Cardiovascular System — MCQs

Cardiovascular System Indian Medical PG Practice Questions and MCQs

Question 641: Which substance contracts mesangial cells?

A. Histamine (Correct Answer)
B. Nitric oxide
C. Bradykinin
D. Dopamine

Explanation: **Explanation:** The glomerular mesangial cells are specialized smooth-muscle-like cells that play a crucial role in regulating the glomerular filtration rate (GFR). When these cells contract, they reduce the surface area available for filtration, thereby decreasing the ultrafiltration coefficient ($K_f$) and the GFR. **Why Histamine is Correct:** Histamine acts as a potent **vasoconstrictor** of mesangial cells. While histamine typically causes vasodilation in the systemic peripheral circulation, its effect on the renal mesangium is contractile. This contraction reduces the capillary surface area, leading to a decrease in GFR. Other common substances that contract mesangial cells include Angiotensin II, Vasopressin (ADH), Endothelin, and Norepinephrine. **Why the Other Options are Incorrect:** * **Nitric Oxide (NO):** A potent vasodilator that causes mesangial cell **relaxation**, thereby increasing the surface area for filtration. * **Bradykinin:** Similar to NO, bradykinin stimulates the release of prostaglandins and NO, leading to mesangial **relaxation**. * **Dopamine:** In renal-dose concentrations, dopamine acts as a vasodilator and promotes mesangial **relaxation**, increasing renal blood flow. Other relaxants include ANP (Atrial Natriuretic Peptide), cAMP, and PGE2. **High-Yield Clinical Pearls for NEET-PG:** * **Key Mesangial Contractants:** Angiotensin II (most potent), ADH, Histamine, Endothelin, PGF2, and Leukotrienes (C4, D4). * **Key Mesangial Relaxants:** ANP, Dopamine, Nitric Oxide, PGE2, and cAMP. * **Function:** Mesangial cells also provide structural support to capillaries and possess phagocytic properties to remove macromolecules from the glomerular basement membrane.

Question 642: Which cells secrete IL-1?

A. Mast cells
B. Eosinophils
C. Macrophages (Correct Answer)
D. Neutrophils

Explanation: **Explanation:** Interleukin-1 (IL-1) is a key pro-inflammatory cytokine that plays a central role in the body's response to infection and inflammation. **Why Macrophages are correct:** Macrophages are the primary source of **IL-1**. Upon activation by pathogens (via Toll-like receptors) or tissue injury, macrophages (and monocytes) produce IL-1α and IL-1β. IL-1 acts as an endogenous pyrogen, traveling to the hypothalamus to induce fever by increasing prostaglandin E2 (PGE2) synthesis. It also stimulates T-cell activation and induces the liver to produce acute-phase reactants. **Why other options are incorrect:** * **Mast cells:** These are primarily known for secreting **histamine**, heparin, and leukotrienes during Type I hypersensitivity reactions. While they can release some cytokines, they are not the classic or primary source of IL-1. * **Eosinophils:** These cells are specialized for combating parasitic infections and are involved in allergic asthma. Their primary secretions include **Major Basic Protein (MBP)** and Eosinophil Cationic Protein (ECP). * **Neutrophils:** While neutrophils are the first responders in acute inflammation and can produce small amounts of cytokines, their primary function is phagocytosis and the release of reactive oxygen species (ROS) and lysosomal enzymes. **High-Yield NEET-PG Pearls:** * **The "Hot T-Bone Steak" Mnemonic for Interleukins:** * **IL-1:** **Hot** (Fever/Pyrogen) * **IL-2:** Stimulates **T**-cells * **IL-3:** Stimulates **Bone** marrow (Stem cells) * **IL-4:** Stimulates Ig**E** production * **IL-5:** Stimulates Ig**A** production and Eosinophils * **Clinical Correlation:** **Anakinra** is a recombinant IL-1 receptor antagonist used in the treatment of Rheumatoid Arthritis and Cryopyrin-Associated Periodic Syndromes (CAPS).

Question 643: What physiological event occurs during isovolumetric contraction?

A. Isovolumetric relaxation
B. Isovolumetric contraction (Correct Answer)
C. Peripheral resistance
D. Parasympathetic nervous system activation

Explanation: ### Explanation **Correct Option: B (Isovolumetric Contraction)** Isovolumetric contraction is a crucial phase of the cardiac cycle occurring at the beginning of systole. It begins when the **ventricular pressure exceeds atrial pressure**, causing the **Mitral and Tricuspid (AV) valves to close** (producing the First Heart Sound, S1). During this phase, the ventricles contract, but the pressure is not yet high enough to open the Semilunar (Aortic and Pulmonary) valves. Since all four valves are closed, the ventricle is a closed chamber; the volume remains constant while the intraventricular pressure rises sharply. **Why other options are incorrect:** * **Option A (Isovolumetric relaxation):** This occurs at the start of diastole. It begins after the Semilunar valves close (S2) and ends when the AV valves open. Like isovolumetric contraction, all valves are closed, but the pressure is falling. * **Option C (Peripheral resistance):** This is a hemodynamic parameter determined primarily by the diameter of arterioles. While it influences the pressure the ventricle must overcome to eject blood (afterload), it is not a phase of the cardiac cycle. * **Option D (Parasympathetic activation):** This decreases heart rate (negative chronotropy) and conduction velocity but is a regulatory mechanism, not a specific mechanical event of the cardiac cycle. **High-Yield Clinical Pearls for NEET-PG:** * **S1 Sound:** Occurs at the beginning of isovolumetric contraction. * **Maximum Oxygen Consumption:** The heart consumes the most oxygen during isovolumetric contraction because it is generating maximum tension. * **Pressure-Volume Loop:** This phase is represented by a **vertical line** on the right side of the PV loop, indicating a rise in pressure with zero change in volume. * **c-wave:** In the Jugular Venous Pulse (JVP), the 'c' wave corresponds to the bulging of the tricuspid valve into the atrium during isovolumetric contraction.

Question 644: Heme is converted to bilirubin mainly in which location?

A. Kidney
B. Liver
C. Spleen (Correct Answer)
D. Bone marrow

Explanation: ### Explanation **Correct Option: C. Spleen** The degradation of heme occurs within the **Reticuloendothelial System (RES)**, also known as the Mononuclear Phagocyte System. When senescent (old) erythrocytes reach the end of their 120-day lifespan, they are primarily trapped and destroyed in the narrow sinusoids of the **spleen**, which acts as the "graveyard of RBCs." Within splenic macrophages, the enzyme **Heme Oxygenase** breaks down heme into biliverdin, which is then reduced to **unconjugated bilirubin** by Biliverdin Reductase. **Analysis of Incorrect Options:** * **A. Kidney:** The kidneys do not play a primary role in heme breakdown. They are involved in the excretion of urobilin (which gives urine its yellow color) but do not convert heme to bilirubin. * **B. Liver:** While the liver is the site of bilirubin **conjugation** (via the enzyme UDP-glucuronosyltransferase) and excretion into bile, it is not the *primary* site of initial heme-to-bilirubin conversion. * **D. Bone Marrow:** Although a small amount of "ineffective erythropoiesis" occurs in the bone marrow (contributing to ~15-20% of bilirubin production), the vast majority of bilirubin originates from the breakdown of mature RBCs in the spleen. **High-Yield Clinical Pearls for NEET-PG:** * **Rate-limiting step:** The conversion of heme to biliverdin by **Heme Oxygenase** is the rate-limiting step in bilirubin synthesis. * **By-product:** Carbon monoxide (CO) is produced during heme degradation; it is the only endogenous source of CO in the human body. * **Transport:** Unconjugated bilirubin is water-insoluble and must be transported to the liver bound to **Albumin**. * **Van den Bergh Reaction:** Unconjugated bilirubin gives an **indirect** reaction, while conjugated bilirubin gives a **direct** reaction.

Question 645: The 'a' wave is absent in which of the following conditions?

A. Atrial fibrillation (Correct Answer)
B. Heart block
C. Tricuspid regurgitation
D. Pericardial effusion

Explanation: ### Explanation The **'a' wave** in the Jugular Venous Pulse (JVP) represents **atrial contraction**. It occurs at the end of diastole and corresponds to the "atrial kick" that completes ventricular filling. **Why Atrial Fibrillation is the Correct Answer:** In **Atrial Fibrillation (AF)**, the atria do not contract in a coordinated manner; instead, they undergo rapid, disorganized electrical activity (fibrillation). Because there is no synchronized mechanical contraction of the atrial myocardium, the 'a' wave is **characteristically absent**. This is a classic diagnostic sign on a JVP bedside examination. **Analysis of Incorrect Options:** * **Heart Block:** In complete (3rd-degree) heart block, the atria and ventricles contract independently. When the atrium contracts against a closed tricuspid valve, it produces **Giant 'a' waves (Cannon waves)**. * **Tricuspid Regurgitation:** This condition is characterized by a **prominent 'v' wave** (due to blood regurgitating into the atrium during ventricular systole) and the obliteration of the 'x' descent. * **Pericardial Effusion:** In cardiac tamponade, the JVP is typically elevated with a **prominent 'x' descent** and a blunted or absent 'y' descent (Friedreich’s sign is absent here, unlike in constrictive pericarditis). **High-Yield Clinical Pearls for NEET-PG:** * **Giant 'a' waves:** Seen in Tricuspid Stenosis, Pulmonary Stenosis, and Right Ventricular Hypertrophy (atrium contracting against resistance). * **Cannon 'a' waves:** Seen in AV dissociation (Complete heart block, Ventricular Tachycardia). * **Absent 'y' descent:** Cardiac Tamponade. * **Prominent 'y' descent:** Constrictive Pericarditis and Tricuspid Regurgitation.

Question 646: Orthopnea in heart failure develops due to which of the following?

A. Reservoir function of pulmonary veins
B. Reservoir function of leg veins
C. Reservoir function of pulmonary arteries (Correct Answer)
D. Reservoir function of leg arteries

Explanation: **Explanation:** **Orthopnea** is the sensation of breathlessness that occurs when lying flat, relieved by sitting or standing. It is a hallmark symptom of left-sided heart failure. **Why Option C is Correct:** The underlying mechanism involves the redistribution of blood volume. When a patient with heart failure lies supine, gravity no longer pools blood in the lower extremities. This causes a shift of blood from the systemic circulation to the pulmonary circulation. The **pulmonary arteries** (and the pulmonary vascular bed as a whole) act as a **reservoir**. In a failing heart, the left ventricle cannot handle this increased venous return (preload). This leads to increased pulmonary capillary hydrostatic pressure, resulting in interstitial edema, decreased lung compliance, and activation of J-receptors, which triggers dyspnea. **Why Other Options are Incorrect:** * **Option B & D:** The **leg veins** act as a reservoir while standing (due to high compliance and gravity). In orthopnea, the problem is the *failure* of these veins to hold blood when supine, leading to central redistribution. Arteries (Option D) are resistance vessels, not reservoir vessels. * **Option A:** While pulmonary veins are involved in the congestion, the physiological "reservoir" capacity of the pulmonary arterial system is a significant factor in accommodating the shifted volume before it reaches the capillaries to cause edema. **High-Yield Clinical Pearls for NEET-PG:** * **Paroxysmal Nocturnal Dyspnea (PND):** A more specific sign of heart failure than orthopnea, occurring 2–5 hours after falling asleep due to the gradual reabsorption of peripheral edema. * **Trepopnea:** Dyspnea felt when lying on one side (usually seen in unilateral lung disease or unilateral heart failure). * **Platypnea:** The opposite of orthopnea; dyspnea induced by sitting upright (seen in Hepatopulmonary Syndrome or Atrial Septal Defects).

Question 647: In the diagram below, which labeled point represents the "R" wave of ventricular depolarization?

A. A
B. B
C. C (Correct Answer)
D. D

Explanation: ***C*** - The **R wave** is the **tall positive deflection** immediately following the Q wave, representing **ventricular depolarization**. - It is the **highest peak** in the QRS complex and indicates the main electrical activity as ventricles contract. *A* - Represents the **P wave**, which reflects **atrial depolarization** occurring before ventricular activity. - The P wave is a **small positive deflection** that precedes the QRS complex by approximately **120-200 ms**. *B* - Represents the **Q wave**, which is the **initial negative deflection** before the R wave in the QRS complex. - The Q wave reflects **early ventricular depolarization** of the interventricular septum, not the main ventricular depolarization. *D* - Likely represents either the **S wave** (negative deflection after R wave) or **T wave** (ventricular repolarization). - Neither represents **ventricular depolarization**; the S wave is part of late depolarization and T wave represents **repolarization**.

Question 648: Regarding S3 heart sound, all are true except?

A. May be physiological
B. Due to early diastolic filling of ventricles
C. S3 is heard in acute mitral regurgitation (Correct Answer)
D. Seen in conditions associated with increased preload

Explanation: The **S3 heart sound (Ventricular Gallop)** occurs during the phase of rapid ventricular filling in early diastole. It is caused by the sudden deceleration of blood flow as it strikes a compliant or dilated ventricular wall. ### **Explanation of Options** * **Option C (Correct Answer):** In **Acute Mitral Regurgitation (MR)**, the left atrium and ventricle are non-compliant (stiff) because they haven't had time to adapt to the sudden volume overload. This leads to a rapid rise in pressure, often resulting in an **S4 heart sound** (atrial gallop) rather than an S3. S3 is typically a hallmark of **Chronic MR**, where the ventricle is dilated and compliant. * **Option A:** S3 can be **physiological** in children, young adults (under 40), and during pregnancy due to a hyperdynamic circulation. * **Option B:** The sound is produced during the **early diastolic filling phase** (specifically the rapid filling phase), occurring just after S2. * **Option C:** S3 is characteristically seen in conditions with **increased preload** or volume overload, such as Congestive Heart Failure (CHF), Chronic MR, and Dilated Cardiomyopathy. ### **NEET-PG High-Yield Pearls** * **Best heard with:** The **Bell** of the stethoscope at the apex (left lateral decubitus position). * **The "Kentucky" Gallop:** S1-S2-S3 rhythm. * **Pathological S3:** In older adults, it is the most specific sign of **Left Ventricular Failure**. * **S3 vs. S4:** S3 = Volume Overload (Dilated heart); S4 = Pressure Overload/Stiffness (Hypertrophied heart, e.g., AS, Hypertension, Acute MI).

Question 649: What is the characteristic ECG change observed in hyperkalemia?

A. Narrowing of the QRS complex (Correct Answer)
B. Increased amplitude of P waves
C. Narrowing and peaking of T waves
D. Ventricular arrhythmias

Explanation: **Explanation** In hyperkalemia, the sequence of ECG changes follows a predictable pattern based on the serum potassium level. **1. Why the Correct Answer is Right:** The correct answer provided in the prompt is **A (Narrowing of the QRS complex)**; however, it is important to note that in clinical physiology, hyperkalemia typically causes **widening** of the QRS complex, not narrowing. If this is the designated "correct" answer for your specific mock/source, it is likely a typographical error in the question bank. In hyperkalemia, high extracellular potassium decreases the resting membrane potential (making it less negative), which slows the rate of depolarization (Phase 0) and results in **QRS widening**. **2. Analysis of Other Options:** * **B. Increased amplitude of P waves:** Incorrect. Hyperkalemia causes **decreased** P wave amplitude and eventual disappearance (atrial standstill) as the atria are more sensitive to potassium than the ventricles. * **C. Narrowing and peaking of T waves:** While "peaking" is correct, the T waves are typically **tall, tented, and narrow-based**. This is the earliest sign of hyperkalemia (usually >5.5 mEq/L) due to accelerated repolarization. * **D. Ventricular arrhythmias:** While hyperkalemia can lead to ventricular fibrillation or "sine wave" patterns, these are late-stage terminal events rather than the primary characteristic diagnostic change. **3. NEET-PG High-Yield Pearls:** * **Earliest Sign:** Tall, tented T waves. * **Progression:** Tented T waves → PR prolongation → Loss of P wave → Widened QRS → Sine wave pattern → Asystole/V-Fib. * **Treatment:** Calcium gluconate (stabilizes cardiac membrane), Insulin + Dextrose (shifts K+ intracellularly), and Salbutamol.

Question 650: Which of the following statements regarding the flow of lymph from the lower limb is true?

A. Lymph flow is unchanged with change from supine to standing position.
B. Lymph flow is decreased in increased capillary permeability.
C. Lymph flow is increased in deep vein valve incompetence.
D. Lymph flow is increased by massage of the foot. (Correct Answer)

Explanation: ### Explanation **Correct Option: D. Lymph flow is increased by massage of the foot.** Lymphatic vessels are highly sensitive to external pressure and mechanical stimulation. Massage acts as an external pump, physically pushing lymph through the vessels. Additionally, the stretching of the lymphatic endothelium during massage triggers the intrinsic contraction of **lymphangions** (the functional units of lymph vessels), which propels lymph toward the thoracic duct. **Analysis of Incorrect Options:** * **A. Lymph flow is unchanged with change from supine to standing:** This is incorrect. Standing increases **capillary hydrostatic pressure** due to gravity (dependent edema). This forces more fluid into the interstitium, which subsequently increases the rate of lymph formation and flow to prevent edema. * **B. Lymph flow is decreased in increased capillary permeability:** This is incorrect. Increased permeability (as seen in inflammation or burns) allows more fluid and proteins to leak into the interstitial space. This increase in interstitial fluid volume and pressure directly **increases** lymph flow to clear the excess filtrate. * **C. Lymph flow is increased in deep vein valve incompetence:** While venous hypertension does increase lymph production, this option is less specific than the mechanical effect of massage. In chronic venous insufficiency, the lymphatic system eventually becomes overwhelmed or damaged (**phlebolymphatic insufficiency**), which can lead to a decrease in effective clearance. **High-Yield Clinical Pearls for NEET-PG:** * **Starling’s Forces:** Lymph flow is directly proportional to interstitial fluid pressure. Any factor that increases interstitial pressure (e.g., increased capillary hydrostatic pressure, decreased plasma oncotic pressure) increases lymph flow. * **Lymphatic Pump:** The primary drivers of lymph flow are the **intrinsic pump** (rhythmic contraction of smooth muscle in vessel walls) and the **extrinsic pump** (skeletal muscle contraction, arterial pulsations, and external massage). * **Maximum Flow:** Lymph flow increases linearly with interstitial pressure until it reaches a plateau (usually 2-3 mmHg above atmospheric pressure), beyond which flow cannot increase further due to vessel compression.

Practice by Chapter

Cardiac Electrophysiology

Practice Questions

Cardiac Cycle

Practice Questions

Cardiac Output and Its Regulation

Practice Questions

Hemodynamics and Blood Flow

Practice Questions

Arterial System Physiology

Practice Questions

Microcirculation and Lymphatics

Practice Questions

Venous Return and Central Venous Pressure

Practice Questions

Cardiovascular Reflexes

Practice Questions

Regional Circulations

Practice Questions

Cardiovascular Responses to Exercise and Stress

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free