Cardiovascular System Practice Questions

Q: What is the first reactionary change to occur after vessel injury and haemorrhage?

Vasoconstriction. **Explanation:** The correct answer is **Vasoconstriction (Option A)**. When a blood vessel is injured and hemorrhage occurs, the body’s immediate priority is to minimize blood loss and maintain perfusion pressure. This is achieved through **local myogenic contraction** and **sympathetic stimulation**. 1. **Local Myogenic Spasm:** Damage to the vascular wall causes direct trauma to smooth muscle cells, leading to immediate contraction. 2. **Humoral Factors:** Platelets at the site of injury release potent vasoconstrictors like **Thromboxane A2** and **Serotonin**. 3. **Sympathetic Reflex:** The drop in blood pressure triggers the baroreceptor reflex, leading to generalized vasoconstriction to increase Total Peripheral Resistance (TPR). **Why other options are incorrect:** * **Bradycardia (Option B):** Hemorrhage typically causes **tachycardia** (increased heart rate) as a compensatory mechanism to maintain Cardiac Output ($CO = HR \times SV$). Bradycardia only occurs in terminal stages (Stage IV shock) or via the Bezold-Jarisch reflex in specific scenarios. * **Raised Cortisol (Option C):** While cortisol increases as part of the stress response, it is a hormonal change that takes minutes to hours to peak, making it much slower than the near-instantaneous vascular response. * **Raised Adrenaline (Option D):** Catecholamine release is a rapid systemic response, but the **local myogenic vasoconstriction** occurs milliseconds after the physical trauma, preceding the systemic endocrine surge. **High-Yield Clinical Pearls for NEET-PG:** * **Hemostasis Sequence:** 1. Vascular Spasm (Vasoconstriction) $\rightarrow$ 2. Platelet Plug formation $\rightarrow$ 3. Coagulation (Fibrin clot). * **Baroreceptor Reflex:** This is the most important short-term mechanism for BP regulation during hemorrhage. * **Shock Index:** Heart Rate / Systolic BP (Normal: 0.5–0.7). An increase is an early indicator of significant blood loss.

Q: Cerebral blood flow is regulated by all except?

Potassium ions. **Explanation:** Cerebral blood flow (CBF) is tightly regulated to ensure a constant supply of oxygen and glucose to the brain. The correct answer is **Potassium ions**, as they are not a primary systemic regulator of CBF, although they may play minor roles in local neurovascular coupling. **1. Why Potassium ions (Option C) is the correct answer:** While local changes in extracellular $K^+$ can cause transient vasodilation, it is not considered a primary regulatory mechanism for global cerebral blood flow. In contrast, factors like $CO_2$, $O_2$, and Mean Arterial Pressure (MAP) have profound, well-documented effects on the entire cerebral vasculature. **2. Analysis of Incorrect Options:** * **Blood Pressure (Option A):** Through **Cerebral Autoregulation**, CBF remains constant despite changes in MAP between **60 and 140 mmHg**. Outside this range, CBF becomes pressure-dependent. * **$PaCO_2$ (Option B):** This is the **most potent physiological stimulus** for CBF. Hypercapnia (high $CO_2$) causes marked vasodilation, while hypocapnia (low $CO_2$) causes vasoconstriction. * **Cerebral Metabolic Rate (Option D):** CBF is directly proportional to metabolic activity (Metabolic Autoregulation). Increased neuronal activity leads to the release of metabolites like Adenosine, $H^+$, and Nitric Oxide, which increase local blood flow. **High-Yield Facts for NEET-PG:** * **Normal CBF:** 50 ml/100g/min (approx. 750 ml/min or 15% of Cardiac Output). * **$CO_2$ Sensitivity:** A 1 mmHg rise in $PaCO_2$ increases CBF by approximately 3-4%. * **Cushing’s Reflex:** A clinical triad of hypertension, bradycardia, and irregular respiration seen in increased intracranial pressure (ICP). * **Monro-Kellie Doctrine:** The sum of volumes of brain, CSF, and intracerebral blood is constant; an increase in one must be offset by a decrease in another.

Q: In healthy individuals, what characteristic is the same for both pulmonary and systemic circulations?

Flow per minute. **Explanation:** The correct answer is **Flow per minute (Cardiac Output)**. In a healthy individual, the pulmonary and systemic circulations are arranged in **series**. According to the principle of continuity, the volume of blood pumped by the right ventricle into the lungs must equal the volume of blood pumped by the left ventricle into the systemic circulation over a given period. If they were not equal, blood would rapidly accumulate in either the lungs or the systemic tissues, leading to immediate circulatory collapse. Therefore, **Cardiac Output (CO) = Right Ventricular Output = Left Ventricular Output.** **Why other options are incorrect:** * **Mean Pressure:** The systemic circulation is a high-pressure system (Mean Arterial Pressure ~93 mmHg), whereas the pulmonary circulation is a low-pressure system (Mean Pulmonary Artery Pressure ~15 mmHg). This protects the delicate alveolar-capillary membrane. * **Vascular Resistance:** Systemic Vascular Resistance (SVR) is significantly higher (about 10 times) than Pulmonary Vascular Resistance (PVR). The right ventricle is thinner because it pumps against much lower resistance. * **Compliance:** The pulmonary vessels are much more compliant (distensible) than systemic arteries. This allows the pulmonary system to accommodate increases in stroke volume without a significant rise in pressure. **High-Yield Clinical Pearls for NEET-PG:** * **Formula:** $Q (Flow) = \Delta P / R$. Since Flow (Q) is constant in both systems but Pressure ($\Delta P$) is much lower in the lungs, it follows that Resistance ($R$) must also be much lower in the lungs. * **Exception:** In the fetus, the circulations are in **parallel** (due to shunts like the ductus arteriosus), meaning flow is not equal. * **Left-to-Right Shunts (e.g., ASD/VSD):** In these pathologies, pulmonary flow ($Qp$) becomes greater than systemic flow ($Qs$), breaking the "equal flow" rule.

Q: What is the resting membrane potential of myocytes?

-90 mV. The Resting Membrane Potential (RMP) of a cell is the electrical potential difference across the plasma membrane when the cell is in a non-excited state. **1. Why -90 mV is Correct:** In ventricular myocytes, the RMP is approximately **-90 mV**. This value is primarily determined by the high resting permeability of the membrane to **Potassium (K+) ions** through inward rectifier K+ channels ($I_{K1}$). Since the Nernst potential for Potassium is roughly -94 mV, the RMP sits very close to this value. The Na+/K+ ATPase pump also contributes by maintaining the ionic gradients (pumping 3 Na+ out and 2 K+ in), ensuring the interior remains electronegative. **2. Analysis of Incorrect Options:** * **-70 mV:** This is the typical RMP for **large myelinated neurons**. While still negative, neurons have a slightly higher permeability to Sodium at rest compared to cardiac myocytes. * **-60 mV:** This is the approximate RMP (or "maximal diastolic potential") of the **SA Node and AV Node**. Nodal tissue is less negative because it lacks $I_{K1}$ channels, which allows for spontaneous depolarization (pacemaker activity). * **-50 mV:** This value is too positive for a healthy resting myocyte and would result in the inactivation of fast Sodium channels, leading to impaired conduction. **3. NEET-PG High-Yield Pearls:** * **Phase 4:** In the cardiac action potential, the RMP corresponds to Phase 4. * **Ion Conductance:** At rest, the membrane is 100 times more permeable to $K^+$ than to $Na^+$. * **Hyperkalemia:** An increase in extracellular $K^+$ makes the RMP less negative (depolarized), which paradoxically decreases excitability over time by inactivating $Na^+$ channels. * **Skeletal Muscle:** Also shares a similar RMP of approximately -80 to -90 mV.

Q: Elevated systolic blood pressure in the right ventricle suggests stenosis of which valve?

Pulmonary. ### Explanation **Correct Option: C. Pulmonary** **Mechanism:** The right ventricle (RV) pumps deoxygenated blood into the pulmonary artery through the pulmonary valve. In **Pulmonary Stenosis**, the valve orifice is narrowed, creating significant resistance to blood outflow. To maintain stroke volume and overcome this obstruction, the RV must generate much higher pressures during systole. This leads to **concentric right ventricular hypertrophy** and elevated systolic pressure within the RV chamber. **Analysis of Incorrect Options:** * **A. Aortic Valve:** Stenosis here increases systolic pressure in the **left ventricle**, as it must work harder to pump blood into the systemic circulation. * **B. Mitral Valve:** Stenosis of the mitral valve restricts flow from the left atrium to the left ventricle. This leads to elevated **left atrial pressure** and pulmonary venous congestion, but does not directly cause primary elevation of RV systolic pressure (though chronic cases may lead to secondary pulmonary hypertension). * **C. Tricuspid Valve:** Stenosis here restricts flow from the right atrium to the right ventricle. This would actually result in **decreased** filling and potentially lower pressures in the right ventricle, while increasing pressure in the **right atrium**. **High-Yield Facts for NEET-PG:** * **Normal RV Pressure:** Typically 15–25 mmHg (systolic) / 0–8 mmHg (diastolic). In severe pulmonary stenosis, systolic pressure can exceed 100 mmHg. * **Clinical Sign:** Pulmonary stenosis typically presents with an **ejection systolic murmur** best heard at the left second intercostal space, often preceded by a systolic click. * **Bernoulli Equation:** In the echo lab, the pressure gradient across the stenotic valve is calculated as $\Delta P = 4v^2$ (where $v$ is peak velocity). * **EKG Findings:** Right axis deviation and tall R-waves in V1-V2 are characteristic of the resulting RV hypertrophy.

Q: Split first heart sound is heard in which of the following conditions?

Complete right bundle branch block. **Explanation:** The **First Heart Sound (S1)** is produced by the closure of the Atrioventricular (AV) valves—the Mitral (M1) and Tricuspid (T1) valves. Normally, M1 occurs slightly before T1 because the left ventricle depolarizes just before the right ventricle. However, this gap is so small that S1 is typically heard as a single sound. **Why Option C is Correct:** In **Complete Right Bundle Branch Block (RBBB)**, there is a delay in the electrical conduction to the right ventricle. This causes delayed depolarization and subsequent delayed contraction of the right ventricle. Consequently, the closure of the Tricuspid valve (T1) is significantly delayed relative to the Mitral valve (M1), resulting in a **wide, audible split of S1**. **Analysis of Incorrect Options:** * **A. Mitral Stenosis:** Characterized by a **loud (accentuated) S1** due to the thickened leaflets being wide apart at the onset of systole, but it does not typically cause a split S1. * **B. Left Bundle Branch Block (LBBB):** This delays the Mitral component (M1). Since M1 normally precedes T1, LBBB often causes M1 to coincide with or follow T1, frequently resulting in a **soft or single S1**, but not a classic split. * **D. Pulmonary Hypertension:** This primarily affects the **Second Heart Sound (S2)**, leading to a loud pulmonary component (P2) and narrow physiological splitting. **High-Yield Clinical Pearls for NEET-PG:** * **S1 Splitting:** Best heard at the tricuspid area (left lower sternal border). * **Reversed Splitting of S1:** Can occur in Mitral Stenosis with rigid valves or occasionally in LBBB (where T1 precedes M1). * **Loud S1:** Seen in Mitral Stenosis, short PR interval (Tachycardia), and hyperdynamic states. * **Soft S1:** Seen in Mitral Regurgitation, long PR interval (First-degree heart block), and obesity/COPD.

Q: Which of the following is a contributing factor in chronic hypertension that, when decreased, is associated with improved outcomes?

Nitric oxide. **Explanation:** The question focuses on the pathophysiology of chronic hypertension and the role of endothelial function. **Why Nitric Oxide (NO) is the correct answer:** Nitric oxide is a potent **vasodilator** produced by the vascular endothelium. In chronic hypertension, there is often "endothelial dysfunction," characterized by a **decrease in the bioavailability of NO**. When NO levels are decreased, the protective vasodilatory, anti-inflammatory, and anti-thrombotic effects are lost, leading to increased peripheral resistance and target organ damage. Therefore, therapeutic strategies or lifestyle changes that reverse this deficit (increasing NO) are associated with improved clinical outcomes. **Why the other options are incorrect:** * **A & B (Aldosterone & Angiotensin II):** These are components of the Renin-Angiotensin-Aldosterone System (RAAS). They are **increased** in many forms of hypertension, causing vasoconstriction and sodium retention. A *decrease* in these factors (via ACE inhibitors or ARBs) improves outcomes, but they are not the factors that, when decreased, represent the *pathological state* mentioned in the context of this specific question's phrasing. * **D (Sympathetic Nerve Activity):** Increased sympathetic drive contributes to hypertension. Similar to RAAS, a *decrease* in sympathetic activity (e.g., via beta-blockers) is beneficial, but it is an excitatory factor, not a protective one like NO. **High-Yield Clinical Pearls for NEET-PG:** * **L-Arginine** is the precursor for Nitric Oxide synthesis via the enzyme **eNOS** (endothelial NO synthase). * **Asymmetric Dimethylarginine (ADMA)** is an endogenous inhibitor of NO synthase; high levels of ADMA are linked to cardiovascular risk. * **Shear stress** on the vessel wall is a physiological stimulus for NO release. * In the kidneys, NO helps maintain glomerular filtration rate (GFR) by dilating the afferent arteriole.

Q: Prolongation of the QRS complex in an ECG represents which of the following?

Bundle branch block. **Explanation:** The **QRS complex** represents ventricular depolarization. In a healthy heart, the electrical impulse travels rapidly through the specialized conduction system (Bundle of His and Purkinje fibers), resulting in a narrow QRS (usually <0.10–0.12 seconds). **Why Bundle Branch Block (BBB) is correct:** In a Bundle Branch Block (either Left or Right), the specialized conduction pathway is interrupted. The electrical impulse must travel through the slower, cell-to-cell myocardial conduction rather than the rapid Purkinje system. This slower spread of depolarization significantly increases the time required for the ventricles to depolarize, leading to a **widened or prolonged QRS complex** (>0.12 seconds). **Analysis of Incorrect Options:** * **Acute Cor Pulmonale:** Typically presents with signs of right heart strain, such as the classic **S1Q3T3 pattern** and Right Axis Deviation, rather than a primary prolongation of the QRS. * **Chronic Cor Pulmonale:** Usually leads to Right Ventricular Hypertrophy (RVH). While it may cause a slight increase in QRS duration, the hallmark ECG findings are **Right Axis Deviation** and tall R-waves in V1. * **Left Ventricular Hypertrophy (LVH):** Characterized by **increased voltage (amplitude)** of the QRS complex (e.g., Sokolow-Lyon criteria) due to increased muscle mass, but the conduction velocity remains relatively normal unless a secondary block occurs. **High-Yield Clinical Pearls for NEET-PG:** * **Normal QRS duration:** 0.06 to 0.10 seconds. * **Complete BBB:** QRS duration ≥ 0.12 seconds (3 small squares). * **RBBB:** "M" pattern in V1 (rsR') and "W" in V6 (Marrow). * **LBBB:** "W" pattern in V1 and "M" in V6 (William). *Note: New-onset LBBB in the context of chest pain is considered an MI equivalent.*

Q: Patients with syncope cannot maintain sufficient cardiac output to meet peripheral perfusion demands. Which of the following BEST describes cardiac output?

Cardiac output = heart rate x stroke volume. ### Explanation **Correct Answer: C. Cardiac Output = Heart Rate × Stroke Volume** **1. Why the Correct Answer is Right:** Cardiac Output (CO) is defined as the volume of blood pumped by each ventricle per unit of time (usually measured in liters per minute). It is the product of two primary variables: * **Heart Rate (HR):** The number of beats per minute. * **Stroke Volume (SV):** The volume of blood ejected by the ventricle during a single contraction. Mathematically, **CO = HR × SV**. In a healthy adult at rest, with an average HR of 72 bpm and an SV of 70 mL, the CO is approximately 5 L/min. **2. Why the Incorrect Options are Wrong:** * **Option A:** This formula describes **Stroke Volume (SV)**, not Cardiac Output. SV is the difference between the volume of blood in the ventricle at the end of filling (EDV) and the volume remaining after contraction (ESV). * **Option B & D:** These options incorrectly incorporate **Mean Arterial Pressure (MAP)**. While CO is related to MAP through the formula **MAP = CO × Total Peripheral Resistance (TPR)**, MAP itself is a measure of pressure, not a component used to calculate the volume of flow (CO) directly. **3. High-Yield Clinical Pearls for NEET-PG:** * **Cardiac Index (CI):** This is CO adjusted for body surface area (CO/BSA). Normal range: 2.5–4.2 L/min/m². * **Fick’s Principle:** A gold-standard method to measure CO: $CO = \frac{\text{Oxygen Consumption}}{\text{Arterial } O_2 \text{ content} - \text{Venous } O_2 \text{ content}}$. * **Syncope Mechanism:** Syncope occurs when CO fails to maintain a MAP of at least 50–60 mmHg, leading to transient cerebral hypoperfusion. * **Preload & Afterload:** SV is determined by preload (EDV), afterload (resistance), and myocardial contractility.

Question 1

What is the first reactionary change to occur after vessel injury and haemorrhage?

Accepted Answer

Vasoconstriction

Answer

Bradycardia

Answer

Raised cortisol

Answer

Raised adrenaline

Question 2

Cerebral blood flow is regulated by all except?

Accepted Answer

Potassium ions

Answer

Blood pressure

Answer

PaCO2

Answer

Cerebral metabolic rate

Question 3

In healthy individuals, what characteristic is the same for both pulmonary and systemic circulations?

Accepted Answer

Flow per minute

Answer

Mean pressure

Answer

Vascular resistance

Answer

Compliance

Question 4

What is the resting membrane potential of myocytes?

Accepted Answer

-90 mV

Answer

-70 mV

Answer

-50 mV

Answer

-60 mV

Question 5

Low-pressure receptors that play a role in minimal aerial pressure changes due to volume changes are located in which of the following locations?

Accepted Answer

All of the above

Answer

Left Atrium

Answer

Right Atrium

Answer

Pulmonary arteries

Question 6

Elevated systolic blood pressure in the right ventricle suggests stenosis of which valve?

Accepted Answer

Pulmonary

Answer

Aortic

Answer

Mitral

Answer

Tricuspid

Question 7

Split first heart sound is heard in which of the following conditions?

Accepted Answer

Complete right bundle branch block

Answer

Mitral stenosis

Answer

Left bundle branch block

Answer

Pulmonary hypertension

Question 8

Which of the following is a contributing factor in chronic hypertension that, when decreased, is associated with improved outcomes?

Accepted Answer

Nitric oxide

Answer

Aldosterone

Answer

Angiotensin II

Answer

Sympathetic nerve activity

Question 9

Prolongation of the QRS complex in an ECG represents which of the following?

Accepted Answer

Bundle branch block

Answer

Acute cor pulmonale

Answer

Chronic cor pulmonale

Answer

Left ventricular hypertrophy

Question 10

Patients with syncope cannot maintain sufficient cardiac output to meet peripheral perfusion demands. Which of the following BEST describes cardiac output?

Accepted Answer

Cardiac output = heart rate x stroke volume

Answer

Cardiac output = end-diastolic volume - end-systolic volume

Answer

Cardiac output = heart rate x mean arterial pressure

Answer

Cardiac output = stroke volume x mean arterial pressure

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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