Cardiovascular System Practice Questions

Q: If the heart rate is 70 beats/min, then the cardiac output of this ventricle is closest to?

5.25 L/min. ***5.25 L/min*** - **Cardiac output** is calculated as **stroke volume × heart rate**; with a typical stroke volume of ~75 mL and heart rate of 70 bpm, CO = 75 mL × 70 = 5,250 mL/min = 5.25 L/min. - This represents the normal **resting cardiac output** for a healthy adult, which ranges between 4.5-5.5 L/min. *4.55 L/min* - This value is **below normal** cardiac output range and would suggest either reduced **stroke volume** (~65 mL) or underlying cardiac dysfunction. - While possible in certain pathological states, it doesn't represent the typical cardiac output for normal **ventricular function**. *8.00 L/min* - This represents an **elevated cardiac output** that would require either increased stroke volume (~115 mL) or higher heart rate conditions. - Typically seen during **exercise**, **fever**, or **hyperthyroid states**, not at rest with normal heart rate. *9.85 L/min* - This is **significantly elevated** cardiac output requiring stroke volume of ~140 mL, which exceeds normal resting ventricular capacity. - Only achievable during **intense exercise** or severe **pathological hyperdynamic states** like arteriovenous fistulas.

Q: Which of the following statements regarding blood flow in various organs is true?

Liver > Kidney > Brain > Heart. This question tests your knowledge of **regional blood flow**, specifically the absolute volume of blood received by various organs per minute (mL/min). ### **Explanation of the Correct Answer** The correct sequence for absolute blood flow is **Liver > Kidney > Brain > Heart**. 1. **Liver (~1500 mL/min):** The liver receives the highest total blood flow, accounting for approximately 25-30% of the cardiac output. This is unique because it has a dual supply: the portal vein (75%) and the hepatic artery (25%). 2. **Kidney (~1100–1200 mL/min):** The kidneys receive about 20-25% of cardiac output. While they have the highest flow **per gram of tissue** (specific conductance), their total volume is second to the liver. 3. **Brain (~750 mL/min):** The brain receives roughly 15% of cardiac output. This flow is kept remarkably constant via autoregulation. 4. **Heart (~250 mL/min):** The coronary blood flow accounts for about 4-5% of cardiac output at rest. ### **Why Other Options are Incorrect** * **Options B, C, and D** are incorrect because they misplace the hierarchy. A common pitfall is confusing **Total Flow (mL/min)** with **Flow per 100g of tissue (mL/min/100g)**. If the question asked for flow per unit weight, the order would change significantly (Kidney > Heart > Brain > Liver). ### **High-Yield NEET-PG Pearls** * **Highest Total Blood Flow:** Liver (~1500 mL/min). * **Highest Blood Flow per 100g tissue:** Carotid Body (2000 mL/100g/min), followed by the Kidney (400 mL/100g/min). * **Highest Oxygen Extraction (A-V O2 difference):** Heart (extracts ~70-80% of delivered oxygen). * **Control of Flow:** Brain flow is primarily controlled by $CO_2$ levels; Heart flow is controlled by local metabolic factors (Adenosine); Kidney flow is controlled by Myogenic and Tubuloglomerular feedback.

Q: If a person has a heart rate of 70 beats/min, a left ventricular end-diastolic volume of 100 ml, and an ejection fraction of 0.50, what is the cardiac output?

3.5 liters/min. To solve this question, we must apply the fundamental physiological relationships between cardiac volumes and output. ### **Step-by-Step Calculation:** 1. **Calculate Stroke Volume (SV):** Stroke volume is the amount of blood ejected by the left ventricle per beat. It is derived from the **Ejection Fraction (EF)**, which is the fraction of the **End-Diastolic Volume (EDV)** pumped out. * $SV = EDV \times EF$ * $SV = 100\text{ ml} \times 0.50 = \mathbf{50\text{ ml/beat}}$ 2. **Calculate Cardiac Output (CO):** Cardiac output is the total volume of blood pumped by the ventricle per minute. * $CO = \text{Heart Rate (HR)} \times \text{Stroke Volume (SV)}$ * $CO = 70\text{ beats/min} \times 50\text{ ml/beat} = 3,500\text{ ml/min}$ * **Conversion:** $3,500\text{ ml/min} = \mathbf{3.5\text{ L/min}}$ ### **Analysis of Options:** * **B (3.5 L/min) is correct** as it accurately follows the physiological formula $CO = HR \times (EDV \times EF)$. * **A (3.0 L/min)** is incorrect; this would occur if the SV was only ~43 ml. * **C (4.0 L/min)** is incorrect; this would occur if the EF was 0.57 or the HR was ~80 bpm. * **D (4.5 L/min)** is incorrect; this would require a higher SV (64 ml) or HR (90 bpm). ### **NEET-PG High-Yield Pearls:** * **Normal EF:** Typically ranges from **55% to 70%**. An EF < 40% is a hallmark of Heart Failure with reduced Ejection Fraction (HFrEF). * **Stroke Volume Determinants:** Preload (EDV), Afterload (Total Peripheral Resistance), and Contractility (Inotropy). * **Cardiac Index (CI):** A more clinical parameter that relates CO to Body Surface Area (BSA). $CI = CO / BSA$ (Normal: 2.5–4.2 L/min/m²). * **Pulse Pressure:** Directly proportional to Stroke Volume and inversely proportional to Arterial Compliance.

Q: Which of the following factors is associated with a decrease in chronic hypertension?

Nitric oxide. **Explanation:** **Correct Answer: C. Nitric Oxide** Nitric Oxide (NO) is a potent endogenous **vasodilator** synthesized from L-arginine by the enzyme endothelial Nitric Oxide Synthase (eNOS). In the cardiovascular system, NO diffuses into vascular smooth muscle cells, activating soluble guanylyl cyclase, which increases cGMP levels. This leads to smooth muscle relaxation and vasodilation, thereby **decreasing peripheral resistance and blood pressure**. In chronic hypertension, there is often "endothelial dysfunction" characterized by reduced NO bioavailability; conversely, increasing NO levels or sensitivity helps counteract hypertensive states. **Why other options are incorrect:** * **A & B (Aldosterone & Angiotensin II):** These are key components of the Renin-Angiotensin-Aldosterone System (RAAS). Angiotensin II is a powerful vasoconstrictor, and Aldosterone promotes sodium and water retention. Both factors **increase** blood pressure and are primary drivers of chronic hypertension. * **D (Reduced sympathetic nerve activity):** While reduced sympathetic activity would lower blood pressure, it is **not typically "associated" with the pathophysiology of chronic hypertension**. In fact, chronic hypertension is characterized by *increased* sympathetic drive (sympatho-excitation), which contributes to sustained elevation of vascular tone. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of NO:** Acts via the **cGMP pathway** (unlike many hormones that use cAMP or IP3). * **Pharmacology Link:** Drugs like Nitroglycerin and Sodium Nitroprusside act as "Nitric Oxide donors" to treat hypertensive emergencies. * **ANP/BNP:** Like NO, Atrial Natriuretic Peptide also works via cGMP to decrease blood pressure through vasodilation and natriuresis.

Q: The "incisura" of the arterial pulse corresponds to:

Closure of the aortic valve. ### Explanation The **incisura** (also known as the dicrotic notch) is a sharp downward deflection followed by a small upward wave seen in the **aortic pressure curve**. **1. Why Option B is Correct:** The incisura occurs at the end of ventricular systole. As the left ventricle stops contracting, intraventricular pressure drops below aortic pressure. This causes a brief backflow of blood toward the heart, which snaps the **aortic valve closed**. This sudden cessation of backflow and the elastic recoil of the aorta create a momentary pressure fluctuation, manifesting as the incisura. It marks the transition from systole to diastole. **2. Why the Other Options are Incorrect:** * **Option A (First heart sound):** S1 is caused by the closure of the AV valves (Mitral and Tricuspid) at the beginning of systole, long before the incisura occurs. * **Option C (Isovolumetric relaxation):** While the incisura occurs just at the *start* of this phase, the incisura itself is specifically the mechanical signature of valve closure, not the entire phase of relaxation. * **Option D (Third heart sound):** S3 occurs during the rapid filling phase of early diastole, well after the aortic valve has closed. **3. High-Yield NEET-PG Pearls:** * **Incisura vs. Dicrotic Notch:** In central aortic pressure tracings, it is called the **incisura**. In peripheral arterial pulse tracings (like the radial artery), it is referred to as the **dicrotic notch**. * **Timing:** The incisura coincides with the **Second Heart Sound (S2)** on phonocardiography. * **Clinical Correlation:** In **Aortic Regurgitation**, the incisura is often absent or poorly defined because the valve fails to close properly, preventing the characteristic pressure rebound.

Q: Which wave in the jugular venous pulse represents the atrial relaxation?

X wave. ### Explanation The **Jugular Venous Pulse (JVP)** reflects the pressure changes in the right atrium during the cardiac cycle. Understanding the correlation between these waves and the mechanical events of the heart is crucial for NEET-PG. **Why Option D is Correct:** The **'x' descent** (specifically the $x_1$ descent) represents **atrial relaxation**. As the right atrium relaxes after contraction, the pressure within it drops, leading to the first downward deflection in the JVP. This is followed by the $x_2$ descent, which occurs during ventricular systole as the tricuspid valve is pulled downward toward the apex, further decreasing atrial pressure. **Why Other Options are Incorrect:** * **A wave:** Represents **atrial contraction**. It occurs just before the first heart sound (S1) and the 'p' wave on an ECG. * **C wave:** Represents the **bulging of the tricuspid valve** into the right atrium during the onset of ventricular systole (isovolumetric contraction). * **V wave:** Represents **passive atrial filling** against a closed tricuspid valve during ventricular systole. **High-Yield Clinical Pearls for NEET-PG:** * **Giant 'a' waves:** Seen in Tricuspid Stenosis, Pulmonary Hypertension, and Pulmonary Stenosis. * **Cannon 'a' waves:** Occur when the atrium contracts against a closed tricuspid valve (e.g., Complete Heart Block, Ventricular Tachycardia). * **Absent 'a' wave:** Characteristic of **Atrial Fibrillation**. * **Prominent 'v' wave:** Classic sign of **Tricuspid Regurgitation** (often associated with a "systolic thrill" in the neck). * **Friedreich’s Sign:** A steep 'y' descent seen in Constrictive Pericarditis.

Q: The isovolumic relaxation phase of the cardiac cycle ends with which event?

Opening of the atrioventricular (AV) valve. ### Explanation **1. Why Option B is Correct:** Isovolumic relaxation is the period during early diastole when the ventricles are relaxing, but the volume remains constant because all four heart valves are closed. This phase begins with the **closure of the semilunar valves** (Aortic/Pulmonary) and ends when the ventricular pressure drops below the atrial pressure. At this precise crossover point, the **Atrioventricular (AV) valves open**, allowing blood to flow from the atria into the ventricles, marking the start of the rapid filling phase. **2. Why the Other Options are Incorrect:** * **Option A (Peak of 'C' waves):** The 'c' wave in the jugular venous pulse occurs during **isovolumic contraction**, caused by the bulging of the tricuspid valve into the right atrium. * **Option C (Closure of the semilunar valve):** This event marks the **beginning** of the isovolumic relaxation phase, not the end. * **Option D (Beginning of the 'T' wave):** The T wave on an ECG represents ventricular repolarization. It begins during the **ejection phase**; the end of the T wave roughly coincides with the closure of the semilunar valves. **3. NEET-PG High-Yield Pearls:** * **Pressure Changes:** During isovolumic relaxation, ventricular pressure falls precipitously, but ventricular volume is at its lowest (End-Systolic Volume). * **Heart Sounds:** The **S2 heart sound** marks the beginning of this phase. * **JVP Correlation:** The **'v' wave** in the JVP reaches its peak just before the AV valves open (at the end of isovolumic relaxation). * **Duration:** It is the shortest phase of diastole but is highly energy-dependent (requires ATP for calcium reuptake into the sarcoplasmic reticulum).

Q: Preload to the heart depends upon which of the following?

Stroke volume. **Explanation:** **Preload** is defined as the initial stretching of the cardiac myocytes prior to contraction. According to the **Frank-Starling Law**, the force of heart contraction is directly proportional to the initial length of the muscle fiber. In a clinical context, preload is represented by the **End-Diastolic Volume (EDV)**. **Why Stroke Volume is the correct answer:** While EDV is the most accurate measure of preload, the options provided require identifying the most direct physiological consequence. According to the Frank-Starling mechanism, an increase in preload leads to an increase in **Stroke Volume (SV)**. In many physiological models and exam patterns, SV is used as a surrogate marker or a direct dependent variable of preload. As preload increases, the stroke volume increases (up to a physiological limit), making it the most appropriate choice among the given options. **Analysis of Incorrect Options:** * **A. End-diastolic pressure:** While related to EDV, pressure is not the same as volume. Due to changes in ventricular compliance (e.g., hypertrophy), pressure may rise without a corresponding increase in fiber stretch (preload). * **B. End-systolic pressure:** This is more closely related to **Afterload** and the contractility of the heart, representing the state after the blood has been ejected. * **D. Cardiac output:** While CO depends on SV (CO = SV × HR), it is a global measure of pump function influenced by heart rate and autonomic tone, making it less specific to preload than SV itself. **Clinical Pearls for NEET-PG:** * **Preload markers:** Left Ventricular End-Diastolic Volume (LVEDV) is the gold standard; Central Venous Pressure (CVP) is a clinical proxy for right-sided preload. * **Factors increasing Preload:** Hypervolemia, valvular regurgitation, and horizontal positioning. * **Factors decreasing Preload:** Diuretics, nitrates (venodilators), and hemorrhage.

Question 1

If the heart rate is 70 beats/min, then the cardiac output of this ventricle is closest to?

Accepted Answer

5.25 L/min

Answer

4.55 L/min

Answer

8.00 L/min

Answer

9.85 L/min

Question 2

Which of the following statements regarding blood flow in various organs is true?

Accepted Answer

Liver > Kidney > Brain > Heart

Answer

Liver > Brain > Kidney > Heart

Answer

Kidney > Brain > Heart > Liver

Answer

Liver > Heart > Brain > Kidney

Question 3

If a person has a heart rate of 70 beats/min, a left ventricular end-diastolic volume of 100 ml, and an ejection fraction of 0.50, what is the cardiac output?

Accepted Answer

3.5 liters/min

Answer

3.0 liters/min

Answer

4.0 liters/min

Answer

4.5 liters/min

Question 4

Which of the following factors is associated with a decrease in chronic hypertension?

Accepted Answer

Nitric oxide

Answer

Aldosterone

Answer

Angiotensin II

Answer

Reduced sympathetic nerve activity

Question 5

The "incisura" of the arterial pulse corresponds to:

Accepted Answer

Closure of the aortic valve

Answer

First heart sound

Answer

Isovolumetric relaxation

Answer

Third heart sound

Question 6

Which wave in the jugular venous pulse represents the atrial relaxation?

Accepted Answer

X wave

Answer

A wave

Answer

V wave

Answer

C wave

Question 7

The isovolumic relaxation phase of the cardiac cycle ends with which event?

Accepted Answer

Opening of the atrioventricular (AV) valve

Answer

Peak of 'C' waves

Answer

Closure of the semilunar valve

Answer

Beginning of the 'T' wave

Question 8

Preload to the heart depends upon which of the following?

Accepted Answer

Stroke volume

Answer

End-diastolic pressure

Answer

End-systolic pressure

Answer

Cardiac output

Question 9

Which of the following statements regarding Purkinje fibers is true?

Accepted Answer

Purkinje fibers have a conduction velocity four times that of cardiac muscle.

Answer

Purkinje fibers are myelinated.

Answer

The action potential duration in Purkinje fibers is approximately one-tenth that of the cardiac muscle.

Answer

All of the above

Question 10

The 'vulnerable period' during cardiac excitation coincides with which of the following?

Accepted Answer

Peak of T wave

Answer

PR interval

Answer

J-point

Answer

U wave

Cardiovascular System — MCQs

Cardiovascular System — MCQs

On this page

Practice by Chapter

Want unlimited practice?