Cardiovascular System Practice Questions

Q: During the Valsalva maneuver, how does the heart rate typically change?

Tachycardia followed by bradycardia. ### Explanation The **Valsalva maneuver** (forced expiration against a closed glottis) involves four distinct phases driven by changes in intrathoracic pressure and the baroreceptor reflex. **Why Option A is Correct:** The heart rate response is biphasic: 1. **Tachycardia (During the maneuver):** In **Phase II**, increased intrathoracic pressure decreases venous return (preload), leading to a drop in cardiac output and blood pressure. The **baroreceptor reflex** detects this hypotension and triggers sympathetic activation, resulting in compensatory **tachycardia**. 2. **Bradycardia (After the maneuver):** In **Phase IV** (Post-maneuver), the sudden release of pressure allows a massive surge of venous return to the heart. This causes an "overshoot" of arterial blood pressure. The baroreceptors respond to this hypertension by triggering the **parasympathetic nervous system (vagus nerve)**, resulting in reflex **bradycardia**. **Why Other Options are Incorrect:** * **Option B:** Reverses the physiological sequence; bradycardia occurs as a late reflex, not an initial response. * **Options C & D:** These options describe a sustained heart rate change. The maneuver is characterized by dynamic fluctuations (tachycardia during strain and bradycardia upon release) to maintain hemodynamic stability. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Use:** Used to terminate **Supraventricular Tachycardia (SVT)** by increasing vagal tone during Phase IV. * **Murmurs:** Valsalva **decreases** most murmurs (due to decreased venous return) but **increases** the intensity of murmurs in **Hypertrophic Obstructive Cardiomyopathy (HOCM)** and **Mitral Valve Prolapse (MVP)**. * **Square Wave Response:** In patients with Heart Failure, the normal BP fluctuations are lost, showing a "square wave" pattern due to fluid overload.

Q: Bilateral cutting of the vagus nerve causes what physiological change?

Increase in heart rate. **Explanation:** The heart is under the constant influence of the autonomic nervous system. Under resting conditions, the **parasympathetic nervous system** (via the Vagus nerve) exerts a dominant inhibitory influence on the Sinoatrial (SA) node, known as **"Vagal Tone."** 1. **Why the correct answer is right:** The Vagus nerve releases acetylcholine, which acts on M2 receptors to slow the firing rate of the SA node. Bilateral vagotomy (cutting both nerves) removes this inhibitory "brake." Without the parasympathetic influence, the intrinsic firing rate of the SA node (approx. 100–110 bpm) prevails, leading to a significant **increase in heart rate (tachycardia).** 2. **Why the incorrect options are wrong:** * **A (Decrease in heart rate):** This would occur with vagal *stimulation*, not cutting. * **B (Decrease in respiratory rate):** While the Vagus nerve carries afferent fibers from pulmonary stretch receptors (Hering-Breuer reflex), bilateral vagotomy typically leads to **slow, deep breathing** (hyperpnea) because the feedback to terminate inspiration is lost, not a simple decrease in rate in the context of cardiovascular regulation. * **D (Decrease in blood pressure):** Initially, an increase in heart rate tends to increase cardiac output, which may slightly elevate or maintain blood pressure. Furthermore, the Vagus carries baroreceptor afferents; losing these would lead to a loss of inhibitory input to the vasomotor center, potentially causing a rise in BP. **High-Yield Clinical Pearls for NEET-PG:** * **Intrinsic Heart Rate:** The rate at which the heart beats when all autonomic influence is removed (pharmacologically or surgically) is ~100 bpm. * **Atropine:** A muscarinic antagonist that mimics the effect of a vagotomy by blocking parasympathetic action, used to treat symptomatic bradycardia. * **Vagal Tone:** Athletes have high vagal tone, explaining their resting bradycardia.

Q: Which structure is known as the gatekeeper of the heart?

AV node. **Explanation:** The **AV (Atrioventricular) node** is known as the **"Gatekeeper of the heart"** because it regulates the electrical impulses traveling from the atria to the ventricles. Its primary function is to provide a physiological delay (approx. 0.1 seconds), ensuring that the atria contract and empty their blood into the ventricles before ventricular contraction begins. Furthermore, in cases of atrial tachyarrhythmias (like atrial fibrillation), the AV node protects the ventricles by limiting the number of impulses that pass through, preventing a dangerously high ventricular rate. **Analysis of Options:** * **SA Node:** Known as the **"Pacemaker of the heart."** It initiates the impulse but does not act as a filter or gatekeeper. * **Purkinje Fibers:** These are responsible for the rapid conduction of impulses throughout the ventricular myocardium to ensure synchronous contraction. They have the fastest conduction velocity in the heart. * **Bundle of His:** This is the only electrical connection between the atria and ventricles, but it functions as a conduction pathway rather than a regulatory gate. **High-Yield Clinical Pearls for NEET-PG:** * **Slowest Conduction Velocity:** AV Node (0.01–0.05 m/s), which accounts for the AV nodal delay. * **Fastest Conduction Velocity:** Purkinje fibers (2–4 m/s). * **Blood Supply:** The AV node is supplied by the **Posterior Descending Artery (PDA)**. In 90% of individuals (right dominant), this arises from the Right Coronary Artery. * **Location:** The AV node is located in the **Koch’s Triangle** (bounded by the Tendon of Todaro, the septal leaflet of the tricuspid valve, and the coronary sinus orifice).

Q: Stroke volume can be decreased by which of the following?

Increasing heart rate. **Explanation:** Stroke Volume (SV) is the volume of blood pumped by the left ventricle per beat. It is determined by three primary factors: **Preload, Afterload, and Contractility.** **Why "Increasing Heart Rate" is correct:** When the heart rate increases significantly (tachycardia), the duration of the cardiac cycle decreases. This reduction occurs primarily at the expense of **diastole** (the filling phase). A shorter diastolic filling time leads to a decrease in **End-Diastolic Volume (EDV)**. According to the Frank-Starling Law, a lower EDV results in a reduced stroke volume. While cardiac output may initially stay stable due to the higher rate, the stroke volume itself decreases. **Analysis of Incorrect Options:** * **A. Increasing ventricular contractility:** This increases the force of contraction, leading to a lower End-Systolic Volume (ESV) and thus an **increase** in stroke volume. * **C. Decreasing total peripheral resistance (TPR):** TPR is a major component of afterload. Decreasing afterload makes it easier for the ventricle to eject blood, thereby **increasing** stroke volume. * **D. Decreasing systemic blood pressure:** Similar to option C, lower systemic pressure reduces the afterload against which the heart must pump, which typically **increases** stroke volume. **High-Yield NEET-PG Pearls:** * **Formula:** $Stroke Volume (SV) = EDV - ESV$. * **Frank-Starling Law:** Stroke volume increases in response to an increase in the volume of blood filling the heart (Preload), within physiological limits. * **Clinical Correlation:** In conditions like Supraventricular Tachycardia (SVT), the heart rate is so high that filling time is severely compromised, leading to a drop in SV and blood pressure (syncope). * **Inverse Relationship:** SV is directly proportional to Preload and Contractility, but inversely proportional to Afterload.

Q: Kupffer cells are a type of?

Macrophages. **Explanation:** **Kupffer cells** are specialized, resident **macrophages** located within the sinusoids of the liver. They form part of the **Mononuclear Phagocyte System (MPS)**. Their primary function is to filter the portal blood, removing bacteria, cellular debris, and aged red blood cells through phagocytosis. They also play a crucial role in innate immunity and iron metabolism by recycling hemoglobin. **Analysis of Options:** * **Option A (Dendritic cells):** While both are antigen-presenting cells (APCs), dendritic cells are specialized for initiating adaptive immune responses by migrating to lymph nodes. Kupffer cells remain stationary in the liver sinusoids. * **Option C & D (B and T cells):** These are **lymphocytes** involved in adaptive immunity. B cells produce antibodies, and T cells are involved in cell-mediated immunity. They are not phagocytic cells like Kupffer cells. **High-Yield NEET-PG Pearls:** * **Location:** They are found on the luminal surface of the endothelial cells in the **hepatic sinusoids**. * **Origin:** Like all macrophages, they originate from **monocytes** (derived from bone marrow hematopoietic stem cells). * **Staining:** They can be visualized using **India ink** or specialized markers like **CD68**. * **Other Tissue-Specific Macrophages (Commonly Tested):** * **CNS:** Microglia * **Lungs:** Alveolar macrophages (Dust cells) * **Skin:** Langerhans cells * **Bone:** Osteoclasts * **Kidney:** Mesangial cells

Q: Von Willebrand factor is produced by which of the following?

Platelets. **Explanation:** Von Willebrand Factor (vWF) is a large multimeric glycoprotein essential for primary hemostasis. It is synthesized and stored in two specific locations: 1. **Endothelial Cells:** Stored in specialized organelles called **Weibel-Palade bodies**. 2. **Platelets:** Stored in the **$\alpha$-granules** (alpha-granules). When a blood vessel is injured, vWF is released to act as a "molecular bridge" between the exposed subendothelial collagen and the **GpIb receptor** on platelets, facilitating platelet adhesion. **Analysis of Options:** * **Option B (Correct):** Platelets produce and store vWF in their $\alpha$-granules. Upon activation, they release vWF to promote further platelet recruitment and stabilize Factor VIII. * **Option A (Incorrect):** While the **liver** synthesizes most coagulation factors (like Factor II, VII, IX, X, and Fibrinogen), it does **not** produce vWF. This is a common distractor; remember that vWF is the exception to the "liver produces clotting factors" rule. * **Option C & D (Incorrect):** Neither the lungs nor the spleen are primary sites for vWF synthesis. The spleen primarily functions in the sequestration and destruction of old platelets, rather than the production of vWF. **High-Yield Clinical Pearls for NEET-PG:** * **Dual Function:** vWF facilitates platelet adhesion (via GpIb) and acts as a carrier protein to stabilize **Factor VIII** in circulation, preventing its rapid degradation. * **vWD (Von Willebrand Disease):** The most common inherited bleeding disorder. It typically presents with mucosal bleeding and a prolonged **Bleeding Time (BT)**. * **Diagnostic Marker:** Factor VIII levels are often low in vWD because vWF is not available to protect it. * **Desmopressin (DDAVP):** Used in treatment as it triggers the release of vWF from endothelial Weibel-Palade bodies.

Q: Which of the following statements is true about capillaries?

Contain 5% of total blood volume. ### Explanation **1. Why Option A is Correct:** The capillaries are the primary site of exchange between blood and tissues. Despite having the largest total cross-sectional area in the body, they contain only a small fraction of the total blood volume—approximately **5%**. This is because capillaries are microscopic and short. In contrast, the systemic veins and venules act as "capacitance vessels," holding about 60-70% of the total blood volume. **2. Why the Other Options are Incorrect:** * **Option B:** 10% is incorrect. As stated above, the volume is significantly lower (5%). The heart and lungs typically hold about 7-9% and 9-12% respectively. * **Option C:** The velocity of blood flow is actually **minimum** in the capillaries. According to the continuity equation ($V = Q/A$), velocity ($V$) is inversely proportional to the total cross-sectional area ($A$). Since capillaries have the highest total cross-sectional area (approx. 1000 times that of the aorta), blood flow slows down to its lowest point (approx. 0.03 cm/s), allowing adequate time for nutrient and gas exchange. * **Option D:** The **arterioles** (not capillaries) offer the maximum resistance to blood flow. They are known as "resistance vessels" because they have thick muscular walls and can significantly alter their diameter to regulate blood pressure. **3. NEET-PG High-Yield Pearls:** * **Capacitance Vessels:** Veins (hold the most volume). * **Resistance Vessels:** Arterioles (highest pressure drop occurs here). * **Exchange Vessels:** Capillaries (lowest velocity of flow). * **Windkessel Effect:** Property of large elastic arteries (like the aorta) to dampen pressure fluctuations. * **Starling Forces:** Movement of fluid across the capillary membrane is determined by the balance of Hydrostatic and Oncotic pressures.

Question 1

During the Valsalva maneuver, how does the heart rate typically change?

Accepted Answer

Tachycardia followed by bradycardia

Answer

Bradycardia followed by tachycardia

Answer

Tachycardia during and after the Valsalva maneuver

Answer

Bradycardia during and after the Valsalva maneuver

Question 2

During the T-P interval in an ECG of a patient with a damaged cardiac muscle, which of the following is true?

Accepted Answer

The entire ventricle is repolarized except for the damaged cardiac muscle

Answer

The entire ventricle is depolarized

Answer

The entire ventricle is depolarized except for the damaged cardiac muscle

Answer

The entire ventricle is repolarized

Question 3

Bilateral cutting of the vagus nerve causes what physiological change?

Accepted Answer

Increase in heart rate

Answer

Decrease in heart rate

Answer

Decrease in respiratory rate

Answer

Decrease in blood pressure

Question 4

Which structure is known as the gatekeeper of the heart?

Accepted Answer

AV node

Answer

SA node

Answer

Purkinje fibers

Answer

Bundle of His

Question 5

Stroke volume can be decreased by which of the following?

Accepted Answer

Increasing heart rate

Answer

Increasing ventricular contractility

Answer

Decreasing total peripheral resistance

Answer

Decreasing systemic blood pressure

Question 6

Kupffer cells are a type of?

Accepted Answer

Macrophages

Answer

Dendritic cells

Answer

B cells

Answer

T cells

Question 7

Discharge from baroreceptors causes inhibition of what?

Accepted Answer

Sympathetic nervous system outflow

Answer

Parasympathetic nervous system outflow

Answer

Renal vascular outflow

Answer

Adrenal medullary outflow

Question 8

Von Willebrand factor is produced by which of the following?

Accepted Answer

Platelets

Answer

Liver

Answer

Lungs

Answer

Spleen

Question 9

In a study measuring blood pressure in a dog, Rakesh used a mercury sphygmomanometer on the right femoral artery, and Arif used a pressure transducer with pulse tracing on the left femoral artery. After injecting adrenaline, Rakesh recorded a mean arterial pressure of 130 mmHg, while Arif recorded 120 mmHg. Both initially had a mean arterial pressure of 100 mmHg. What best explains the observed difference in blood pressure readings after adrenaline injection?

Accepted Answer

Pulse tracing tends to underestimate pressure at high values.

Answer

Pulse tracing underestimates pressure at low values.

Answer

The right femoral artery is more sensitive to adrenaline than the left.

Answer

Ventricular filling significantly affects the diastolic period.

Question 10

Which of the following statements is true about capillaries?

Accepted Answer

Contain 5% of total blood volume

Answer

Contain 10% of total blood volume

Answer

Velocity of blood flow is maximum

Answer

Offer maximum resistance to blood flow

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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