Cardiovascular System Practice Questions

Q: What is the approximate amount of blood present in the capillaries at any given time?

250 ml. **Explanation:** The total circulating blood volume in an average adult is approximately 5,000 ml. The distribution of this volume across the vascular system is uneven and is governed by the **capacitance** and **cross-sectional area** of the vessels. **Why 250 ml is correct:** Although capillaries have the largest total cross-sectional area (approx. 2500–3000 cm²), they contain only about **5% of the total blood volume**, which equates to roughly **250 ml**. This small volume is functional: it ensures that blood flow velocity is at its slowest (approx. 0.3 mm/sec), providing maximum time for the exchange of gases, nutrients, and waste products across the thin capillary walls. **Analysis of Incorrect Options:** * **B (1000 ml):** This represents roughly 20% of the blood volume, which is closer to the volume found in the systemic arteries. * **C & D (2000–2500 ml):** These values represent 40–50% of the blood volume. The **systemic veins and venules** hold the majority of the blood (approx. 60–65% or 3200 ml), acting as the "blood reservoir" or capacitance vessels. **High-Yield Facts for NEET-PG:** * **Capacitance Vessels:** Veins (hold ~64% of blood). * **Resistance Vessels:** Arterioles (site of maximum peripheral resistance). * **Exchange Vessels:** Capillaries (highest cross-sectional area, lowest velocity). * **Velocity of Flow:** Inversely proportional to the total cross-sectional area ($V = Q/A$). Therefore, velocity is highest in the aorta and lowest in the capillaries.

Q: Which of the following is required for iron absorption, synthesized in the liver, and transported to the intestine via bile secretion?

Apotransferrin. ### Explanation **Correct Answer: B. Apotransferrin** The absorption of iron in the small intestine involves a specific mechanism involving **Apotransferrin**. The liver synthesizes apotransferrin and secretes it into the **bile**, which then carries it to the duodenum and jejunum. In the intestinal lumen, apotransferrin binds with free iron (forming **Transferrin**) or hemoglobin/myoglobin iron. This complex then binds to specific receptors on the brush border of intestinal epithelial cells and is internalized via endocytosis. Inside the cell, the iron is released into the blood, and the apotransferrin is recycled back to the lumen to pick up more iron. **Analysis of Incorrect Options:** * **A. Apoferritin:** This is the protein shell that stores iron *inside* cells (primarily in the liver and intestinal mucosa). When iron binds to apoferritin, it becomes **Ferritin**. It is not secreted in bile for absorption. * **C. Transferrin:** While apotransferrin becomes transferrin once it binds iron, the question specifically asks for the substance *synthesized and secreted* by the liver to facilitate the process. Furthermore, plasma transferrin (the transport form in blood) is distinct from the biliary apotransferrin involved in the initial luminal uptake. **High-Yield NEET-PG Pearls:** * **Site of Absorption:** Iron is primarily absorbed in the **duodenum** and upper jejunum. * **Hepcidin:** The "Master Regulator" of iron metabolism. It is a liver-derived peptide that inhibits iron release by binding to and degrading **Ferroportin** (the basal outlet for iron). * **Vitamin C:** Enhances iron absorption by reducing ferric iron ($Fe^{3+}$) to the more soluble ferrous form ($Fe^{2+}$). * **DMT-1 (Divalent Metal Transporter 1):** The primary transporter for non-heme iron across the apical membrane of enterocytes.

Q: Ejection fraction denotes the performance of which chamber?

Left ventricle. ### Explanation **1. Why Left Ventricle is Correct:** Ejection Fraction (EF) is a key physiological index used to evaluate the **systolic function** (pumping capacity) of the heart, specifically the **Left Ventricle (LV)**. It represents the percentage of blood pumped out of the LV with each contraction. * **Formula:** $EF = \frac{Stroke Volume (SV)}{End Diastolic Volume (EDV)} \times 100$ * Since the LV is responsible for systemic circulation, its performance is the primary determinant of cardiac output and clinical stability. A normal LV ejection fraction typically ranges from **55% to 70%**. **2. Why Other Options are Incorrect:** * **Left Atrium:** The atrium acts primarily as a reservoir and a conduit to the ventricle. While it has an "atrial kick," its performance is measured by volumes and strain, not ejection fraction. * **Aortic & Pulmonary Valves:** These are anatomical structures (valves) that regulate the direction of blood flow. They do not have an "ejection fraction"; their performance is measured by pressure gradients and orifice area (e.g., in stenosis or regurgitation). **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Gold Standard Measurement:** Transthoracic Echocardiography (ECHO) is the most common clinical tool, but **Cardiac MRI** is the gold standard for volume and EF assessment. * **Heart Failure Classification:** * **HFrEF** (Heart Failure with reduced EF): $\leq 40\%$ * **HFpEF** (Heart Failure with preserved EF): $\geq 50\%$ * **Right Ventricle (RV):** While the RV also has an ejection fraction (normally lower, ~45-50%), in standard clinical practice and exam questions, "Ejection Fraction" implicitly refers to the **Left Ventricle** unless specified otherwise. * **Indicator of Prognosis:** EF is the single most important predictor of survival in patients with cardiovascular disease.

Q: What is the most important factor determining the strength of a pulse?

Pulse Pressure. ### Explanation **1. Why Pulse Pressure is the Correct Answer:** The strength (or volume) of a peripheral pulse is clinically defined by the **Pulse Pressure (PP)**, which is the difference between Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP). * **Physiological Basis:** Pulse pressure is primarily determined by two factors: **Stroke Volume (SV)** and **Arterial Compliance**. When the heart ejects blood into the aorta, the pressure rises to its peak (systole); the magnitude of this pressure "swing" determines the tactile sensation of the pulse. A higher stroke volume or decreased arterial compliance (stiffness) leads to a wider pulse pressure and, consequently, a "bounding" or stronger pulse. **2. Why Other Options are Incorrect:** * **Mean Blood Pressure (MBP):** This represents the average pressure in the arteries throughout one cardiac cycle. While it is the critical parameter for **tissue perfusion**, it does not reflect the pulsatile nature of blood flow. A patient can have a normal MBP with a very weak pulse (e.g., in heart failure where SBP and DBP are close together). * **Total Peripheral Resistance (TPR):** TPR primarily influences **Diastolic Blood Pressure**. While high TPR can lead to hypertension, it often reduces pulse pressure by increasing the DBP, potentially making the pulse feel "thready" rather than strong. **3. High-Yield Clinical Pearls for NEET-PG:** * **Water-Hammer Pulse (Corrigan’s Pulse):** A classic example of a "strong" pulse caused by a very wide pulse pressure, typically seen in **Aortic Regurgitation**. * **Pulsus Alternans:** A sign of left ventricular failure where pulse strength alternates between strong and weak despite a regular rhythm. * **Pulsus Paradoxus:** A decrease in pulse strength (SBP drop >10 mmHg) during inspiration, classically seen in **Cardiac Tamponade**. * **Formula:** $PP = SBP - DBP$. Remember: Pulse Volume $\propto$ Stroke Volume.

Question 1

Cardiac output decreases during which of the following conditions?

Accepted Answer

Standing from a lying position

Answer

High environmental temperature

Answer

Anxiety and excitement

Answer

Eating

Question 2

Which statement best describes Starling's law of the heart?

Accepted Answer

It explains the increase in cardiac output that occurs when venous return is increased.

Answer

It does not operate in the failing heart.

Answer

It does not operate during exercise.

Answer

It explains the increase in heart rate produced by exercise.

Question 3

Which one of the following is a potent stimulus for the production of erythropoietin?

Accepted Answer

Hypoxia

Answer

Alpha interferon

Answer

Interleukin-3

Answer

Hypercarbia

Question 4

In a normal electrocardiogram (ECG or EKG), which of the following is correct?

Accepted Answer

The QRS complex results from depolarization of the ventricles.

Answer

The P wave results from repolarization of the atria.

Answer

The T wave represents repolarization of the auricles.

Answer

During the P-R interval, the ventricles contract.

Question 5

All are true regarding capillaries except?

Accepted Answer

Contain larger quantity of blood than veins

Answer

Have large total cross-sectional area

Answer

Site of gaseous exchange

Answer

Lined by endothelium

Question 6

What is the approximate amount of blood present in the capillaries at any given time?

Accepted Answer

250 ml

Answer

1000 ml

Answer

2000 ml

Answer

2500 ml

Question 7

Which of the following is required for iron absorption, synthesized in the liver, and transported to the intestine via bile secretion?

Accepted Answer

Apotransferrin

Answer

Apoferritin

Answer

Transferrin

Answer

All of the above

Question 8

Ejection fraction denotes the performance of which chamber?

Accepted Answer

Left ventricle

Answer

Left atrium

Answer

Aortic valve

Answer

Pulmonary valve

Question 9

What is the most important factor determining the strength of a pulse?

Accepted Answer

Pulse Pressure

Answer

Mean Blood Pressure

Answer

Total Peripheral Resistance

Answer

None of the above

Question 10

With normal cardiac function, a 10 mm Hg change in which of the following pressures would have the greatest effect on cardiac output?

Accepted Answer

Right atrial pressure

Answer

Pressure in the carotid artery

Answer

Pressure in the pulmonary artery

Answer

Aortic pressure

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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