Cardiovascular System Practice Questions

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.

Q: Which peptide causes increased capillary permeability and edema?

Bradykinin. **Explanation:** **Bradykinin (Correct Answer):** Bradykinin is a potent vasodilator peptide belonging to the kinin system. It acts primarily on **B2 receptors** to stimulate the release of nitric oxide and prostacyclin. Its hallmark physiological effect is a significant increase in **capillary permeability** by causing the contraction of endothelial cells, which creates gaps in the microvasculature. This allows fluid and proteins to leak into the interstitial space, leading to **edema**. **Analysis of Incorrect Options:** * **Histamine (Option A):** While histamine also increases capillary permeability and causes edema (e.g., in type I hypersensitivity), it is an **amine**, not a **peptide**. The question specifically asks for a peptide. * **Angiotensin II (Option B):** This is a potent **vasoconstrictor**. It generally increases blood pressure and decreases capillary hydrostatic pressure downstream, which does not typically promote edema. * **Renin (Option D):** Renin is an **enzyme** (aspartyl protease) secreted by the juxtaglomerular cells. It does not directly affect capillary permeability; its role is to convert Angiotensinogen to Angiotensin I. **NEET-PG High-Yield Pearls:** * **ACE Inhibitors & Cough:** ACE (Angiotensin-Converting Enzyme) is responsible for the breakdown of Bradykinin. ACE inhibitors lead to Bradykinin accumulation, causing the classic side effects of **dry cough** and **angioedema**. * **Hereditary Angioedema:** This condition is caused by a **C1 esterase inhibitor deficiency**, leading to overproduction of Bradykinin, resulting in episodes of severe swelling. * **Triple Response of Lewis:** Bradykinin and Histamine are both involved in the "wheal and flare" reaction following skin injury.

Q: Cushing phenomenon is characterized by which combination of findings?

High blood pressure and low heart rate. **Explanation:** The **Cushing phenomenon** (or Cushing reflex) is a physiological response to **increased intracranial pressure (ICP)**. It is a classic high-yield topic in neurophysiology and neurosurgery. **Mechanism:** When ICP rises (due to tumor, hemorrhage, or edema), it eventually exceeds the mean arterial pressure (MAP), leading to cerebral ischemia. To restore cerebral blood flow, the vasomotor center in the medulla triggers a massive sympathetic discharge. This causes a significant increase in peripheral resistance, resulting in **Systemic Hypertension** (to "push" blood into the brain). The sudden rise in blood pressure is detected by baroreceptors in the carotid sinus and aortic arch. This triggers a compensatory parasympathetic response via the Vagus nerve, leading to **Reflex Bradycardia** (low heart rate). **Analysis of Options:** * **Option D (Correct):** High BP (sympathetic response to ischemia) and Low HR (baroreceptor-mediated reflex bradycardia). * **Option A & C:** Incorrect because the body must raise BP to overcome ICP; low BP would worsen cerebral ischemia. * **Option B:** Incorrect because while BP is high, the baroreceptor reflex ensures the heart rate drops; a high BP with a high HR is more characteristic of a sympathetic storm or pain response, not the Cushing reflex. **Clinical Pearls for NEET-PG:** 1. **Cushing’s Triad:** Includes (1) Hypertension, (2) Bradycardia, and (3) Irregular respirations (Cheyne-Stokes breathing). 2. **Significance:** It is a late sign of brain herniation and a medical emergency. 3. **Contrast:** Do not confuse with **Cushing’s Syndrome** (hypercortisolism). 4. **Widened Pulse Pressure:** The hypertension in Cushing reflex often presents with a specifically increased systolic pressure, leading to a widened pulse pressure.

Q: What is the basis of Korotkoff sound?

Turbulent blood flow. **Explanation:** The **Korotkoff sounds** are the sounds heard through a stethoscope during the non-invasive measurement of blood pressure using a sphygmomanometer. **Why Turbulent Blood Flow is Correct:** Under normal conditions, blood flow in the arteries is **laminar** (silent and streamlined). When a blood pressure cuff is inflated above systolic pressure, the artery is occluded, and no flow occurs. As the cuff is slowly deflated, the pressure drops just below the systolic level, allowing blood to squirt through the partially compressed vessel at high velocity. This sudden change in vessel diameter and high velocity converts laminar flow into **turbulent flow**. The vibrations produced by this turbulence create the audible Korotkoff sounds. Once the cuff pressure falls below diastolic pressure, the artery remains fully open, laminar flow is restored, and the sounds disappear. **Analysis of Incorrect Options:** * **A & D (Aortic Valve Closure/Expansion):** These relate to the cardiac cycle and the production of the second heart sound ($S_2$), not the peripheral arterial sounds heard during BP measurement. * **B (Production of Heart Sound):** Heart sounds ($S_1, S_2, S_3, S_4$) are primarily caused by the closure of valves and the vibration of cardiac chambers, whereas Korotkoff sounds are vascular in origin. **High-Yield Clinical Pearls for NEET-PG:** * **Phase I:** First appearance of clear tapping sounds (corresponds to **Systolic BP**). * **Phase V:** Complete disappearance of sounds (corresponds to **Diastolic BP** in adults). * **Phase IV:** Muffling of sounds (used for Diastolic BP in children or hyperdynamic states like pregnancy/thyrotoxicosis). * **Auscultatory Gap:** A period of silence between Phase I and II; failure to recognize it can lead to underestimating systolic or overestimating diastolic pressure.

Q: During which stage of the cardiac cycle are all heart valves closed?

None of the above. ### Explanation The correct answer is **None of the above** because the question asks for "the stage" (singular), but in the cardiac cycle, there are actually **two distinct stages** during which all four heart valves (Mitral, Tricuspid, Aortic, and Pulmonary) are closed. #### 1. Why "None of the above" is correct: For a valve to be closed, the pressure in the chamber ahead must be higher than the pressure in the chamber behind. All valves are closed during: * **Isovolumetric Contraction:** Ventricular pressure rises above atrial pressure (closing AV valves) but remains below arterial pressure (semilunar valves stay closed). * **Isovolumetric Relaxation:** Ventricular pressure falls below arterial pressure (closing semilunar valves) but remains above atrial pressure (AV valves stay closed). Since both Options B and C are correct, selecting only one would be incomplete. In competitive exams like NEET-PG, if two options are equally valid and a "Both" option is missing, "None of the above" or the most comprehensive choice is sought. #### 2. Analysis of Incorrect Options: * **A. Systolic Ejection:** The semilunar valves (Aortic/Pulmonary) are **open** to allow blood to leave the ventricles. * **B & C (Individually):** While all valves are closed during these phases, neither phase alone represents "the" single stage. #### 3. High-Yield Clinical Pearls for NEET-PG: * **Volume Change:** During isovolumetric phases, the ventricular volume remains constant (hence "isovolumetric"), making them the steepest vertical lines on a Pressure-Volume loop. * **Heart Sounds:** * **S1** (Lubb) occurs at the beginning of Isovolumetric Contraction (closure of AV valves). * **S2** (Dupp) occurs at the beginning of Isovolumetric Relaxation (closure of Semilunar valves). * **Maximum Oxygen Consumption:** The heart consumes the most oxygen during **Isovolumetric Contraction** because it is generating high pressure against closed valves.

Question 1

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

Question 2

What happens when the availability of oxygen to tissues decreases?

Accepted Answer

Vasodilation and increase in blood supply to the tissue takes place.

Answer

Vasoconstriction and decrease in blood supply to the tissue takes place.

Answer

Venoconstriction and increase in tissue perfusion pressure occurs.

Answer

Venodilation and decrease in tissue perfusion pressure occurs.

Question 3

During the surgical removal of an invasive glioma from the base of the skull, cranial nerves IX and X are accidentally cut bilaterally. What would be the immediate change in the patient's hemodynamic condition?

Accepted Answer

Tachycardia with hypertension

Answer

Bradycardia with hypertension

Answer

Bradycardia with hypotension

Answer

Sinus arrhythmia with hypotension

Question 4

The vasodilatation produced by carbon dioxide is maximum in which organ system?

Accepted Answer

Brain

Answer

Kidney

Answer

Liver

Answer

Heart

Question 5

Which of the following can cause hypertension and heart disease?

Accepted Answer

Elevated blood levels of aldosterone and renin resulting from an atherosclerotic plaque in a renal artery.

Answer

Hyperprolactinemia due to a pituitary tumor.

Answer

Acromegaly due to a GH-producing tumor that developed in adulthood.

Answer

Cushing syndrome due to an adrenal tumor.

Question 6

Which peptide causes increased capillary permeability and edema?

Accepted Answer

Bradykinin

Answer

Histamine

Answer

Angiotensin II

Answer

Renin

Question 7

Which of the following statements about the vasomotor centre is true?

Accepted Answer

Acts along with the cardiovagal centre to maintain blood pressure

Answer

Independent of hypothalamic inputs

Answer

Influenced by baroreceptor signals but not by chemoreceptors

Answer

Essentially silent during sleep

Question 8

Cushing phenomenon is characterized by which combination of findings?

Accepted Answer

High blood pressure and low heart rate

Answer

Low blood pressure and high heart rate

Answer

High blood pressure and high heart rate

Answer

Low blood pressure and low heart rate

Question 9

What is the basis of Korotkoff sound?

Accepted Answer

Turbulent blood flow

Answer

Aortic valve closure

Answer

Production of heat sound

Answer

Aortic valve expansion

Question 10

During which stage of the cardiac cycle are all heart valves closed?

Accepted Answer

None of the above

Answer

Systolic ejection

Answer

Isovolumetric relaxation

Answer

Isovolumetric contraction

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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