-I collagen, but it is **not the most accurately recognized ratio** for mature collagen remodeling. - While the ratio moves in this direction, 3:1 is a less precise representation compared to the more commonly cited 2:1 for mature scar tissue.
Question 7: Which of the following are the functions of larynx ? 1. Fixation of the chest 2. Aids in swallowing of food 3. Phonation 4. Respiration Select the correct answer using the code given below :
- A. 1, 2 and 3
- B. 2, 3 and 4
- C. 1, 3 and 4
- D. All of the above (1, 2, 3 and 4) (Correct Answer)
Explanation: ***All of the above (1, 2, 3 and 4)*** - The larynx performs **all four functions** listed in the question. - **Respiration**: The larynx serves as a vital conduit for airflow. The posterior cricoarytenoid muscles actively abduct the vocal cords during inspiration, and the larynx regulates airflow through glottic opening and closure. - **Phonation**: The vocal cords housed within the larynx vibrate to produce sound, making this the primary organ of voice production. - **Aids in swallowing**: During deglutition, the larynx elevates and the epiglottis closes the laryngeal inlet to prevent aspiration of food into the trachea. - **Chest fixation**: The larynx closes the glottis during the Valsalva maneuver, creating a closed air column that stabilizes the chest for activities like lifting, coughing, defecation, and parturition. *1, 2 and 3* - This option incorrectly excludes **respiration**, which is a fundamental function of the larynx as part of the conducting airways. - The larynx is not merely a passive tube but actively regulates airflow through intrinsic muscle activity. *2, 3 and 4* - While these are all valid laryngeal functions, this option incorrectly excludes **chest fixation**, which is accomplished through glottic closure during the Valsalva maneuver. *1, 3 and 4* - This option incorrectly excludes the larynx's role in **aiding swallowing** through laryngeal elevation and airway protection during deglutition.
Question 8: Carbohydrate metabolism in normal pregnancy shows :
- A. Fasting hypoglycaemia (Correct Answer)
- B. Decreased plasma glucagon levels
- C. Postprandial hypoglycaemia
- D. Increased sensitivity of insulin receptors in mother
Explanation: ***Fasting hypoglycaemia*** - Due to the **fetus continuously drawing glucose** from the mother's circulation, the mother's glucose levels can fall between meals or during prolonged fasting. - This is exacerbated by the **increased insulin secretion** in early pregnancy and **increased peripheral glucose utilization**. *Decreased plasma glucagon levels* - Plasma **glucagon levels are generally increased** or unchanged in normal pregnancy to counteract the tendency towards hypoglycemia. - Glucagon helps **mobilize glucose from liver stores** to maintain maternal blood glucose levels. *Postprandial hypoglycaemia* - Pregnancy is typically characterized by **postprandial hyperglycemia** due to increased insulin resistance later in pregnancy and a slower insulin response. - The delayed insulin response means that glucose levels can rise higher after a meal before insulin restores them to normal. *Increased sensitivity of insulin receptors in mother* - In normal pregnancy, especially in the **second and third trimesters**, there is a physiologic **decrease in maternal insulin sensitivity**. - This **insulin resistance**, mediated by placental hormones, ensures adequate glucose supply to the fetus.
Question 9: Smoking is considered to be a modifiable risk factor for Coronary Heart Disease. Consider the following statements with regard to possible mechanisms on the basis of which it acts as a risk factor : 1. Nicotine stimulation of adrenergic drive raises the blood pressure and myocardial oxygen demand. 2. It increases carbon monoxide and induces atherogenesis. 3. It leads to fall in protective high density lipoproteins. 4. It reduces the apolipoprotein-B plasma levels. Which of the statements given above are correct ?
- A. 2, 3 and 4
- B. 1 and 3 only
- C. 1 and 2 only
- D. 1, 2 and 3 (Correct Answer)
Explanation: **1, 2 and 3** - **Nicotine** in cigarette smoke stimulates the adrenergic nervous system, leading to increased heart rate, **vasoconstriction**, and elevated blood pressure, which **increases myocardial oxygen demand**. - **Carbon monoxide** from smoking binds to hemoglobin, reducing oxygen delivery to the myocardium, and also contributes to **endothelial damage** and **atherogenesis**. Smoking also **lowers HDL ("good" cholesterol)**, which normally helps remove cholesterol from arteries. *2, 3 and 4* - This option is incorrect because statement 4 is false; smoking typically **increases** apolipoprotein-B levels, associated with increased LDL cholesterol, not reduces them. - While statements 2 and 3 are correct mechanisms, the inclusion of statement 4 makes this option incorrect. *1 and 3 only* - This option is incomplete as it misses the crucial role of **carbon monoxide** in inducing atherogenesis (statement 2), which is a well-established mechanism of smoking-related CHD. - While statements 1 and 3 are correct mechanisms, the absence of statement 2 makes this option less comprehensive. *1 and 2 only* - This option omits the significant effect of smoking on **high-density lipoproteins (HDL)**; smoking is known to cause a **fall in protective HDL levels**, contributing to increased CHD risk. - While statements 1 and 2 are correct mechanisms, the exclusion of statement 3, which is also correct, makes this option incomplete.
Question 10: With reference to human body's requirement for proteins, they are essential because they are: 1. an important alternative source for energy during specific metabolic states. 2. the primary molecules responsible for maintenance of osmotic pressure within the extracellular compartment. 3. critical for upkeep of cell mediated immune response. 4. vital for the synthesis of certain hormones. Which of the statements given above are correct?
- A. 2, 3 and 4
- B. 1, 2 and 3
- C. 1, 3 and 4 (Correct Answer)
- D. 1, 2 and 4
Explanation: ***1, 3 and 4*** - Proteins can be used as an **alternative energy source** during specific metabolic states, such as prolonged fasting or starvation, when carbohydrate and fat stores are depleted, through processes like **gluconeogenesis** and protein catabolism. - Proteins are critical for the **cell-mediated immune response**, as T-lymphocytes, cytokines, MHC proteins, and various immune mediators are protein-based. Protein-energy malnutrition significantly impairs cell-mediated immunity. - Many hormones, such as **insulin**, **growth hormone**, **ACTH**, and various **peptide hormones**, are protein-based or derived from amino acids, making proteins vital for hormone synthesis. *2, 3 and 4* - Statement 2 is **incorrect** because while proteins (particularly albumin) do contribute to osmotic pressure in the **intravascular compartment**, the statement refers to the "extracellular compartment" broadly, where **electrolytes (especially sodium)** are the primary molecules responsible for osmotic pressure maintenance, not proteins. - Proteins contribute to **oncotic pressure** (colloid osmotic pressure) specifically, which is distinct from total osmotic pressure. *1, 2 and 3* - This option incorrectly includes statement 2, which overstates the role of proteins in osmotic pressure across the entire extracellular compartment. - It correctly identifies proteins as an energy source and their role in cell-mediated immunity, but fails to include their vital role in **hormone synthesis**. *1, 2 and 4* - This option incorrectly includes statement 2 about osmotic pressure in the extracellular compartment. - It correctly recognizes proteins as an alternative energy source and for hormone synthesis, but omits their critical role in the **cell-mediated immune response**.