Cardiovascular System Practice Questions

Q: The cardiac output can be determined by all of the following methods except?

Ventilation-perfusion ratio (V/Q ratio). **Explanation:** **1. Why Ventilation-perfusion (V/Q) ratio is the correct answer:** The **V/Q ratio** is a physiological parameter used to assess the efficiency of gas exchange in the lungs. It compares the amount of air reaching the alveoli (ventilation) to the amount of blood reaching the alveoli (perfusion). While it involves blood flow (perfusion), it is a **ratio**, not a quantitative measure of the total volume of blood pumped by the heart per minute (Cardiac Output). Therefore, it cannot be used to determine Cardiac Output (CO). **2. Analysis of other options:** * **Fick’s Principle:** This is the "Gold Standard" for measuring CO. It states that the uptake of a substance (usually Oxygen) by an organ is equal to the product of the blood flow to that organ and the arteriovenous concentration difference of that substance. Formula: $CO = \text{O}_2 \text{ consumption} / (A-V \text{ O}_2 \text{ difference})$. * **Thermodilution:** This is the most common clinical method used in ICUs via a **Swan-Ganz catheter**. A cold saline bolus is injected into the right atrium, and the temperature change is measured in the pulmonary artery. The change in temperature over time is inversely proportional to the CO. * **Echocardiography:** A non-invasive method that calculates CO by measuring the **Stroke Volume** (using ventricular dimensions or Doppler flow across the aortic valve) and multiplying it by the Heart Rate ($CO = SV \times HR$). **Clinical Pearls for NEET-PG:** * **Indicator Dilution Method:** Uses **Indocyanine green** (dye) to calculate CO; it follows the same principle as thermodilution. * **Most accurate method:** Fick’s Principle. * **Most common bedside method:** Thermodilution. * **Normal Cardiac Index:** $3.2 \, \text{L/min/m}^2$ (CO adjusted for body surface area).

Q: Which neurotransmitter is released in the SA node of the heart in response to increased blood pressure?

Acetylcholine. **Explanation:** The correct answer is **Acetylcholine (ACh)**. This response is mediated by the **Baroreceptor Reflex**, a high-yield physiological mechanism for blood pressure regulation. **1. Why Acetylcholine is Correct:** When blood pressure increases, baroreceptors (stretch receptors) in the carotid sinus and aortic arch are stimulated. They send signals to the Nucleus Tractus Solitarius (NTS) in the medulla, which increases **parasympathetic (vagal) outflow** to the heart. The postganglionic parasympathetic fibers release **Acetylcholine** at the SA node. ACh binds to **M2 muscarinic receptors**, leading to: * Opening of K+ channels (hyperpolarization). * Decreased cAMP, slowing the rate of diastolic depolarization. * **Result:** Decreased heart rate (bradycardia) to help lower blood pressure. **2. Why Other Options are Incorrect:** * **Adrenaline & Noradrenaline:** These are sympathetic neurotransmitters/hormones. They are released in response to *decreased* blood pressure (hypotension) or stress to increase heart rate and contractility via β1 receptors. * **Dopamine:** While a precursor to norepinephrine, it is not the primary neurotransmitter involved in the baroreceptor reflex at the SA node. **3. Clinical Pearls for NEET-PG:** * **The "Vagal Tone":** At rest, the heart is under dominant parasympathetic influence via the Vagus nerve (ACh). * **Reflex Bradycardia:** This is the classic response to a sudden rise in BP (e.g., during a Phenylephrine bolus). * **Receptor Mechanism:** M2 receptors are G-protein coupled (Gi), which inhibits Adenylyl Cyclase. * **Afferent Pathways:** Carotid sinus (CN IX - Glossopharyngeal) and Aortic arch (CN X - Vagus). Remember: **"S-I-N"** (Sinus is IX).

Q: Which event in the cardiac cycle is responsible for a wave in the Jugular Venous Pulse (JVP)?

Atrial systole. ### Explanation **1. Why Atrial Systole is Correct:** The **'a' wave** in the Jugular Venous Pulse (JVP) is the first positive deflection and is caused by **atrial systole**. When the right atrium contracts to pump blood into the right ventricle, the pressure within the atrium increases. Since there are no functional valves between the superior vena cava and the right atrium, this pressure is transmitted retrogradely into the internal jugular vein, creating the 'a' wave (a = atrial contraction). **2. Analysis of Incorrect Options:** * **Atrial Diastole (Option B):** During atrial diastole (specifically early diastole), the pressure in the atrium drops as it relaxes and fills. This corresponds to the **'x' descent**, which is a negative deflection, not a wave. * **Ventricular Systole (Option C):** While ventricular systole occurs simultaneously with some JVP components, it is primarily associated with the **'c' wave** (bulging of the tricuspid valve into the atrium) and the **'v' wave** (atrial filling against a closed tricuspid valve). However, the specific 'a' wave is strictly an atrial event. * **Ventricular Diastole (Option D):** Early ventricular diastole, when the tricuspid valve opens, leads to the **'y' descent** as blood flows rapidly from the atrium to the ventricle. **3. High-Yield Clinical Pearls for NEET-PG:** * **Giant 'a' waves:** Seen in conditions with resistance to atrial emptying (e.g., Tricuspid stenosis, Pulmonary hypertension, Right ventricular hypertrophy). * **Cannon 'a' waves:** Occur when the atrium contracts against a closed tricuspid valve (e.g., Complete Heart Block, Junctional rhythms, Ventricular Tachycardia). * **Absent 'a' waves:** A classic finding in **Atrial Fibrillation** (due to lack of coordinated atrial contraction). * **Prominent 'v' waves:** Characteristic of **Tricuspid Regurgitation**.

Q: Renin plays an important role in which of the following conditions?

Renovascular hypertension. **Explanation:** **Renovascular hypertension** is the correct answer because it is the classic clinical manifestation of the **Renin-Angiotensin-Aldosterone System (RAAS)** activation. The underlying mechanism is typically renal artery stenosis (due to atherosclerosis or fibromuscular dysplasia), which leads to decreased renal perfusion pressure. The juxtaglomerular cells sense this "hypoperfusion" and secrete excess **Renin**. Renin converts Angiotensinogen to Angiotensin I, which is then converted to Angiotensin II (a potent vasoconstrictor) by ACE, leading to systemic hypertension. **Analysis of Incorrect Options:** * **Malignant hypertension:** While RAAS can be secondarily involved due to end-organ damage, the primary pathology is severe arteriolar damage and fibrinoid necrosis. It is a clinical syndrome of extremely high BP (>180/120 mmHg) rather than a renin-dependent etiology. * **Coronary artery disease (CAD):** This is primarily a disease of atherosclerosis and plaque formation in the coronary arteries. While hypertension is a risk factor for CAD, renin is not the primary driver of the disease process itself. * **Essential hypertension:** Also known as primary hypertension, the exact cause is unknown (idiopathic). In many cases, patients actually have "low-renin" hypertension, especially in older populations or certain ethnic groups. **High-Yield Clinical Pearls for NEET-PG:** * **Goldblatt Kidney:** The experimental model for renovascular hypertension. * **Bruit:** A systolic-diastolic abdominal bruit is a highly specific clinical sign for renal artery stenosis. * **ACE Inhibitors:** These are contraindicated in **bilateral** renal artery stenosis because they can cause a precipitous drop in GFR and acute renal failure. * **Hypokalemia:** Excess renin leads to excess aldosterone, which may cause metabolic alkalosis and hypokalemia.

Q: Peripheral resistance is best indicated by:

Diastolic blood pressure. **Explanation:** **1. Why Diastolic Blood Pressure (DBP) is the correct answer:** Peripheral resistance (PR) is the resistance offered by the systemic vasculature (primarily the arterioles) to the flow of blood. During diastole, the heart is not ejecting blood; however, the blood pressure does not drop to zero because of the elastic recoil of the large arteries and the resistance offered by the peripheral arterioles. Therefore, **Diastolic Blood Pressure** is the best clinical indicator of peripheral resistance. If arterioles constrict (increasing PR), DBP rises; if they dilate (decreasing PR), DBP falls. **2. Analysis of Incorrect Options:** * **B. Pulse Pressure:** This is the difference between systolic and diastolic pressure ($SBP - DBP$). It is primarily determined by the **stroke volume** and the **compliance (distensibility)** of the arterial tree, rather than peripheral resistance. * **C. Systolic resistance in the aorta:** Systolic pressure is primarily a reflection of cardiac output, stroke volume, and the elasticity of the aorta. Resistance is a property of the microvasculature (arterioles), not the aorta itself. * **D. Mean Arterial Pressure (MAP):** While MAP is the average pressure driving blood to organs, it is a product of both Cardiac Output and Total Peripheral Resistance ($MAP = CO \times TPR$). It is a global hemodynamic parameter rather than a specific indicator of resistance alone. **High-Yield Clinical Pearls for NEET-PG:** * **Resistance Vessels:** Arterioles are known as the primary "resistance vessels" of the body. * **Windkessel Effect:** The elastic recoil of the aorta during diastole that maintains blood flow is called the Windkessel effect. * **Formula:** $TPR = \frac{8\eta L}{\pi r^4}$ (Poiseuille’s Law). Note that resistance is inversely proportional to the **fourth power of the radius**, making vessel diameter the most potent determinant of peripheral resistance.

Q: Which of the following is the order of activation after stimulation of Purkinje fibers?

Septum Endocardium Epicardium. ### Explanation The sequence of ventricular depolarization is determined by the anatomical distribution of the specialized conduction system (Bundle of His and Purkinje fibers). **1. Why Option A is Correct:** The electrical impulse travels down the Bundle of His and enters the **Interventricular Septum** first via the left bundle branch. This causes the septum to depolarize from left to right. Following septal activation, the impulse travels through the Purkinje network, which is located in the **sub-endocardial** layer of the ventricular walls. Consequently, the wave of depolarization spreads from the **Endocardium to the Epicardium** (inside to outside). Therefore, the correct sequence is: **Septum → Endocardium → Epicardium.** **2. Why Other Options are Incorrect:** * **Option B & D:** These are incorrect because the septum is always the first part of the ventricular myocardium to depolarize, preceding the free walls of the ventricles. * **Option C:** This describes the sequence of **repolarization**, not depolarization. Ventricular repolarization occurs from the epicardium to the endocardium because the epicardial cells have a shorter action potential duration. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Septal Vector:** Since the septum depolarizes from left to right, it produces the initial small 'q' wave in lateral leads (V5, V6) and a small 'r' wave in V1. * **Conduction Velocity:** Purkinje fibers have the fastest conduction velocity in the heart (~4 m/s) due to a high density of gap junctions and large fiber diameter. * **Last to Depolarize:** The posterobasal part of the left ventricle and the pulmonary conus are typically the last regions to depolarize. * **Papillary Muscles:** These are activated early in the sequence to ensure the AV valves are braced before full ventricular contraction, preventing regurgitation.

Q: What is the normal systolic blood pressure in the right ventricle?

25 mmHg. **Explanation:** The right ventricle (RV) is a low-pressure pump designed to propel deoxygenated blood into the pulmonary circulation. Unlike the left ventricle, which must overcome high systemic vascular resistance, the RV encounters the low resistance of the pulmonary vascular bed. **1. Why 25 mmHg is correct:** In a healthy adult, the normal **systolic pressure of the right ventricle ranges from 15 to 25 mmHg**, while the diastolic pressure is near zero (0–8 mmHg). Since the pulmonary valve is open during systole, the RV systolic pressure is equal to the Pulmonary Artery Systolic Pressure (PASP). **2. Analysis of Incorrect Options:** * **80 mmHg (Option B):** This represents the normal **diastolic** blood pressure in the systemic circulation (Aorta/Large arteries). * **95 mmHg (Option C):** This is a typical value for the **Mean Arterial Pressure (MAP)** in the systemic circulation. * **120 mmHg (Option D):** This is the normal **systolic** blood pressure of the **left ventricle** and the systemic arteries. The left ventricle is significantly thicker because it must generate roughly five times the pressure of the right ventricle. **3. High-Yield Clinical Pearls for NEET-PG:** * **Pulmonary Hypertension:** Defined as a mean pulmonary artery pressure (mPAP) >20 mmHg at rest. * **Pressure Equivalency:** During systole, RV pressure ≈ Pulmonary Artery pressure. During diastole, RV pressure drops to near zero, while Pulmonary Artery pressure remains higher (~8–10 mmHg) due to the closure of the pulmonary valve. * **Bernoulli Equation:** In echocardiography, RV systolic pressure is often estimated using the Tricuspid Regurgitation (TR) jet velocity: $PASP = 4(V_{TR})^2 + \text{Right Atrial Pressure}$.

Question 1

The cardiac output can be determined by all of the following methods except?

Accepted Answer

Ventilation-perfusion ratio (V/Q ratio)

Answer

Fick's principle

Answer

Echocardiography

Answer

Thermodilution

Question 2

Which neurotransmitter is released in the SA node of the heart in response to increased blood pressure?

Accepted Answer

Acetylcholine

Answer

Dopamine

Answer

Adrenaline

Answer

Noradrenaline

Question 3

Which event in the cardiac cycle is responsible for a wave in the Jugular Venous Pulse (JVP)?

Accepted Answer

Atrial systole

Answer

Atrial diastole

Answer

Ventricular systole

Answer

Ventricular diastole

Question 4

Renin plays an important role in which of the following conditions?

Accepted Answer

Renovascular hypertension

Answer

Malignant hypertension

Answer

Coronary artery disease

Answer

Essential hypertension

Question 5

Peripheral resistance is best indicated by:

Accepted Answer

Diastolic blood pressure

Answer

Pulse pressure

Answer

Systolic resistance in the aorta as it increases in its length

Answer

Mean arterial pressure, which is responsible for blood flow to an organ

Question 6

Sympathetic innervation of the heart is by which spinal nerve segments?

Accepted Answer

T1-T5

Answer

T1-T3

Answer

T3-T7

Answer

L1-L5

Question 7

Which of the following is the order of activation after stimulation of Purkinje fibers?

Accepted Answer

Septum 	 Endocardium 	 Epicardium

Answer

Endocardium 	 Septum 	 Epicardium

Answer

Epicardium 	 Septum 	 Endocardium

Answer

Septum 	 Epicardium 	 Endocardium

Question 8

What is the normal systolic blood pressure in the right ventricle?

Accepted Answer

25 mmHg

Answer

80 mmHg

Answer

95 mmHg

Answer

120 mmHg

Question 9

A patient with increased blood pressure and decreased heart rate is likely to have which of the following conditions?

Accepted Answer

Increased intracranial pressure

Answer

Deep sea diving

Answer

Brain tumor

Answer

Head tumor

Question 10

Spurious hypertension is seen in which of the following conditions?

Accepted Answer

Auscultatory gap

Answer

Small cuff size

Answer

Thick calcified vessels

Answer

Obesity

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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