Cardiovascular System Practice Questions

Q: Maximum blood flow per 100 gm of tissue is observed in which organ?

Kidney. **Explanation:** The correct answer is **Kidney**. In cardiovascular physiology, it is crucial to distinguish between **total blood flow** (cardiac output) and **blood flow per unit mass** (tissue perfusion). 1. **Why Kidney is Correct:** The kidneys receive approximately 20–25% of the total cardiac output (about 1100–1200 ml/min). When normalized for weight, the kidneys receive roughly **360–400 ml/min per 100g** of tissue. This high flow rate is not primarily for metabolic demand, but to maintain a high Glomerular Filtration Rate (GFR) for effective waste excretion and electrolyte balance. 2. **Analysis of Incorrect Options:** * **Liver:** While the liver receives the largest *total* blood flow (~1500 ml/min), its large mass results in a lower perfusion rate of approximately **95 ml/min per 100g**. * **Heart:** The coronary blood flow is roughly **70–80 ml/min per 100g**. While the heart has the highest oxygen extraction ratio, its flow per unit mass is lower than the kidney. * **Brain:** The brain receives about 15% of cardiac output, translating to roughly **50–54 ml/min per 100g**. **High-Yield NEET-PG Pearls:** * **Highest total blood flow:** Liver (1500 ml/min). * **Highest blood flow per 100g:** Carotid Body (~2000 ml/min/100g). *Note: If Carotid Body is an option, it is the absolute highest; among major organs, Kidney is the answer.* * **Highest oxygen extraction (A-V O2 difference):** Heart (extracts ~75% of delivered oxygen). * **Organ most sensitive to hypoxia:** Brain.

Q: Which of the following is responsible for the Bezold-Jarisch reflex?

Serotonin. ### Explanation The **Bezold-Jarisch Reflex (BJR)** is a cardioinhibitory reflex characterized by a triad of **bradycardia, hypotension, and apnea**. It is mediated by the stimulation of non-myelinated C-fiber vagal afferents located in the ventricles (chemoreceptors and mechanoreceptors). **Why Serotonin is Correct:** Serotonin (5-HT) is a potent chemical trigger for the BJR. It acts on **5-HT3 receptors** located on the vagal nerve endings in the heart. When these receptors are stimulated—often by exogenous administration or endogenous release (e.g., during myocardial ischemia)—it triggers a reflex increase in parasympathetic (vagal) tone and a decrease in sympathetic tone, leading to the characteristic triad. **Analysis of Incorrect Options:** * **B. Histamine:** While histamine can cause vasodilation and hypotension, it typically triggers a *reflex tachycardia* (via baroreceptors) rather than the bradycardia seen in BJR. * **C. Prostaglandin:** Prostaglandins are involved in inflammatory responses and ductal patency but do not serve as the primary chemical mediators for the BJR. * **D. Angiotensin:** Angiotensin II is a potent vasoconstrictor that increases blood pressure and does not trigger cardioinhibitory reflexes. **High-Yield Clinical Pearls for NEET-PG:** * **Receptors:** The reflex is mediated by **C-fiber sensory endings** in the left ventricle. * **Afferent/Efferent Path:** Both the afferent and efferent limbs of this reflex are carried by the **Vagus nerve**. * **Clinical Significance:** * **Myocardial Infarction:** BJR is often seen in **inferior wall MI** because the inferior wall has a high density of these vagal receptors. * **Anesthesia:** It can be triggered by spinal anesthesia or certain drugs like **Propofol**. * **Other Stimuli:** Besides serotonin, the reflex can be triggered by **veratridine alkaloids**, capsaicin, and certain contrast media.

Q: In hypovolemic shock, which of the following occurs EXCEPT?

Heart rate decreases. **Explanation:** In hypovolemic shock, the primary pathology is a significant loss of blood or fluid volume, leading to decreased venous return and reduced stroke volume. To maintain mean arterial pressure (MAP), the body activates the **baroreceptor reflex**. **1. Why "Heart rate decreases" is the correct answer (The Exception):** When blood pressure drops, baroreceptors in the carotid sinus and aortic arch decrease their firing rate. This inhibits the nucleus tractus solitarius (NTS), leading to **increased sympathetic outflow** and decreased parasympathetic activity. The result is a **compensatory tachycardia** (increased heart rate) to maintain cardiac output ($CO = HR \times SV$). Therefore, a decrease in heart rate is physiologically incorrect in typical hypovolemic shock. **2. Analysis of Incorrect Options:** * **A. Constriction of capacitance vessels:** Sympathetic stimulation causes venoconstriction (constriction of veins/capacitance vessels). This shunts blood from the peripheral venous reservoir toward the heart to maintain preload. * **B. Constriction of arterioles in the skin:** Increased sympathetic activity causes alpha-1 mediated vasoconstriction in non-essential organs like the skin and kidneys to divert blood to the brain and heart. This explains why patients in shock present with "cold and clammy" skin. * **C. Decrease in cardiac output:** This is the hallmark of hypovolemic shock. The loss of circulating volume directly reduces stroke volume, which the body tries (but often fails) to fully compensate for via tachycardia. **Clinical Pearls for NEET-PG:** * **Bezold-Jarisch Reflex:** A rare exception where profound hypovolemia can cause *bradycardia* due to paradoxical activation of ventricular mechanoreceptors. * **Shock Index:** Heart Rate / Systolic BP. An index > 0.9 suggests significant blood loss. * **Urine Output:** The most sensitive clinical indicator of organ perfusion in shock management.

Q: What is true about the third heart sound?

Normal physiologically in athletes. ### Explanation The **third heart sound (S3)**, also known as the "ventricular gallop," occurs during the early phase of diastole (rapid ventricular filling) [1]. It is caused by the sudden deceleration of blood flow into a compliant ventricle. **Why the correct answer is right:** * **Option D:** S3 can be a **physiological** finding in children, young adults (under 40), pregnant women, and **athletes**. In athletes, it is associated with a highly compliant, physiologically dilated left ventricle that accommodates increased stroke volume. **Why the other options are wrong:** * **Option A:** In chronic constrictive pericarditis, a similar sound called a **Pericardial Knock** is heard. While it occurs in early diastole like S3, it is higher pitched and results from the sudden cessation of ventricular filling by a rigid, calcified pericardium. * **Option B:** An aortic aneurysm does not typically affect the early diastolic filling phase of the ventricles in a way that would consistently abolish an S3. * **Option C:** This is a classic "trap." S3 is **absent in significant mitral stenosis** because the narrowed valve restricts the rapid inflow of blood into the ventricle [2], preventing the sudden "thud" required to produce the sound. (Note: The question asks what is *true*; while S3 is absent in MS, Option D is the definitive physiological characteristic often tested). **High-Yield Clinical Pearls for NEET-PG:** * **Pathological S3:** In older adults, it is a hallmark of **Congestive Heart Failure (CHF)** and indicates ventricular overfilling or reduced ejection fraction. * **Mnemonic:** S3 follows the cadence of the word **"Kentucky"** (S1-S2-S3). * **Best heard:** At the apex with the **bell** of the stethoscope in the left lateral decubitus position. * **S4 (Atrial Gallop):** Always pathological (except in some elderly patients); associated with "stiff" ventricles (LVH, Hypertension). Cadence: **"Tennessee."**

Question 1

Compensatory mechanisms during acute hemorrhage include:

Accepted Answer

Increased respiratory rate

Answer

Decreased cerebral and coronary blood flow

Answer

Decreased myocardial contractility

Answer

Renal and splanchnic vasodilation

Question 2

What is the state at the end of ventricular diastole?

Accepted Answer

Coronary flow is maximum

Answer

Atrial volume is more

Answer

Flow in aorta drops

Answer

All of the above

Question 3

The ECG of a 40-year-old male was recorded using standard bipolar limb leads. The sum of the voltage of the three standard leads was found to be 5 millivolts. What does this indicate?

Accepted Answer

Increased cardiac muscle mass

Answer

A normal heart

Answer

Right ventricular hypertrophy

Answer

Left ventricular hypertrophy

Question 4

Maximum blood flow per 100 gm of tissue is observed in which organ?

Accepted Answer

Kidney

Answer

Brain

Answer

Heart

Answer

Liver

Question 5

Which of the following is responsible for the Bezold-Jarisch reflex?

Accepted Answer

Serotonin

Answer

Histamine

Answer

Prostaglandin

Answer

Angiotensin

Question 6

In a graph illustrating Starling's curves, a mild hemorrhage would cause the stroke volume to shift from point X to which point?

Accepted Answer

Point A

Answer

Point B

Answer

Point C

Answer

Point E

Question 7

In hypovolemic shock, which of the following occurs EXCEPT?

Accepted Answer

Heart rate decreases

Answer

Constriction of capacitance vessels

Answer

Constriction of arterioles in the skin

Answer

Decrease in cardiac output

Question 8

What is true about the third heart sound?

Accepted Answer

Normal physiologically in athletes

Answer

Absent in chronic constrictive pericarditis

Answer

Absent in aortic aneurysm

Answer

Absent in mitral stenosis

Question 9

Myocardial oxygen demand depends upon which of the following factors?

Accepted Answer

Preload

Answer

Afterload

Answer

Intramyocardial tension

Answer

Blood hemoglobin concentration

Question 10

What effect does parasympathetic stimulation have on the heart?

Accepted Answer

Decreased firing rate of the SA node

Answer

Increased excitability of the AV node

Answer

Decreased ventricular contractility

Answer

Tachycardia

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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