Cardiovascular System Practice Questions

Q: Which of the following is NOT true regarding endothelin-1?

Bronchodilatation. **Explanation:** Endothelin-1 (ET-1) is a potent 21-amino acid peptide produced primarily by vascular endothelial cells. It acts as a powerful paracrine and autocrine mediator through two main receptors: $ET_A$ and $ET_B$. **Why Option A is the Correct Answer:** Endothelin-1 is a potent **bronchoconstrictor**, not a bronchodilator. It acts on $ET_A$ receptors located on bronchial smooth muscle, leading to airway narrowing. Elevated levels of ET-1 are often implicated in the pathophysiology of asthma and pulmonary hypertension. **Analysis of Incorrect Options:** * **B. Vasoconstriction:** This is the hallmark effect of ET-1. It is one of the most potent endogenous vasoconstrictors known (10 times more potent than Angiotensin II), acting via $ET_A$ receptors on vascular smooth muscle. * **C. Decreased GFR:** In the kidneys, ET-1 causes potent constriction of both afferent and efferent arterioles. This leads to a reduction in renal blood flow and a subsequent **decrease in Glomerular Filtration Rate (GFR)**. * **D. Inotropic effect:** ET-1 exerts a **positive inotropic effect** on the myocardium (increasing the force of contraction) and also possesses chronotropic properties, though its systemic vasoconstrictor effects usually dominate the clinical picture. **High-Yield Clinical Pearls for NEET-PG:** * **Stimulus for Release:** ET-1 release is stimulated by Thrombin, Epinephrine, Angiotensin II, and low shear stress. It is inhibited by Nitric Oxide (NO) and Prostacyclin. * **Receptor Specificity:** $ET_A$ receptors primarily mediate vasoconstriction and bronchoconstriction; $ET_B$ receptors (on endothelium) can stimulate NO release, causing transient vasodilation. * **Clinical Correlation:** **Bosentan** is a dual $ET_A/ET_B$ receptor antagonist used in the treatment of Pulmonary Arterial Hypertension (PAH).

Q: All of the following are true regarding ECG findings, except:

The QRS wave represents ventricular repolarization.. **Explanation:** The correct answer is **B** because it is a false statement. In a standard ECG, the **QRS complex represents ventricular depolarization**, not repolarization. Ventricular depolarization triggers the contraction of the ventricles. **Analysis of Options:** * **Option A (True):** The PR interval (normal: 0.12–0.20s) represents the time taken for the impulse to travel from the SA node to the ventricles. In first-degree heart block, there is a delay in AV conduction, leading to a **prolonged PR interval**. * **Option C (True):** The **T wave** is the electrical representation of **ventricular repolarization**, during which the ventricles recover and prepare for the next cycle. * **Option D (True):** The **QT interval** (from the start of the QRS to the end of the T wave) encompasses the entire period of ventricular electrical activity, including both **depolarization and repolarization**. **Clinical Pearls for NEET-PG:** 1. **Atrial Repolarization:** It occurs during the QRS complex but is not visible on a standard ECG because it is masked by the much larger electrical signal of ventricular depolarization. 2. **U Wave:** If present, it represents the repolarization of the **Purkinje fibers** or papillary muscles; it is most commonly seen in **hypokalemia**. 3. **ST Segment:** This represents the "plateau phase" (Phase 2) of the ventricular action potential. Elevation or depression is a critical marker for myocardial ischemia/infarction. 4. **QT Interval Rule:** A rough guide is that the QT interval should be less than half of the preceding R-R interval. Prolongation can predispose patients to *Torsades de Pointes*.

Q: The P2 sound is best appreciated in which of the following locations?

2nd left intercostal space. **Explanation:** The second heart sound (S2) is produced by the closure of the semilunar valves (Aortic and Pulmonary) at the beginning of ventricular diastole. It consists of two components: **A2** (Aortic valve closure) and **P2** (Pulmonary valve closure). **Why Option A is Correct:** The **Pulmonary Area** is located at the **2nd left intercostal space (ICS)**, just lateral to the sternal border. Because the pulmonary artery is closest to the chest wall at this specific anatomical location, the vibrations produced by the closure of the pulmonary valve (P2) are best transmitted and auscultated here. **Analysis of Incorrect Options:** * **Option B (2nd right ICS):** This is the **Aortic Area**. While S2 is heard here, it is primarily the A2 component. * **Option C (4th left ICS):** This is the **Tricuspid Area** (lower left sternal border), where the S1 sound and tricuspid murmurs are best appreciated. * **Option D (5th left ICS):** This is the **Mitral Area** (apex), located in the mid-clavicular line. It is the best site for hearing S1 and mitral valve sounds. **High-Yield Clinical Pearls for NEET-PG:** * **Physiological Splitting:** During inspiration, P2 is delayed due to increased venous return to the right heart, causing S2 to split into A2 and P2. * **P2 Intensity:** A loud or palpable P2 at the 2nd left ICS is a classic clinical sign of **Pulmonary Hypertension**. * **Order of Closure:** Under normal conditions, A2 precedes P2 because the systemic resistance is higher than pulmonary resistance, causing the aortic valve to close slightly earlier.

Q: What is the most common non-cardiac peripheral factor that leads to decreased cardiac output?

Decreased blood volume. **Explanation:** Cardiac output (CO) is determined by the product of Heart Rate and Stroke Volume. From a peripheral standpoint, CO is governed by **Venous Return (VR)**. According to the Frank-Starling law, the heart pumps whatever volume of blood flows into it from the veins. **1. Why Decreased Blood Volume is Correct:** Decreased blood volume (hemorrhage or dehydration) is the **most common** peripheral factor leading to low CO. A reduction in blood volume decreases the **Mean Systemic Filling Pressure (MSFP)**—the pressure that pushes blood toward the heart. When MSFP drops, the pressure gradient for venous return falls, leading to decreased end-diastolic volume, reduced stroke volume, and ultimately, a fall in cardiac output. **2. Analysis of Incorrect Options:** * **Acute Venous Dilation (B):** This increases the vascular capacity (venous pooling), which decreases MSFP and VR. While a valid cause, it is clinically less common than simple hypovolemia. * **Obstruction of Large Veins (C):** Obstruction (e.g., IVC syndrome) increases resistance to venous return. While it reduces CO, it is a localized pathological event rather than the "most common" factor. * **Decreased Tissue/Muscle Mass (D):** This occurs in aging or prolonged bed rest. It reduces the metabolic demand and the size of the vascular bed, leading to a lower CO, but it is a chronic physiological adaptation rather than an acute clinical cause of decreased output. **Clinical Pearls for NEET-PG:** * **MSFP:** The normal value is **7 mmHg**. It is the primary determinant of venous return. * **Venous Return Curve:** A decrease in blood volume shifts the venous return curve to the **left and downward**. * **The "Gold Standard":** In clinical practice, the most common cause of "Shock" (low CO leading to tissue hypoxia) is **Hypovolemic Shock**.

Q: Which of the following increases turbulence in blood flow?

Increase in diameter of blood vessel. The tendency for blood flow to become turbulent is determined by the **Reynolds number (Re)**. This dimensionless value is calculated using the formula: $$Re = \frac{\rho \cdot d \cdot v}{\eta}$$ *(Where $\rho$ = density, $d$ = diameter, $v$ = velocity, and $\eta$ = viscosity)* ### Why Option D is Correct According to the formula, the Reynolds number is **directly proportional** to the diameter of the vessel. As the diameter increases, the Reynolds number increases. When $Re$ exceeds a critical threshold (typically >2000–3000), laminar flow transitions into turbulent flow, characterized by eddies and whorls. This is why turbulence is commonly seen in large vessels like the **ascending aorta**. ### Explanation of Incorrect Options * **A. Reynolds number < 2000:** At values below 2000, blood flow is typically **laminar** (smooth and streamlined). Turbulence generally begins when $Re$ exceeds 2000 and becomes significant above 3000. * **B. Decrease in velocity:** Velocity is directly proportional to $Re$. A decrease in velocity reduces the kinetic energy of the blood, making it more likely to remain laminar. * **C. Decrease in density:** Density is directly proportional to $Re$. A decrease in density (though rare in clinical scenarios) would mathematically decrease the Reynolds number and reduce turbulence. ### NEET-PG High-Yield Pearls * **Anemia & Turbulence:** In anemia, blood viscosity ($\eta$) decreases. Since viscosity is in the denominator, a decrease in viscosity **increases** the Reynolds number, explaining why "hemic murmurs" (turbulent flow) are heard in anemic patients. * **Bruits and Murmurs:** Turbulent flow is clinically significant because it generates sound. In peripheral arteries, this is called a **bruit**; in the heart, it is a **murmur**. * **Most common site of turbulence:** The root of the aorta and the pulmonary artery during ejection, due to high velocity and large diameter.

Q: What organ has the greatest resting arteriovenous difference in oxygen content?

Heart. **Explanation:** The **Arteriovenous (A-V) oxygen difference** represents the amount of oxygen extracted by an organ from the blood. The **Heart** has the highest resting A-V oxygen difference because it has the highest oxygen extraction ratio of any organ in the body. 1. **Why the Heart is Correct:** Under resting conditions, the myocardium extracts approximately **70-80%** of the oxygen delivered to it (A-V difference of ~11-15 ml/dL). Because the extraction is already near-maximal at rest, the heart cannot significantly increase oxygen extraction during periods of high demand (like exercise). Instead, it must rely almost entirely on **increasing coronary blood flow** to meet increased metabolic needs. 2. **Why the Other Options are Incorrect:** * **Kidney:** Has the lowest A-V oxygen difference (~1.5 ml/dL). Although it consumes significant oxygen, its blood flow is disproportionately high for its metabolic needs to facilitate filtration. * **Brain:** Has a high metabolic rate but a moderate A-V difference (~6 ml/dL), extracting about 25-30% of delivered oxygen. * **Skeletal Muscle:** At rest, the A-V difference is low (~5 ml/dL). However, during **strenuous exercise**, skeletal muscle can surpass the heart's extraction rate, but the question specifies "resting" conditions. **High-Yield NEET-PG Pearls:** * **Coronary Sinus:** The blood in the coronary sinus has the lowest oxygen saturation in the entire body (~25-30%). * **Adenosine:** The primary local metabolic vasodilator that increases coronary blood flow in response to hypoxia. * **Flow-Limited:** Since oxygen extraction is maximal at rest, myocardial oxygen consumption is "flow-limited," not "extraction-limited."

Q: CVP denotes the pressure of which chamber?

Right atrium. **Explanation:** **Central Venous Pressure (CVP)** is defined as the pressure measured in the central veins close to the heart, specifically the superior vena cava. Because there are no valves between the central veins and the heart, CVP is considered a direct reflection of the **Right Atrial Pressure (RAP)**. 1. **Why Right Atrium is Correct:** The right atrium receives deoxygenated blood from the systemic circulation via the vena cavae. CVP serves as an estimate of right ventricular end-diastolic pressure (in the absence of tricuspid stenosis) and is a key indicator of venous return and intravascular volume status. 2. **Why Other Options are Incorrect:** * **Left Ventricle & Left Atrium:** These represent the "left-sided" pressures. Left atrial pressure is clinically estimated using **Pulmonary Capillary Wedge Pressure (PCWP)**, not CVP. * **Right Ventricle:** While CVP influences right ventricular filling, the pressure within the ventricle during systole is significantly higher than the CVP. CVP only equals right ventricular pressure during diastole when the tricuspid valve is open. **NEET-PG High-Yield Pearls:** * **Normal Range:** 2–8 mmHg (or 3–11 cm $H_2O$). * **Reference Point:** The zero point for CVP measurement is the **phlebostatic axis** (4th intercostal space, mid-axillary line). * **Waveforms:** Remember the "a" wave (atrial contraction), "c" wave (tricuspid bulging/ventricular contraction), and "v" wave (venous filling). * **Clinical Use:** A low CVP typically indicates hypovolemia, while a high CVP may suggest fluid overload, right heart failure, or cardiac tamponade.

Question 1

Which of the following is NOT true regarding endothelin-1?

Accepted Answer

Bronchodilatation

Answer

Vasoconstriction

Answer

Decreased GFR

Answer

Has inotropic effect

Question 2

All of the following are true regarding ECG findings, except:

Accepted Answer

The QRS wave represents ventricular repolarization.

Answer

Heart block causes an increase in the PR interval.

Answer

The T wave represents ventricular repolarization.

Answer

Ventricular depolarization and repolarization occur during the QT interval.

Question 3

Electromechanical systole is best defined as the interval between?

Accepted Answer

The Q wave and S2 (Q-S2 Interval)

Answer

The Q wave and SI (Q-Sl Interval)

Answer

The Q wave and the beginning of the T wave

Answer

The Q wave and the R wave

Question 4

Which of the following statements is not true regarding the measurement of blood pressure?

Accepted Answer

Diastolic pressure is indicated by the disappearance of Korotkoff sounds.

Answer

The cuff length should be 80% and the width should be 40% of the mid-arm circumference.

Answer

Using a cuff that is too small will result in a falsely high blood pressure reading.

Answer

The cuff should be tied at the level of the heart.

Question 5

The P2 sound is best appreciated in which of the following locations?

Accepted Answer

2nd left intercostal space

Answer

2nd right intercostal space

Answer

4th left intercostal space

Answer

5th left intercostal space

Question 6

What is the most common non-cardiac peripheral factor that leads to decreased cardiac output?

Accepted Answer

Decreased blood volume

Answer

Acute venous dilation

Answer

Obstruction of the large veins

Answer

Decreased tissue mass, especially decreased skeletal muscle mass

Question 7

Which of the following increases turbulence in blood flow?

Accepted Answer

Increase in diameter of blood vessel

Answer

Reynolds number < 2000

Answer

Decrease in velocity of blood

Answer

Decrease in density of blood

Question 8

When a person changes position from standing to lying down, which of the following changes is observed?

Accepted Answer

Venous return to the heart increases immediately

Answer

Heart rate increases

Answer

Cerebral blood flow increases

Answer

Blood flow at the apices of the lungs decreases

Question 9

What organ has the greatest resting arteriovenous difference in oxygen content?

Accepted Answer

Heart

Answer

Kidney

Answer

Brain

Answer

Skeletal muscles

Question 10

CVP denotes the pressure of which chamber?

Accepted Answer

Right atrium

Answer

Left ventricle

Answer

Left atrium

Answer

Right ventricle

Cardiovascular System — MCQs

Cardiovascular System — MCQs

On this page

Practice by Chapter

Want unlimited practice?