Cardiovascular System Practice Questions

Q: Cardiac muscle contraction is primarily dependent on which of the following?

Extracellular Ca2+. **Explanation:** The correct answer is **Extracellular Ca2+** because of the unique mechanism of **Calcium-Induced Calcium Release (CICR)** in cardiac muscle. 1. **Why Extracellular Ca2+ is correct:** Unlike skeletal muscle, which can contract without external calcium, cardiac muscle contraction is highly dependent on the influx of extracellular calcium. During the plateau phase (Phase 2) of the cardiac action potential, **L-type calcium channels (Dihydropyridine receptors)** open, allowing extracellular Ca2+ to enter the cell. This "trigger calcium" then binds to **Ryanodine receptors (RyR2)** on the Sarcoplasmic Reticulum (SR), causing a massive release of stored calcium into the sarcoplasm. Without the initial influx of extracellular Ca2+, the SR cannot release its stores, and contraction cannot occur. 2. **Why the other options are incorrect:** * **Sarcoplasmic Ca2+:** While this is the immediate source for cross-bridge cycling, its release is *dependent* on the prior entry of extracellular calcium. Therefore, the primary dependency lies with the external source. * **Extracellular/Intracellular Na+:** Sodium ions are responsible for the rapid depolarization (Phase 0) of the action potential but do not directly initiate the contractile machinery (actin-myosin interaction). **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Inotropy:** Drugs like **Digitalis** increase cardiac contractility by indirectly increasing intracellular Ca2+ (by inhibiting the Na+/K+ ATPase pump, which slows the Na+/Ca2+ exchanger). * **Calcium Channel Blockers (CCBs):** Verapamil and Diltiazem act on L-type channels, reducing the "trigger" calcium and exerting a negative inotropic effect. * **Skeletal vs. Cardiac:** Skeletal muscle uses **electromechanical coupling** (direct physical link between receptors), whereas cardiac muscle uses **electrochemical coupling** (CICR).

Q: What causes Korotkoff sounds?

Turbulent blood flow during occlusion of a vessel. **Explanation:** **Korotkoff sounds** are the sounds heard via stethoscope over the brachial artery during the measurement of blood pressure using a sphygmomanometer. **Why Option C is Correct:** Under normal conditions, blood flow in the arteries is **laminar** (silent). When a blood pressure cuff is inflated above systolic pressure, the artery is completely occluded. As the cuff pressure is gradually released to just below systolic pressure, blood begins to spurt through the partially constricted vessel. This high-velocity flow through a narrowed opening creates **turbulence**, which produces the audible vibrations known as Korotkoff sounds. **Analysis of Incorrect Options:** * **Option A:** Laminar flow is streamlined and silent; it does not produce sound. Korotkoff sounds occur because the cuff *disrupts* laminar flow. * **Option B:** Closure of the aortic valve produces the **S2 (second heart sound)**, heard over the precordium, not the peripheral Korotkoff sounds. * **Option D:** In a healthy individual, no sound is heard over a peripheral artery without cuff application because the flow is naturally laminar. **High-Yield NEET-PG Pearls:** * **Phase I:** The first appearance of clear tapping sounds (corresponds to **Systolic BP**). * **Phase V:** The point where sounds disappear completely (corresponds to **Diastolic BP** in adults). Note: In children or hyperdynamic states (e.g., pregnancy, thyrotoxicosis), Phase IV (muffling) is used for diastolic BP. * **Auscultatory Gap:** A silent interval between Phase I and Phase II; failure to recognize it can lead to underestimating systolic or overestimating diastolic pressure. It is common in hypertensive patients.

Q: In general, systolic blood pressure in young females is less than that in males of the same age due to which of the following reasons?

Estrogen, which prevents atherosclerosis. **Explanation:** The difference in systolic blood pressure (SBP) between young males and females is primarily attributed to the protective hormonal profile of premenopausal women. **Why Option B is Correct:** Estrogen exerts a significant cardioprotective effect. It promotes the production of **nitric oxide (NO)** and **prostacyclin**, which are potent vasodilators that maintain arterial compliance. More importantly, estrogen improves the lipid profile by increasing HDL ("good" cholesterol) and decreasing LDL ("bad" cholesterol). This prevents the early development of **atherosclerosis** (hardening and narrowing of arteries). In males, the lack of high estrogen levels leads to earlier arterial stiffening, resulting in higher systolic pressures compared to age-matched females. **Why Other Options are Incorrect:** * **Option A:** While diet influences BP, there is no universal dietary difference between genders that consistently accounts for the lower SBP in females across diverse populations. * **Option C:** Progesterone generally has a minimal or slightly hypertensive effect in some contexts (via mineralocorticoid receptors), but it does not provide the primary vascular protection seen with estrogen. * **Option D:** While sympathetic tone can vary, it is not the fundamental physiological reason for the baseline SBP difference; hormonal influence on the vessel wall is the dominant factor. **High-Yield NEET-PG Pearls:** * **Post-menopausal Shift:** After menopause, the decline in estrogen causes a rapid rise in SBP, often leading to a higher prevalence of hypertension in older women compared to men. * **Estrogen & NO:** Estrogen stimulates **eNOS (endothelial Nitric Oxide Synthase)**, which is a key mechanism for maintaining low peripheral resistance. * **Pulse Pressure:** SBP is a major determinant of pulse pressure; lower SBP in young females results in lower pulse pressure compared to males.

Q: Which of the following is not a naturally occurring anticoagulant in the body?

Von Willebrand factor. **Explanation:** The correct answer is **Von Willebrand factor (vWF)** because it is a **pro-coagulant** protein, not an anticoagulant. Its primary roles in hemostasis are: 1. **Platelet Adhesion:** It acts as a molecular bridge between platelet glycoprotein Ib (GpIb) receptors and exposed subendothelial collagen at the site of vascular injury. 2. **Stabilization of Factor VIII:** It binds to and protects Factor VIII from rapid degradation in the plasma. **Analysis of Incorrect Options:** * **Protein C and Protein S:** These are Vitamin K-dependent natural anticoagulants. Activated Protein C (with Protein S as a cofactor) proteolytically inactivates **Factors Va and VIIIa**, thereby limiting the coagulation cascade. * **Antithrombin III (AT-III):** This is the most potent circulating anticoagulant. It inactivates **Thrombin (IIa)** and **Factor Xa** (as well as IXa, XIa, and XIIa). Its activity is increased several thousand-fold in the presence of Heparin. **High-Yield Clinical Pearls for NEET-PG:** * **vWF Deficiency:** The most common inherited bleeding disorder (Von Willebrand Disease), characterized by mucosal bleeding and prolonged Bleeding Time (BT). * **Virchow’s Triad:** Deficiency of Protein C, Protein S, or Antithrombin III leads to a hypercoagulable state (thrombophilia), increasing the risk of Deep Vein Thrombosis (DVT). * **Factor V Leiden:** The most common cause of inherited thrombophilia, where Factor Va is resistant to inactivation by Protein C. * **Site of Synthesis:** Most clotting factors and anticoagulants are synthesized in the liver; however, vWF is synthesized in **endothelial cells (Weibel-Palade bodies)** and megakaryocytes.

Q: What is the conduction velocity in the AV node and SA node?

0.05 m/sec. ### Explanation The conduction velocity of the cardiac impulse varies significantly across different parts of the heart to ensure coordinated contraction. **1. Why Option A is Correct:** The **AV node** has the slowest conduction velocity in the entire heart, measured at approximately **0.05 m/sec**. This slowness is physiologically essential as it creates the **AV nodal delay** (approx. 0.1 second). This delay allows the atria to finish contracting and empty their blood into the ventricles before ventricular systole begins, ensuring optimal stroke volume. The **SA node** also shares this slow conduction velocity (0.05 m/sec). The slow speed is primarily due to a smaller fiber diameter and fewer gap junctions between cells. **2. Analysis of Incorrect Options:** * **Option B (0.5 m/sec):** This is the conduction velocity of the **Atrial pathways** (Internodal tracts) and the **Ventricular muscle** (myocardium). * **Option C (1 m/sec):** This is an intermediate speed, faster than the nodes but significantly slower than the specialized conduction system. * **Option D (5 m/sec):** This represents the **Purkinje fibers**, which have the **fastest** conduction velocity in the heart (approx. 1.5 to 4.0 m/sec). This rapid speed ensures that the entire ventricular myocardium contracts almost simultaneously. **3. NEET-PG High-Yield Pearls:** * **Slowest Conduction:** AV node (0.05 m/sec) — "The Bottleneck." * **Fastest Conduction:** Purkinje fibers (up to 4 m/sec) — "The Express Highway." * **Order of Velocity (Slowest to Fastest):** AV node < SA node < Ventricular muscle < Atrial muscle < Purkinje system. * **Mechanism of Delay:** The slow conduction in the AV node is due to a decreased number of gap junctions (increased resistance) and slow-response action potentials (calcium-dependent).

Q: The Windkessel effect is seen in which of the following conditions?

Elastic arteries. ### Explanation The **Windkessel effect** refers to the ability of large, elastic arteries to act as a pressure reservoir during the cardiac cycle. **1. Why Elastic Arteries are correct:** During ventricular systole, the heart ejects a stroke volume into the aorta and large arteries (e.g., pulmonary artery, carotid). Because these vessels contain high amounts of **elastin**, they distend to accommodate this blood, storing potential energy. During diastole, when the aortic valve closes, the elastic walls recoil. This recoil converts the stored potential energy back into kinetic energy, pushing blood forward into the peripheral circulation. This ensures **continuous blood flow** even when the heart is resting and prevents systolic blood pressure from rising too high or diastolic pressure from falling too low. **2. Why the other options are incorrect:** * **Muscular arteries:** These contain more smooth muscle and less elastin. Their primary role is distributing blood and regulating flow via vasoconstriction/dilation, rather than acting as a pressure reservoir. * **Arterioles:** Known as the **"Resistance Vessels,"** they have the highest resistance to flow and are responsible for the largest drop in mean arterial pressure. * **Capillaries:** Known as **"Exchange Vessels,"** they have the thinnest walls (single layer of endothelium) and the slowest blood flow velocity to facilitate nutrient exchange. **Clinical Pearls for NEET-PG:** * **Aging/Atherosclerosis:** With age, elastin is replaced by collagen (stiffening). This reduces the Windkessel effect, leading to **Isolated Systolic Hypertension** and increased pulse pressure. * **Compliance:** The Windkessel effect is a direct function of vascular compliance ($C = \Delta V / \Delta P$). * **Velocity of Flow:** Blood flow is pulsatile in the aorta but becomes continuous in the capillaries due to the Windkessel effect and high resistance in arterioles.

Question 1

Delayed afterdepolarization implies what?

Accepted Answer

All of the above

Answer

Increased intracellular Ca2+

Answer

Excessive catecholamines

Answer

Digitalis toxicity

Question 2

Which of the following statements about Reynolds' number is incorrect?

Accepted Answer

A Reynolds' number greater than 2500 suggests turbulent blood flow.

Answer

Reynolds' number predicts the likelihood of turbulent flow.

Answer

Reynolds' number is calculated as ρDV / η.

Answer

A Reynolds' number less than 2000 suggests laminar blood flow.

Question 3

Cardiac muscle contraction is primarily dependent on which of the following?

Accepted Answer

Extracellular Ca2+

Answer

Sarcoplasmic Ca2+

Answer

Extracellular Na+

Answer

Intracellular Na+

Question 4

What is Charles's Law?

Accepted Answer

Volume divided by Temperature equals a constant (V/T = constant)

Answer

Pressure times Volume equals a constant (PV = constant)

Answer

Pressure times Volume equals the number of moles (PV = n)

Answer

None of the above

Question 5

What causes Korotkoff sounds?

Accepted Answer

Turbulent blood flow during occlusion of a vessel

Answer

Increased laminar flow on application of pressure

Answer

Closure of aortic valve in diastole

Answer

Normal sound existing even without the application of a cuff

Question 6

Clamping of the carotid arteries above the carotid sinus results in what physiological changes?

Accepted Answer

Decrease in blood pressure and decrease in heart rate

Answer

Increase in blood pressure and increase in heart rate

Answer

Increase in blood pressure and decrease in heart rate

Answer

Decrease in blood pressure and increase in heart rate

Question 7

In general, systolic blood pressure in young females is less than that in males of the same age due to which of the following reasons?

Accepted Answer

Estrogen, which prevents atherosclerosis

Answer

Dietary habits

Answer

Progesterone effect on blood vessels

Answer

Low sympathetic activity

Question 8

Which of the following is not a naturally occurring anticoagulant in the body?

Accepted Answer

Von Willebrand factor

Answer

Protein C

Answer

Protein S

Answer

Antithrombin III

Question 9

What is the conduction velocity in the AV node and SA node?

Accepted Answer

0.05 m/sec

Answer

0.5 m/sec

Answer

1 m/sec

Answer

5 m/sec

Question 10

The Windkessel effect is seen in which of the following conditions?

Accepted Answer

Elastic arteries

Answer

Muscular arteries

Answer

Arterioles

Answer

Capillaries

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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